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Focus on Florida : Ectoparasite content of swallow-tailed kite (Elanoides forficatus) nests

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Focus on Florida : Ectoparasite content of swallow-tailed kite (Elanoides forficatus) nests
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Andrews, John
Meyer, Kenneth D.
Zimmerman, Gina
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Gainesville, Fla.
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University of Florida
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The objectives of this study were to 1) identify common commensal organisms in six nests of Swallow-tailed Kites (Elanoides forficatus), 2) extract and quantify ectoparasites, and 3) determine if unsuccessful nests contained greater numbers of ectoparasites than successful nests. Nest materials were processed in Berlese funnels, then sorted and examined further by hand. The resulting data were analyzed using SAS statistical software. Among the parasitic species (i.e., not including Soldier fly pupae, Stratiomyidae), significantly greater numbers were found in nests that failed than in those that fledged young. Ectoparasites have been shown to affect various aspects of reproduction for many bird species, yet little research has been done on nest parasites in raptors or their effects on breeding. Highly infested nests are probably avoided by breeding adult Kites all together.

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Ectoparasite Content of Swallow-tailed Kite (Elanoides
forficatus) Nests

John Andrews, Kenneth D. Meyer, and Gina Zimmerman
College of Agriculture and Life Sciences, University of Florida and The Avian Research and
Conservation Institute

The objectives of this study were to 1) identify common commensal organisms in six nests of Swallow-tailed Kites (Elanoides
forficatus), 2) extract and quantify ectoparasites, and 3) determine if unsuccessful nests contained greater numbers of ectoparasites
than successful nests. Nest materials were processed in Berlese funnels, then sorted and examined further by hand. The resulting data
were analyzed using SAS statistical software. Among the parasitic species (i.e., not including Soldier fly pupae, Stratiomyidae),
significantly greater numbers were found in nests that failed than in those that fledged young. Ectoparasites have been shown to affect
various aspects of reproduction for many bird species, yet little research has been done on nest parasites in raptors or their effects on
breeding. Highly infested nests are probably avoided by breeding adult Kites all together.


Introduction

Understanding the influence of ectoparasites on species
of conservation concern is necessary for effective
management of such species. In recent years, the study of
parasites of Swallow-tailed Kites (Elanoides forficatus) has
gained importance in conservation planning for this
Neotropical hawk. Most studies of ectoparasitism in birds
have focused on colonial species and those that are easily
captured, e.g., ground dwelling or captive birds (Loye and
Zuk 1991). In general, parasitology is understudied in
raptors due to the difficulties in studying and capturing
them (Zimmerman 2004).
Ectoparasites have a wide range of negative effects on
their avian hosts, including nest and nestling abandonment
(Duffy 1983), reduced survival and slower growth of
nestlings (Merino and Potti 1995, McKilligan 1996, Ramos
et al. 2001), and reduced quality and quantity of offspring
(Moss and Camin 1970, Brown and Brown 1986). High
loads of ectoparasites can cause nest abandonment in some
species (Loye and Carroll 1998) and can sometimes cause
species that frequently re-use nest sites to avoid infested
nests all together (Ontiveros et al. 2008). No studies thus
far have specifically focused on the parasite content of
Swallow-tailed Kite nests.
Swallow-tailed Kites are rare neo-tropical migrating
raptors that breed in the U.S. The range of this species has
shrunk considerably since the late 1800s, and they
currently breed in only seven states (Meyer 1995).
Currently, one of the biggest threats that Shallow-tailed
Kites face is the lack of suitable nesting and foraging
habitat. Increased agriculture, logging, and shooting most
likely led to the initial decline of these birds (Meyer 1995).
One of the U.S. strongholds of nesting Swallow-tailed
Kites is in Levy County, Florida, where they frequently
nest in Loblolly Pines (Pinus taeda, Coulson 2002) and


other commercial timber species. Swallow-tailed Kite nest
structures are infrequently re-used from year to year, unlike
those of many other raptors, and a possible reason could be
parasite loads within old nests (Brown and Brown 1986,
Ontiveros et al. 2008). Many ectoparasites can overwinter
in nests (Brown and Brown 1996); however, it is unknown
whether this is the case with the ectoparasites in nests of
the Swallow-tailed Kite.
To investigate some of these issues, we examined the
content of six formerly used Swallow-tailed Kite nests
from the 2008 breeding season and extracted and sorted
parasites and other organisms to describe commensal
organism contents and determine parasite loads within
nests. Commensal organisms are those living in nests
without harming the nesting organism. The breeding
outcome of all nests was known. Our objectives were to 1)
identify common commensal organisms in six nests of
Swallow-tailed Kites, 2) extract and quantify ectoparasites,
and 3) determine if unsuccessful nests contained greater
numbers of ectoparasites than successful nests. We
hypothesize that parasites will be present in nests and that
parasite loads would be greater in unsuccessful nests than
those of successful nests.

Methodology

Six Swallow-tailed Kite nests were removed from Levy
County breeding sites in Florida in February-March 2009
prior to the arrival of breeding adults. Three nests
successfully fledged young and three failed. Two
successful nests fledged two chicks and the third fledged
one chick. Nest height in trees ranged from 21 to 24.7
meters. All nests were in either Loblolly Pines or Longleaf
Pines (Pinus palustris). The nests were composed of
Spanish Moss (Tillandsia usneoides), pine needles, small
cypress (Taxodium spp.), and/or oak (Quercus spp.) twigs


University of Florida I Journal of Undergraduate Research I Volume 12, Issue 2 I Spring 2011





JOHN ANDREWS, KENNETH D. MEYER, AND GINA ZIMMERMAN


(Meyer 1995). Each extracted nest was double bagged in
black plastic trash bags to retain as many organisms as
possible. Mean nest mass was 1.25 kg (range: 0.835 to
1.672 kg). Mean length (i.e., longest axis) was 23.2 cm,
mean width was 36.2 cm, and mean height (i.e., top to
base) was 47.2 cm.
For each nest, all materials, except for small amounts of
fine debris, were divided into five Berlese funnels on the
same day of extraction (Proctor and Owens 2000). Berlese
funnels consisted of a light source over a collected
substrate (usually soil) from which the light forces
organisms that avoid light downward through the funnel
and a mesh barrier into a preservative (Gullan and Granstor
2010). Our specimens fell into plastic jars under the
funnels containing a 70% ethyl alcohol solution. We
emptied jars into petri dishes and examined contents under
a dissecting microscope to record total organism counts
within common order categories. We left nest materials in
the funnels for 48 hours before we removed and bagged
them again and then stored them in a refrigerator. Nest
materials from the funnels and the small amount of debris


and detritus withheld from the funneling process were later
sifted through by hand with tweezers for insects and any
other organisms still present. Sections were examined
separately within a large white tray (30 x 20 cm).
Specimens were organized into six groups based on the
five most common taxonomic orders represented plus a
category for the casings of Soldier fly pupae
(Stratiomyidae).
Organisms for both sifted and funneled groups were
identified to no lower than order due to the high volume of
specimens and the fact that many specimens were in larval
or pupal stages (Table 1).
The orders represented by the most common specimens
were used as the categories in the final analyses. We also
compared parasite numbers between successful and
unsuccessful nests. We calculated means and standard
errors and performed paired t-tests using SAS v 9.1 (SAS
Institute 2003) to compare numbers of soldier fly pupae
and all other parasites numbers between successful and
unsuccessful nests.


Table 1: Orders of Specimens Found in Six Swallow-Tailed Kite Nests from the 2008 Breeding Season in Florida


Successful Unsuccessful

Arthropod orders Procedure Mean SE Mean SE t - value p - value


Acari (with outlier)* F 18.67 4.10 774.00 725.54 1.04 0.18

Acari (without outlier)* 18.67 4.10 48.50 12.50 2.78 0.03**

Araneae F 6.33 5.36 8.00 6.51 1.05 0.46

Blattaria HS/F 7.67 6.23 6.67 5.70 0.105 0.46

Coleoptera* HS 27.33 17.37 23.00 6.03 0.185 0.41

Collembola F 20.00 9.71 13.67 13.67 1.37 0.15

Diptera* HS/F 40.33 19.20 25.67 19.00 0.508 0.31

Soldierfly Pupae* HS 89.33 87.84 394.33 140.42 1.84 0.07

Hemiptera HS 2.67 1.45 3.67 0.67 1.00 0.21

Hymenoptera* F 45.33 22.93 71.00 34.12 0.812 0.25

Lepidoptera HS 3.67 2.33 19.00 13.50 0.997 0.21

Psocoptera F 24.67 12.81 16.33 6.33 1.24 0.20

Thysanoptera F 11.33 4.84 25.67 12.00 1.28 0.16


Note. HS=hand sifted and F=funneled specimens. * indicates orders that were used in further analysis due to their potential as ectoparasites. Paired t-
tests were conducted between successful and unsuccessful nests to obtain t and p values. Two tests were conducted for the order Acari, with and
without an extreme outlying value. ** denotes significant p-values (p<0.05).


University of Florida I Journal of Undergraduate Research I Volume 12, Issue 2 I Spring 2011
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ECTOPARASITE CONTENT OF SWALLOW-TAILED KITE (EL4AVOIDES FORFICATUS) NESTS


Results

Commensal Organism Description. We found a high
number of soldier fly pupae within all nests and, after
parasites, these were the most common organisms found,
with a mean of 241.83 � 100.69. The mean number of
pupae for successful nests was 89.3 � 87.84 (N=3) versus
394.3 � 140.42 (N=3) for unsuccessful nests. Although
pupae numbers did not differ significantly between
successful and unsuccessful nests (t=1.84, df=4, p=0.07),
greater numbers of soldier fly pupae were found in
unsuccessful nests (Figure 1). Hymenopterans, mostly ants,
were the next most common group with a mean of 58.17 �
19.26. Dipterans and Coleopterans, some of which can be
parasitic, were the next most common specimens with
means of 33.00 � 12.51 and 25.17 � 8.28, respectively.

600

500

A n n\ -----------------------------


300 *


200

100


Successful Unsuccessful

Figure 1: Mean number of Soldier fly pupae found in successful (N=3)
and unsuccessful (N=3) Swallow-tailed Kite nests in Florida, 2009. Bars
represent one SE.

Ectoparasite Description and Comparisons. We
found a total of 2,378 parasite specimens of the Acari order
(mites, ticks) in all six nests. The mean number of Acarian
specimens per nest was 396.33 � 365.80. One of the
unsuccessful nests had a count of 2,225 Acarian specimens,
and this number is most likely an outlier, since the next
highest count of an unsuccessful nest was 61. We
hypothesized that greater numbers of parasites would be
found in unsuccessful nests. In order to compare the
Acarian numbers between nest success categories, we
excluded the nest with the outlying value from analysis to
achieve a more equal variance. After this was done, the
mean number of Acarian specimens within unsuccessful
nests (N=2, mean=48.5 + 12.5) was significantly greater
than those in successful nests (N=3, t=2.78, df=3, p=0.03;
Figure 2).

Discussion

Transmission of ectoparasites among Swallow-tailed Kites
is probably accomplished by direct contact through social
behaviors, such as nesting and communal roosting.


Swallow-tailed Kites are highly social raptors, and their
communal roosts may contain over 3,000 individuals
(Meyer 1998), providing a plethora of habitat choices for
searching ectoparasites. However, the composition and
behavior of nest dwelling parasites and mites in Swallow-
tailed Kite nests is unknown. Generally, nest mites reside
and/or breed in nests and only approach the hosts to feed
(Proctor and Owens 2000). This study is one of the first to
explore the nest-substrate parasites of the Swallow-tailed
Kite to determine taxa, presence/absence, and prevalence
and to identify and quantify other common organisms
within nests.

70
60
7 0 ------------------------


Succesful


Unsuccessful


Figure 2: Mean number of Acarian specimens found in successful (N=3)
and unsuccessful (N=2) Swallow-tailed Kite nests in Florida, 2009. Bars
represent one SE.

Due to small sample sizes coupled with high variability
among specimen counts, we had considerable variability in
the abundance of specific groups (e.g., Soldier fly pupae
and Acarians). Examining more nests may resolve these
problems and allow stronger conclusions on ectoparsite
relationships with Swallow-tailed Kites in future research.
Identifying parasites to species is also critical to
understanding the interplay of their ecology with that of
their hosts. Previous ectoparasite studies on Swallow-tailed
Kites only extracted specimens from the bird's body, not
from nest materials, and only one parasitic species of mite
was found in those studies (Zimmerman 2004).
We found high numbers of ants (Hymenoptera), beetles
(Coleoptera), and flies (Diptera) in nests. Some ant species,
like the red imported fire ant (Solenopsis invicta), are
known to depredate birds, particularly in their nests, and
may cause population declines (Allen et al. 2004), but we
are unaware of reports on ant predation of raptors. The ants
we collected most likely arrived after the nests were
abandoned to take advantage of feces, prey, and other
materials remaining in the nests. Beetles are among the
most common organisms found in many arthropod studies
of bird nests (Kristofik et al. 2007), and in high abundances
some beetles can be parasitic (Philips and Dindal 1977).
However, we found no parasitic beetles in nests.
We found very few Dipteran specimens, which may be
due to the Swallow-tailed Kites' nesting tree preference.
Kites frequently nest in Long leaf or Loblolly pines (Meyer
2004), and these aromatic trees can provide protection


University of Florida I Journal of Undergraduate Research I Volume 12, Issue 2 I Spring 2011





JOHN ANDREWS, KENNETH D. MEYER, AND GINA ZIMMERMAN


from flies and other insects (Levin 1971). A negative
relationship was found between Dipterans and the presence
of pine greenery in the Bonelli's Eagle (Ontiveros et al.
2008). Interestingly, this may also explain the high number
of immature Soldier fly pupae in nests, as some resins from
green plants can inhibit growth phases of many arthropods
(Clark and Mason 1988). Soldier flies are detritivores, and
their abundance could also be explained by the ample food
that would be present in decomposing nests. Whether these
flies inhabit nests during breeding attempts is unknown,
but it is unlikely that they would be anything but an
annoyance to breeding kites.
Substantial numbers of Acarian specimens were present
in kite nests well after the kite's breeding season had
ended. Indeed, we found significantly more ectoparasites in
failed nests (Figure 3). Ectoparasites are by definition
harmful to their hosts (Loye and Carroll 1998), and
Acarians were by far the most abundant organisms
collected (Figure 3). Ectoparasites have been shown to
cause reduced growth rates in young nestlings (Eggert and
Jodice 2008) and reduced quality and quantity of offspring
(Moss and Camin 1970, Brown and Brown 1986, Delop
and Moller 1993). If ectoparasites are negatively affecting
Swallow-tailed Kite reproduction, efforts need to be
directed toward managing these old nest sites.


0.009.


0.069






0.472


u. )20
u.u24


Figure 3: Proportions of invertebrate fauna found
Kite nests in Florida, 2009


* Lepidoptera
" Diptera
* Coleoptera
SBlattaria
* Hemiptera
* Diptera Pupae
* Collembola
* Psocoptera
Acari
* Thysanoptera
* Hymenoptera
* Araneae

in six Swallow-tailed


Finding proper nesting habitat can be difficult for
Swallow-tailed Kites, making older nests particularly
valuable if we can encourage re-use by returning breeders.
However, nesting in Florida frequently occurs on pine


plantations where nest stands are regularly managed for
timber (Meyer & Collopy 1995), and all nests in this study
were extracted from land owned by a timber company in
Central Florida. Old nests that are present from previous
seasons are re-used 15-20% of the time in Florida (Meyer
1995) and may contain high numbers of other organisms
(Brown and Brown 1996). However, it may be useful to
perform nest fumigation as a management practice to
increase chances of nest reuse and success. Nest
fumigation has been used in colonial birds and has been
shown to increase reproductive success in colonial nesting
birds (Delop and Moller 1993). Nest fumigation has also
been tested on a few Swallow-tailed Kite nests with some
promising results (Meyer & Zimmerman, unpublished
data). In one instance, a breeding pair reoccupied an old
kite nest that was fumigated. Although this breeding
attempt failed, re-use of the nest occurred after fumigation.
Re-use of a fumigated nest could suggest that there is some
kind of nest evaluation of invertebrate content prior to
breeding. Some birds of prey are thought to evaluate
ectoparasite content and have been known to avoid old
nests due to ectoparasites within it (Ontivaros et al. 2008),
and this may be happening with Swallow-tailed Kites as
well. We suspect that kites avoid nests with high
incidences of invertebrates and recommend further
investigation into ectoparasite content of Swallow-tailed
Kite nests. Nest fumigation as a means to reduce
ectoparasite content of nests may be a way to increase re-
use and breeding success of Swallow-tailed Kites in
Florida.

Acknowledgments

This study was funded by the University of Florida's
Scholars Program. We thank Dr. Philip Kaufmann and Lois
Wood of the Entomology and Nematology Department,
University of Florida; Dr. Emilio Bruna of the Wildlife
Ecology & Conservation Department, University of
Florida; and Serena Bloom and Marjesca Brown for
assistance in sorting and identifying specimens. The study
of Swallow-tailed Kite nesting ecology that provided our
nest sample was funded by grants to K. D. Meyer from the
Florida Fish and Wildlife Conservation Commission and
the National Fish and Wildlife Foundation.


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University of Florida I Journal of Undergraduate Research I Volume 12, Issue 2 I Spring 2011





ECTOPARASITE CONTENT OF SWALLOW-TAILED KITE (ELANOIDES FORFICATUS) NESTS


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University of Florida I Journal of Undergraduate Research I Volume 12, Issue 2 I Spring 2011