Form and function of the long-range calls of Scrub Jays, Aphelocoma coerulescens obscura


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Form and function of the long-range calls of Scrub Jays, Aphelocoma coerulescens obscura
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v, 211 leaves : ill. ; 28 cm.
Webber, Tom
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Florida scrub jay   ( lcsh )
Birdsongs   ( lcsh )
bibliography   ( marcgt )
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Thesis (Ph. D.)--University of Florida, 1984.
Includes bibliographical references (leaves 204-207).
Statement of Responsibility:
by Tom Webber.
General Note:
General Note:

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University of Florida
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Full Text

Aphelocoma coerulescens obscura







J.W. Hardy, John H. Kaufmann, Thomas J. Walker, and S. David Webb

all provided trenchant criticisms of the manuscript. Jeff Cox and John

Robinson gave me indispensable advice on statistics.

My parents, Mr. and Mrs. Martin Webber, generously allowed me to

use their home as a field station during 1980.








THE VOCABULARY OF A. c. obscura .


Contexts of Perched Calls .

Contexts of Flight Calls .











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Abstract of Dissertation Presented to the Graduate Council of the
University of Florida in Partial Fulfillment of the Requirements
for the Degree of Doctor of Philosophy

Aphelocoma coerulescens obscura


Tom Webber

April 1984

Chairman: John W. Hardy
Major Department: Zoology

Scrub Jays in and around Griffith Park, Los Angeles County,

California, have a vocabulary of at least 18 calls. The loud

long-range calls in this vocabulary can be divided into four categories

according to their acoustic structure: scolds, zeep/scolds, zeeps,

zhraanhs, and shlenks in one group; weeps and screlches in another; the

chuk, given only by males; and the rattle, given only by females. The

more the calls in the scold-shlenk group diverge in structure from

scolds, the less they are used in predator mobbing, the greater is the

variety of contexts in which they are used, the more they are used in

display flights for territory advertisement and defense, the more they

are used in response to flights of the calling jay's mate, and the

greater is the proportion of the total number of calls given by the

males. The jays tended to give weeps in chases and screlches in

display flights. I am unable to find any significant difference

between the way the males used screlches and the way they used

shlenks. In this way these two major long-range calls resemble one

another more than they do their own acoustic relatives. The males

matched one another's shlenks and screlches during territory

advertisement, repeating each call type several times before switching

to another call type. Thus Scrub Jays, usually not considered to have

a territorial advertising "song" in the usual sense of the term, used

these two calls in a manner resembling the way in which some singing

birds use their several song types. Scrub Jays usually did not match

their own mate's screlches, shlenks, or weeps, and instead responded

with their sex-specific calls. Several of the calls described here are

similar to calls given by the Scrub Jay's closest relatives, but none

of these species appears to have a homologue of screlches or shlenks.

All of these relatives live in forests. I consider screlches and

shlenks to be calls derived from two different acoustical groups that

have converged in their use in long-range display flights in the Scrub

Jay's open habitat of chaparral.


One's first impression upon hearing the voice of any of the jays

(Corvidae : Garrulinae) is that its main vocalizations are somehow

importantly different from the songs of many other songbirds. The loud

territory-proclaiming sounds made by jays have generally been referred

to as calls rather than songs by both ornithologists and the general

public. This designation reflects, however imprecisely, the fact that

jay sounds lack the tonality, rhythm, order, and complexity

characteristic of the songs of such familiar songbirds as wrens,

thrushes, buntings, and even titmice. It is also rare to see lone jays

deliver their calls in the way many other songbirds deliver their

songs: they seldom call continuously from a conspicuous song perch in

what appears to be spontaneous advertising of their presence and their

ownership of a territory. In addition, jays do not call at such easily

predictable times of day or year as many other songbirds.

Despite this distinctiveness, or perhaps because of it, few

ornithologists have studied the voices of the jays in detail. This is

undoubtedly due, at least in part, to the fact that many of the New

World jays live inconspicuously in cloud forests and other places in

Latin America where travel is expensive, inconvenient, or impossible.

Even so, some abundant and conspicuous jays have received little

attention. The only detailed study of the voices of Blue Jays

(Cyanocitta cristata) is that of Conant (1972), and it was conducted in

captivity. Scrub Jays (Aphelocoma coerulescens) are common over about

one-fifth of North America, but before the study on which I report

here, the voice of only one race, the Florida Scrub Jay (A. c.

coerulescens)--unusual among Scrub Jays because it is a cooperative

breeder--had been studied in much detail (Barbour 1977).

Altogether, of the 32 species of New World jays (see Hardy 1969

for a review of their relationships and distribution), the voices of 18

remain almost unknown, and until the present study, only the Steller's

Jay (Cyanocitta stelleri), was very well known.

It was inducement enough for me to study Scrub Jays that they

should be so little known, and that they should produce sounds whose

peculiar clangor is so intrinsically interesting. Just as good, or

even better, depending upon one's concern for the cachet of the

results, is that the reasons for studying jay calls in general, and

those of Scrub Jays in particular, can be stated in the beloved

language of hypothesis-testing.

The New World jays form a variety of types of social units (see

Brown 1974 for a review), depending upon the species and its location.

These social units range from unaided pairs defending territories (the

western races of the Scrub Jay; Brown 1974, Carmen 1982, this paper) to

pairs that defend territories assisted by helpers, who also assist in

raising the breeding pair's other young (Florida Scrub Jays; Woolfenden

1975, Stallcup and Woolfenden 1978), to groups of more than 20 adults

who occupy a common group home range, and assist one another in raising

their young (Southern San Blas Jays, Cyanocorax sanblasianus

sanblasianus; Hardy et al. 1981). The jays of the New World live in

habitats from desert scrub (Aphelocoma coerulescens cactophila; Pitelka

1951) to cloud forest (various species of Cyanolyca; Hardy 1964). They

also vary from species to species (or subspecies) in the size of their

vocabularies. The Dwarf Jay (Aphelocoma nana) seems to have only two

calls (Hardy 1971), while the Yucatan Jay Cyanocorax yucatanicus has

about 24 (Hardy 1979). Thus the New World jays offer an opportunity to

study the way in which these two important influences, social

organization and habitat, affect the size and form of the jay's


It seems plausible enough at first that a relatively complex

social life would require a relatively large vocabulary. Barbour

(1977:94), for instance, attributes the fairly large size of the

Florida Scrub Jay's vocabulary in part to the fact that it is a

cooperative breeder, saying that its large vocabulary provides the

basis for "a highly sophisticated signal system for the subtleties of

communication necessary for such a highly social existence." Does it

follow then that other races of Scrub Jays that are not cooperative

breeders will have smaller vocabularies than the Florida Scrub Jay? Or

that in general the less social jays will have simpler vocabularies

than the more social? It is true that the Yucatan Jay, with its large

vocabulary, is a cooperative breeder that lives in groups of from six

to 13 birds, but on the other hand, the Southern San Blas Jay, the most

socially complex of all, gives only two calls at all commonly (Hardy

1979, pers. obs.). So it is possible to find some exceptions to the

expected rule, but it would require much more study to see if this rule

holds even in general, and to determine the extent to which it might be

modified by the nature of the habitat or other influences.

To the extent that I can claim at all to have been a deliberate

tester of hypotheses, it is only in that I took as an assumption that

each call may well have a quite specific use, and that therefore I

would have to try to break down the jay's associated behavior into as

many categories as possible in order to detect the differences in the

way the calls were used.

My goals were simple: I wanted to find out what kinds of sounds

Scrub Jays make, how they use them, and to compare them and their uses

to the vocabularies of the Scrub Jay's near relatives.

To this end I spent more than a year studying Scrub Jays of the

race obscura near Los Angeles, California.

Scrub Jays live in chaparral and open oak woodland from the

southern tip of the Mexican Plateau to about the northern edge of the

Great Basin, and from the Pacific Coast to the eastern base of the

Rocky Mountains. A separate population, at least 1500 km from the

nearest western Scrub Jays, inhabits scattered patches of scrub on the

Florida peninsula.

The western Scrub Jays are divided into 17 subspecies, and the

Florida birds constitute a single race. At various times the Florida


Scrub Jays have been considered a species distinct from those of the

west, but all Scrub Jays are now considered to constitute a single

species (Pitelka 1951).


I studied Scrub Jays in Griffith Park, Los Angeles County,

California. Griffith Park is a 5,000 acre city park at the eastern tip

of the Santa Monica Mountains. My principal study site was in a

section of the park composed of low granite hills, covered with a

sparse growth of chaparral, and with a fringe of riparian woodland at

their base.

I studied Scrub Jays in Griffith Park and vicinity for two months

in the summer of 1978, and from 18 January to 26 December 1980.

I color-banded 55 Scrub Jays in and around the park. All received

an aluminum U.S. Fish and Wildlife Service band, and all but one also

received one or more colored celluloid bands designated in this paper

by the following abbreviations: white, W; light blue, lBl; dark blue,

dBl; red, R; orange, 0; yellow, Y; pink, Pi; light green, IG; dark

green, dG; aluminum, S.

Following Woolfenden (1975) I refer to band combinations by naming

the bands on the right leg first, from top to bottom, then a dash (-),

then the bands on the left leg, from top to bottom. Thus 1GS-R means

light green above aluminum on the right, red on the left. An X

indicates that there were no bands on that leg; thus Pi-X means a pink

band on the right, none on the left.

I also refer to jays by the names of their territories. When

these names are single words I have written them out (e.g., COSMIC,


VICTORY); when more than one word I have abbreviated them (e.g., HS,

MT). None of these abbreviations has a dash in it. The jays and

territories on my study site are listed in APPENDIX I. APPENDIX II

shows the locations of the territories that I was able to map.

Some jays were too wary to be caught, especially if they had seen

other jays trapped. Most of these unbanded jays were paired to a

banded bird, so that I could at least identify them as being of a

certain sex and belonging in a certain territory. I made a special

effort to find peculiar body markings on several unbanded jays of

unusual importance (such as the two successive females of EBS), and

found that the whitish bib and blue necklace on the chest differed from

one individual to another. Minor details, such as the outline of the

bib, changed when the jays preened, but major details, such as the

presence of outlying blobs of white in certain positions (male RC) or a

scattering of hair-like white lines on the margin (female I EBS)

persisted despite preening and movement, and I could see them easily

with my 7X 35 mm binoculars.

The jays on my study site would usually approach me to within

about 3 or 4 m. The small size of their territories made them fairly

easy to find and to follow, and the hills provided vantage points that

allowed me to watch some jays continuously for several hours from a

single spot.

I made recordings with a JVC 1636 cassette recorder and an AKG

D900 dynamic shotgun microphone. I made sonograms on a Kay Elemetrics

Corp. Sona-Graph, model 7029A, set on wide band (300 Hz), and using

the linear scale, the flat equalization setting, and no automatic gain


The few times of day referred to in the text are Pacific Daylight

Time if occurring from 27 April through 26 October, and Pacific

Standard Time otherwise. I usually timed events only to the minute,

with a wristwatch.

I incited and prolonged some territory conflicts by drawing jays

to the boundary with peanuts.

Measuring and counting Scrub Jays calls.-- It is common for

studies of territorial advertising song to feature quantitative

analysis of variation based upon measurements of sonograms. For

instance, the individual figures in a series of sonograms might be

classified or measured according to some quasi-objective criterion, and

these figures grouped to define song types (e.g. Bradley 1977). Then

the entire analysis of say, geographical variation, or the association

of song types with different activities, is conducted using only these

data. These techniques are possible with many songbirds that sing

territorial advertising songs from song perches. A bird of a certain

species may sing hundreds of renditions of its songs from a single

perch within a matter of minutes. So, for instance, Smith et al.

(1978) tape-recorded 9,419 songs of eight Yellow-throated vireos (Vireo

flavifrons) in fewer than 42 hours, and Verner (1975) recorded 3,988

songs of seven Marsh Wrens (Cistothorus palustris) in 12 hours.

Not only is it possible in many cases to record all of the song

renditions wanted for analysis, but in some it may be necessary in

order to distinguish the song types from one another, because they are

indistinguishable by ear. For instance, Verner's Marsh Wrens each had

more than 100 song types, each of them recognizable as a Marsh Wren

song but most of them too finely detailed for a human to identify more

than a few of them readily by ear.

Scrub Jays behave in such a way as to make impossible the

continuous recording of large samples of their. Compensating for this

difficulty is the fact that their calls are (with practice) readily

distinguishable by ear, so that if the observer is skillful and

circumspect enough, it is unnecessary to record all of the actual call

renditions used in the analysis.

Scrub Jays, as mentioned earlier, do not sing a typical

territorial song in a typical songbird manner. Scrub Jays give most of

their long-range territorial calls in flight, and they deliver their

perched calls (see my distinction between flight and perched calls, pp.

78-79) at unpredictable places. When Scrub Jays can be counted on to

call continuously, such as in a boundary dispute, they move too fast to

be recorded well. When they are not involved in boundary conflicts,

and when they can be followed or approached closely, they call so

seldom and unpredictably that making large numbers of high-quality

recordings is impossible. It is no coincidence that the only two

detailed quantitative studies of jay vocalization based on recordings

(Conant 1972 and Berger and Ligon 1977) were done with captive birds.

This is not to say that it would be impossible to record enough

Scrub Jay calls to analyze quantitatively for variation, but to do so

would require sacrificing other, more important, kinds of information.

One of the cardinal rules of making album-quality recordings (and that

is what would be required for a quantitative analysis of variation in

Scrub Jay calls) is that one must concentrate on making recordings and

nothing else.

Thus I had a choice: I could concentrate on making recordings

while neglecting most of what the jays were actually doing when they

called or I could learn the calls by ear and concentrate on trying to

understand the patterns in which the calls occurred--which is what I

did. I devoted a certain amount of time to recording examples of the

call types that I recognized by ear in the field.

The unpredictbility of the jays' behavior made it difficult or

impossible to schedule in advance observations in particular

territories. I could not, for instance, count on being able to watch

the jays in one territory for an hour, then watch another pair for an

hour, etc. Instead, it might take me 45 minutes to find the first

pair, and then they might begin doing something, such as working on a

nest, that continued for an hour or more--or I might lose them again.

As a result, I collected data any time the opportunity arose and for as

long as it lasted. For example, if I heard the jays across the canyon

mobbing a predator or contesting over a boundary, I usually stopped

what I was doing and went to watch. Or when the jays in a certain

territory were building a nest or forming a pair, both activities that

took at least three days and as long as two weeks, I concentrated on

watching them until they were done. If nothing happened in a

particular territory after a prudent wait, I went elsewhere.

I began the year banding jays in the picnic areas of the riparian

woodland and in the nearby suburbs, and by late spring had worked my

way into the hills (see the next section for more about the study

site). As a result, my data on early spring breeding behavior came

from the suburb-and-picnic area territories (COSMIC, GARDEN, VICTORY,

RC, EMR, MR), while most of my data on territory defense and all of my

data on pair formation, two subjects better studied in the hills, came

from the hill-canyon territories, especially WD, EBS, HS, BS, MT, HT,

and SEHT.

I was in the field every week of the year from mid-January until

the end of December, and for at least six days in an average week. I

usually spent three to five hours in the field during the first half of

the day, beginning at about 0800 or 0900, and two or three hours later

in the afternoon. I took notes in a shorthand of my own devising,

using abbreviations and symbols to designate, for instance, flights

parallel or perpendicular to a territory boundary. I did not dictate

notes into a tape recorder. Occasionally when my field notes were

especially sloppy, I transcribed them later in a neater fashion, but

most of my data have been compiled directly from my original field

notes. Several examples of my notebook entries, written out in normal

English, appear in the section on "THE BEHAVIOR OF CALLING SCRUB JAYS."


The Los Angeles River runs past the hills at the eastern tip of

the Santa Monica Mountains at an elevation of about 140 m. From the

concrete-encased banks of the river the hills rise sharply to an

elevation of 270 m. A narrow canyon, called Deer Canyon by the local

people, runs eastward through the midst of these hills for about

one-half mile until opening out onto a gravelly plain now occupied by

the Los Angeles Zoo. Most of the banded Scrub Jays that I came to know

well lived in this canyon and its surrounding hills (APPENDIX II).

The chaparral of the hill-canyon part of my study site consisted

mainly of sumac (Rhus ovata) and mountain mahogany (Cercocarpus

betuloides). These grew in clumps separated by bare ground or patches

of short introduced grasses sown to hold the soil after the frequent

fires. Wild buckwheat (Eriogonum sp.), sage (Salvia spp.), and poison

oak (Rhus diversiloba) formed low, smaller, thickets in the canyon, the

first two on the sunnier south-facing slopes and the last on the

shadier north-facing slopes. A few individuals of toyon (Heteromeles

arbutifolia), holly-leaf cherry (Prunus ilicifolia), Ceanothus spp.,

and elderberry (Sambucus caerulea) were scattered about on both open

hillsides and in the canyon.

Scrub oaks (Quercus dumosa), whose acorns were too big for the

Scrub Jays to carry and thus probably too big for them to eat, grew

singly and sparsely on the slopes. A few tree-sized California

sycamores (Platanus racemosa) and coast live oaks (Q. agrifolia) whose

acorns the jays ate commonly, grew along the gravelly beds of the

intermittent streams. Planted Eucalyptus lined some of the ridges.

The overall effect was of scattered, scrubby growth from 1 to 2 m high,

with occasional small stands of full-size trees in the canyon bottom

and on some ridgelines.

The flat woodland, across the river from the chaparral-covered

hills, consisted of open groves of planted California sycamores and

coast live oaks over a mowed lawn. This area was a picnic ground.

Except for the short grass, the overall effect resembles that of a

natural lowland streamside of southern California.

Territories.-- All except one Scrub Jay territory in the picnic

area lay partly in the backyards of the neighbors, who were often

hostile, so I could not measure the size of these territories

accurately. The hill-canyon territories were more easily mapped, and

it was in these that I collected most of my data on territory defense

and related behavior. Scrub Jays in Deer Canyon and on the surrounding

hills usually placed their territory boundaries along ridges and dirt

roads (APPENDIX II).

The territories had sharp boundaries. Those that I visited often,

such as the one between MT and BS, were no more than 2 m wide. That

is, when jays from one territory approached the boundary while their

neighbors were watching, the point to which they could advance before

they were chased by the neighbors did not vary by more than 2 m. I

detected no permanent changes in territory boundaries during 1980.

The territories in the hills and in the canyon were much smaller

(0.73-1.7 hectares, x=l.l hectares) than the Florida Scrub Jay

territories (2.0-14.6 hectares, 1=7.7 hectares; for pairs without

helpers) mapped by Woolfenden and Fitzpatrick (1978). My measurements

represent the area of a horizontal section of a column of air above the

territory, so that the actual surface area of the land in the territory

must be greater (perhaps by 25 to 50%) than the figure given. The

small size of the territories and the hilly landscapes combined to make

the line of sight and hearing between the interiors of the territories

quite short (Table 1). Some of the hillside territories were, in

effect, turned on their sides, so that the activities of their

residents could easily be seen and heard by their neighbors in the

middle of their own territories. As a result, territory conflicts and

counter-calling matches did not need to be held at the boundary, and

the residents of as many as five adjacent territories sometimes

counter-called at once. Some territories were close enough so that

their residents could counter-call over the heads of their common

neighbor, whose territory lay between them. Kramer (1981) and Weaver

(1981) estimated population densities of Scrub Jays in oak and sycamore

woodlands in southern California, and arrived at figures of 46 and 26

pairs per 100 acres (40.5 hectares), respectively. If I extrapolate my

estimates of territory size to make them comparable to these estimates,

I get a nearly intermediate estimate of 38 pairs per 100 acres.

Table 1.

Distances between the centers of Deer Canyon territories in
which I often saw and heard long-distance territorial
displays. Centers of territories located by eye. See
Appendix II for a map of these and other territories in Deer

Territories Distance (m)



MT-BS 130


MT-TT 170



Adult longevity.-- Of seven adult territory holders and one

hatching-year jay (IGS-, which was acquiring a territory) that I banded

in August 1978, seven, including IGS-, were present on my study site

when I arrived in January 1980. All seven of these were still there

when I left at the end of December.

Pair bond fidelity.-- In 1978 I was able to band both members of a

pair in only one territory, MR. These two birds were still together in

MR at the end of 1980. During 1980 I banded, or was otherwise able to

identify consistently both members of five more pairs by the middle of

the year. During the rest of 1980 none of these pairs broke up except

by disappearance of one member. In some cases I never knew the fate of

the birds that disappeared.

Site fidelity.-- In January 1980, when I found the seven survivors

from 1978 that I have just mentioned, all were living in the same

territories they had occupied in 1978. In 1980, none of the territory

holders that were banded, or recognizable in some other way, changed

territories in the course of the year. Again, I simply could not

account for some disappearances.

Nesting.-- In 1980 I first found a nest (COSMIC) under

construction on 25 February. On that date this nest consisted of only

a few foundation sticks. I found MR's first nest two days later in a

similar rudimentary state. The latest nest of which I was aware was

the fourth nest of EMR, which that pair started on about 1 June. The

last nestling left this nest on 16 July.

Dispersal of young.-- When juveniles disappeared from their home

territories, I usually had no way of telling whether they died or

departed. I was lucky enough to catch glimpses of two young-of-the-

year, long after their last regular appearances on their respective

territories, that showed that these two birds had reached independence

but had remained for awhile within visiting distance of home.

In their first nesting attempt of the season, the breeders at HT

produced two flying juveniles that survived until at least the end of

July, when both disappeared from the territory. I saw neither of these

birds again until 16 October, when one of them, Y-SPi, flew into HT

with a flock of about six wanderers. At least two of the jays in this

flock, in addition to Y-SPi, were hatching-year birds. Y-SPi landed

high on the tip of a bare tree, less than 1 m from its mother, and both

sat quietly watching one another for about a minute. Then, as the

little flock moved on, Y-SPi rejoined it and flew over the ridge and

out of view. I never saw Y-SPi again.

The pair of VICTORY, in the picnic area, fledged two young on

about 29 June, in their second nesting attempt. One of these, SlBl-lG,

survived to the flying stage. I last saw SlBl-lG at home on 25

August. I found it again on 31 August about one-half mile away, as a

surreptitious wanderer in EBS and WD, two of the hill-canyon

territories. Within the next month it made three more short

appearances in other territories of Deer Canyon, after which I never

saw it again.

The juveniles on my study site could be divided roughly into an

"early" and a "late" group. The early group consisted of young

produced in the first nesting attempts of the season at LAKE, HT, BS,

and MT. These juveniles all disappeared within about two weeks of one

another in the second half of July. The late group came from second

and third nesting attempts at GARDEN, COSMIC, and VICTORY (neither of

the two known fourth nesting attempts produced flying young). All of

these juveniles disappeared from their natal territories within about

two weeks of one another in late August and early September.

The disappearance of both groups coincided with an influx onto my

study site of juveniles of unknown origin, many with incomplete head

molt and pink flanges at the corners of their mouths.

Two male hatching-year jays of unknown origin, X-S (EBS II) and

Y-PiS (LO) established themselves as resident territory-holders by

December of 1980. Presumably they became breeders the following


I spent little time watching nests, but there were never more than

two adults at those that I checked regularly (COSMIC, GARDEN, VICTORY,

RC, and EMR).

No territory that I watched carefully at any other time of year

contained more than two adults that acted as though they were


Fall.-- In September and October, territory-holders from the

hillsides often left their territories to collect acorns in the dense

oak groves of the picnic area across the river.

Because it was located on a promontory between Deer Canyon and

these oak groves, HT territory served as a funnel for jays travelling

between the two. At the peak of acorn-gathering in mid-October, more

than 60 jays passed through HT per hour on their way to and from

gathering acorns. In some of the picnic area territories such as

VICTORY, there were sometimes as many as 20 intruding acorn gatherers

within a radius of 20 m. These jays, like those passing through HT,

included many of the banded residents of the hills and canyon, and many

of unknown origin. After the territory-holders on my study area ceased

most of their wandering, loose flocks of jays, most of them unbanded

and of unknown identity, except that some were hatching-year birds,

continued to patrol the canyon and vicinity. Presumably, at least the

hatching-year birds were searching for a territory in which to settle.

One of them, X-S, replaced the male that I shot in EBS in December.

The few banded birds in these flocks were often the same from one visit

to another, so that composition of the flocks may have been fairly

constant. The largest such flock that I saw consisted of about 15


In a later section I will describe the reactions of residents when

their territories were invaded by such large numbers of intruders.

In summary, my Scrub Jays were territorial, with territories of a

size about typical for Scrub Jays of southern California. They gave

the appearance of being sedentary, long-lived, and permanently

monogamous. Their young left their natal territories permanently

before the following breeding season, often wandering conspicuously

through the study site, apparently in search of a breeding territory.

It appears that some yearlings were breeders.


In the field, I distinguished by ear 18 different calls of A. c.

obscura. Of these, I count nine as being long-range calls (Table 2).

I have given each call an onomatopoeic name when possible. The

oddity of the names that result is the price paid for objectivity.

I have usually limited description of the sonograms to pointing

out the details that I think are important in giving each call its

distinctive sound, and that reveal the similarities and differences

between calls.

I have tried to identify homologues of A. c. obscura's calls in

the vocabularies of the Scrub Jay's closest relatives: the two other

species of Aphelocoma and the eight species of Cyanolyca (Hardy 1969).

In identifying supposed homologues, I restricted my choices to calls

that are obviously similar in form and sound to those of A. c.

obscura. The vocabularies of most of the Scrub Jay's relatives are so

little known that apparently dissimilar calls may in fact be linked to

sounds of obscura by calls yet unknown.

I have based my comparisons of the various species' calls on all

of the information available, including published descriptions and

sonograms, recordings in the Bioacoustic Archives of the Florida State

Museum, and word of mouth. When I say that a certain species of jay

seems not to have a certain call, it may simply be because the call has

TABLE 2. The vocabulary of A. c. obscure.

Long Range










Intermediate Range




Distress Call


Intra- and inter-pair

mainly intra-pair

intra- and inter-pair

Short Range





Sotto Voce Song

mainly intra-pair

not been described. In this and later sections I will say when I am

fairly confident that a certain species really lacks a certain call.

It was surprisingly difficult to make comparisons with the calls

of Florida Scrub Jays as described by Barbour (1977). Detailed

comparison will be a separate major project requiring many more

sonograms than I have now, and a better knowledge of geographical

variation in Florida Scrub Jay calls.

Finally, I show sonograms, and give brief descriptions, of three

other calls (nhyuck, kuk, wheeze) that I will mention occasionally in

the process of discussing the nine major long-range calls.

Weeps and screlches.-- Weeps and screlches are acoustically

similar, and they grade into one another. Neither grades into any

other call.

Weep.-- I refer to this call type as a "weep," because I consider

it to be homologous to the Florida Scrub Jay calls named "weeps" by

Barbour (1977), and because that term is a fair phonetic approximation

of the call's sound. As the name implies, the call sounds short,

sharp, and rather high-pitched. It does not sound scratchy or raspy.

Though they vary from one rendition to another (Figs. 1-3), weeps

always consist of at least two frequency bands of about the same

duration: a lower one that rises and then falls again, and an upper

one that rises only. Depending on the particular rendition, each of

these bands consists of a rapid vibrato (at about the limit of

resolution of the Sona-Graph's wide-band filter) for much or all of its

duration. Because of the differences between these two bands in the

pattern of their vibrato and in their pattern of overall frequency

change (the bands' "inflection"), it appears that the two bands are

produced by two different sound sources.

Most renditions of the weep also have a third frequency band,

above the rising band just described (Figs. 1-3). This band's pattern

of vibrato and inflection repeat quite precisely that of the lowest

band, and its frequency at any given time appears, within the limits of

my ability to estimate it, to be double that of the lowest band. This

third band is apparently a harmonic of the first. Of course, the

Sona-Graph can produce false harmonics when it is overloaded (Davis

1964, Greenewalt 1968), but for two reasons I think that this third

band is probably a real part of the call. First, when I have

deliberately created false harmonics on the Sona-Graph, using a pure

tone at too high a gain, the loudest harmonic produced is the third,

not the second. Davis (1964) and Greenewalt (1968) have described or

shown similar results. Second, in at least some renditions (Fig. 2a,

f) the third band of the weep is darker (louder) than the first. I am

not aware that the Sona-Graph can produce false harmonics that are

louder than the fundamental.

Paradoxically, whole harmonics are not predicted by the theory

describing movements of vibrating membranes, such as those in the

syrinx. "Edge-clamped" membranes are supposed to produce partial, not

whole, harmonics (Gaunt 1983). Gaunt ibidd.) points out, though, that

there are several examples of bird vocalizations that appear to contain

genuine harmonic series, and that the apparent contradiction may result

from lack of understanding of how syringes work.

The sharp sound of the weep is probably the result of its short

duration, relatively high pitch, and sudden beginning (a term I prefer

to the "attack" of musical and acoustical jargon).

The two-part, rising and falling inflection of the call is

apparent to the ear, especially after one has seen a sonogram of it and

knows what to listen for.

Scrub Jays gave weeps both while flying and while perched. When

flying, Scrub Jays usually gave weeps in bouts of from two to about a

dozen calls at fairly regular and closely spaced intervals. Figure 1

shows a typical example. The flights in which Scrub Jays gave weeps

tended to be straight, direct, and fast (the jay that gave weeps in

flight was often chasing another bird). When perched, Scrub Jays

usually gave weeps at longer and more irregular intervals than when


Several of A. c. obscura's close relatives give calls similar to

weeps. The Florida Scrub Jays of Archbold Biological Station,

Highlands County, produce a variety of sounds collectively called

"weeps" by Barbour (1977). These calls themselves resemble the weeps

of A. c. obscura very little, but they grade into another call given by

Scrub Jays of northern Florida that does resemble obscura weeps, in

that it shows a pattern of rising-and-falling spectral bands (T.

Webber, unpubl. data). Florida Scrub Jays use weeps in territory

defense, as overhead predator calls, and as long-distance contact calls

(Barbour 1977).

A. c. superciliosa, whose range in California's Central Valley

lies directly to the north of obscura's, has a call that appears (in

sonograms) and sounds virtually identical to obscura's weep (pers.


Of the two other species in the genus Aphelocoma, the

Gray-breasted Jay, A. ultramarina, almost certainly lacks any call

homologous to the weep (Brown 1963, J.W. Hardy pers. comm.), and the

Unicolored Jay, A. unicolor, may lack one also, though its vocabulary

is not so well known as that of ultramarina (J.W. Hardy pers. comm.).

A few northern species of the genus Cyanolyca have calls similar

to the weep. C. pumilo of Mexico and Central America gives a call that

closely resembles the weep, in that it consists of a lower doubly

inflected (up-down) frequency band and an upper, rather diffuse, band,

apparently inflected in the same way. Two other species of Cyanolyca

in Mexico give weep-like calls. C. nana, the Dwarf Jay, which looks

like a miniature Scrub Jay, gives a quadruply inflected (up-down-

up-down) call that looks a bit like two weeps run together. C.

mirabilis gives a call that consists of doubly inflected pure tones,

without overtones, that are combined with other figures of a different

form (Hardy 1964). C. pumilo, nana, and mirabilis use their respective

calls as "flock social signals" (Hardy 1964).

The rest of the genus Cyanolyca is composed of the Mexican and

Central American cucullata, the Central American argentigula, and the

South American viridicyana, turcosa, and pulchra. None of these jays

has a call that I consider to be homologous to the weep.

Screlch.-- As I have tried to imply by their name, screlches sound

scratchier, longer, and somewhat lower-pitched than weeps.
















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Screlches are composed of the same two or three frequency bands as

are weeps, but in some renditions screlches are so unlike weeps that

the frequency bands might not be recognizable as such if there were no

weeps with which to compare them.

Each of the differences named above between weeps and screlches

can be accounted for in the appearance of the sonograms (Figs. 4 and

5). The scratchy sound might be accounted for by the frequency change

of the vibrato in each band. In contrast to weeps, in which the

frequency change of the vibrato often barely exceeds the 300 Hz

band-width of the Sona-Graph, the frequency change of the vibrato in

screlches often spans a range of 1 kHz, and sometimes exceeds it. All

of the frequency bands of screlches show this effect. At first I

attributed the diffuseness of the screlch sonograms to distortion, but

I found that by especially careful printing of the sonograms most of

the wispy traces, including even those at the higher frequencies, can

be resolved into a recognizable pattern of vibrato. Jays can produce

plain noise of course, and noise may account for some of the scratchy

sound of screlches and their foggy appearance in sonograms.

The apparent differences between weeps and screlches in duration

and pitch (I use the term loosely) are visible in sonograms, but the

differences are not very great. The screlches in Figs. 4 and 5 are

about 25% longer than the weeps in Figs. 1-3 (about 0.2 sec and 0.15

sec respectively). The frequency bands in these screlches lie about

0.5 to 1 kHz lower than the corresponding bands in weeps.

When Scrub Jays gave screlches in flight, they gave them with much

the same close spacing and regular tempo with which they gave weeps in

flight (Fig. 4). The flights in which they gave screlches tended to be

undulating, slow, and indirect, sometimes describing curves or even

circles in the horizontal plane.

On the rare occasions when Scrub Jays gave screlches while they

were perched or hopping about, they gave them in the same regular and

rapid cadence with which they gave them in flight. It is as though the

regular spacing of the screlches was an integral part of the call,

regardless of the circumstances under which it was given. One jay, the

male of RC, was more inclined than others to give screlches while

perched. When he did so he always gave screlches in rapid bursts, with

the individual screlches within each burst spaced the same way as in

Fig. 4. I wrote down the number of screlches in each burst during

several of his performances, of which the following sequence is an


2-2-2-3-2-3-3-2-3-3-3-2-"long pause"-l-"long pause"


In other words, he gave two screlches in rapid sequence, then paused

several seconds, then two more, and so on. Yet when this same jay gave

other calls, such as weeps or shlenks, while he was perched, he gave

them singly (1-1-1-1-1 etc.) and at irregular intervals, even when he

followed or preceded them with screlches, which he gave in bursts as I

have described. In a later section, I will say more about the rigid

cadence in which jays gave screlches.

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Cyanolyca possess a homologue of the screlch, except for those calls I

previously mentioned that I suppose to be homologues of the weep.

These few calls all resemble weeps more than they do screlches.

Scolds to shlenks.-- The first five calls that I describe next,

scolds, zeep/scolds, zeeps, zhraanhs, and shlenks, form a second group

of calls that is unified by its acoustic structure, at least some of

whose members grade into one another. None of these five calls grades

into any call other than the ones in this group. The end points of the

series that makes up this group, scolds and shlenks, resemble each

other very little, but the other three calls in the group span the

difference between them.

Scold.-- I could not come up with a name for this call that

approximates its sound, and that I would be willing to try to pronounce

in public. Fortunately, the name "scold" serves well enough because

this call is used in only one way: mobbing predators at close range.

The call sounds harsh, raspy, uninflected, and toneless.

Individual scolds seem to consist of five or six frequency bands

(Fig. 6). Some parts of these bands give the appearance of being

pulsed sounds (e.g., the latter part of the second bands in Fig. 6a),

and others look like a vibrato (e.g., first parts of the bands in Fig.

6b). In either case, it is presumably this segmentation of the sound

that contributes to the raspiness of the call.

The uninflected sound of the call is a result of the fact that the

frequency bands lie essentially flat.

I can devise no simple scheme to account for all of the frequency

bands in scolds, or in any of the four calls related to them, as

harmonics of one or two fundamental frequencies. Some scolds do show

slight patterns of frequency inflection that reveal the presence of two

sound sources. In the third scold of Fig. 6a, and in Fig. 6c, some

bands within single scolds are somewhat upwardly inflected, while

others are flat. Each of these two types of bands must each have its

own sound source (Gaunt 1983).

Scrub Jays almost never gave scolds in flight, but when they did

so, it was in short flights between perches as they mobbed a predator.

Scrub Jays mobbing a predator with scolds usually perched with the

body horizontal, or even tilted head-downward if the predator was below

them, and called directly toward the predator, without any of the

bobbing movements so common when they gave calls such as zeeps.

The jays rarely gave scolds in bursts of more than three or four.

When mobbing a ground predator, a jay typically alternated scolds in an

irregular pattern with zeep/scolds, zeeps, and even weeps. A jay

might, for instance, give a few scolds close to the predator in the

peculiar static stance just described, then fly to a perch a bit

farther away, and there give zeeps with bobbing motions, then fly or

hop back toward the predator to give more scolds, and so on.

To my knowledge only one other jay in Aphelocoma or Cyanolyca

gives a call closely similar to the scold. Dwarf Jays, C. nana, gave a

harsh "rasp," seemingly of "fear" or "rage" when humans touched their

nests (Hardy 1971). The sonogram of this call shows what appear to be

two horizontal bands with an abundance of accompanying noise.

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Scrub Jay mobbing call that he named the "screech scold," but so far as

I can see there is no particular resemblance between this call and the

scolds of A. c. obscura.

Zeep/scold.-- This call is intermediate in sound and structure

between scolds and zeeps.

Zeep/scolds retain the harsh, toneless, raspy sound of scolds, but

like zeeps they are longer than scolds and they sound upwardly


Sonograms of zeep/scolds (Fig. 7) show four, five, or six

frequency bands, which presumably are the same as those in scolds. As

in scolds, portions of these bands appear plainly to be composed of a

vibrato, others, not so clearly printed, may represent pulsed sounds.

The rising inflection of the call plainly results from the fact

that each band increases in frequency from beginning to end by about

0.5 to 1 kHz.

As in the case of scolds, I cannot account precisely for the

origins of each of these bands, except to repeat that there appear to

be two sound sources (note, for instance, the difference between the

inflections of the first and second bands of the scold on the left in

Fig. 7a).

Scrub Jays gave zeep/scolds in flight as rarely, and under the

same conditions, as they gave scolds. When they gave zeep/scolds while

perched, they often performed the same bobbing movements with which

they performed zeeps, zhraanhs, and shlenks: they lowered the whole

body by flexing the legs at the ankle, simultaneously dipping the

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bill downward. They then immediately reversed the movement, raising

the body by straightening the legs again a bit, and raising the tip of

the bill to its former position or even higher. When calling, the jays

usually synchronized the call and the bob so that the call ended just

as they completed the upward bounce of the bob. This is only a very

general description of bobbing, of which there were many variants,

ranging from only a slight dip of the head to rapid and repeated

flight-intention movements with the tail held aloft and the torso held


Jays gave zeep/scolds at wide and irregular intervals, similar to

those at which they gave zeeps.

I will talk about possible homologues of this call in other

species in the section on zeeps.

Zeep.-- This call is intermediate in sound and structure between

zeep/scolds and zhraanhs. Zeeps retain much of the raspy sound of

scolds and zeep/scolds. They are upwardly inflected as are

zeep/scolds, but the inflection sounds noticeably steeper, and the call

sounds higher-pitched over all. While zeep/scolds have a continuously

and uniformly rising sound, zeeps sound almost as though they consist

of two parts, and some extreme forms of the zeep could be phoneticized

as "za-eep."

The differences in sound between zeep/scolds and zeeps can be

accounted for in the sonograms (Fig. 8); some need no comment. The

frequency bands in many zeeps have much the same appearance of vibrato

as in the two previously described calls. Zeeps seem to have fewer

frequency bands than do zeep/scolds; this is the first clear indication

of a trend in reduction of the number of bands that continues from

zeeps through zhraanhs to shlenks.

The characteristic segmented or two-part sound of zeeps results

from the slight dip in frequency at the end of the frequency bands. A

number of these bands seem to end in short (about 0.05 sec) segments of

either pure tones, or of vibrato that cannot be resolved by the

Sona-Graph's 300 Hz filter. This is unlike either scolds or

zeep/scolds, and is the first indication of a trend, toward traces that

give the appearance of pure tones, that continues through zhraanhs and

is most fully elaborated in shlenks.

Zeeps are unlike scolds or zeep/scolds in that the onset of the

call is sudden. The various frequency bands begin almost

simultaneously, producing a sharp vertical line at the beginning of the

call as shown on the sonogram (see especially Fig. 8a, c, e).

Scrub Jays almost never gave zeeps in flight. When they gave

zeeps while perched, they usually bobbed in the way that I have

described under the heading zeep/scolds. They gave zeeps at widely and

irregularly spaced intervals.

Several other species in Aphelocoma and Cyanolyca have calls

similar in a general way to zeep/scolds and zeeps in that they are

(usually) multi-banded sounds with a rising inflection. Because little

or nothing is known about most of these calls except that they exist, I

have tried to avoid a false impression of precision in the comparison

by mentioning them all here under the heading of zeeps, the most

commonly heard of A. c. obscura's upwardly inflected calls.

Both A. ultramarina and A. unicolor have upwardly inflected calls

that I consider to be homologous to the upwardly inflected calls of A.

c. obscura. A. ultramarina has at least two variants of such a call,

one rising slowly and one rising rapidly. A. unicolor has at least one

upwardly inflected call, which is quite similar to the slowly rising

call of ultramarina. The frequency bands in these three calls lack the

strongly segmented look or vibrato of the zeep. None of the calls has

more than two frequency bands (pers. obs.). A. ultramarina gives its

upwardly inflected calls while mobbing ground predators, and when mates

greet one another or confront a stranger at their nest (Brown 1963).

Strangely enough, none of the Florida Scrub Jay calls described by

Barbour (1977) seems to me to be very much like the zeep.

Three northern species of Cyanolyca, C. pumilo, cucullata, and

argentigula, all have upwardly inflected calls that resemble the

upwardly inflected calls of A. c. obscura more than do those of A.

ultramarina or unicolor. Those calls all consist of at least three

frequency bands, which individually look much like the bands in

zeep/scolds and zeeps, along with much noise (at least in the sonograms

that I have seen). The frequency bands are all less sharply inflected

than in zeeps, coming closer to zeep/scolds in this respect. When I

played the upwardly inflected call of C. cucullata at twice normal

speed, it sounded almost exactly like a zeep. Hardy (1964) states that

these upwardly inflected calls of Cyanolyca are used "in alarm."

Zhraanh.-- Zhraanhs are intermediate in sound and structure

between zeeps and shlenks. The name is intended to imply the fact that

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this call sounds less sharp and raspy than zeeps, and that it seems to

begin more gradually.

When identifying calls by ear in the field I considered zeeps and

zhraanhs to be quite distinct calls, and I did not expect them to be

very similar structurally. I was shocked to see the similarity between

the first sonograms of zeeps and zhraanhs, but more sonograms showed

that there is a consistent and easily recognizable difference between

the two. The "soft," gradually developing, sound of zhraanhs seems to

be a result of the fact that the frequency bands in this call do not

begin simultaneously. The frequency bands appear to diverge gradually

from a point (Fig. 9), in contrast to those of zeeps, which begin from

well-separated places on a vertical line. Specifically, the third

frequency band, instead of beginning at a point above and clearly

separated from the first and second bands, originates on the left

toward the base of the call before the first and second bands appear.

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to the left that it lies on a horizontal, rather than on a vertical,

line with the origins of the first and second bands, or at least the

louder parts thereof. The fourth band, when visible, also seems to

emerge from the lower left near the origin of the third band.

The frequency bands retain a downward dip at the end, but this

inflection is not so easily audible as in zeeps. This may be because,

as the sonograms show, the bands do not dip so sharply as in zeeps.

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shlenks. This effect is represented in the sonograms where the ends of

many of the frequency bands appear to consist of pure tones. These

short segments of pure tones are lined up vertically (see Fig. 9b, c)

in a way that resembles the vertical stack of pure tones in shlenks.

When Scrub Jays gave zhraanhs while perched, they often bobbed as

they did when they gave zeeps. They gave zhraanhs in the same kind of

relatively slow, undulating display flights in which they gave

screlches. When perched, they gave zhraanhs at wide and irregular

intervals. In flight, they gave them at regular and more closely

spaced intervals, such as those in the series of screlches shown in

Fig. 4.

Schlenk.-- The shlenk, in contrast to all other Scrub Jay calls,

has a bell-like, almost musical sound. The shlenk resembles the sound

of several medium-size bells struck almost simultaneously, and then

muffled quickly. I rarely had difficulty telling shlenks from zhraanhs

in the field.

In shlenks, the number of frequency bands is reduced in comparison

to zhraanhs (Figs. 10, 11). Presumably the two main bands are the same

as the first two dark bands of zhraanhs. The upper band is upwardly

inflected in all renditions of the schlenk; in some the lower is

upwardly inflected, in others it is essentially horizontal.

More than in any other call, the frequency bands contain segments

that appear to be pure tones. This is especially true of the

flat-lying lower bands. Most of the bands end in short pure-toned

segments. Even bands that are faint or otherwise invisible show such

segments at the end. In each shlenk, these terminal tones occur almost

simultaneously. Because these tones are most conspicuous in the

shlenks, I assume that they have at least something to do with the

relatively musical sound of shlenks. They do not form a harmonic

series, such as those that contribute to the characteristic sounds of,

say, a piano or a clarinet, but it is at least true that sounds

considered to be "mellow" or musical tend to be pure tones or series of

them (Marler 1969). Several calls given by jays in the genus

Cyanocorax (subgenus Cissilopha) have a clanking resonance (Figs. 1K-M

and 3H in Hardy 1979). These calls consist at least in part of short

pure tones with overtones.

It is easy to see that there is much variation among the different

renditions of the shlenk (Figs. 10, 11). When listening to these calls

in the field, though, I did not distinguish among the various

versions. To my ear, all of the renditions shown in the sonograms

sounded unambiguously like shlenks. I never thought that the

difference between any two renditions of the shlenk was as great as the

difference between, say, zeeps and zhraanhs.

I am aware of no other jays in Aphelocoma or Cyanolyca that have a

call similar to the shlenk. Barbour (1977) informally referred to one

call of the Florida Scrub Jay as a "rink" but did not illustrate it.

C. van Riper tells me that A. c. superciliosa around Davis, California,

do not give shlenks, a fact that I find astonishing.

Scrub Jays usually gave shlenks in the same postures and types of

flights in which they gave screlches and zhraanhs.


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When perched, they gave shlenks at wide and irregular intervals.

When flying they gave shlenks at regular and closely spaced intervals,

as shown in Fig. 10.

Within each of the two acoustic groups that I have just described

(the scold-shlenk group and the weep-screlch group), the calls are

structurally related to one another, and at least some of the calls

grade into one another. Even so, I think that the Scrub Jays gave the

calls that I have named here more often than they gave intermediates

between them. I found few intermediates in my recordings. The match

between the sonograms and my field identifications confirms my ability

to recognize the sounds by ear, and I seldom heard what I considered to

be intermediates. The intermediate calls given consistently by the

pair at COSMIC (see Fig. 16) show that I was able to recognize

intermediates when they occurred.

My impression is that intermediates occurred most commonly between

scolds and zeep/scolds, and between weeps and screlches. The first two

may in fact grade smoothly into one another. A thorough job of

determining the precise degree of gradation between the sounds would

require measurements of many more recordings than I made.

Rattle.-- A rattle has the sound of a small stick run rapidly

across the slats of a small picket fence.

A single rattle consists of a series of what appear to be clicks

(Fig. 12). Similar-looking figures can be produced by very rapidly

inflected pure tones, or by short pulsed sounds of relatively narrow

frequency range that produce transients when they start (Davis 1964,

Greenewalt 1968).

Only females gave the rattle. They rarely rattled in flight.

When they perched and rattled, they bobbed in any of the variants of

the bobbing motions that I have described in the section on

zeep/scolds. One type of bobbing was especially common when rattling.

The calling jay held her torso at about the normal perching angle, with

her tail closed and held straight down. She pointed her bill upward so

that it was vertical, or nearly so, and moved her head and torso up and

down in a smooth bobbing motion, at the rate of perhaps one complete

bob per second. This is quite similar to the motions of female Florida

Scrub Jays when they give the Hiccup call, except that the Florida jays

spread their tails (Barbour 1977).

Rattles varied continuously in length from only a dozen or so

"clicks" to perhaps 50 percent longer than the one shown in Figure 12.

Jays usually gave rattles at very long and irregular intervals--nothing

like the spacing of, say, shlenks in flight or even shlenks while

perched. In a typical performance, a male and female might be at the

boundary opposite their neighbors. Then the male flies deep into his

own territory giving screlches, and the female rattles once in response

while bobbing with her bill up. There may now be an immediate

continuation of, a pause in, or an end to the conflict. In any case

the female may not rattle again for several minutes, hours, or days.

A. c. superciliosa has a rattle call virtually identical to that

of A. c. obscura (pers. obs.). The Florida Scrub Jay's Hiccup, also

given only by females, is certainly homologous to the rattle, but it is

much slower, and each "click" consists of two more-or-less separate

parts (Barbour 1977).


















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Rattling or mechanical-sounding click-like calls are widespread

among the jays and crows, but many of the Scrub Jay's close relatives,

including some species that have one or two homologues of other Scrub

Jay calls, seem to lack such a sound.

Gray-breasted Jays of southern Texas have a rattling call quite

similar to the rattle, but the same species in southern Arizona seems

to 'lack it. Brown (1963) suggests that this difference might somehow

reflect the fact that the latter is a cooperative breeder while the

former seems not to be.

The only other species in Aphelocoma or Cyanolyca that (to my

knowledge) has such a call is C. cucullata (recording in FSM

Bioacoustic Archives).

Chuk.-- A single chuk is a short dry-sounding burst of complex

sound. Scrub Jays almost always gave chuks in series spaced like those

in Fig. 13. This series in Fig. 13 is one of the longest that I heard.

Only males gave chuks. They often gave chuks while bobbing in a

posture (bill almost vertical, tail down) that to my eye was identical

to the female's posture while rattling. As a result a male giving a

series of chuks resembled a female giving the rattle call. Males gave

chuks in contexts similar to those in which females gave the rattle.

Despite these similarities, a series of chuks is easy to distinguish by

ear from the rattle. I do not consider the two calls to be homologous.

Nhyuck.-- A short-range call, the nhyuck (Fig. 14b) grades into

the chuk; the similarity between the two may reveal a little about the

structure and origin of the chuk.

Nhyucks, as implied by their name, begin with a soft "n'-like

sound that grows gradually in volume until changing into a harder "k"

sound that stops abruptly. In a sonogram, the soft, gradual sound of

the beginning is represented by one or two rising tones that break up

into what appears to be a vibrato, or a foggy-looking zone that may

represent noise. Scrub Jays sometimes gave calls that sounded

intermediate between nhyucks and chuks, in that they sounded

lower-pitched than nhyucks and lacked much of the "n" sound at the

beginning. Sonograms of this intermediate (Fig. 14c) show these

differences clearly, and that chuks are more like the intermediate than

they are like nhyucks. Chuks (Fig. 13) can be considered to represent

the continuation of a short trend that includes reduction of the higher

frequencies, and increasing emphasis upon those parts corresponding to

the latter rather than the earlier parts of the nhyuck. So the chuk

has a lower-frequency "tail" at the end of the call (Fig. 13), while

the nhyuck has one at the beginning of the call (Fig. 14b).

Scrub Jays of both sexes gave nhyucks most commonly when they and

their neighbors perched near their common territory boundary, or when

an intruder came within a few meters of them. The nhyuck could be

heard at less than half the distance at which the loud calls could be

heard. When giving nhyucks at the approach of a neighbor or intruder,

Scrub Jays held their ground and performed a partial bob with the bill

raised a bit above the horizontal; sometimes they just raised the bill

without bobbing. They gave the intermediate call in much the same

postures. I sometimes saw and heard males give calls that graded from

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nhyucks into chuks in a single brief performance. They began with

nhyucks with the bill tilted up a bit, then the calls grew louder as

they graded into chuks, and the male held its bill higher and higher

until it was giving loud chuks in series (such as those in Fig. 13)

with its bill almost vertical.

I have relatively few recordings of nhyucks, chuks, and the

intermediate between them, and I seldom heard nhyucks and the

intermediate. As a result I am less certain about the relationship

between nhyucks and chuks than the one between, say, zeeps and

zhraanhs. I think that the nhyuck is homologous to the Florida Scrub

Jay call that Barbour (1977) has named the "chiop."

As I have mentioned briefly, and as I will explain later in more

detail, males of A. c. obscura used chuks in much the same way as

females used the rattle. Even considering the uncertainty about the

acoustic relationships of this call, I think that the chuk is a call

that has converged toward the rattle in both form and function with

surprising precision.

I do not know of any other jay in Aphelocoma or Cyanolyca that has

a homologue of the chuk. Even A. c. superciliosa (at least at Davis,

California) lacks this call (C. van Riper, pers. comm.).

Kuk.-- I consider this short-range call to be homologous to the

Florida Scrub Jay call of the same name as described by Barbour

(1977). The call (Fig. 14a) is short, throaty, and toneless. It was

usually hard to hear at a distance of greater than 15 m.

Members of mated pairs used kuks as a contact call as they foraged

at home, and whenever the distance between them changed significantly,

so that they often appeared to use it as a "greeting" call. During

pauses in territory boundary conflicts, the jays often exchanged kuks

with their mates or with the opposing birds, or both. I often heard

kuks from intruders when residents confronted them at close range.

Wheeze.-- Well-named.

This is a specialized call, not often heard. Scrub Jays,

especially males, sometimes gave this call just before they arrived at

their nest or nest site at the end of display flights. Once on the

nest they sometimes continued giving the wheeze call for awhile and

then changed to another call type, often juvenile-like begging calls.

Several times during the non-nesting season I saw jays perform flights

identical to these, landing in nest-site-like places, in response to

the appearance of intruders in or near the territory. I interpret such

flights as an attempt to lead the female away from the intruder. I

will describe display flights to the nest site in more detail in a

later section. I have no recordings of the wheeze of A. c. obscura. A

Florida Scrub Jay in an aviary at the University of Florida gave the

call shown in Fig. 15. To my ear it is virtually identical to

obscura's wheeze.

Sotto voce song.-- A rambling sequence of a great variety of

figure types (a "figure" is any sound that produces a continuous trace

on a sonogram), rarely audible at more than about 7 m. Scrub Jays sang

the sotto voce song during courtship displays when less than 1 m from

one another, and did not use it in territory defense or advertisement.

I have no recordings of A. c. obscura's sotto voce song.

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For the purposes of this paper I divide the behavior of calling

jays into 33 categories, each of which is described in one of the

following two sections ("Contexts of Perched Calls," "Contexts of

Flight Calls"). These categories represent a compromise between my

desire to subdivide the jays' behavior as finely as possible, and the

need to have enough data in each category for comparisons between

them. I could have further subdivided almost any of these categories.

For instance, I could have subdivided the category "Away from mate

after feeding, song display" according to the behavior, sex, status,

and proximity of any jays other than the mate, but as a result I would

have refined my data so well that they would be invisible.

I give some idea of the range of variation in behavior within each

category, often illustrating it with examples that I consider to be

important, but not necessarily typical.

In most descriptions, I do not go into much detail about the

particular calls used in particular contexts. I devote a later section

solely to that subject.

I divide all of these categories ("contexts") into two groups:

those in which the jays called while perched, and those in which they

called while flying. Reading the rest of this paper will make the

reasons for this division plainer than will any explanation that I can

give in a single paragraph. There are two reasons for this distinction

that I can summarize here: 1) the things scrub jays did while perched

(e.g., mobbing a predator, calling to locate the mate) usually differed

from the things they did while flying (e.g., chasing an intruder,

advertising their ownership of a territory), and 2) without any change

in its surroundings, the call type that a Scrub Jay gave often seemed

to depend only on whether the jay flew or perched. To illustrate this

second reason: the male of SEHT lost his old mate on or before 17

December, and on that date he and his new mate spent more than three

hours disputing with their neighbors at TT. Most of this conflict

consisted of parallel flights along their territories' common boundary,

alternated with periods in which all of the jays perched near the

boundary at the top of the bushes. They often gave screlches in flight

but almost never gave them while perched; they often gave zhraanhs

while perched but almost never gave them in flight. Dozens of times I

saw and heard jays give screlches as they flew along the boundary, then

switch to zhraanhs as soon as they perched, and then resume giving

screlches as soon as they took flight again. The relation between

perched and flight calls gets much more complicated than this, as I

show later.

The number that follows the name of each category of behavior in

the following descriptions is the same number that identifies that

category in Figures 19-22.

Contexts of Perched Calls

As can be seen from Figures 19 and 20, most of the calling that

Scrub Jays did while perched falls into several broad categories: (A)

calls used to make contact with an absent jay, (B) calls used in

reacting to something done by the caller's mate, and (C) calls used in

response to the presence of predators.

Mobbing ground predators (1).-- Scrub Jays on my study site mobbed

housecats (Felis domesticus), coyotes (Canis latrans), the introduced

fox squirrels (Sciurus niger), and humans (usually me). They also

occasionally mobbed perched Great Horned Owls (Bubo virginianus).

Once, in the non-breeding season, I saw a gray fox (Urocyon

cinereoargenteus) walk directly beneath a Scrub Jay perched 2 m up in a

bare bush; the jay watched the fox closely but did not call. I know of

only two instances of predation on my Scrub Jays during 1980. A cat

killed one of the COSMIC juveniles, and (so I was told by a gardener

who saw it) a fox squirrel carried away a VICTORY nestling: the

parents mobbed and even attacked the squirrel, but they could not

prevent it from making off with the nestling.

When the jays had nests, they regularly mobbed me and cats. At

other times of year, they either ignored me and the cats or else left

when we approached too closely.

The jays began scolding me immediately as soon as I came within

40 m or so of the young. On the other hand, the jays remained silent

when humans other than myself stumbled upon their young or wandered

into the general vicinity of their nest. For instance, within one hour

on 8 July the male of GARDEN mobbed me, starting when I got to within

30 m of its fledgling, and then remained silent as a man who strayed

away from a nearby picnic almost stepped on it.

Thus, the jays' first line of defense was silence, but if the

predator gave some indication that it had a good chance of finding the

nest or young, they did what little they could to ward it off as soon

as possible.

Scrub Jays that mobbed me used at least three different calls, and

the calls they used depended upon my distance from the young and the

amount of time I had been near them. Furthermore, the calls that they

used differed consistently between pairs (Fig. 16). At long distances,

the male of GARDEN used shlenks, when I got closer he gave zeep/scolds,

and when I got closer still he shifted to scolds. When I actually

handled his young he gave yet another call--a screechier version of the

scold, which I was never able to record, that sounded like a saw

cutting light sheet metal. The male of VICTORY, the next door neighbor

of GARDEN, gave zhraanhs at long distances, zeeps and zeep/scolds at

intermediate distances, and scolds mixed with occasional weeps at the

closest range. The female of COSMIC gave a call intermediate between

zhraanhs and shlenks at long distances, zeeps and zeep/scolds at

intermediate distances, and scolds at yet closer distances. When I

actually touched their nest, the pair at COSMIC pounded me on the head

with their bills and gave a variant of the scold similar to the one

given by the male of GARDEN.

A typical encounter with breeding Scrub Jays was as follows, as

paraphrased from my field notes:


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11 July 1980. AM. Pass COSMIC nest. The female is perched on a

bush, the male is on the ground. When I'm about 20 m from

the female, she starts giving zhraanh/shlenks and keeps

giving them until I get to about 7 m from her. She then

shifts to zeeps and zeep/scolds. The male doesn't call. I

pass the female; she keeps giving zeeps and zeep/scolds until

I am 20 m away from her; she then stops calling.

In this incident, as in most others, the calling jay did not

revert to the long-distance call type (in this case "zhraanh/shlenks")

when I left after passing the nest, but instead kept using a call from

a distance at which it would not have been used if I had been

approaching instead of leaving. Apparently it was harder for the jay

to calm down than to get excited, if those terms can be used.

Occasionally the calling bird did revert to the long range calls as I

departed, making a nicely symmetrical pattern:

11 July 1980. 0900. Walk past VICTORY nest. The female is not

present. The male gives zhraanhs when I get to within 20 m

from the nest, shifts to zeeps when I get 7 m away, and

continues zeeps until I'm about 20 m away again. I stand

about 20 m away for about 3 min, after which the male resumes


In each pair that scolded me regularly, one bird or the other

consistently did most of the mobbing (Fig. 16). In other pairs, such

as MR, neither bird gave long-range mobbing calls; they instead waited

until I was within a few meters of the nest or young, and then gave


So all of the jays used the same calls for mobbing at close range,

but for some reason, they used several different calls interchangeably

at long distances (though individual callers were always consistent in

which of these they used). This is an example of what I think is one

principle upon which the calling behavior of A. c. obscura is founded,

namely that within certain (even rather narrowly defined) categories of

behavior, some calls do not have specific meanings and seem to be used

interchangeably. What seems to be important, instead, is that the jays

have a collection of calls that they can alternate; the "message" lies

in changing from one call type to another, not in any one call. Of

course, consistency appears to be important for any particular Scrub

Jay. Even though there may be no consistent specific meaning to

shlenks, say, throughout the local population of Scrub Jays, the

consistency with which individual jays used their particular long-range

mobbing calls suggests that the members of each pair, who are after all

the ones that have most reason to pay attention to another's mobbing

calls, agree on or at least learn the meaning of the particular long-

distance call used by their mate.

Why the long-distance mobbing call should differ at all from pair

to pair is not clear to me.

Alone, no intruders, no boundary conflict (2).-- Scrub Jays

usually made no special effort to stay within sight of their mates.

Except during the egg-laying period, when the males followed their

mates closely at all times, the members of a pair sometimes wandered

widely from one another for more than half an hour at a time, but their

movements were not entirely independent of one another. They did tend

to seek one another out after long periods out of one another's view.

Often during such separations one jay called to its mate from a

conspicuous perch, while bobbing and looking out over the territory.

It is this sort of behavior that one would expect to see if the perched

caller was trying to contact its mate; the jay seemed to be looking for

something. Sometimes the calling jay's mate answered, sometimes not.

Here is an example, paraphrased from my field notes:

26 Nov. 1980. 1001. The male and female of VICTORY forage

quietly in trees within 6 m of one another. 1004. The

female flies quietly more than 70 m away in one flight; the

male flies up to a higher perch to watch her go, but does not

follow her, and resumes foraging. The female forages

silently. They are now out of view of one another. 1008.

Female gives several zeeps (bobbing?); no visible response

from the male. 1008:30. Male flies silently, straight, and

rapidly about half way to the female, perches up, looking in

her direction. 1012. The female flies back silently to about

8 m from the male. Both continue to forage here quietly for

10 min.

This is a typically ambiguous example of the relation between

calls and their supposed or possible effects. I cannot say whether the

male flew toward the female because he was drawn to the call, or

whether it was just a coincidence. About the best I can say about such

isolated incidents is that the perched contact calls, such as zeeps,

occurred at about the same time that the birds were separated and

seemed to be looking for one another.

Another example; this time one member of the pair responds to the

first bird that calls:

30 Nov. 1980. 0933. The male and female of VICTORY forage

quietly in their territory at distances from 10 to 20 m

apart. 0937. The male flies silently across river in one

flight of over 100 m; no visible response from the female.

They continue to forage out of view of one another on

opposite sides of the river with no calling. 0940. The

female flies silently across the river and lands 3 m from the

male; they forage together silently here. 0944. The female

flies back across the river silently, more than 100 m,

leaving the male behind. He does nothing. They forage

quietly in their respective places. 0946. The female gives

one zhraanh, then gives a series of zeeps, irregularly spaced

about 5 to 10 sec apart. By the female's third zeep, her

mate replies with zeeps from the other side of the river, not

one-for-one, but at about the same rate as the female. This

goes on for about 1 min, after which the female stops

calling. The male stops soon after. Neither changes

position; they continue to forage quietly. 0950. The female

flies directly and without calling, joins the male. 0953.

The female re-crosses the river to chase three intruders, the

male does nothing; when the female has chased them out of

territory, she stays on her side of the river. 0955. The

female resumes calling to the male with zeeps; this time, the

male responds to her calls one-for-one [i.e., every time the

female gives one zeep the male responds with one zeep, so

that the interval between the female's call and the male's

reply is much shorter (say, 1 sec) than the interval between

any two consecutive calls by the female (from about 5 to 10

seconds]. This goes on for about one minute, then both

resume foraging quietly on opposite sides of the river, out

of view of one another. They continue doing so until at

least 1001, when I lose track of them.

The foregoing examples give a fair enough idea of the three main

types of calling in this category: calling without an answer, calling

with a not very precisely spaced answer, and calling with a precisely

spaced answer. They also serve to show the loose connection between

calling and following. The calling back and forth seems to be a way of

announcing one bird's presence to another, but not necessarily a way of

bringing the two together.

Some jays called often when separated from their mates, and others

called little, if at all. In most pairs only one bird, either the male

or the female, seemed consistently to call when alone (see Table 3).

Table 3 also shows that jays did not reply to the majority of contact

calls from their isolated mates.

Table 3. Use of long-distance contact calls in 10 pairs of Scrub Jays.
The calls included in this tabulation are zeeps, zeep/scolds,
zhraanhs, and shlenks.
The pairs fall roughly into three groups: (1) those in
which the male did most of the calling (EMR to VICTORY), (2)
those in which the male and female called about equally
(GARDEN and MR), and (3) those in which the female did most
of the calling (EBS and ARROYO).

Male Female Female Male
Pair Calls Answers Calls Answers

EMR 14 0 0

COSMIC 10 0 0

LO 4 0 0 -

RC 63 3 4 0

VICTORY 12 4 3 1

GARDEN 3 0 3 0

MR 5 0 5 0

Female EBS II,

Male EBS II 2 0 8 0

Female EBS II,

Male EBS I 0 -6 0

ARROYO 0 9 0

I do not know of any characteristic of any of these pairs that

would explain why they should differ from one another in the way they

used long-range contact calls.

With mate, pause in boundary conflict (3).-- Boundary conflicts

were not continuous. They usually consisted of one or more flights

somewhere near the boundary, punctuated by pauses of up to three or

four minutes. When a jay on one side of the boundary was alone, facing

the opposing birds, the long-distance perched calls that it gave were

obviously given in an attempt to locate the mate. When both members of

a pair were present, however, they called less often during these

pauses; when a jay did so it was sometimes joined in calling by its

mate or by the opposing birds. The function of the calls at these

times is much less clear than when one member of the pair was missing;

the calls given were usually the same as when the mate was gone, that

is, long-range location calls. One possibility is that the amount of

calling during pauses between the flight displays is some measure of

the mate's or the opponent's willingness to keep the skirmish going.

Certainly the most continuous perched calling bouts occurred during the

drawn-out boundary conflicts that accompanied pair formation.

Here is a fairly typical example of the calling that went on

during a conflict of medium length, as paraphrased from my field notes:

9 Sept. 1980. 1113. All four jays of MT and BS perched up at

boundary. The female of MT flies silently and directly away

from the boundary; the male of MT immediately gives shlenks,

then a series of chuks as he perches, watching her go. The

male and female of BS watch, do not call. 1118. All four

are perched up at the boundary again. The male of MT gives

some shlenks, then a series of chuks, while perched and

bobbing. No response from any other jays. 1119. The female

of BS flies parallel to the boundary silently, the male of BS

bobs silently as he watches her. The male and female of MT

watch silently without bobbing. 1120. The male of MT bobs,

gives shlenks. No reply from other three jays. 1121. The

male of MT flies silently away from the boundary, the female

of MT immediately rattles in response. No reaction from the

BS jays.

Alone, finds food (4).-- Scrub Jays that found concentrations of

food called, presumably to their mates, to announce the presence of the

food. Every time that I saw a jay call in this way, it was to alert

its mate to food--peanuts--that I had given it, or to other kinds of

food that had been left by humans. Presumably Scrub Jays also call to

help their mates locate naturally occurring concentrations of food,

most plausibly acorns, but perhaps also local insect outbreaks.

With mate, confronting intruder (5).-- Even when they were close

to their mates, Scrub Jays usually called as a warning or as a way of

alerting their mates when intruders entered their territories.

For example:

21 December 1980. 0845. The male and female of EBS perched

silently in the center of their territory. An unbanded jay

flies in quietly over the ridge, lands in the top of a bush

in EBS' territory. The male of EBS immediately bobs, gives

one zhraanh. The female does nothing. The male then gives a

series of five widely spaced zeeps while bobbing--again no

reply from the female or intruder. The intruder wanders

away. Neither resident chases or follows it.

The elements in this encounter that were typical include the lack

of anything conclusive happening at the end; the residents' willingness

to leave the intruder alone, even though they watched carefully until

it left; and the lack of any noticeable reaction to the male's calls.

This sort of calling may be a way of alerting the female to the

presence of an intruder that she may not have noticed.

Another possibility, about which I can only speculate, is that the

males who called in such situations were inviting the female to give

some sign that they were willing to join the male in expelling the

intruder. I say this because in many cases territory defense was so

obviously a cooperative endeavor. The Scrub Jays called to their mates

when they faced their neighbors alone at the boundary, and they had two

calls, rattles and chuks, that were specialized for use in response to

the mate's defense of the territory. As I will describe in more detail

later, this sort of behavior immediately showed me, and therefore

presumably showed Scrub Jays as well, that there was a pair of jays at

home and paying attention to the duties of territory defense. Scrub

Jays sometimes called in response to other Scrub Jays' calls alone, so

I think that it is plausible that the male in this example was

prompting the female to call, as an indication to the intruder that it

had entered a territory occupied by a mated and vigilant pair.

Alone, confronting an intruder (6).-- Lone Scrub Jays faced with

intruders in their territories often acted in much the same way as lone

Scrub Jays encountering their neighbors at the territory boundary.

They usually gave one of the long-range location calls while bobbing,

apparently trying to recruit the mate to help in expelling the

intruder. This category does not include any calls given by the jays

that were actually chasing intruders.

An example:

9 Mar. 1980. 0825. The male of COSMIC is alone near the nest.

R-IBS, a wandering jay with no known home territory, is

loitering near the nest. The male chases it about 10 m with

weeps; R-IBS flees immediately, but then stops, perches,

faces the male; they stalemate here. The male drops to the

ground directly below R-IBS, digs in the ground with his

bill, thrashing it back and forth through leaves. A short

scramble through the bushes ensues when R-IBS again starts to

leave; again they stalemate at the top of the bushes, 3 m

apart. The male is now facing obliquely away from R-IBS; he

gives six series of chuks with his tail straight down and

closed, his bill pointed up continuously at an angle of about

450, bobbing his whole body up and down. No response from

R-IBS who merely holds still, and the female, who is nowhere

to be seen. After 2 min of this, R-IBS dashes away about 30

m, and the male now chases him with weeps. Here in a tree

they stalemate again, about 10 m apart. Suddenly the female

of COSMIC arrives, landing about 3 m from the male. The male

immediately gives two more series of chuks in the same

posture as before. R-IBS disappears into thick vegetation.

The male and female do not follow; the intruder seems to have


The foregoing incident illustrates several common responses to

intruders: even though the resident birds were plainly dominant to

intruders, they seldom attacked intruders or even started chases.

Instead, they performed various kinds of displacement behavior (bill-

thrashing was the commonest) close to the intruder and often waited

until the intruder fled (as a result of oblique threats or just

waiting), then they chased the intruder.

Alone, confronting neighbors at boundary (7).-- Lone Scrub Jays

confronted by their neighbors near the boundary often tried immediately

to locate their mates by calling to them. Unlike in territory

conflicts in which the mate was present, lone Scrub Jays turned in

toward the centers of their own territories, bobbed deeply with their

tails elevated, and called with one of the long-range location calls.

Altogether they gave the appearance, not just of facing in a certain

direction, but of looking in that direction--a distinction that is

difficult to convey, but an impression that is easy to receive when one

watches the birds. The jay's expression (if you will) at this time was

similar to the intent appearance that they had when looking in the

direction from which unseen Scrub Jays had just given overhead predator

calls. A Scrub Jay that was perched calmly, just happening to face in

a certain direction, usually scanned the landscape with jerky and

unpredictable horizontal head movements, at the rate of about one per

2 sec. These head movements covered an angle of about 1000, so that

the jay probably had something close to a 3600 field of view. When a

Scrub Jay seemed to be looking for something in a particular direction,

however, it usually craned its neck and narrowed the range of its head

movements so as to concentrate on one particular area. Something also

seemed to change in the expression of the jay's eye, a change that I've

never been able to describe objectively.

Here is an example, paraphrased from my field notes, of the

behavior of a lone jay confronting its neighbors and recruiting its


26 Oct. 1980. 1440. The male and female of MT are perched

silently near their common boundary with BS territory. The

female of BS, alone deep in her own territory, sights the MT

birds. She flies more than 50 m directly toward them, with

weeps, and lands opposite them near the boundary. 1440,:30.

The male of MT gives nhyucks in response to her arrival.

1441. The female of BS turns to face toward her own

territory, away from the MT pair. She bobs and calls with

zeeps. No response from MT. 1443. The male of BS arrives

silently; the female of BS stops calling, turns to face the

MT pair. All perch up, looking at one another, exchanging

kuks. 1446. The male of MT flies along the boundary with

screlches. The female of MT immediately rattles in response;

no response from the pair of BS. All perch again. 1446+.

All slowly and silently drift away from the boundary.

Pause during or between nest flights, to wait for mate (8).--

Especially during the early stages of nest building, Scrub Jays made

long, conspicuous, undulating flights, often while calling, to the nest

site or to the rudimentary nest. Jays performed these nest flights to

get their mates to agree on a nest site and to get them involved in

nest-building (see "Nest flights" in "Contexts of Flight Calls"). When

the mate lagged behind, the nest-building jay often stopped short of

the nest or nest-site, turned around, looked in the mate's direction,

and called while bobbing. If the mate still did not follow, the

calling bird rarely continued on to the nest; instead, it either

waited, lost interest in the nest flight, or returned to the mate.

When it returned to the mate, it sometimes kept the nest material that

it had been carrying and tried to pass it to its mate. At other times

it tried to pass any small object that happened to be nearby.

Most of the examples that I have of calling during pauses in nest

flights come from RC territory, which I watched almost continuously

during the breeding season.

An example:

27 Mar. 1980. 1027. I find the male of RC adding sticks to the

first nest of the season. He is alone near the nest, the

female is nowhere in view. The male is obviously looking for

her. He perches up, bobbing, makes three undulating zhraanh

flights toward or past the nest tree, never actually going to