Front Cover
 Table of Contents
 Pair bond persistence
 Natality and mortality
 Food and feeding habits
 Nonbreeding season
 Literature cited
 Back Cover

Group Title: Bulletin of the Florida State Museum
Title: Communal social biology of the southern San Blas jay
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00095808/00001
 Material Information
Title: Communal social biology of the southern San Blas jay
Series Title: Bulletin - Florida State Museum ; volume 26, number 4
Alternate Title: San Blas jay
Physical Description: p. 204-263 : ill. ; 23 cm.
Language: English
Creator: Hardy, John William
Webber, Thomas A.
Raitt, Ralph J.
Donor: unknown ( endowment )
Publisher: Florida State Museum, University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1981
Copyright Date: 1981
Subject: Cyanocorax -- Behavior   ( lcsh )
Animal communities -- Mexico -- Acapulco Region   ( lcsh )
Animal societies   ( lcsh )
Genre: bibliography   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Bibliography: p. 250-251.
Statement of Responsibility: John William Hardy, Thomas A. Webber and Ralph J. Raitt.
 Record Information
Bibliographic ID: UF00095808
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 22543745
lccn - 82623267

Table of Contents
    Front Cover
        Page 201
        Page 202
        Page 203
    Table of Contents
        Page 204
        Page 205
        Page 206
        Page 207
        Page 208
        Page 209
        Page 210
        Page 211
        Page 212
        Page 213
        Page 214
        Page 215
        Page 216
        Page 217
        Page 218
        Page 219
        Page 220
        Page 221
        Page 222
        Page 223
        Page 224
        Page 225
        Page 226
        Page 227
        Page 228
        Page 229
    Pair bond persistence
        Page 230
        Page 231
        Page 232
        Page 233
        Page 234
    Natality and mortality
        Page 235
        Page 236
        Page 237
        Page 238
        Page 239
        Page 240
        Page 241
        Page 242
    Food and feeding habits
        Page 243
    Nonbreeding season
        Page 244
        Page 245
        Page 246
        Page 247
        Page 248
        Page 249
    Literature cited
        Page 250
        Page 251
        Page 252
        Page 253
        Page 254
        Page 255
        Page 256
        Page 257
        Page 258
        Page 259
        Page 260
        Page 261
        Page 262
        Page 263
        Page 264
    Back Cover
        Page 265
Full Text

of the

Biological Sciences


Number 4






Volume 26


are published at irregular intervals. Volumes contain varying numbers of pages and are not
necessarily completed in any one calendar year.


RHODA J. BRYANT, Managing Editor

Consultants for this issue:



Communications concerning purchase or exchange of the publications and all manuscripts
should be addressed to: Managing Editor, Bulletin; Florida State Museum; University of
Florida; Gainesville, Florida 32611.
Copyright 1981 by the Florida State Museum of the University of Florida.

This public document was promulgated at an annual cost of
$5025.00 or $5.03 per copy. It makes available to libraries, scholars,
and all interested persons the results of researches in the natural
sciences, emphasizing the circum-Caribbean region.

Publication date: December 18, 1981

Price: $5.00



SYNOPSIS: We studied the communally-breeding Southern San Bias Jay, Cyanocorax
(Cissilopha) s. sanblasianus. from 1974 to 1978 near Acapulco, Cuerrero, Mexico. In this area
it inhabits only palm plantations and the small remnants of native woodland scattered among
them. Most nests are built in the crowns of coconut palms.
This jay lives year-round in nonmigratory groups of fairly constant composition, which on
our study areas ranged in size from 13 to 26 birds one year old and older. In each group
62-82'7 of the members were at least 3 years old. Each group contained 6-10 breeding pairs
that were probably permanently monogamous, plus a smaller number of nonbreeders. With
the exception of replacement nests and the rare occurrence of second broods, female breeders
laid in only one nest per breeding season, and only one female laid in each nest.
Breeding pairs were assisted in feeding and defending their young by both the nonbreeders
and breeders of their communal group. Some nests were attended by as many as 13 birds.
Helpers, whether breeders or nonbreeders. preferred to feed fledglings rather than nestlings.
Nests begun earlier in the breeding season attracted more helpers than did later ones, because
of the accumulation of fledglings as the season progressed.
The feeding rate per nest increased with brood size, but there was no correlation between
the feeding rate per nestling and brood size. The positive correlation between feeding rate per
nest and brood size is probably a result not of greater rates of feeding per attendant, but of
larger numbers of attendants, each of which feeds at a rate independent of the number of
nestlings. All birds of known parentage helped at their parents' nests, though none helped its
parents exclusively.
Most birds began breeding at 3 years of age or older, but 1- and 2-year-olds were breeders
more commonly than is at present evident in the other three species of Cissilopha. Younger
breeders tended to nest later in the breeding season than older breeders.
Each communal group inhabited an exclusive home range, whose boundaries with other
groups were maintained by mutual avoidance rather than by active defense. In one large
group, whose members were dispersed over a comparatively large home range, breeders with
active nests confined their activities to a small fraction of their group's home range and ex-
erted a quasi-territorial dominance over other group members who entered these areas. Such
individual "core areas" were not evident in smaller groups.
The commonest clutch sizes were 3 and 4. Incubation lasted 17-18 days, and the nestling
period was about 18-20 days. Breeding pairs were usually single-brooded. Between 50 and
68% of nests that had clutches produced at least one fledgling, and 22-38% of all eggs
resulted in fledglings. From 0 to 50% of young that fledged survived to at least 1 year of age.
The annual survival rate of yearling and older birds was about 75% in most years. Changes in
group membership, by both young and adults, appear to be of infrequent but regular oc-

'John William Hardy is Curator in Ornithology, Florida State Museum. University of Florida. Gainesville FL 32611:
Thomas A. Webber is a graduate student in the Department of Zoolog., University of Florida; and Ralph J. Raitt is a Pro-
fessor in the Department of Biology. New Mexico State University. Las Cruces NM 88003

munal Social Biology of the Southern San Blas Jay. Bull. Florida State Mus., Biol. Sci.


currency. Females seemed to change groups more often than did males. Most of the im-
migrants to our study groups were of unknown origin.
The movements of dependent juveniles and their attendants are described.
Southern San Bias Jays are omnivorous. They seemed to forage about equally in palms,
herbaceous growth, hedgerows, and jungle patches. During the breeding season they did not
usually forage in flocks. There was little or no mixing of birds from different communal
groups during the nonbreeding season. At that time of year they typically foraged in flocks
and were less vocal than in the breeding season.
We speculate on the way in which each Cissilopha species' characteristic group size,
number of breeders per group, and age at first breeding, may be related to one another and to
the productivity of the habitat.


INTRODUCTION ............ ..... .................................... 205
ACKNOWLEDGMENTS ......... . ............................ 206
MATERIALS AND METHODS ......... ..... . .................. 206
RESULTS .................. ...... ........... ...... 207
NESTS AND PRINCIPAL HABITAT .......... ..... .......... ............ 207
OCCURRENCE IN OTHER HABITATS .......................................... 210
COMMUNAL STRUCTURE .................. .............................. 212
Group Composition ............................................. 212
N est D ispersion .................................................... 2 14
The Roles of Helpers ................... ........ .......... ....... 214
Temporal Patterns of Nest Attendance and Social Status of
Nest Attendants ............ ................... ........... 218
Variation in Rate of Nest Attendance ................................ 224
Kinship As a Factor in Attendance .................................... 226
Age at First Breeding ..... ........ .................. ......... 228
Breeding Time of Adults vs. Subadults ................... .............. 229
PAIR BOND PERSISTENCE .................................................. 230
HOME RANGE ............... ....... ..... .. ........................ 230
INTRAGROUP CORE AREAS .................... .................. ...... 230
NATALITY AND MORTALITY . . ..... ... . .......................... 235
Overall Nesting Success ...... ....... .................. ...... 235
Breeding Success of Subadults vs. Adults ............................. 235
Causes of Nestling Loss ............................................ 236
Post-fledgling Survival and Mortality ................................ 236
Emigration and Immigration ............................. ....... . 238
Juvenile Movements: Home Range and Core Area Fidelity ................ 241
FOOD AND FEEDING HABITS .................. ................. ........... 243
NONBREEDING SEASON ................................................... 244
D ISC U SSIO N ................... ................. ................. ... . 245
LITERATURE CITED ............... ........ ............ ............... 250
APPENDICES ......... ................................................. 252


Four allopatric species of Middle American jays, known as the black-
and-blue jays, constitute the subgenus Cissilopha of the widespread
neotropical genus Cyanocorax (see Hardy 1969 for the taxonomic revision
that we follow here, which submerges Cissilopha in Cyanocorax). These
four species are the Yucatan Jay, C. yucatanicus, of southeastern Mexico
and adjacent Belize; the Beechey Jay, C. beecheii, of central western
Mexico in Sonora and Sinaloa; the Bushy-crested Jay, C. melanocyaneus,
of Guatemala, Honduras, and El Salvador; and the San Bias Jay, C.
sanblasianus, of southwestern Mexico.
There are two races of the San Bias Jay. The Nelson San Bias Jay (C. s.
nelsoni) ranges from the state of Sinaloa south to northern Guerrero,
Mexico. The Southern San Bias Jay (C. s. sanblasianus) occurs from about
100 km northwest to about 70 km southeast of Acapulco, Guerrero. These
two races are separated by about 200 km, and they differ in certain
aspects of their vocalizations, softpart color, and plumage (Hardy and
Raitt 1977).
We have studied the breeding biology of all four species of black-and-
blue jays, including both races of the San Bias Jay (Raitt and Hardy 1976,
1979; Hardy 1976; Raitt et al., ms.). Each of these forms exhibits a varia-
tion on the theme of communal social behavior, in which birds live year-
round in groups of basically stable composition, and breeding pairs
receive assistance from other group members in feeding and defending
their young.
Prior to our work, the behavior of these four species in the wild was
virtually unknown. These studies help to fill a large Middle American
geographical gap in our knowledge of communal New World jays.
Our objective in studying these four species was to determine at least
the outlines of their social organization, especially their communal
breeding behavior, their demography, and the nature of their habitats.
The ethology and systematics of the subgenus were of secondary impor-
tance to us.
We decided not to attempt a long-term intensive investigation, such as
that being conducted on the Florida Scrub Jay (Aphelocoma c.
coerulescens) by Woolfenden (Woolfenden and Fitzpatrick 1978 and
references therein), of a single species of neotropical jay. We could not
conduct such a study year-round from our base in the United States. Also
the study areas themselves lead a precarious existence at the mercy of
neotropical agriculture and forestry (one of our study sites was razed in
the midst of our work), so that we were wary of investing effort in the sort
of study that depends on having a site secure from interference for a
decade or more. Finally, we felt the urgency of getting some information
about each species before it becomes extinct or so rare as to be impossible


to study (this is most likely in the case of the Beechey Jay; see Raitt and
Hardy 1979). In short, we decided we would rather have limited informa-
tion on four species than somewhat more information on only one.
This paper presents our findings on the fifth and final form to be
studied in the subgenus, the Southern San Bias Jay. Because of the relative
ease with which it could be studied, it yielded richer information than did
any of the other black-and-blue jays, showing it to have the most
elaborate and peculiar communal breeding behavior of any New World
jay studied so far.

Erik Bitterbaum, Alan B. Bolten, Howard Gates, Gary L. Grabowski, Harold F.
Mayfield, James R. Raitt, James R. Reitzel, Sarah Sloane, and John T. Vollertsen all par-
ticipated in the field work. We gratefully acknowledge their contributions, which in many
cases extended well beyond routine assistance. L.W. Oring, G.E. Woolfenden, and R.S.
Balda refereed the manuscript and made many helpful suggestions. J.A. Cox gave assistance
with statistical analysis. We thank them very much.
We are also grateful to the Direcciof General de la Fauna Silvestre, Rep6blica de M6xico,
for permission to collect and mark birds, to Rogers McVaugh, University of Michigan, for
identification of certain plants, and to Richard Franz for identification of stomach contents of
Financial support was provided by National Science Foundation Grants BMS 74-11107
and DEB 76-99735.

Our principal study site was 13 km northwest of Pie de la Cuesta, Guerrero, about 2 km
north of the Laguna de Coyuca. Our other study site was 6 km southeast of Acapulco Interna-
tional Airport, about 2 km inland from Playa Encantada.
We captured, aged, sexed, color-marked, and released jays of four communal groups at
the main study site and one group at the other site hereafter called the southern site. Birds
were caught in mist nets or by hand.
We determined the birds' ages by criteria of Hardy (1973) and Hardy and Raitt (1977). By
using a combination of plumage characters and eye color, one can distinguish in the field be-
tween juveniles, yearlings, 2-year-olds, and "adults." Through their second year Southern San
Bias Jays have brown eyes. The irides then gradually change through various shades of green
until by 3 years of age they are pure yellow and remain so for life. We have found few excep-
tions to this rule. Since 1977 we have encountered two 2-year-olds with greenish-yellow eyes
that at a distance were difficult to distinguish from those of adults. Some 3-year-olds retained
a greenish tinge to the eye, which could be distinguished from pure yellow only with the bird
in hand. On the whole, age classes remained distinguishable with remarkable reliability.
Sex was determined by a combination of weight, presence of a cloacal protuberance or
brood patch, and reproductive role.
The birds were marked with colored plastic tarsal flags ("Saflag") and usually with
anodized aluminum or plastic leg bands in the same color combinations. Individual birds are
referred to by their color markers, the left leg first. Thus PiG means pink on the left, green on
the right and Pi/G-L means pink over green on the left. Colors and their symbols in this paper
are: O, orange; Bl, blue; Bk, black; W, white; Pi, pink; P, purple; G, green. An "X" denotes
absence of a band. A suffix numeral indicates that the combination was used previously on a
bird now presumed to be dead. In each year of the study some birds (usually females) re-

Vol. 26, No. 4


mained unmarked in each group, but usually could be distinguished by a combination of their
age, association with a particular site or marked bird, degree of hostility toward humans, and
peculiarities of voice. In some cases these characteristics were deemed reliable enough to iden-
tify unmarked birds from year to year.
We studied the Southern San Bias Jay in five breeding seasons from 1974 through 1978.
Field work in 1974 was conducted from 25 to 30 June by three persons (approximately 16
man-days). Some birds in group 1 were flagged, two nests were found and studied, and the
general nature of the main study site and the jays was assessed, including verification of the
detectability of age classes in the field.
Field work in 1975 was conducted from 21 June to 28 July by four to six persons (approx-
imately 160 man-days), all at the main study site except for two man-days at the southern site.
Field work in 1976 was conducted from 23 June to 28 July by two to seven persons in ap-
proximately 160 man-days (18 days at the southern site).
In 1977 study was conducted from 10 June to 27 July by four to eight persons (appprox-
imately 240 man-days).
In 1978 eight days (18-25 June) were spent by two people censusing the two best-studied
communal groups, ascertaining the survival of flagged birds, the size and composition of the
groups, and pair bond persistence, with some effort devoted to determining the number of
nests, their distribution, timing, and success. From 1975 through 1977 attention was given to
netting birds; following flagged birds to detect group membership, individual roles, home
ranges, and core areas (subdivisions of home ranges); and to studying nests and fledglings.
Figure 1 is a map of the study site, showing the distribution of vegetation, roads, lanes,
fences, and other features.


In the present study, 52 nests were found or were known circumstan-
tially to have existed in the communal groups that we have designated 1,
2, and 3. Of these, 48 were in coconut palms on a bract or cluster of
coconuts at the base of the fronds. Two were in the crowns of lime trees
and two on bracts of small native palms (species not determined). All nests
were within the palm groves and none within the patches of native
woodland nearby. Nests ranged in height of placement from 2 m (lime
tree) to 18 m. Most of the nests were 9 to 15 m up, the smallest and the
very tallest palms rarely being selected as nest trees. Mean height of 39
nests that we were able to measure was 11.8 m.
Certain portions of each group's home range were consistently pre-
ferred for nesting from year to year. Figure 2 shows all nests given a num-
ber in the main study area from 1974 through 1978. The jays nested in
those parts of the groves that satisfied three requirements: (1) the canopy
of the palm crowns was not too dense; (2) there were no acacia thickets
but lush herbaceous growth instead; and (3) there was native woodland
nearby. The frequency with which any fronds of adjacent palms touched
(expressed as a percent of the total possible) was used as an index of
canopy closure (Table 1). The palms were planted in straight rows and


Vol. 26, No. 4

I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20



I ''




R :

I 2 3 1. 4 5
1 2 3 4 5

I-.- '.;,




s i I


FIGURE 1. Map of the main Southern San Bias Jay study site, showing landmarks and vegeta-
tion. Areas bounded by coordinates A-B/12-13 and R-S/12-16 have palms and ground level
vegetation of herbaceous growth, shrubs, and brushy thickets.

columns, so that each tree (unless on the edge of the grove) had four
nearest neighbors. Thus, if a given palm touched, say, three of its four
neighbors, its closure index was 75%. The closure index for a sample
quadrat is the mean of the closure indices of all the trees in the quadrat.
Eight square quadrats, each of one hectare, were censused in 1977. Three
of these were selected because they contained jay nests (quadrats 1, 4, 7);
the other five represented habitat variations not used for nesting. The in-
dex of closure for those having nests is 7.2% or less. Of the five having no
jay nests in the five years, three (2, 3, 8) had 10% or greater closure in-




S -- : --

'. i i

-or C

*L"L'* I : -i LL

-4-----,-, - ..

-Y I

8 9 10 II 12 13 14 15 16 17 18 19 20



0 0o 100

FIGURE 2. Locations of all known active nests at the main study site, 1974-78. Double circles
= 1974; circles = 1975; squares = 1976; hexagons = 1977; triangles = 1978. Nest l's exact
location not ascertained. Approximate positions of nest 51 and 52 indicated by question-
marked designations.

dices; one (5) had a low index of 0.17%; and one (6) had a 5.3% closure,
was frequented by jays, and probably had nests occasionally. The
relatively open-canopied groves may be selected as a means of reducing
predation by snakes and squirels. In groves where the trees are far enough
apart to prevent a climbing predator from traveling from crown to
crown, these animals must return to the ground and ascend each tree.
This difficulty may make open groves unattractive to such predators. We
rarely saw squirrels in the nest areas, but found them frequently in the
groves not used for nesting and having relatively closed canopies, where
they moved easily between adjacent trees with intermingling fronds.
Rich herbaceous growth, both for foraging and for the protection it
affords fledglings, also is a feature of good nesting groves. Groves with the
ground cleared and plowed for corn planting had nests only where


TABLE 1. -Coconut grove quadrat comparisons.

Quadrat No. of No. of No. of Index of Jay Other
number trees possible touches closure use features
1 156 594 43 7.2 Nests Ground forbs
and hedgerows
2 196 698 133 19.0 Rare Sparse ground
forage cover
3 360 1478 163 11.0 Forage Sparse ground
4 191 984 34 3.4 Nests Heavy forb
5 144 600 1 0.17 No Jay Brushy acacia
use understory
6 144 600 32 5.3 Forage, Similar to
probably 4 above
7 152 591 31 5.2 Nests Sparse ground
cover, many
8 195 861 87 10.1 No Nests Heavy forb

bordering on preferred habitat. The failure of quadrat 5 to have jay nests
is possibly related to the brushy acacia growth at ground level. We found
no nests where these acacias and shrubs grew in dense thickets.
The jays favored nesting sites near remnants of native broadleaved
woodland, either as islands of at least a few hundred m2 or as hedgerows
in and around a grove. Each communal group seemed to have its own
more or less exclusive woodland foraging ground. A particularly striking
example of the importance of such tracts was seen in the case of group 4.
The hill on the north side of that group's home range (Figs. 1 coordinates
18-19/J-K; 2, 14) was covered with a dense low jungle in 1976. By the
time we arrived in 1977, the hill was completely denuded for planting
corn. This jungle patch had been the major tract of native vegeta-
tion available to group 4 (see Fig. 14). The group had completely disap-
peared by 1977. By July 1978 the hillside jungle had begun to grow back
and birds of group 2 were foraging there, but the palm grove portion of
group 4's former home range was never reoccupied by jays of any group.
Figure 3 shows several views of the coconut palm groves the jays in-


Northwest of Acapulco we found Southern San Blas Jays nesting only

Vol. 26, No. 4


a -I

FicURE 3. Vegetation of the main study site. (A) Spotting scope is directed toward nest site
(white arrow) in coconut palm. (B) Mango foodtree with overstory of coconut palms, and
herbaceous ground cover. (C) Palm at the south edge of the "jungle"-a patch of native
broadleaved evergreen woodland-in the group 2 home range.


in palm groves. At the southern site, southeast of the city, a large remnant
of coastal plain broadleaved scrub woodland is intermingled with the
coconut groves and open corn fields, where, in addition to the adjacent
palm groves, we found the jays nesting in the edges of the scrub. This
habitat, shown in Figure 4, was very patchy; we found two patches large
enough to constitute true woodland and ascertained that the jays were not
nesting in their interior. The relationship of the San Bias Jay to the
original vegetation is considered further in the Discussion.

GROUP COMPOSITION. -Appendix I summarizes basic information on
all the jays studied in groups 1 and 2. Only some of the group 1 birds and
none in group 2 were flagged in 1974. Thus the 1974 column of Appendix
I does not fully show group l's composition for that year and is given to
show persistence of some individuals throughout later years. The same is
true for the 1975 column with respect to group 2. Data on the member-
ship of group 1 are complete for 1975-78 and for group 2, 1976-78. Table
2 summarizes the age composition of groups 1 and 2 for the years in which
adequate data are available.
Southern San Bias Jays live in groups that are unusually large for com-
munal breeders (see Brown 1978). The sizes of the two groups (1 and 2)
that we studied most intensively usually were about 14 and 24 respec-
tively (Table 2). The three groups (3, 4, and 5) that we studied in less
detail never had fewer than 10 birds each.
From 1976 to 1977 the size of group 1 remained unchanged. Group 2
increased in size from 22 to 26 birds by immigration of GPi from group 3
and possibly by recruitment of some unmarked birds from group 4
(although only 22 of these were observed regularly; the remaining four

TABLE 2.-Proportion of age classes (marked and unmarked birds) in groups 1 and 2 of
Southern San Bias Jays.
1975 1976 1977 1978
Group 1
Adults, 3 yr + 8 11 10 9
2 yr 3 1 2 2
lyr 2 3 3 1
13 15 15 12
Group 2
Adults, 3 yr + 18 19 19
2yr 1 3 2
lyr 3 4 4
22 26 25

Vol. 26, No. 4



- mcj


FIGURE 4. Patchy second-growth scrub woodland of the southern study site. (A) and (B) Men are indicating approximate locations ot jay nests. (LU
Thicket edge; the tallest middle tree held a jay nest. (D) Worker attaching a marker tag to indicate a jay nest tree.



were seen only once or twice each and their status was never determined).
Groups 3 and 4 were never counted accurately. Our impression of group 3
was that it was slightly smaller than in the previous year. Group 4 had
disappeared by 1977, as discussed previously under Nests and Principal
Habitat. In 1978, group 1 had 13 members, and group 2 had 26
members. Other groups were not censused in 1978.
In most species of communally breeding birds, each communal group
usually cares for only one or two nests (Brown 1978). The Cissilopha jays
conform to this pattern (see Raitt and Hardy 1976 on Yucatan Jays, 1979
on Beechey Jays) with the exception of the Southern San Bias Jay. Groups
1 and 2 had from 6 to 10 active nests at one time. We were never able to
count accurately the number of nests in groups 3, 4, and 5.
We found that most members of the Southern San Bias Jay groups were
breeders, including some birds 1 and 2 years old. While it is not unusual
in some other communal species for 1- and 2-year-olds to breed (Brown
1978), it is rare in the other Cissilopha jays.
NEST DISPERSION. Table 3 shows that group 1 nests were in a single
cluster and that group 2 nests were in two subclusters, with one linking
nest (33) and two outlying ones (30, 38). Table 4 shows the sizes of the
nest cluster areas and the percentage of the total home ranges that they
The nest clusters in the two groups in 1977 were of approximately
equal density. Table 5 shows the mean distance from each nest to all other
nests in its group that existed at the same time (not counting overlaps of
up to 3 days). In group 1 the mean distance from each nest to all four
neighbors was 117 m. To ascertain the comparable figure for group 2 we
calculated the mean distance from each nest to its four nearest neighbors,
which yielded a figure of 127 m.
We found no evidence that breeding pairs having one or more
subadult members nested farther from their nearest neighbors (Table 5,
nests 39, 33, and 38) than did older pairs.
The significance of nest cluster density and the placement of
subadults' nests are considered in the Discussion.
THE ROLES OF HELPERS. We found 10 nests being built. We were
able to study construction at half of these; building was mostly by the
female of the breeding pair, assisted or accompanied by her mate. In only
one of these five cases was any bird other than the pair involved in any
way: at nest 32 a female (Pi/Bl-R) accompanied the breeding pair for
several days during nest building but did not add material to the nest.
Other nearby birds apparently did not visit the nest in the construction
We found no instance in which an incubating female (always the
female breeder) was fed on the nest by any bird other than her mate.

Vol. 26, No. 4


TABLE 3.-Shortest distances between neighbor nests inside and outside their communal

Distance from each nest to its Distance Nearest intergroup Distance2
nearest intragroup neighbor (m)' in meters neighbors in meters

Group 1, 1975
N-4 -3
N-5- 3
Group 1, 1976
N-12- 14
N-13- 12
N-14 15
N-16-14, 15, 20
Group 1, 1977
N-26- 36
N-27- 36
N-34 39
N-36- 26
N-39 26
Group 2, 1975

Group 2. 1976
N-21- 18
N-23 -22
Group 2. 1977

N-29 28
N-30- 29
N-37 29



(only three
nests found)

(only first nesting
attempts included)

N-4-6 (group 2)

N-13-17 (group 2)

N-27-28 (group 2)

N-6-4 (group 1)

N-21- 19 (group 3)

N-28-27 (group 1)

N-30-29 (group 3)

I Mean distance between nearest neighbor nests in group 1: 62 m. group 2. 80.3 m.
2 This figure is given only for nests closest to borders of groups in which nests were known.



TABLE 4. Sizes of home ranges and nest clusters (m2) of communal groups of San Bias Jays.

Groups Home Ranges Nest Clusters Nest Cluster/Home Range
1, 1976 90,500 20,500 22.6%
1, 1977 120,500 24,500 20.3%
2, 1976 130,749 13,049* 10.0%
2, 1977 250,000 68,000* 27.2%
"totals of 2 sub-clusters

TABLE 5.-Mean distance (m) from each nest to all other nests in its group.

Group 1

26 27 34 36 392 X

26 160 160 60 75 113.0
27 160 125 120 120*3 135.0
34 160 125 170 85 135.0
36 60 120 170 90 110.0
39 75 120 85 90 -92.5

Group 2

28 29 30 31 32 33 35 37 38 40 X

28 504 180 230
29 50 140 200
30 180 140 260
31 230 200 260
321 370 320 300 170
33' 170 140 220 70
35 300 260 280 80
37 70 30 140 140
381 320* 280' 200* 200
40 410 370 360 360

370 170
320 140
300 220
170 70
90 140
290 110
150 240
60 260

300 70 320* 410 117.5
260 30 280* 370 90.0
280 140 200* 360 170.0
80 170 210 200 122.5
90 290 150 60 117.5
140 110 240 260 115.0
230 170 120 108.0
230 250 340 87.5
170 250 180 175.0
120 340 180 155.0

I Nests 26, 32, 33, and 38 each had one subadult breeder.
SAlthough technically this was a second nesting, see text p. 26 for account of unique circumstances that justify its inclusion
s Asterisked numbers were not used in calculating means because of nonsimultaneity.
* Underlined numbers designate four nearest simultaneous neighbors.

Vol. 26, No. 4


Helpers began to appear at the nest once the young hatched. Except
for incubating or brooding females, most breeders were helpers
simultaneously at one or more nests in their group, with some birds serv-
ing as attendants at all nests in their group having nestlings. Using only
data from 1977, when we achieved the most complete record of nest at-
tendance, we can see some manifestations of the communality of groups 1
and 2. In Figure 5 a line connects each two nests that had attendants in
common, regardless of their identity or status. The number of lines as a
fraction of the number of possible lines depicts the communal unity
(C.U.) of the group. If a line has one arrow on it, the attendants were
helpers first at the nest from which the arrow originates and then later at
the nest to which the arrow is directed. Similarly, two arrows on a line in-
dicate reciprocity in this regard. The fraction of reciprocities recorded of
the total number possible (given a biological "need" in the form of nest-
lings requiring feeding) is a communality index (C.I.). The C.I. of 0.83 (5
of 6 lines between nests that produced nestlings having two arrows) for
group 1 in 1977 was about as high as it could be, because nest 39 failed
prior to hatching and nest 34 failed when the nestlings still required little
food. The subdivided nature of the group 2 nest clusters seems to account
for that group's lower C.I., which at 0.29 (9 of 31 lines double-arrowed) is
still indicative of communality. Initial study of this group suggested that
it might not be unified in that no network of attendants seemed to connect
the subgroup nest clusters. Long-term study revealed that while the fre-
quency of appearance of birds at each other's nests was low when nests
were far apart, such attendance did occur, as the lines and arrows show.
A line and one arrow need be based upon only a single feeding visit from a
bird primarily associated with another nest, and it might be argued that
this is slim evidence for communality. This record of social relationship
becomes more impressive, however, when one realizes that in the five
seasons of study, the inter-nest-cluster C.I. and C.U. were zero.
A comparison of the roles of parents and nonparents (pure helpers) in
maintaining unity and communality shows little difference between the
two (Figs. 5 and 6). Male breeders had relatively little to do at their own
nests while their mates laid and incubated, and spent some of this time
helping at neighboring nests. Thus most social connections by breeders
were maintained by the males. Breeding females were helpers prior to
egglaying, or after their young were fledged or their nests abandoned.
The C.U. of group 1, based only on parental contacts, was 0.80 (8 of 10),
the same as with pure helper representation. The C.I. of only 0.17 (1 of 6)
is expectable when one considers the roles of breeding vs. nonbreeding at-
tendants: the earlier-nesting, successful parents may be wholly involved
with fledged young and have less time to reciprocate by visiting later nests
to feed nestlings. Some helpers may have involvement with earlier broods


FIGURE 5. Communal contacts of groups 1 and 2 based on all nestling or fledgling attendants
in 1977. Numbers near circles are nest number designations. See text, page 15 for definition of
C.U. and C.I. and discussion and explanation of arrow directions.

as well, but not to the same degree. Group 2 had only 12 of 36 possible
social connections by parents only, for a C.U. of 0.33 and 3 of 9 (0.33)
social connections were reciprocal. Apparently this lower C.U. was
caused by two factors: the long distances between many nests and the
greater number of nests having virtually identical timing. Birds feeding
their own nestlings seldom visited other nests. Breeders of nests 33 and 37
were prominent assistants at nest 29 while building their own nests. The
male breeder of nest 40 attended at nest 29 after nest 40 was abandoned.
Breeders at nests 32 and 41 became helpers at nest 38 after both their at-
tempts failed.
ATTENDANTS. In Southern San Bias Jays at least five factors interact to
produce a complex sociality: (1) the groups are unusually large for a com-
munal species, (2) the number of breeding pairs per group is high, (3) the
timing of the various nests within a group is staggered (Figs. 7 and 8), (4)

Vol. 26, No. 4


most birds are both parents and helpers, and (5) successful early nests
reduce attendance at later nests and perhaps their success.
Early nests were virtually certain to attract assistance from non-
breeding helpers and from late breeders who were just starting to select
nest sites or to build. Later nests often had few or no helpers: parents that
nested earlier were renesting if they failed or attending their own fledg-
lings if they succeeded.
Nonbreeding helpers also tended to move around with the juveniles
and not visit later nests. Figures 9 and 10 illustrate the above points.
These figures as well as Figures 11 and 12 are constructed from observa-
tion periods that were virtually or completely uninterrupted, contained
few or no questionable identifications of individual birds, and
represented, when possible, days throughout the nesting period or a se-
quence of days in the week before fledging. With two exceptions, the

FIGURE 6. Communal contacts of groups 1 and 2, 1977, based only on attendants that were
breeders in the same season. See page 15 for definition and discussion of C.U. and C.I. See
Fig. 11 for other symbols.



Nest x>






\ \ \\\\\\\\\\ \\\\\\I



N-22 filed


0 15 20 25 30 5 10 15 20 25
June July
[| ]No activity or unknown Nestbuilding
[' Nestling period Incubation period I Fledgling/Juvenile period
(No. of lines = no. of young surviving)

FIGURE 7. Timing of stages in the development of nests in groups 1 and 2 at the main study
site, 1976. Note staggered timing of nests in both groups.

periods selected were an hour or more long. Some birds recorded as
helpers in Appendices I and II did not happen to visit a nest during the
observation periods represented in Figures 9-12, hence the discrepancy
between the figures and appendices.
In 1977, nest 27 was the first active nest in group 1. The many atten-
dants included yearling nonbreeders such as B1B1 and Pi/Bl-L, as well as
all male parents at later nests: OPi, OB1, PiG, and PP. The young from
nest 27 fledged on 18 June, though only one survived the first few days.
Nest 26 (Fig. 9) was the second to fledge young, on 4 July. There-
fore, nest 26 also had a sizeable group of attendants, although note that




Group I
1\\\\\\\\\\7-- i
N 27

N 26

N 34 27 July

N 36

N 39 Predatorizedt
in incubation'

10 15 20 25 30 5 10 15 20 25
Group 2

Nest 29, 45 N-45t(found) 2nd Nest of pair
L\\\\\\\\\-- ------- I
N-28 Associates


N-40, 43 \Predatorlzed

N-33 Predatorized (I day fledgling)


i /V /vV\VVVnf VlI\\\f\\\\\ff\\\


N-32,41 N-41 \Deserted
I EMEW\7\7\ 44


10 15 20 25 30 5 10 15 20 25


I\|1 Nestbuilding


SNestling care

SFledgling/Juvenile period
(No of lines=no of young surviving)

FIGURE 8. Timing of stages in the development of nests of groups 1 and 2 at the main study
site, 1977. Note staggering of nests in group 1 but near-simultaneity of some nests in group 2.

compared to the small parental contribution to feeding at nest 27, nest
26's nucleus pair contributed roughly half the feeding visits per hour.
Nest 26 fledged three young and simultaneously we introduced three or-
phan fledglings from outside the study area. Unfortunately for the com-
parison of the number of helpers at all nests of group 1 in 1977, nest 34
(Fig. 10A) failed after about one week of nestling life, too early to allow








2 50-

- 40-

O 30-


215 170 77 108
Pi? PP
PiW -8

BIBI-2 p

B B J Pi/B i/BI-L


195 125 26

Pi W


I OPi/



BIBI-2 -5

24 -



12 13 15 16 17 18 (26min)
June PM only
Days Day of fledging
of 2 young
Nest 27.2 to3 Young (Much disturbance)

27 29 30 I 2 3 4 6
June July (Fledging Day)
Nest 26:3 young
FIGURE 9. Percentage contribution of attendants and rates of feeding visits at nests 27 and
26, 1977. Note a larger number of attendants at both nests but higher contribution of parents
at nest 26.



10 --
10 II






t 60-





200m-n 156 201 94 195 120



27 28 29 30 2
Pg oat nest June July
totol time Days
(156 in)


First week Early second week
Nest 34:2 or 3 young
Food for sitter Helpers fed 7
100 50 mm180 65 only 52 190 65 o through P 168 80 175

901 65
i -6

fPd -5
I 70-

a 60- -4

"P, Much
C- 50- d sturbonce


30by PP

a 20-

12 13 14 15 16 17 20 21 24 25 26 27
Pg feeds with (Fledging Day)
July food brought I young
by PC

Nest 36:2 then I young


FIGURE 10. Percentage contribution of attendants and rates of feeding visits at nests 34 and
36, 1977. Note low feeding rate at nest 36 with only one young, and compare to the rate at
nest 37 (Fig. 12) with the same number of attendants, but with three nestlings.


examination of the helper's contributions. Nest 36 (Fig. 10B), however,
clearly shows the effects of the existence of seven juveniles needing care in
group 1. Note that virtually all attendance was by the breeding pair. We
saw only three contributions by others. Of these, only PiW actually fed
the young; in the other two feedings, food was delivered to the female
breeder who gave it to the young. One of the two nestlings fledged at nest
In group 2, 1977, nests 28, 29, and 30 show variations on the above-
described theme (Fig. 11). In the western part of the group's range, these
three nests were almost simultaneous in development, nest 29 fledging its
young on 18 June, the other two on 20 June. At nest 28, the only regular
attendant other than the breeding pair was WBk, their offspring of
the previous year. In the observation periods shown in Figure 11, B1W
may have fed once (identification not certain); outside these periods the
breeding pair of nest 29 (OW, XX ad.) and the female breeder of nest 33
(BlPi) were definitely recorded as feeding once each at this nest. It seems
as though nest 29, in operation at the same time as nest 28, attracted more
helpers because of its central position (see Fig. 2). Nest 29 drew regular at-
tendance from the breeders of nests 33 and 37, both of which were under
construction. Less help came from WO, WB1, WBk (nest 28), the breeders
at nest 30, Bl/G-R, a 2-year-old, and the helper Pi/G-R at nest 31. Figure
11 of nest 30 suggests that it suffered similarly from isolated position and
the concentration of helpers at nest 29, but the data are too few for this to
be certain. Ten birds were seen to attend the young of nest 30. The
parents were the principal caretakers at this nest, assisted mainly by the
2-year-old Bl/G-R. Others were seen to visit only once each. The virtual
absence of helpers at nest 36 in group 1 and nest 37 in group 2 seemed in
both cases to be due to the nearby presence of fledglings. By the time the
nestlings of nest 37 (Fig. 12) were ready for helpers, nest 28 had fledged
three young, nest 28 had fledged two, and nest 30 had fledged one (Fig.
11). Of these young, five survived and were being cared for by parents
and helpers of nests 28, 29, and 30. Figure 12 shows that in the long watch
periods at nest 37 only the two parents, OBk and Pi/O-R, attended the
nestlings. (Otherwise, only P/G-R, the female breeder of nest 30, was seen
to visit that nest.)
data on the frequency of feeding visits, number of attendants, and rates of
feeding visits per nestling. Total observation time and days spanned by
observations varied considerably. From Table 6 we have used the seven
nests (numbers 12, 22, 26, 27, 28, 29, and 30) with the best data on care of
nestlings, either throughout their nest life or in the latter part of that
period when helpers are prevalent, to examine relationships between
brood size, feeding rates, and number of attendants. Spearman correla-

Vol. 26, No. 4


80. WBK> WBK WBK 80
S/I *5
70 70

o 604 60 OP BL/G- 4
S50 BLW WO 50

3 40. 40 3

30 30- 2 30 2
i2 20
10 10

0 0 I0
14 15 16 17 (3daysbefore 13 14 14
June fledging) (AM) (AM) (PM)
Nest 28 3 Young Nest30.2Young

90 wO 6
81 PI
80 08BK OBK Pi/O-R
|i 80 W 08K O

70 8K

S40- OP

30 7


0o- I0-
12 13 14 15 16 17 18
June (Fledging day)
Nest 29.2 Young

FIGURE 11. Percentage contribution of attendants and rates of feeding visits at nests 28, 29,
and 30, 1977. Note that of these three simultaneous nests in close proximity to one another,
only one had a large and persistent complement of helpers, and most of these were breeders.

tion coefficient tests yielded the following results: a highly significant
negative correlation between number of frequent attendants and feeding
rate per frequent attendant (rs= -0.906, P < 0.01), and a significant
positive correlation between brood size and total feeding rate (r = 0.798,
P < 0.05). The correlation between feeding rate per frequent attendant
and feeding rate per nestling is just below significance at the 0.05 level


S80 k
IC /d' 5
S60- -4

-3 ,,


12 13 14 15 17 19 20 22 24
(2-4 day July ( 10-12day\
old young) Days 1old young)
Nest 37:3 Young
FIGURE 12. Percentage contribution of attendants and rates of feeding visits at nest 37. Com-
pare high rate of feeding of the three nestlings with lower rate at nest 36 (Fig. 10) by the same
number of attendants.

(r,= 0.746). There is a suggestion of a correlation between number of
frequent attendants and feeding rate per nestling, but it is not statistically
significant (r,= 0.717, P > 0.05). The feeding rate per nestling did not
increase with brood size (r,= -0.16, P > 0.05). The feeding rate per
nest is not correlated with number of frequent attendants (r,= 0.321).
The brood size is not correlated with the number of frequent attendants
(r,= 0.083). In summary, the amount of food received by nestlings and
the work of bringing it by attendants form a complex relationship in
which the availability of more attendants reduces the work load of in-
dividual attendants, and the number of feeding visits required to serve the
young is directly related to the size of the brood. Still, nests attended only
by parents and a few helpers apparently received just as many feeding
visits as those with many attendants.
We do not have enough data to provide information on the relation-
ship between the number of attendants and nesting success.
KINSHIP AS A FACTOR IN ATTENDANCE. We were able to follow only
six birds of known parentage from fledging through to their roles as at-
tendants at nests. All these birds helped their parents if their parents had

Vol. 26, No. 4

TABLE 6. -Summary of nest attendance data for San Bias Jays, groups 1 and 2, 1976, 1977.

Frequent Rate/
Group, Attendants Total Obs. Span of Rate of Rate/ Frequent
Year Nest Brood Size (Total No.) Time in Hrs. Obs. Feeding Nesting' Attendant

36 2-3(early)
1, mid-late
28 3
29 2
30 2
31 2
33 ?>1
37 3

38 ?>1

40 ?>1



3 or 4(8?)




9-21 July
16.8 Last 11 days of
nestling period
4.3 3 days,
beginning of
last week of
nestling period
7.45 18-22 July




4 July

Last 7 days
Last 9 days
First week

11.1 Final week
22.73 Final week
3.08 Final week
6.70 First week
9.50 First 11 days
17.30 First 2 weeks
(almost entire)
14.5 From 13th to 15th day


2 days at end of
ca first week

Where data are not supplied in the last two columns, it is because they were too few or from early in the nesting period and thus do not reflect accurately the rates of attendance.











young to feed, although help was delivered to the first nest that produced
young, regardless of the identity of the breeders there.
OBI was an offspring of OPi and PiO in 1975. In 1976 he was known
to have been a helper at three nests, the first that of OPi, his father, and
Bl/G, his stepmother, PiO his mother having disappeared. In 1977, as a
2-year-old, OBI was paired to BlBk at nest 26. That nest and its eggs were
taken over by OBl's father OPi and OPi's mate, Bl/G-L. OBI then was
mate, Bl/G-L (G/O-L having been killed by a predator). OBI then was
recorded as a helper at nest 26, thus being a helper to his own young for
his father, the grandfather of the young! In 1978, OB1 was apparently
breeding with B1Bk again, although the nest was not found.
WBk was the sole offspring of WO and WB1 at nest 18 in 1976. In 1977
he was a nonbreeding helper at his parents' nest (28) and rarely at nearby
nest 29. WBk was apparently still a helper at his parents' nest in 1978, but
the young had fledged before we arrived.
Pi/G-R was an offspring of OP and Pi/Bl-R at nest 22 in 1976. Pi/G-R
helped at three nests in 1977. It helped first at nest 31, which produced
young early in the breeding season. Later it helped at nest 33, its father's
nest, and at nest 38, both of which had nestlings of about the same age.
All three offspring of BO1 and O/G-L at nest 13 in 1976, B1B1-2, Pi/Bl-
L, and PiPi-2, were helpers in group 1 in 1977. Nest 27, owned by GG
and P/O-R, was the first nest known to have nestlings in group 1 in 1977.
All three sibling yearlings helped there. B1B1-2 and Pi/Bl-L were also ac-
tive helpers at nest 26 (owned by OPi), the second nest in the group to pro-
duce nestlings. Thus at nest 26 they were feeding nestlings, which, though
in a nest "owned" by OPi were actually the offspring of OBl. BlB1-2 and
Pi/Bl-L were also active feeders of the fledglings of nests 26 and 27 and the
orphans we introduced. In 1978, only Pi/Bl-L of the three sibs remained
in group 1 and was seen as a helper with the putative fledglings of OPi
and Bl/G-L. Some young, such as WBk, may even show some nearly ex-
clusive attachment to their parents, but nearby nests with earlier young
usually attracted attendance by such birds.
AGE AT FIRST BREEDING. Of seven jays marked as either fledglings or
yearlings and followed at least to their first nesting attempts (see Appen-
dix I), two males PiG and OBI, and one female, BlPi, attempted to nest as
2-year-olds; three, PP and Bl/G-R, both males, and BlW, a female, nested
first as 3-year-olds. GG, a male, nested first as a 4-year-old. Of all 14
yearlings whose activities were well known, only 2 (both females) attemp-
ted to nest; of all 10 well-known 2-year-olds, only 4 (3 males, 1 female) at-
tempted to nest. We conclude that although most individuals first at-
tempt to breed in their third year, and rarely the fourth, attempts by
yearlings and 2-year-olds to breed were of regular occurrence in the

Vol. 26, No. 4


groups studied. The possible significance of breeding by subadult birds
(less than 3 years old) is treated in the Discussion.
BREEDING TIME OF ADULTS VS. SUBADULTS. Nests involving subadults
as breeders were usually late, among the last to be initiated in the com-
munal groups studied (Fig. 13). The one exception was nest 26 in group 1,
at which OBI was the 2-year-old male breeder. This nest was second only
to nest 27 in the temporal sequence. It may be significant that OB1
matured early in plumage and softpart color, being without crest feathers
and having yellow irides only faintly tinted with green in the second year.
Because we terminated study each year before the fate of late nests could
be known with certainty, we lack data on the relative success of late and
early breeding attempts.

40 3O/BI-R 1 PPI
3GP Lri O/PP-R

37 Pi/0-R

35 @ ,

38 G/O-R

o OBI [ PP I--PiG
26 BIBk 34 XX 36 x

23 GPiO-R

21 O/pi-R
18 wxx 170Wo

13 81-L




1977 GROUP 2

1977 GROUP I

1976 GROUP 2

1976 GROUP I


508k PG 1975 GROUPI

II 13 15 17 19 21 23 252729 31 3 5 7 9 11 13 15 17 19 21 23 25 27 29 3 '3 5 7 9 II 13 15
FiGURE 13. Approximate dates of egg-laying for three age classes of breeders in first breeding
attempts of the season. Pairs in which yearlings or 2-year-olds are members tend to nest later.

30 BkP
Loj P/G-R

29 0

28 ow
28" ,


In 17 cases both members of the pair survived from one year to the
next. (Three of these cases involved unmarked adults: OW's mate from
1976 through 1978 and PP's mate from 1976 through 1977 were un-
marked.) In only one known case were the birds not mated to each other
in the second year. OP's 1976 mate, Pi/Bl-R, was seen briefly in June 1977
and then disappeared. The bird may have been sick and was associating
with another pair (XX, a 2-year-old, and BlW) that was building nest 32.
However, OP already had another mate, BlPi, at this time. We conclude
that these jays normally mate for life or until one leaves the communal

Figures 14 and 15 show the almost exclusive home ranges (as well as
nest locations) of San Blas Jay communal groups in 1976 and 1977. These
home ranges were maintained by mutual avoidance rather than by active
defense. On many occasions birds of neighboring groups came close to
each other at boundaries between ranges, sometimes into the same trees,
without any signs of intergroup hostility. We noted no vocalizations or
postural displays specialized for territory defense. On the rare occasions
when trespassing occurred the intruder moved swiftly and inconspicu-
ously and avoided confrontation with residents. In 1975, group 2 birds,
such as OW and WO, occasionally flew at palm-crown height with at
most one stop across the nest area of group 1 to the west jungle patch (Fig.
1). This behavior apparently stopped in 1976 after the west jungle patch
was largely cut down. An adult stranger netted in the heart of group 1's
range in June 1975 and never found there again was finally found to be a
member of group 5 from 1975 through 1977.

Within communal group 2 we regularly saw strong evidence that
breeding pairs verged on territoriality toward members of their own
group. Especially when their nests had contents, male breeders restricted
their movements to small "core areas" around their nests and exerted
various degrees of dominance over intruders. Figure 16 shows the core
areas of males G/O-R, OP, XX ad, and OBk in 1977.
Group 1 rarely showed such intragroup hostility, probably because of
its small size, smaller home range, and the resulting greater familiarity
among its members.
Male breeders of group 2 restricted their visits away from their core
areas almost exclusively to gathering food hastily and returning as soon as
possible. When inside their core areas, they typically made short flights

Vol. 26, No. 4


FIGURE 14. Distribution of known nests and group home ranges at the main study site, 1976.
for communal groups 1-5.

interrupted by long pauses, but when venturing outside, they made long
uninterrupted flights to the objective and spent relatively little time there
(Table 7). Of 72 recorded pauses in his core area, G/O-R preened in 7, did
sentry duty in 24, foraged in 32, and scolded in 19. In his 10 visits to the
central mango out of his core area, G/O-R only gathered food. Once
while birds of the nest 33 subgroup were mobbing the observer at the
mango tree because their fledgling was nearby, G/O-R fed in the same
tree but took no part in the mobbing. Moments later G/O-R retreated to
his core area and at its boundary immediately began to scold the
observer. Of the 71 recorded pauses of OP in his core area, he preened in
3, did sentry duty in 13, foraged in 63, and scolded in 6. Outside his core
area, OP was never seen to perform any of these behaviors except forag-
Birds other than the breeding pair rarely entered the core area when
the residents' nest held eggs. After the young were about one week or
more old, the traffic of nonbreeding helpers became more frequent and


-...... "/ /...-
/>^' -'-46 44 41

S------ 35
I 239 1 2 321
34 0 321
2 7 2

0 29

\ l 28100
SV 0? 30 (BARE)

the retreat of the stranger, chased briefly by the resident male, but if the
Si i 7 i i
,,. _- ; o? 42?
// I -l C?

-;<--<~ '-- ; --1.-'l- "---
/ \ 0 100

FIGURE 15. Distribution of known nests and home ranges at the main study site for com-
munal groups 1-3, 1977. Note that group 4 no longer existed, that group 2 had usurped part of
group 3's range, and that group 3 had extended into part of group 4's range.

the sudden appearance of less frequent helpers, including other breeders,
was noted more often. Within his core area, each male breeder con-
fronted all pausing strangers by approaching, perching near them, peer-
ing at them intently, and sometimes supplanting them. Intruders typi-
cally remained quite still at first. Sometimes the action was broken off by
the retreat of the stranger, chased briefly by the resident male, but if the
intruder remained, the male approached closely, the stranger begged,
gaping and fluttering its wings, and the male appeared to feed it. On oc-
casion actual feeding occurred if the male happened to have food in its
bill; but as often as not the male merely poked its bill into or at the
stranger's gape. Sometimes the intruder itself already had a mouthful of
food, further emphasizing the ritualistic nature of the act. On rare occa-
sions the intruder would Upfluff when confronted by the resident, and in
response the resident would Peck-preen it, as described by Hardy (1974).
As in the captive jays Hardy (1974) studied, the full ritual display of

Vol. 26, No. 4


FIGURE 16. Core areas of 4 males in group 2, 1977.

begging and feeding was seldom seen between individuals that were in
daily contact with each other. In the captives one could stimulate the full
display by introducing strangers or removing a familiar bird from the
group for a few days to a week, and then reintroducing it. Upfluffing and
Peck-preening were seen daily in captives, because confinement probably
led to an increased frequency of encounters, but were seen far less often in
wild birds.
In the wild, regular visitors, usually yearling or 2-year-old helpers,
were not treated in this ritualistic way. Relative strangers that persisted in
visiting were soon ignored as well. For example, B1W and XX 2-year-old
failed in two nesting attempts in 1977 (nests 32,41). A few days after their
second nest failed, they began to visit the core areas around nests 40 and
38. In these initial visits they begged to and were fed by the resident male
breeders. A few days later it became clear that XX 2-year-old and B1W
had foregone further nesting attempts and had "adopted" nest 38, for
their visits had increased to several per hour. Not only were they allowed
to enter the core area and visit the nest unconfronted by G/O-R, but their
attention to the nest became so regular that they could easily have been


TABLE 7.-Movement of two male San Bias Jays inside and outside their core areas.

Distances Flown (m) Duration of Pauses (min.)
Bird Xout Xin Xout Xin
G/O-R 74 (N=17) 26 (N=72)a 2.4 (N=10) 7.2 (N=85)C
OP 86 (N= 14) 9 (N=75)b
aone-tailed Mann-Whitney U test; ts = 5.21; P<0.001
bone-tailed Mann-Whitney U test: ts = 6.29: P<0.001
Cone-tailed Mann-Whitney U test: ts = 2.83: P<0.005

mistaken for the breeding pair. Once when P/G-R, the female breeder of
nest 30, paid a rare visit to the nest 38 tree, XX 2-year-old confronted her,
stared at her intently, and she left. Thus the male helper behaved like an
owner in the absence of the actual male breeder, G/O-R.
The changing nature of interactions between birds reflected changes
in their nesting status. For example O/Pi-R, the male breeder of nest 31,
often confronted visitors to the mango tree at his core area border with
ritualized dominance behavior. In a 2-day period when the nestling in
nest 31 was fledging and then was killed, O/Pi-R was first dominant
toward one neighbor, XX ad. male, and in the same area the following
day performed appeasement begging toward another, G/O-R. Appar-
ently its tendency toward dominance in this part of its core area waned
with the loss of the fledgling. Not only did the dominant nature of the
resident male wane when the nesting was interrupted, but he also re-
sumed wandering much more widely over the group's home range, some-
times alone and sometimes with his mate, seemingly in search of a new
nest site. When the pair of nest 31 renested farther northwest, the male's
core area boundaries shifted accordingly.
On rare occasions the behavioral roles of the confrontees were
switched. On three occasions we saw the patrolling male resident beg
from the intruder. In one of these cases, the roles then abruptly switched,
with the intruder begging to the resident. In the other two only the in-
truder performed the feeding ritual. In these two cases, both involving the
same two males, we were sufficiently familiar with the circumstances and
individuals involved to offer the following explanation. Older birds gen-
erally dominate younger ones (Hardy 1974). We judge that this domi-
nance prevailed in the reversed roles. OPi, the breeding male at nest 26,
was at least 5 years old when the interaction occurred in 1977. PiG, a
4-year-old, commenced building nest 36 when OPi and his mate Bl/G-L
had large nestlings. Nest 36 was well within the frequent foraging area of,
and perhaps in an area dominated by, OPi and his mate. As mentioned
previously, nest 36 young were being cared for almost completely by the
parents when OPi's young were nearly full-grown juveniles. So few of the

Vol. 26, No. 4


otherwise occupied group 1 members ever approached nest 36 that all
could be considered virtual strangers in that area and thus not freely
allowed at the nest. On one of the rare occasions that one of the birds
(OPi) caring for fledglings in the group's range approached nest 36 with
food, the food and OPi's probably dominant relationship to PiG triggered
the begging response in the latter, who accepted the food and took it to
the nestlings.

OVERALL NESTING SUCCESS. Of accessible nests in the main study area
with apparently complete clutches, four had four eggs and three had
three. Most nests could not be examined safely or accurately because of
their height, protective placement, or both. For the purposes of Table 8
and the following discussion of mortality, clutch size is assumed to be 3.6
eggs. Although 50-67 % of the nestings that had clutches produced at least
one fledgling, only 22-38% of eggs resulted in fledglings (see Table 8, col-
umns 4 and 5).
more successful breeders than 1- or 2-year-olds. Twenty-six nestings, the
results of which were known or strongly suspected, were used to compare
nesting success of adults and subadults. Nesting attempts in which both
parents were adults (nests 4, 5, 9, 12, 13, 15, 26, 27, 34, 36 of group 1
and 17, 18, 21, 22, 23, 28, 29, 30, 31, 35, 40 of group 2) succeeded in
fledging at least one young in 15 of 21 cases and a total of 30 young,
almost two young per nest. All four nests involving at least one subadult
pair member were unsuccessful. Of these nests, one involved a 2-year-old
male and a yearling female, and three involved a 2-year-old male and an

TABLE 8. -Nest success in San Bias Jay Groups 1 and 2.

Groups No. of nests of No. of these nests No. of these nests No. fledg. per
and years known fate producing producing at least total eggs 2
nestlings one fledgling (% nests (%)
(%) producing fledg.)'
Group 1
1975 5 5 (100) 3 (60) 4/18 (22)
1976 6 4 (67) 3 (50) 8/21 (38)
1977 5 4 (80) 3 (60) 6/18 (34)
Group 2
1976 6 5 (83) 4 (67) 8/22 (38)
1977 8 5 (62) 4 (50) 8/29 (29)
Totals 30 23 (77) 17 (57) 34/108 (31)
'Fledglings/nests 17/30 (0.56/nest).
'Based on all nests in column 2 and a 3.6 mean clutch size.



adult female. Nests 33 and 38, the fates of which were not discovered, in-
volved adult males and 2-year-old and yearling females, respectively.
Both had mid-stage nestlings at the termination of study in 1977. Com-
parative numbers are disparate, as pairs involving subadults are in the
distinct minority, but a chi-square test confirmed that the proportion of
successful breeders was significantly greater in adult x adult pairs than
among others (X2 = 7.15, d.f. = 1, P < 0.01).
CAUSES OF NESTLING Loss. The causes of nestling mortality were dif-
ficult to detect. We saw Great-tailed Grackles (Quiscalus mexicanus) and
Groove-billed Anis (Crotophaga sulcirostris) around jay nests, and saw
jays attack both species there. These seem the most likely avian predators
on nest contents, but we saw no such predation. Skutch (1958) mentioned
this grackle as a possible predator on eggs of a small tanager (Euphonia
lauta), and Lamb (1944) saw a Great-tailed Grackle seize in its bill and
kill a Yellow Warbler (Dendroica petechia) as she tried to defend her nest
against it. Wetmore (1927) recorded the Smooth-billed Ani (C. ani) as an
egg predator of the Greater Antillean Grackle (Holoquiscalus niger) in
Puerto Rico. Olivares and Munves (1973) reported Smooth-billed Ani
predation on nestlings of Vermilion Flycatchers (Pyrocephalus rubinus) in
Colombia. In groves the',jay used for nesting, squirrels were too rare to
constitute an important hazard. Snakes seemed uncommon. We noted
one unidentified small snake try unsuccessfully to climb a palm trunk. We
saw no snakes among the palm fronds. Although iguana lizards (Iguana
iguana) live in the native woods and we saw a dead one on the road
through the coconut groves, we did not see any in the palms. Heavy
storms can blow down palm fronds or coconut clusters and the nests sup-
ported by them. In 1975 one nest was blown down in the late nestling
stage, killing the single nestling it contained. Clearly in years of much
stormy weather in July, weather can be an important cause of mortality,
although such weather failed to materialize in 1976 and 1977. The major
cause of prefledging mortality during our study may have been predation
by grackles and anis. Another possible cause is human disturbance. Each
grove was occasionally harvested of coconuts, and nests resting on
coconut clusters came down with the harvest, but no nest failures noted in
our prefledging figures (Table 8) could be attributed to such disturbance.
Nest 31 and its two nestlings were knocked down, but we replaced it in a
low tree near by and the attendants resumed care of the young. Nest 22
nestlings were force-fledged perhaps 2-3 days prematurely when their
nest was knocked down by coconut harvesters, but survived the fall and
were not abandoned.
show that the annual survival rate of birds after their first year was never
below 57% and generally ranged above 75%. In contrast, of 19 flagged

Vol. 26, No. 4


TABLE 9.-Annual survival, based on marked birds only of Southern San Bias Jay groups 1
and 2.

Adults (3 yrs. +) 1- and 2-year-olds Fledglings Over-all total
% (N) % (N) % (N) % (N)
Group 1
1974-5 60 (3/5) 100 (3/3) 25 (1/4) 58 (7/12)
1975-6' 57 (4/7) 60 (3/5) 50 (1/2) 57 (8/14)
1976-7 80 (8/10) 50 (2/4) 43 (3/7) 62 (13/21)
1977-8 78 (7/9) 60 (3/5) 0 (0/6) 50 (10/20)
Group 2
1974-5 -
1975-6 100 (8/8) 67 (2/3) 0 (0/2) 77 (10/13)
1976-7 81(13/16) 75 (3/4) 25 (2/8) 64 (18/28)
1977-8 88 (15/17) 67 (4/6) 0 (0/8) 61 (19/31)
'Ioes not consider PiBk, which immigrated to group 1 in 1976.

fledglings in group 1, only 5 (26%) were present on the study area one
year after hatching, while in group 2, 2 (11%) of 18 were present. Nor
were any of those missing found elsewhere.
In group 1 we banded 39 birds of all ages. Of these, 19 (49 %) survived
to at least the next breeding season. Of the 39, 19 birds were banded at
yearling age or over, of which 13 (68%) lived at least to the following
year. Of the 13 banded as adults, 9 (69%) survived at least one year.
We banded a total of 43 birds in group 2. Of 25 (58% of the total)
banded as yearlings or older, 21 (84%) lived to at least the next year. As
Table 9 and Appendix III show, the lower rate of survival in group 1 is
due to the unusually low survival rate of yearling or older birds from 1975
to 1976. All the above survival rates are minimal because they ignore the
possibility of undetected survival of marked birds that might have
We did not directly observe any predation on fledglings. Postfledging
mortality occurs mainly in the 2-3 week period before juveniles can fly
strongly, when they seek concealment on the ground or on low perches
and are vulnerable to terrestrial predators, including humans and dogs,
and to death by exposure.
None of us has ever worked for an extended period in the Neotropics
where we saw so few hawks. In the five summer study sessions we saw
only one Gray Hawk (Buteo nitidus) on the study area; one bird, perhaps
the same one each year, was seen only occasionally. Rarely a blackish
hawk (species not determined, probably a Buteogallus) soared over at
high altitude and constituted no threat as a predator, but the Gray Hawk
could surely take preflying fledglings. The jays mobbed the Gray Hawk
and reacted to its flights over or through the groves with the overhead


predator call (Hardy 1979) and escape flight, suggesting experience with
this raptor as a predator. Brown and Amadon (1970) mentioned birds as
Gray Hawk prey, specifically listing a parakeet (Aratinga). A pair of Mot-
tled Woodowls (Ciccaba virgata) were on the study tract and certainly
constituted potential predators of juveniles, as we saw jays mob them
several times.
We found evidence of predation on three non-nestling jays. O/G-L, an
adult female of group 1, was killed in June 1977. We found her flags, a
tarsus, and scattered feathers on the ground. O/Bk-R, a fledgling of nest
31. was killed one day after leaving the nest. We found its flags in the
nearby jungle, where the bird had moved on the ground. PiBk, a yearling
female, was found alive with all remiges clipped. She was obviously a vic-
tim of human vandals and probably felled with a slingshot. The first two
birds may also have been downed by humans and then eaten by dogs or
natural predators. An odd accident was the cause of another death: 00,
an adult male in group 1, died by hanging. While foraging it had flut-
tered upward in pursuit of a prey item and then had fallen slightly, catch-
ing its neck in the constricted distal end of a palm bract. Death caused by
this occupational hazard must be rare. Evidence is slim and mostly cir-
cumstantial, but deaths of yearlings or older birds may be mainly due to
humans-specifically boys with slingshots. The boys carry slingshots as
they patrol the cornfields to keep out the Great-tailed Grackles that pilfer
the corn sprouts.
EMIGRATION AND IMMIGRATION.-The disappearance of birds after
fledging gives a maximum mortality figure that undoubtedly includes
emigration. Between the nesting seasons of 1975 and 1976, four adults,
one yearling, and one young of the year disappeared from group 1, while
three adults and two yearlings immigrated to the group. Between 1976
and 1977, four yearling or older birds and four first-year birds disap-
peared, while one adult immigrated. From 1977 to 1978, two yearlings
and six first-year birds disappeared and one yearling and one 2-year-old
immigrated to the group. Thus in a 4-year period 22 birds of fledgling
age or older disappeared and eight immigrated to group 1. For group 2,
the figures are similar: from 1976 to 1977, four yearling or older birds,
and five or six first-year birds disappeared, while five yearling or older
birds immigrated to the group. In the 1977 to 1978 period, two adults,
two yearlings, and seven first-year birds disappeared, while four yearlings
joined the group. Thus 20 or 21 disappeared and 9 immigrated in the
3-year period.
Two marked birds are known to have changed groups. PiBK, a female
banded as a fledgling in group 3 in June 1975, was found in group 2 in
contents of which could not be determined. A few days later the bird was
found alive with its wing feathers clipped. Its actual role in group 1 was

Vol. 26, No. 4


never determined accurately, as the nest it was found on had a few days
earlier been occupied by an adult female. GPi, a female flagged as an
adult in group 3 in 1975, was not detected in 1976, but was found as a
breeder in group 2 (nests 35, 44, 58) in 1977 and 1978. No other changes
of group membership were known to have occurred among groups 1-5,
1974-78, nor were any marked birds ever found in immediately
peripheral groups. Therefore, immigration probably involves saltation
beyond neighboring groups.
Most of the birds that immigrated to our study groups were of
unknown origin. At the end of field work in late July 1975, all adults and
fledglings in group 1 were flagged, and had shown no evidence of nesting
behavior for several weeks. Yet in June 1976 four unmarked adult
females were present as breeders and two yearlings as helpers. Except for
one (XX ad. female, mate of PP, 1976-7) these were flagged as follows:
adult females O/G-L, BlBk, Bl/G-L; yearlings PiP, PiW. Subsequently
O/G-L was taken by a predator (June 1978), PiW was still a helper as a
2-year-old in 1976 but had disappeared in 1977, and PiP was apparently
still a helper as a 3-year-old in 1978. The 1976 field study ended on 28 July
with some nests still active in group 2. Therefore we could not tell
whether the unmarked yearling found in group 2 in 1977 was hatched in
group 2 or had immigrated to it. A pair of unbanded adults, subsequently
female Bk/Pi-R and male P/G-R (nests 30, 54), were present as we began
study in June 1977. That male is positive evidence of immigration of adult
males, as we were certain that at the end of study in 1976 all birds of
yearling age or over in group 2 were flagged; apparently females are more
likely than males to change groups.
We secured our best evidence for dispersal of young in 1978. In 1977
we banded all 17 fledglings in groups 1 and 2 (Table 10) of which 13 were
known to be alive and able to fly in late July. Eight of these were in group
1 and five were in group 2. At that time nesting had ceased in group 1, but
group 2 still had six active nests, three of which had late nestlings. We
found none of these banded birds in 1978, but group 1 had two unbanded
yearlings and group 2 three. The two unbanded yearlings in group 1
substantiate immigration there. The only interpretation that disallows im-
migration or emigration in group 2 in significant quantities requires the
assumption that all five banded young had died and that only unbanded
young survived.
Our data do not allow us to state whether adults are more likely than
young to disperse to other groups.

FLEDGLINGS. Departure of young from the nest was gradual. During
the 1-3 days prior to leaving permanently, the nestlings typically perched


TABLE 10. -History of fledgling San Bias Jays, 1977.

Group 1 Tag code Wt. (g) Date fledged Survived (Date)
26 PiBk-2 92 4/7 (forced)
O/G-L-2 76 4/7 (forced) yes (27/7)
B10-2 93 4/7 (forced)
27 G/O-L 84- 18/6 yes? (27/7)
P/Pi-L 85 18/6 no
34 Nestlings
only Did not fledge
36 Bl/O-L 90 27/7 yes
39 Nest failed, no young
(Orphans introduced on 3 July)
00-2 80
GG-2 80 yes
PiC-2 83

Group 2 Tag code Wt. (g) Date fledged Survived (Date)
28 Pi/Pi-R 87 20/6 yes (27/7)
Pi/Bk-R 95 20/6 yes (27/7)
BI/Bl-R 86 20/6 yes 27/7)
29 0/0-R 101 18/6 yes 27/7)
G/G-R 98 18/6 no
30 O/P-R 92 18/6 yes (27/7)
G/P-R 78 18/6 no
31 O/Bk-R 84 13/7 no
(No other nests in group 2 produced fledglings in 1977 before we completed field work for the

on limbs within a few feet of the nest, and returned to the nest several
times. When nests are in native trees the young probably climb about in
branches up to several meters away, but departure from the immediate
nest area in coconut palms usually means rapid descent to the ground.
This normally occurred when the young were about 18-20 days old and
weighed between 80 and 100 g. All fledglings that survived more than a
few days weighed at least 80 g at fledging, and most weighed between 90
and 100 g (Table 10). With no known exceptions in our study, fledglings
remained on the ground or within a few meters of it for about the first
week after leaving the nest. In this time they moved by running and flut-
tering. It is important that ground-level vegetation be present for the
young to hide in during this period. They would cross bare ground to
reach such vegetation, but their detectability, at least to human
observers, was greatly decreased if little movement across open ground

Vol. 26, No. 4


was necessary. The adults seemed to urge them toward cover by gathering
in hedgerows or trees over such vegetation and calling the young toward
protection, rather than landing in the open near them. Fledgling
members of a single brood tended to stay together; this is probably why
puny nestlings seemingly fledged prematurely, being stimulated to do so
by the departure of their stronger siblings and by the rapid decline of
feeding visits to lone individuals that stayed in the nest.
By approximately one week after fledging, juveniles could fly a few
meters by launching from perches about a meter off the ground, but they
tired easily and still could not fly upward. In the second week after fledg-
ing, they climbed higher in trees and flew from tree to tree. From this age
onward, although they landed clumsily, they remained above ground and
flew with increasing strength upward and into the tall palms, but in our
general experience they usually stayed from about 3 to 6 m up in dense
broadleaved vegetation of hedgerows and jungle areas.
niles seldom strayed beyond their communal group home range bound-
ary. This site fidelity was probably a result of the reluctance of their at-
tendants to cross such boundaries. In 1976 we performed two experi-
mental transportation of fledglings that seemed to demonstrate home
range exclusivity and fidelity. On 2 July we found three probable sibling
fledglings in group 4's home range. After they were flagged, we carried
one of them, BkW, in full sight of the attending group of jays into the
nearby southeastern portion of group 2's home range. The attendant jays
of group 4 followed, scolding, to the boundary (as previously determined)
between the two home ranges and no farther. These attendants then
silently withdrew. At this time PPi and O/Pi-R of group 2 began mobbing
the observers, diving at them and scolding. The fledgling then became
silent and stopped struggling. When it was brought back to the group 4
area 10 minutes later, the attendants greeted the approaching human and
mobbed him. The fledgling again called and struggled. The following day
the same fledgling and two others from group 4 were taken one at a time
at 15 min intervals into the same part of group 2's range, about 50 m from
group 4. Group 4 members scolded but would not follow into group 2's
range. The cries of the young obviously could be heard by their attend-
ants. The young were placed in a shrub at the base of a palm and left
alone. Within 15 min of the transportation of the third juvenile, the pair
of nest 21 in group 2 was feeding them.
At about the same time that the young fledged from nest 26 in group 1
in 1977, we introduced three young orphan fledglings (brought to us by
local children) to the area. These were adopted immediately by group 1
birds and cared for in a way and with a frequency indistinguishable from
that afforded to the group's own offspring. The orphans were still alive at


the close of the summer's study and apparently incorporated into group 1.
These experiments first confirm the reality of home range boundaries
and their value against trespass. Second, parents may recognize their own
young by their location rather than by means of intrinsic characteristics.
In 1977 experiments involving transport of fledglings in group 2, we
discovered that core area boundaries also may prevent adults from follow-
ing their young. On 18 June the fledglings from nest 30 were carried
toward nest 29. The parents followed but refused to enter the core area of
nest 29. On 3 July the nestlings of nest 31, with their nest, which had been
knocked down in a coconut harvest, were transported to the nest 31-35
core area mutual boundary at the mango tree in the middle of the grove
(Fig. 16). The parents would not go beyond that point, and their yearling
helper Pi/G-R stopped 10 m beyond the mango. Thus parents and attend-
ants intimately involved in the care of their young, in addition to respect-
ing home range boundaries of the group, also did not follow far from the
nest site or near to another pair's nest site, during the preflight juvenile
As the young began to fly well, their wanderings increased. In group 1
all the flying young traveled over most of the home range. In group 2
adults followed flying juveniles without regard to core area boundaries.
Young of nests 28, 29, and 30, whose movements were followed carefully
for over a month, did not use the entire home range of group 2, at least up
to 28 July. This seemingly had nothing to do with core area boundary
observance but was simply a result of the large size of the home range
itself. Figure 17 shows the movements of Pi/Pi-R, Pi/Bk-R, and B1/B1-R,
the young of nest 28, and O/O-R and O/P-R, young of nests 29 and 30,
respectively, all in 1977. The nest mates of the latter two birds vanished
soon after fledging, and the two survivors joined together. They were still
together at the end of the study on 27 July. The three birds from nest 28
were banded on 20 June and remained together at least to 27 July. Note
that some overlap occurred in the movement of these two groups of
young, but they did not share any attendants. The young of nest 28 were
attended almost exclusively by their parents and the yearling WBk.
Juveniles of nest 29 and 30 were attended primarily by the nest 30
parents. The nest 29 parents relinquished care as if their offspring did not
exist, and, like the nest 31 parents that lost their surviving fledgling the
day after it left the nest, began a second nest.
Strongly flying juveniles even crossed home range boundaries and
were followed by their attendants when portions of the adjacent home
ranges into which they wandered had been essentially deserted by the
residents. The young of nest 28 were observed in the groups 1 and 5 areas
on 23 July, and were being attended by their parents and helpers, but the
area of trespass into group l's range had been virtually vacated by its resi-

Vol. 26, No. 4


0 \\ 0I_ \__ _
FIGURE 17. Movements of Pi/Pi-R, Pi/Bk-R, and B1/Bl-R, the fledglings from nest 28, and
0/0-R and O/P-R, fledglings from nests 29 and 30, respectively, in 1977.

dent jays for more than a week, the resident nesters having moved with
their fledged young to the western part of their home range. A similar
trespass of boundaries occurred between groups 2 and 3 after the outlying
nest 30 of group 2 fledged its young in 1977. Because this nest had no pro-
tective ground vegetation in its vicinity, the fledglings quickly moved
north and east. Within one week thereafter group 3 birds were attending
a strongly flying juvenile within 5 meters of nest 30.
As in Yucatan and Bushy-crested Jays, full-grown juveniles of the
Southern San Bias Jay that were still being fed regularly by their attend-
ants sometimes visited later nests of the group where nestlings were being
fed. Juveniles in groups 1 and 2 were never quite old enough to make such
visits before our summer field season ended, but in group 3 in late July
1977, two juveniles visited nestlings at nest 47. At first they merely fol-
lowed feeders to the nest to beg for food, then they came to the nest in the
adults' absence and looked at the nestlings. Within the next few days they
progressed to arriving at the nest with food, giving guttural calls
characteristic of jays feeding nestlings, and occasionally poking their bills
into the nest toward the begging young. It seems likely that had observa-
tions continued for several more days, actual feeding by the juveniles
would have been seen.

We did not measure food resources but did make frequent observa-


tions of their existence in time and space and according to habitat during
the breeding season. Even though rainless periods of several weeks might
have produced a food shortage in a more arid habitat, we saw no evidence
of any such shortage in our study areas. Insects such as katydids and small
lizards, including Anolis sp. and occasionally Iguana, seemed to compose
the bulk of the foods fed to the young and of the animal portion in the
diets of older birds. We frequently saw them catching Anolis lizards and
insects high on the palm fronds. Insects were taken in herbaceous vegeta-
tion as well. We never saw the jays feeding on the fruit of native trees or
shrubs; mangos were the dominant vegetable item eaten. Foraging in
broadleaved native vegetation,ln hedgerows, and the jungle patches was
mostly at middle and high levels and, from what we could see, involved
animal food. Foraging at low levels occurred in the jungle where the open
canopy created thicket undergrowth. We often saw jays visit piles of
coconut shells to feed on copra waste. We saw no evidence of vegetable
matter being fed to the young, in contrast to the case in Nelson San Bias
Jays in Nayarit, Mexico, which brought bits of the fleshy pericarp of oil
palm nuts to nestlings (Hardy 1976).
Southern San Bias Jays are omnivorous and highly enterprising in
their search for food. It was clear that the palm groves provided not only
good nesting places but a considerable proportion of the birds' food. The
birds moved along the fronds peering into their crevices and poking with
their bills to seize prey. They also diligently searched palm fruit and
flower clusters, sometimes hanging upside down or fluttering upward to
peer into places difficult to reach. It was more difficult to watch the ac-
tual capture of prey when the jays foraged in the hedgerows, dense
ground-level vegetation, and jungles. It was our impression that the birds
split their time in foraging about equally among palms, herbaceous
growth beneath palms, hedgerows, and jungle patches. The birds usually
foraged singly or in groups of two or three.

We visited the study area only once in the nonbreeding season, in
early December 1976. We found groups 1 and 2 almost completely
within their respective summer home ranges. We found no mingling of
marked birds from different communal groups except for PiBk, a first-
year bird, discussed earlier under Emigration and Immigration. The birds
moved in larger and tighter units than was characteristic of them in the
breeding season, and at times moved more rapidly. Group 1 birds were
once seen just beyond the easternmost part of their summer home range
as shown on the maps (Figs. 14, 15) where breeding jays never occurred
1974-1978. Group 2 birds were mainly in that portion of their home range
along the creek bed, in the groves beyond, and in the jungle/marsh

Vol. 26, No. 4


area. We counted 20 birds in one loose flock moving through the edge of
the jungle. The birds were mostly high in the trees and were more wary of
us and less vocal than in the breeding season. Consequently, they were
difficult to follow and observe. No evidence suggests an influx of jays from
outside the area or of jays occupying markedly different habitat from that
used in the nesting season.

Brown (1974) argued that the various expressions of communal
breeding seen in New World jays are all elaborations upon the retention
of young in their natal territories in "K-selected" species, i.e., those whose
life-history characteristics have shifted toward sedentariness, long life,
and iteroparity, while living at or near the carrying capacity of stable,
mature habitats. He also pointed out that such birds may be expected to
have the capacity for individual recognition, and that retention of certain
aspects of juvenile morphology is common in those species so far known.
All four species of the subgenus Cissilopha, the black-and-blue jays,
are communal. They live in flocks year round, with a single breeding pair
per nest (only one female lays in a nest) and helpers, which, depending on
the species, may be of any age from a few months to four or more years.
Our evidence (Hardy 1976; Raitt and Hardy 1976, 1979) suggests that
such groups arise by retention of young within the flock. All species are
probably sedentary and have high annual adult survival rates judging
from the Beechey Jay (Raitt et al., ms) and Southern San Bias Jay (this
paper), and our impressions of the Yucatan Jay (Raitt and Hardy 1976),
Nelson San Bias Jay and Bushy-crested Jay (Hardy 1976). All are also
usually single-brooded (same references). In all four species the yearlings
are morphologically separable from the adults (see Hardy 1973). At least
in the Southern San Bias Jay each adult apparently has unique vocal
characteristics that probably are used in individual recognition (Webber
and Hardy, ms), although there is reason to doubt their ability to
recognize their own young. Table 11 presents a comparative summary of
similarities and differences among the five forms of the Cissilopha jays.
The unusually complex nature of communality in the Southern San
Bias Jay, which has large numbers of breeders per group and extensive
mutual helping between breeders, might suggest that communality in this
species is not a variation upon the retention-of-young theme, but has
arisen by aggregation of formerly separate breeding pairs. We believe
that complex ontogeny of plumage and soft-part color, as well as such
postural displays as Upfluffing and Peck-preening (Hardy 1974) that are
associated with the sociality of other communal black-and-blue jays, are
indicators of a long history of communality in this jay as well. Also, if
such groups had arisen as aggregations of neighbors, we would expect to



TABLE 11.-Social breeding characteristics, density, and habitat features in Cissilopha.

Unit Size
Social in Useable Vocal Non- Age at first
Form System/Type' Habitat Repertoire2 breeders breeding Habitat
Beechey Simple/S 2-6 Small Subad, 3 yrs Trop. decid.
(10/km2) Ad forest
Yucatan Intermed./P 6-11 Large Subad, 3 yrs? Forest edge
(70/km2) Ad with fields
Nelson Intermed./P 5-6 Medium Subad, 2 yrs Palm-forest
San Bias (?) Ad edge
Bushy- Intermed./P 11 Medium Subad, 3 yrs? Coffee plan-
crested (100/km2) Ad stations
tall forest
Southern Complex/P 10-26 Medium Subad, As early Coconut palm
San Bias (150/km2) Ad as 1 yr, plantations,
usually Scrub-woodland
3 edge

'See Brown's (1978) social breeding structure classification. S and P stand for one and two or more breeding
femalesper communal unit, respectively.
2See Hardy (1979).

see group "membership" based solely on geographic proximity, but in
some instances it is not. For example, OW and WO, parents at nests 17
and 18 in group 2 in 1976, fed the nestlings in nest 21 of their group over
200 m away, but did not even approach nest 13 in group 1, only 100 m
from their own nests. Presumably group membership is dependent on a
history of acquaintance based on an extended family relationship.
Although demographically the black-and-blue jays share the at-
tributes expected in Brown's (1974) early outline, we did not find them
living in stable, "mature" habitats (as acknowledged in Brown 1978). In-
stead, they live in highly modified or disturbed and, in some cases, cer-
tainly transient habitat types.
There seems to be a relationship between the "complexity" of com-
munal breeding and the extent of habitat disturbance. Those species in
the less-disturbed habitats tend to have lower population densities,
smaller groups, fewer breeders per group, and relatively older breeders.
Those in the more disturbed habitats have higher population densities,
larger groups, more breeders per group, and relatively younger breeders.
The habitats occupied by the jays can be grouped roughly into three
classes: (1) "least disturbed"; (2) "moderately disturbed"; and (3)
"severely disturbed." The class 1 habitat of the Beechey Jay, while cut-
over probably many times, exists in fairly large tracts of continuous
habitat, and the jays do not breed in the denser and brushier part of this

Vol. 26, No. 4


habitat, the sort that prevails for perhaps 5 to 10 years after complete raz-
ing, but in the more open, taller portions of the second growth. In short,
they nest in the interior of native woodland that, while immature, is not
mingled or interdigitated to any great extent with cultivated land. The
class 2 habitats, moderately disturbed, are those of the Bushy-crested Jay,
Yucatan Jay, and Nelson San Bias Jay, all of which live in thorough mix-
tures of native vegetation and cultivated crops, both of which the jays use
extensively. The Bushy-crested Jay nests in coffee plantations under a
canopy of tall natural forest trees. The jays may move through more
nearly undisturbed forest along cattle trails, but apparently nest only in
the forest edge or where the understory has been removed and replaced by
the coffee trees (Hardy 1976). Yucatan Jays nest in the edge of native
second-growth woodland interspersed with cornfields, and they forage in
both types of habitat. Nelson San Bias Jays nest where oil palms grow in
plantations or intermixed with native tropical deciduous woodland
(Hardy 1976). Class 3, heavily disturbed habitat of Southern San Bias
Jays, consists mainly of coconut palm groves with only occasional patches
of native growth and fence rows. The jays nest almost entirely in the palm
groves or on the edge of scrubby second-growth broadleaved vegetation
adjacent to the groves.
In Beechey Jays, each communal group has only one breeding pair,
usually but not always accompanied by nonbreeding helpers. Group size
is small, ranging from two to five birds. Population density is low at 10
birds/km2 (2 kg/km2). There is never more than one successful nest per
group per year, and only birds three years old or older breed. Vocal reper-
toire is comparatively small (Hardy 1979). The three species in the
moderately disturbed habitats generally breed in larger groups averaging
about 6 in Yucatan Jays, sometimes reaching 11 in Bushy-crested Jays,
and about 5 or 6 in Nelson San Bias Jays, and have more than one pair of
breeders per group. Some, at least, exist at higher densities than do
Beechey Jays. Yucatan Jays (Raitt and Hardy 1976) occurred near Xpujil,
Campeche, at a density of 70/km2 (8.5 kg/km2). Data are few on Bushy-
crested Jays, but Hardy (1976) had one group of 11 birds occupying 7.1 ha
(15kg/km2). For Nelson San Bias Jays there are no data on density. Sub-
adult Yucatan and Bushy-crested Jays are not known to breed in the wild,
and subadults may do so in Nelson San Bias Jays only when populations
have been reduced by humans (see Hardy 1976).
In Southern San Bias Jays, occupying the most disturbed habitat,
group size seems to be a minimum of about 10 birds yearling age or more
and can range up to 26. Densities are high (150/km2; 19 kg/km2). Almost
all group members are breeders (up to 10 nests/group have been noted),
2-year-olds sometimes breed, and even 1-year-olds are known to breed,
though rarely. Table 11 summarizes the foregoing comparison.


In discussing the relatively simple sociality and low reproductive ef-
fort of the Beechey Jay, Raitt and Hardy (1979) postulated as the underly-
ing cause the very extreme and long dry season of its habitat and conse-
quent low productivity of food resources. What we are postulating here is
a parallel factor, which is degree of habitat disturbance and reliance on
ecosystems highly influenced by human intervention.
As in the earlier attempt to explain the social characteristics and body
size of Beechey Jays as responses to low food supplies, we speculate that an
important factor linking greater habitat disturbance with greater popula-
tion density and greater group size is the increased availability of food
prey. We did not measure insect abundance in the jay habitats, though
we take some comfort from Janzen's (1973) assertion that all previous at-
tempts to measure such abundances probably were unreliable.
R.P. Balda reviewed this paper in manuscript and commented on the
foregoing speculation as follows: "One major point seems to be overlooked
here. That is, how 'full' is the available habitat for these birds? If it is not
full then young should go off and nest on their own rather than stay and
help. Their help should not be necessary if insect and vertebrate produc-
tivity is high."
We have no objective, independent way of measuring how full the San
Bias Jay habitat is, nor do we know whether helpers help wholly or partly
because their efforts increase overall reproduction. Balda's comment does
point out the necessity of offering a plausible explanation of how in-
creased population density could result in an increase in group size, in-
stead of merely the addition of more "normal"-sized groups. At least two
such explanations are possible, depending upon the factors that govern
dispersal in San Bias Jays.
Perhaps helpers will disperse from their home groups unless the
habitat is so full of other jays that few or no places exist for them to go, as
Balda suggested. Any factor that increased population density would in-
crease the fullness of the habitat. At some point this increased filling of the
habitat would result in reduced opportunities for dispersal, and thus at
least some growth in group size would occur with the retention of helpers.
Or perhaps the helpers might not disperse even if space was available
elsewhere, because of some overriding reason for staying home, such as
the protection afforded by living with a larger group of relatives. In this
case, population growth, regardless of cause, would automatically result
in an increase in group size.
Some within-species comparisons in other communal breeders suggest
that habitat productivity or structure can affect group size. For example,
Hall's Babblers (Pomatostomus halli) prefer to forage in grass and forbs.
Brown and Balda (1977) found that group size in these babblers was
positively correlated with percent of flock home range having such her-

Vol. 26, No. 4


baceous growth. Gaston (1978) found that larger groups of Common Bab-
blers (Turdoides caudatus) were characteristic of local populations of
above average density and implied that greater habitat productivity pro-
motes larger communal group size.
With greater group size, more birds per group (as well as younger
birds) may be allowed to breed because it is more difficult for dominant
birds to suppress breeding by other group members. This proposal re-
quires two conditions: first that the delayed breeding observed in the
black-and-blue jays is not a result of physiological inability to breed but a
socially or habitat-mediated suppression of breeding behavior, and sec-
ond that changes in habitats (such as to cultivated land) that must have
occurred recently could plausibly affect breeding organization of the
birds in such a short time.
Evidence suggests that breeding in communal New World jays can be
suppressed socially. In 1968 Hardy (1976) caged a presumed family group
of six Yucatan Jays consisting of two adults, two 2-year-olds, and two
yearlings. Each year through 1972 the oldest birds, apparently a mated
pair when captured, attempted to breed. Although all the others occa-
sionally handled nest material, none made any coordinated attempt to
build a nest or demonstrated any other evidence of concerted breeding
behavior. In 1972, after the pair again attempted to breed, the other four
birds, by then all adults, were removed to another aviary. Within nine
days, the next oldest male and female paired, built a nest, and produced
their first eggs. Gonads of the nonbreeding 1- to 6-year-old members of
this group were enlarged in the period when the dominant pair was at-
tempting to breed.
Parallels exist in some other communally breeding species. Common
Babblers usually have only one breeding pair per communal group, but
two pairs may breed simultaneously in larger groups, apparently because
of spatial separation that reduces interpair rivalry (Gaston 1978). Fur-
thermore at least the male nonbreeders in communal groups had enlarged
gonads, suggesting their potential for breeding. Similarly Carrick (1972)
found that subordinate females in communal groups of Australian
Magpies (Gymnorhina tibicen) are often prevented from breeding by
dominant females, but may nest if they find a site suitably distant from
that of the dominant female. Otherwise, they begin to nest only after the
dominant female is occupied with incubation. Florida Scrub Jays will
breed when 1 year old, given the opportunity. A pair of 1-year-olds bred
in an aviary at the University of Florida, evidently because they had an
exclusive "breeding territory" (Webber, ms). On very rare occasions
yearlings breed in the wild (G.E. Woolfenden, pers. comm.).
The major factors allowing more birds to breed in Southern San Bias
Jay groups may be the abundance of nest sites and food in the palm groves


and the sheer numbers of potential breeders. Greater spatial separation of
breeders in larger groups may not be an important factor in this regard.
At least the youngest, most subordinate birds seem to create opportunities
to breed by temporal rather than spatial segregation from the older birds
(Table 5). Furthermore the apparent greater simultaneity of nesting in
group 2 probably cannot be attributed to greater spatial segregation in
that group, for nest cluster densities were about the same in groups 1 and
2. (The difference of 10 m in the mean inter-nest distance is of doubtful
significance.) The apparent difference in simultaneity may itself be an ar-
tifact of sampling.
The difference in core area behavior between groups 1 and 2 indicates
the degree of flexibility that can exist in the social organization of the
Southern San Bias Jay. Group 2, while nesting in clusters of about the
same density as those in group 1 (Table 5), was spread out over a larger
absolute area, which resulted in a reduced frequency of contact between
many members of the group, reflected in the lower C.I. and C.U. in
group 2 than in group 1. Also, group 2's home range was compartment-
alized into several clumps separated by relatively large patches of jungle,
stream-side vegetation, and grove areas unsuitable for nesting (Fig. 1).
Group l's home range, in contrast, was in much more uniform palm
groves. In group 2 the jungle patches greatly reduced visibility within the
home range, which may be one reason why breeders remained relatively
close to their own nests. The reduction of contacts between breeders in the
group thus resulted in a form of quasi-territorial behavior within the
group and an increased frequency of ritualized agonistic displays. Even
greater plasticity in social organization has been demonstrated by Stacey
and Bock (1978) in the Acorn Woodpecker (Melanerpesformicivorus). in
which nonmigratory communal groups live side by side with migratory
unaided pairs in southeastern Arizona.


Brown, J.L. 1974. Alternate routes to sociality in jays-with a theory for the evolution of
altruism and communal breeding. Am. Zool. 14: 63-80.
S1978. Avian communal breeding systems. Ann. Rev. Ecol. Syst. 9: 123-155.
and R. P. Balda. 1977. The relationship of habitat quality to group size in Hall's
Babbler (Pomatostomus halli). Condor 79: 312-320.
Brown, L., and D. Amadon. 1968. Eagles, hawks and falcons of the world. Vol. 2. New
York, McGraw-Hill Book Co., 945 p.
Carrick, R. 1972. Population ecology of the Australian Black-backed Magpie, Royal Penguin,
and Silver Gull; pp. 41-99 in Population ecology of migratory birds: A symposium. U.S.
Dept. Inter. Wildl. Res. Rept. 2: 278 p.
Gaston, A.J. 1978. Ecology of the Common Babbler Turdoides caudatus. Ibis 120: 415-432.

Vol. 26, No. 4


Hardy, J.W. 1969. A taxonomic revision of the New World jays. Condor 71: 360-375.
1973. Age and sex differences in the black-and-blue jays of Middle America.
Bird-Banding 44: 81-90.
1974. Behavior and its evolution in neotropical jays (Cissilopha). Bird-Banding
45: 253-268.
1976. Comparative breeding behavior and ecology of the Bushy-crested and
Nelson San Bias Jays. Wilson Bull. 88: 96-120.
1979. Vocal repertoire and its possible evolution in the black-and-blue jays
(Cissilopha). Wilson Bull. 91: 187-201.
and R. J. Raitt. 1976. Ecology and evolution and communal habits in the black-
and-blue jays (Cyanocorax. Cissilopha). Int. Ornithol. Congr. 16, Canberra, Abstr.:
1977. Relationships between the two races of the San Blas Jay Cyanocorax
sanblasiana. Bull. British Ornithol. Club 97: 27-31.
Janzen. D.H. 1973. Sweep samples of tropical foliage insects: Effects of seasons, vegetation
types, elevation, time of day. and insularity. Ecology 54: 687-701.
Lamb, C.C. 1944. Grackle kills warbler. Condor 45: 245.
Olivares, OFM. A., and J.A. Munves. 1973. Predatory behavior of Smooth-billed Ani. Auk.
Raitt, R.J., and J.W. Hardy. 1976. Behavioral ecology of the Yucatan Jay. Wilson Bull. 88:
1979. Social behavior, habitat, and food of the Beechey Jay. Wilson Bull. 91:
Skutch, A., in A.C. Bent. 1958. Life histories of North American blackbirds, orioles,
tanagers, and allies. U.S. Natl. Mus. Bull. 211:335-350.
Stacey, P.B.. and C.E. Bock. 1978. Social plasticity in the Acorn Woodpecker. Science
Wetmore, A. 1927. The birds of Porto Rico and the Virgin Islands (Psittaciformes to Passeri-
formes). New York Acad. Sci. 9:409-598.
Woolfcnden. G.E.. and J.W. Fitzpatrick. 1978. The inheritance of territory in group-
breeding birds. Bioscience 28:104-108.


Color Year Age Sex ROLES
Code' Marked Marked (Crit.) 1974 1975 1976 1977 1978

00 74 Ad o0

2 PiPi 74 Ad 9
3 BkBk 74 Ad ao
4 WW 74 Ad 9 ?
(Role 75)
5 BIBI 74 Ad ?
6 XX Ad 9
7 XX Ad ?
8 XX 2 ?
9 GG 74 1 op
10 PP 74 1 oa
11 PiG 74 1 oa

74 sibi
74 sib
74 sib
74 sib-

A-1 P?-Nx2
H-Nx, 3, 5, 9


P?-1 P-9, H-5?

A-1 P?-Nx


H-13, 15

June 3

H-Nx, 13, 15

? H-5 H-12, 13, 14?

A-fl H-5,9 P-15
? P-3 P-Nx?
H-4, 5, 9 P of O/Pi-L?
H-13, 15

H-26, 27, 36
H-26, 27




H-3, 5, 9


17 OPi 75 Ad r P-5 P-12 P2-264 P-48
(Role) H-9 H-13 H-36
18 BIO 75 Ad cr P-4 P-13
(Role) H-3, 5, 9 H-Nx fl
19 GBI 75 Ad 9 P-4
(Role) H-5, 9?
20 PiO 75 Ad 9 P-5
(Role) H-3, 9
21 XX Ad 9 P-9
22 GW 75 1 ? H-5, 9
23 XX 1 9 P-3
24 GO 75 0 ? 5 fl
25 OBL 75 0 c, 5 fl H-12, 13, 15 Pi-264 P-Nx?
(Role) P-39 with BIBk?
26 Bl/G-L 76 Ad 9 P-12 P2-264 P-48 fl
27 XX 76 Ad 9 P-15 P-34
(Role) H-36
28 O/G-L 76 Ad 9 P-13 Predatorized
(Role) H-12 June
29 BlBk 76 Ad 9 P?-Nx Pi-26 P-Nx? with
(Role) P-39 OBI? A
30 PiP 76 1 ? H-12, 13, 15
H-BIP fl
31 PiW 76 1 ? H-Nx, 12, 13 H-26, 27, A-fl
34?, 36
32 PiBK 75 0 9 Group 3 fl P-14?
(Role) sitter, dead
33 BIP 76 0 ? Nx fl
34 PiPi-2 76 sib 0 ? 13 fl H-27
35 B1B1-2 76 sib 0 ? 13 fl H-27, 34, 36
36 Pi/Bl-L 76 sib- 0 o? 13 fl H-26,27 A-fl

APPENDIX I (continued)

Color Year Age Sex ROLES
Code' Marked Marked (Crit.) 1975 1976 1977 1978

37 O/Pi-L 76 0 ? Nx fl
38 Bl/Pi-L 76 sib 0 ? 12 fl
39 G/B1-L 76 sib 0 ? 12 fl
40 XX Ad 9 P-36
41 P/O-R 77 Ad 9 P-27 P-50
(Role) H-26
42 PiBk-2 77 sibl 0 ? 26 fl
43 O/G-L-2 77 sib 0 ? 26 fl
44 BIO-2 77 sibJ 0 ? 26 fl
45 G/O-L 77 sibl 0 ? 27 fl
46 P/Pi-L 77 sibJ 0 ? 27 fl
47 Bl/O-L 77 0 36 fl
48 XX 2 ? A-fl
49 XX 1 ? A-fl
GROUP 2 1975 1976 1977 1978

OG 75 Ad ?
WO 75 Ad o
OW 75 Ad a
PPi 75 Ad 9
OP 75 2 o


H-15?, 21
P-18, H-21

? P-17, H-18,
? P-21

? P-22, H-23

P-29, 45, H-28,
H-30 fl
P-31, 46


P-51 fl

P-52 fl


(BP) seen once
7 OBk 75 Ad u ? H-24? P-37, H-29 P-55
(Role) 30 fl
8 GPi 75 Ad 9 Group 3 ? P-35, 44 P-58
9 BkO 75 Ad ? H-8 H-18
10 GP 75 Ad 9 ? P-23 P-40, 43 P-59
(Role) H-24
11 BIW 75 1 ? H-8 H-18 P-32, 41 H-59
H-28? 30, 31, 38
12 PiX 75 1 ?
13 PG 75 0 ? 9 fl
14 BIG 75 0 ? 6 fl
15 PiBK 76 Ad 9 H-22, 23.
16 WBI 76 Ad 9 P-18 P-28, H-29 P-51 fl
17 Pi/Bl-R 76 Ad 9 P-22, H-23 fl ? seen with
(Role) H-24 P's of 32 twice
18 G/O-R 76 Ad o P-24, H-23 P-38, H-30 P-59, H-58
(Role) 31 fl
19 O/Pi-R 76 Ad Co P-21 P-31 P-57
20 Pi/O-R 76 Ad 9 P-23, H-22 P-37, 46, H-29, 30 fl P-55
21 O/BI-R 76 Ad a H-22, 23 P-40, 43
(Role) H-29
22 XX Ad 9 P-17 P-29, P-45, H-28 P-52 fl
(Role) H-18, 21? 23?
23 XX Ad 9 P-24, 21? 23?
(Role) H-18
24 BlPi 76 1 9 H-18, 23? P-33, H-28, 29 P-56
25 Bl/O-R 76 1 ? H-22, 23

H-8? H-28 fl

6 PO 75 Ad 9


APPENDIX I (continued)

Color Year Age Sex ROLES
Code' Marked Marked (Crit.) 1975 1976 1977 1978

26 Bl/G-R 76 1 op H-22, 23 H-30, 33, 29 fl P-53


H-28, 29

H-29, 30, 31, 33, 38
H-31 seen once

34 G/Bl-R 76 sib- 0 ?
35 XX Ad Cp
36 P/G-R 77 Ad oC
37 Bk/Pi-R 77 Ad 9
38 XX 2 o'
39 Bk/O-R 77 1 9

P-35, 44

P-30, H-29, 37, 38?

P-30, H-29 fl

P-32, 41
H-31? 38, 40


H-51, 52






76 sib]
76 sibJ
76 sib"I
76 sibJ
76 sibI
76 sib


77 sibi
77 sib
77 sib-
77 sib
77 sibJ
77 sib
77 sibJ

31 fl (Predatorized)

77 0 ?
Ad 9
1 ?

1 ?

1 ?

1 ?


with OW, XX,
with OW, XX,
with G/O-R,
GP, and B1W
with O/Pi-R,
and PPi

ICode: color flag tarsal markers. A slant mark between two colors indicates they were on the same leg, designated by a suffix "L" or "R." A suffix numeral indicates that a bird dead or long missing
was previously marked with this combination. X means no band. Sex (crit ): birds were sexed by role, or brood patch (BP). Roles: P = parent: H = helper: A = attendant, whether helper or
parent not known; fl = fledgling; numerals = numbers) of the nest(s) at which role was played.
Nx = undiscovered nest; ? = designation probable but not based on "best" information.
'Probably dead several days: as a result, could not be sexed by gonadal condition.
'The genetic parent P, roles and surrogate parent roles P2 of birds at nest 26, 1977, are discussed in the text on p. 26.


Nest by Number in Temporal
Order, Left to Right
Group 1, 1975 51 9 4 3
Breeding 0 9 o 9a 9 0 9
Pair OPi, PiO BkBk, XXad B1O, GB1 PiG, XXyrl
Attendants OPi, PiO, PiG, BkBk, XXad, GBI, B10, GB1, PiG, XXyrl, GBI
00, GBl, B1O, B10, PiO, PiG, OPi, PiG PiO, BIO, OO,
GW, PP, GG, XPi, BkBk? 00, XPi, GW, PP XPi

Nests by Number in Temporal
Order Left to Right
Group 1, 1976 NX2 14 16 13 12 15
Breeding a o 9 o" 9 9 ao 9 9
Pair PiG, BIBk ?? 00, ? B10, O/G-L OPi, Bl/G-L PP, XX ad
Attendants PiG, BIBk, PiBk3 OO, ? BO1, O/G-L, 00 OPi, Bl/G-L, PiP, PP, XXad, WW,
OO, WW, B1O, PiW, WW, OPi, OBI, PiG, OB1, PiW, O/G-L, OB1, PiP, PiG, 00
others? GG, PiP, PiW, PP GG

Nests by Number in Temporal
Order, Left to Right
Group 1, 1977 27 26 34 36 39
Breeding ag 9 Oa 9 a 9 9 a 9
Pair GG, P/O-R OBI, BIBk4 PP, XXad PiG, XXad OBI, BlBk'
Attendants GG, P/O-R, PiG, PP, OBI, BIBk, OPi, PP. XXad, B1BI-2, PiG, XXad, OPi, OBI, BlBk
PiW, PiPi-2, BIB1-2, Bl/G-L4, PiG, GG, PiW B1B1-2, PP,
Pi/Bl-L 1B1B-2, PiW, Pi/BI-L, PiW, XXad of
P/O-R, PP N-34

Nests by Number in Temporal
Order, Left to Right
Group 2, 1976 17 18 21 23 22 24
Breeding ac r g9 9 a 0 9 ca 9
Pair OW, XXad WO, WBI O/Pi-R, PPi GP, PilO-R OP, Pi/Bl-R G/O-R, XXad
Attendants OW, XXad BIW, XXad, PPi, O/Pi-R, GP, Pi/O-R, OP,Pi/Bl-R, GP, OBK?,
WO, WBI, XXad, XXad, O/BI-R, BI/G-R, B1/O-R, BkPi, Pi/Bl-R,
OW, XXad, OG, WO, OW OP, Pi/Bk-R, BI/G-R, G/O-R, XXad
BkO, BlPi G/O-R. BkPi, Pi/O-R, O/BI-R
XXad, Bl/O-R,
XXad, BlPi?
(or Pi/Bl-R)

APPENDIX II (continued)

Nest by Number in Temporal
Order, Left to Right

Group 2, 1977 28 29 30 31 32
Breeding a 9 a 9 o 9 c 9 c 9
Pair WO, WBI OW, XXad BkPi, P/G-R O/Pi-R, PPi XX 2 yr, BLW
Attendants WO, WBI, WBk, OW, XXad, WO, OBk, Bk/Pi-R, P/G-R, O/Pi-R, PPi, XX 2 yr, BIW,
XXad, B1W? WBI, O/B1-R, P/G-R, POP, G/O-R, OP, G/Pi-R,Pi/G-R, Pi/Bl-R?
OW, BlPi Pi/O-R, OP, Bk/Pi-R B1W, Bl/G-R, BIW, G/O-R,
P/G-R, BlPi, OW, Pi/G-R, OBk XX 2 yr?
Bl/G-R, WBk,

Nests by Number in Temporal
Order, Left to Right

Group 2, 1977 33 35 37 38 40
Breeding a 9 C 9 c 9 9 9
Pair OP, BlPi XXad, GPi OBk, Pi/O-R G/O-R, Bk/O-R O/Bl-R, GP
Attendants OP, BlPi, XXad, GPi OBk, Pi/O-R, G/O-R, Bk/O-R, B1W, O/Bl-R, GP, XX 2 yr
Bl/G-R, Pi/G-R P/G-R XX 2 yr, Pi/G-R, (mate of B1W)

Nests by Number in Temporal
Order, Left to Right
Group 2, 1977 41 43 44 45 46
Breeding C 9 O 9 0 9 Y 9 a 9
Pair XX 2 yr, BIW O/BI-R, GP XXad, GPi OW, XXad O/Pi-R, PPi
(See N-32) (see N-40) (see N-35) (see N-29) (see N-31)
Attendants XX 2 yr, BIW O/BI-R, GP XXad, GPi OW, XXad O/Pi-R, PPi
'A sixth, earlier, nest was undiscovered, having fledged at least 1 young (found dead) prior to our arrival at study site. Nucleus pair may have been 00 and WW.
*Nest X not found prior to fledging. Though differing greatly in size, 2 fledglings found shared same putative parents.
'PiBk began to sit on nest 14 after its apparent desertion by unmarked adult female, PiBk was vandalized, see text p. 36.
OBI and BlBk were the pair when the nest was discovered. But later, OPi and BI/G-L had replaced them, the latter being found incubating. See text, p. 26, for discussion.


Individual Annual Survival,San Bias Jay Group I
1974 1975 1976 1977 1978

Pi Pi
Adults BkBk
Banded f G
1974 Yearlings P P
Pi G

Fledglings X P
(Siblings) X G

Adults B0
Banded PO
1975 Yearling G W
Fledglings 0 BI
Group 3- P Bk
/ BI Bk
Adults BI/G-L
Yearlings P W

Bonded BI P
1976 Pi Pi-2
Fledglings PI/BI-L

Adult ( P/O-R
SPi Bk-2
Banded BI 0-2
1977 Fledglings G



Vol. 26, No. 4


Individual Annual Survival,San Bias Jay Group 2
1975 1976 1977 1978

P Pi
O Bk
Bk 0
2yr. old- OP
Yearlings BI W

Fledglings BI G

Bk Pi
Adults G/O-R



Yearlings BI/O-R
W Pi
Pi Bk
Fledglings G/B-

G Pi
Adults Bk/Pi-R
Yearling Bk/O-R















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