Use of appeasement display and recruitment by an adult Striated Caracara (Phalcoboenus australis) to overcome territorial defense

Full text

Use of appeasement display and recruitment by an adult
Striated Caracara (Phalcoboenus australis) to overcome
territorial defense
Authors: Harrington, Katie J., and Meiburg, Jonathan
Source: The Wilson Journal of Ornithology, 133(1) : 127-131
Published By: The Wilson Ornithological Society
URL: https://doi.org/10.1676/20-00060
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The Wilson Journal of Ornithology 133(1):127–131, 2021 DOI: 10.1676/20-00060
Use of appeasement display and recruitment by an adult Striated Caracara
(Phalcoboenus australis) to overcome territorial defense
Katie J. Harrington
1
* and Jonathan Meiburg
2
ABSTRACT—Adult animals across many taxa use
appeasement signaling to minimize or avoid costly conflict
in social settings by jointly communicating their consent to
defer and an interest to remain. When foraging, however,
appeasement may not be enough to gain access to a resource
controlled by a dominant conspecific. In this case,
conspecific recruitment can shift the social dynamic, so the
resource becomes accessible to all. Striated Caracara
(Phalcoboenus australis) are Near Threatened scavenging
falconids that breed in high densities on the extreme
southern coasts of South America and the Falkland
Islands. While juvenile caracaras recruit other caracaras to
concentrated food resources, neither recruitment nor
appeasement has been reported in adults. Here we describe
a female adult caracara that appeared to use both
appeasement signaling and recruitment to access food in
another pair’s defended territory on New Island, Falkland
Islands. Appeasement and recruitment calls are one of
several behavioral parallels that researchers have noted
among Striated Caracara, Common Raven (Corvus corax),
and Kea (Nestor notabilis). Although falconids are not
typically considered in comparative studies of avian
cognition and social behavior, we suggest that caracaras
merit further attention, especially given their relationship to
parrots in the clade Eufalconimorphae. Received 11 May
2020. Accepted 9 June 2021.
Key words: Eufalconimorphae, Falconidae, foraging,
scramble competition, territory, vocal repertoire.
Uso de un despliegue de apaciguamiento y reclutamiento
de un adulto del caracara Phalcoboenus australis para
sobreponerse a defensa territorial
RESUMEN (Spanish)—Los adultos de muchos taxa usan se ˜
nales
de apaciguamiento para minimizar o evitar el costoso conflicto en
situaciones sociales, comunicando su consentimiento para ceder y un
1
Acopian Center for Conservation Learning, Hawk
Mountain Sanctuary, Orwigsburg, PA, USA
2
Dripping Springs, TX, USA
* Corresponding author: katiejharrington@gmail.com
127Short Communications
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inter´
es de permanecer. Sin embargo, cuando esta´n forrajeando, la
se˜
nal de apaciguamiento podr´
ıa no ser suficiente para tener acceso a
un recurso controlado por un conespec´
ıfico dominante. En este caso,
el reclutamiento podr´
ıa modificar la dina´mica social para que el
recurso est´
e disponible para todos. Los caracaras Phalcoboenus
australis son falc´
onidos carro˜
neros Casi Amenazados que anidan a
altas densidades en las costas extremas del sur de Sudam´
erica y las
Islas Malvinas. Si bien los caracaras juveniles reclutan a otros
caracaras hacia recursos alimenticios concentrados, dicho
reclutamiento y apaciguamiento no se han reportado en adultos.
Aqu´
ı describimos una hembra adulta de caracara que parece usar
ambos, se˜
nales de apaciguamiento y reclutamiento, para acceder a
alimento en un territorio bajo defensa de otra pareja en Isla
Goicoechea, Islas Malvinas. Los llamados para apaciguar y reclutar
son uno de varios paralelos conductuales que los investigadores han
notado entre este caracara, el cuervo (Corvus corax) y el kea (Nestor
notabilis). Aunque los falc´
onidos no son t´
ıpicamente considerados
en estudios comparativos de capacidad cognitiva y comportamiento
social aviar, sugrimos que estos caracaras merecen mayor atenci´
on,
especialmente dada su relaci´
on con los loros en el clado
Eufalconimorphae.
Palabras clave: competencia trepadora, Eufalconimorphae,
Falconidae, forrajeo, repertorio vocal, territorio.
Adult animals across many taxa use appease-
ment signaling to minimize or avoid costly conflict
in social settings by jointly communicating their
consent to defer and an interest to remain (Signe
and Van Schaik 2000). For example, rhesus
macaque (Macaca mulatta) navigate socially
dominant conspecifics by silently baring their
teeth, and meerkat (Suricata suricatta) grovel at
the feet of dominant females (Kutsukake and
Clutton-Brock 2006). These social tactics also
have been documented in birds, as when juvenile
Kea (Nestor notabilis) hunch in the presence of
dominant adult males to avoid displacement at a
feeding event (Diamond and Bond 1991), or when
Common Guillemot (Uria aalge) use a ritualized
walking behavior to appease neighbors while
moving through high-density colonies (Birkhead
1978).
When foraging, however, appeasement may not
be enough to gain access to a resource controlled
by a dominant conspecific. In this case, conspecific
recruitment is sometimes used to shift the social
dynamic from contest to scramble competition, in
which the resource becomes accessible to all
(Nicholson 1954, Parker 2000). For example,
juvenile Common Raven (Corvus corax) attempt-
ing to scavenge at carcasses produce recruitment
calls that attract conspecifics who overwhelm
territorial adult pairs (Heinrich 1988).
Striated Caracara (Phalcoboenus australis; here-
after ‘‘caracaras’’ ) are Near Threatened scavenging
falconids that breed in high densities on the
extreme southern coasts of South America and
the Falkland Islands (Balza et al. 2017, Reeves et
al. 2018, BirdLife International 2020). During the
austral summer, they forage in colonies of
breeding seabirds; in winter, when most seabirds
migrate offshore, caracaras consume invertebrates,
penguin and seal excreta, and bonanzas of carrion
(e.g., carcasses of Gentoo Penguin [Pygoscelis
papua], cast sheep [Ovis aries], and pinnipeds;
Strange 1996, Rexer-Huber and Bildstein 2013).
While juvenile caracaras recruit other caracaras to
concentrated food resources (Strange 1996, Autilio
et al. 2019), this behavior has not been reported in
adults. Here we describe an adult caracara that
appeared to use both appeasement signaling and
recruitment to access food in another pair’s
defended territory.
New Island (51843012 00 S, 618180000 W) is a 22
km
2
formerly farmed nature preserve in the
Falkland Islands. Since becoming a preserve in
1972, its breeding population of caracaras has
rebounded from 0 to over 80 pairs, reaching a
density of 4.3 nests/km
2
. Caracara age classes are
easily defined by plumage and bill color (Strange
1996), and much of the coastline is occupied by
territorial adult pairs (Catry et al. 2008). Two
wardens who live at a central settlement are the
island’s only human inhabitants. GPS data indicate
an adult pair of banded caracaras (M30 female and
M31 male, hereafter the ‘‘M pair’’ ) includes the
settlement in their territory (KJH, 2019, unpubl.
data), which they defend against intruders and in
which they have nested and fledged young (G.
Hazell, New Island Warden, 2020, pers. comm.).
On 9 August 2019 (austral winter), during a
trapping effort (see Harrington et al. 2018 for
methods) in the M pair’s territory, we observed an
adult female intrude and use appeasement displays
and recruitment calls to access food. Prior to
opening the trap, we had surveyed an 800 m radius
around the settlement. The only birds present were
the M pair and the neighboring pair, H37 and H38
(hereafter, the ‘‘H pair’’), who hold an adjacent
territory (KJH, 2019, unpubl. data).
At 0940 h (GMT-3), we opened the trap. After 2
min, M30 approached, fed, and then defended the
bait against 2 circling Turkey Vultures (Cathartes
aura). At 0950 h, we trapped and released M30,
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who remained close to the trap. Meanwhile, 2
unbanded caracaras, a juvenile and an adult,
landed within 20 m of the trap. The H pair visibly
remained 150 m from the trap and performed a
territorial ‘‘duetting’’ display with heads thrown
back while calling simultaneously (Strange 1996).
At 1001 h, we trapped and banded the juvenile
female as R30. We next trapped and banded the
adult female as R31, while the M pair duetted 40
m away. Both R30 and R31 were trapped within 1
min of approaching the bait, and neither was able
to feed before ensnaring their tarsus.
When we released R31 at the trap, she
immediately postured with her back hunched,
body feathers ruffled, head bowed, and wings
spread downward (Fig. 1), and began uttering a
soft, high-pitched, intermittent vocalization, a
behavior commonly seen in fledgling Striated
Caracara and Northern Crested Caracara (Caraca-
ra cheriway) when begging for food from their
parents (KJH, pers. obs.; J. Morrison, Trinity
College, 2020, pers. comm.). The M pair
approached and supplanted R31, who flew to a
perch within 15 m of the trap.
M30 approached R31 again and made brief
agonistic contact. R31 flew off with one talon
dangling slightly, then returned to within 2 m of
the trap and resumed the ‘‘begging’’ call and
posture for over 2 min, while the M pair remained
at 40 m distance, duetting.
We stood atop the trap to prevent R31 from
being recaptured. R31 walked around the trap
begging and posturing, then flew to a perch within
5 m of the trap and switched to a loud, repeating
cry we recognized as a ‘‘recruitment’’ call (Strange
1996, Autilio et al. 2019). Within 60 s, 9 additional
unbanded adult caracaras arrived, along with one
unbanded subadult and R30. We moved to stand 5
m from the trap. The newly arrived birds swarmed
the trap and consumed the bait. The M pair joined
in, and we observed no agonistic interactions
between birds as they fed. At 1040 h we closed
and removed the trap. By 1052 h, M30 and M31
had chased away all birds except R30 and R31.
Striated Caracara throughout the Falkland
Islands show little fear of humans (Strange
1996), and the presence of observers at or near
the trap during trapping efforts does not appear to
deter them (Harrington et al. 2018). We acknowl-
edge that the trap is an artificial situation, but their
behavior at traps appears similar to their behavior
at naturally occurring carcasses of injured Upland
Geese (Chloephaga picta) and cast sheep. Fur-
thermore, we observed another instance of adult
begging on New Island 5 d prior, in which a
banded adult female (G6) attempting to forage in a
Gentoo Penguin colony assumed the same posture
as R31 and was tolerated by an adult pair who had
previously been defending against intruders (Fig.
2).
R31’s glossy-black plumage, white terminal tail
band, pale striations on head and neck, yellow
legs, and silver bill indicated that she was an adult
of breeding age. Her sex was later confirmed via
DNA analysis (following the methods in Morrison
1999). Many adult female birds perform begging
displays for several reasons, although they do so
primarily during the breeding season to signal
Figure 1. Adult female R31 calling and displaying in the
appeasement posture: head bowed, back hunched, wings
held away from the body. New Island, Falkland Islands, 9
August 2019. Photo by K. Harrington.
Figure 2. Adult female G6 (left) performing appeasement
posture in the presence of territorial adult pair (right) at
Gentoo Penguin colony. New Island, Falkland Islands, 4
August 2019. Photo by K. Harrington.
129Short Communications
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nutritional need (Ellis et al. 2009). As this occurred
outside the breeding season, we suggest that R31’s
most likely motivation was ‘‘appeasement’’ in
which she signaled to avoid conflict (Lorenz 1935,
Heinrich et al. 1993, Ellis et al. 2009). Juvenile
Common Raven, when attacked by dominant
adults, perform a similar submissive display and
begging call, with head bowed, feathers fluffed,
and wings spread (Heinrich 1988, 1989).
We speculate that R31, like a juvenile raven,
was acknowledging her subordinate status and
signaling to the M pair that she was not an
immediate threat so she could be permitted to feed.
While she may have been a floater frequenting this
territory (sensu Smith et al. 1978), it is also
possible that she was seasonally territorial; al-
though New Island appeared to support a similar
number of adult birds as in the previous summer,
an island-wide survey revealed fewer pairs main-
taining territories through the winter (KJH, unpubl.
data). It is also possible that R31 was a previous
offspring of the M pair, and thus perhaps more
likelytoshowbeggingbehaviortowardher
parents, since Striated Caracara are long-lived
birds (at least 12 years old in the wild [KJH, 2020,
unpubl. data] and 32 in captivity [A. Wallace,
Falconry and Me, 2020, pers. comm.]) and our
survey data suggests site fidelity among females
(KJH, 2019, unpubl. data). Ravens show long-term
memory of group members and can distinguish
affiliates from nonaffiliates (Boeckle and Bugnyar
2012), although further research is needed to
understand these capabilities in Striated Caracara.
We also surmise that R31’s subsequent recruit-
ment behavior may have been a response to our
guarding the trap. Her recruitment call, function-
ally similar to that of juvenile Common Raven
recruitment calls to a carcass (Heinrich 1989), and
the swift response of conspecifics, suggests
caracaras are aurally observant and primed to take
advantage of sudden feeding opportunities sig-
naled by this call. We also note that the
neighboring territorial H pair, though visible, did
not respond to R31’s recruitment call. This may be
evidence of the ‘‘dear enemy effect’’ (Fisher 1954),
a phenomenon in which territorial neighbors
respect territorial boundaries, which would suggest
that the newly arrived birds were not holding
territories adjacent to the M pair. Prior to these
observations, we had observed juvenile Striated
Caracara recruiting at food sources, but we had
never seen adults use both appeasement and
recruitment to overcome a territorial pair.
We also note the similarity of R31’s behavior,
not only to ravens, but to the ‘‘hunch’’ display used
by juvenile Kea to appease dominant conspecifics
(Diamond and Bond 1991), one of several
behavioral parallels that researchers have noted
between these 2 species (Rexer-Huber and Bild-
stein 2013, Autilio et al. 2019). Despite their close
relationship to parrots in the recently defined clade
Eufalconimorphae (Suh et al. 2011), falconid birds
are not typically considered in comparative studies
of avian group dynamics, social intelligence, and
cognitive evolution (i.e., Emery and Clayton 2004,
Guti´
errez-Iba´ ˜
nez et al. 2018). We suggest that
caracaras, whose lineage is basal to the widespread
‘‘true’’ falcons of the genus Falco, merit further
attention. Recent studies of social learning and
behavior in Chimango Caracara (Phalcoboenus
chimango; Biondi et al. 2010, Solaro and Sarasola
2019) and group dynamics in Northern Crested
Caracara and Striated Caracara (Dwyer and
Cockwell 2011, Dwyer 2014, Dwyer et al. 2018)
suggest that caracaras could show similar social
behavior and cognitive abilities to parrots and
crows, including social learning and object play
(Diamond and Bond 2003, Miller et al. 2014).
Striated Caracara’s high density, sociality, ap-
proachability, and behavioral flexibility (sensu
Mayr 1974) make them ideal candidates for further
study, and we suggest that research into their social
landscape and cognitive skills could shed light on
the ancestral cognitive abilities of their clade.
Acknowledgments
Funding for this study was provided by Falklands
Conservation, the Falkland Islands Government Environ-
mental Studies Budget, the John Cheek Trust, and Hawk
Mountain Sanctuary. We thank the Falkland Islands
Government Environmental Planning Department for pro-
viding permission to work on the islands and the New Island
wardens, Alec and Giselle Hazell, for being gracious hosts
and providing logistical support during our stay. We thank
K. Bildstein for initiating Hawk Mountain Sanctuary’s
longitudinal study of Striated Caracara in the Falklands. We
also thank J. Morrison, J. Dwyer, A. Bond, and 2
anonymous reviewers for providing critical comments that
improved an earlier version of this manuscript. All research
was conducted in accordance with the Falkland Island
Government Conservation of Wildlife and Nature Ordinance
under Research License No. R22/2015. This is Hawk
Mountain Contribution to Conservation Science No. 349.
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Literature cited
Autilio AR, Bechard MJ, Bildstein KL. 2019. Social
scavenging by wintering Striated Caracaras (Phalco-
boenus australis) in the Falkland Islands. Behavioral
Ecology and Sociobiology. 73:27.
Balza U, Lois NA, Raya Rey A. 2017. Status and
reproductive outcome of the breeding population of
Striated Caracaras (Phalcoboenus australis) at Franklin
Bay, Staten Island, Argentina. Wilson Journal of
Ornithology. 29:890–898.
Biondi LM, B´
o MS, Vassallo AI. 2010. Inter-individual and
age differences in exploration, neophobia and problem-
solving ability in a Neotropical raptor (Milvago
chimango). Animal Cognition. 13:701–710.
BirdLife International. 2020. Species factsheet: Phalcoboe-
nus australis [cited 28 Apr 2020]. http://www.birdlife.
org
Birkhead TR. 1978. Behavioural adaptations to high density
nesting in the Common Guillemot Uria aalge. Animal
Behaviour. 26:321–331.
Boeckle M, Bugnyar T. 2012. Long-term memory for
affiliates in ravens. Current Biology. 22:801–806.
Catry P, Lecoq M, Strange IJ. 2008. Population growth and
density, diet and breeding success of Striated Caracaras
Phalcoboenus australis on New Island, Falkland
Islands. Polar Biology. 31:1167–1174.
Diamond J, Bond AB. 1991. Social behavior and the
ontogeny of foraging in the Kea (Nestor notabilis).
Ethology. 88:128–144.
Diamond J, Bond AB. 2003. A comparative analysis of
social play in birds. Behaviour. 140:1091–1115.
Dwyer JF. 2014. Correlation of cere color with intra- and
interspecific agonistic interactions of Crested Caraca-
ras. Journal of Raptor Research. 48:240–247.
Dwyer JF, Cockwell SG. 2011. Social hierarchy of
scavenging raptors on the Falkland Islands, Malvinas.
Journal of Raptor Research. 45:229–235.
Dwyer JF, Fraser JD, Morrison JL. 2018. Evolution of
communal roosting: A social refuge–territory prospect-
ing hypothesis. Journal of Raptor Research. 52:407–419.
Ellis JM, Langen TA, Berg EC. 2009. Signalling for food
and sex? Begging by reproductive female White-
throated Magpie-Jays. Animal Behaviour. 78:615–623.
Emery NJ, Clayton NS. 2004. Comparing the complex
cognition of birds and primates. In: Rogers LJ, Kaplan
G, editors. Comparative vertebrate cognition: Are
primates superior to non-primates? New York (NY):
Springer; p. 3–55.
Fisher J. 1954. Evolution and bird sociality. In: Huxley J,
Hardy AC, Ford EB, editors. Evolution as a process.
London (UK): Allen & Unwin; p. 71–83.
Guti´
errez-Ib´
a˜
nez C, Iwaniuk AN, Wylie DR. 2018. Parrots
have evolved a primate-like telencephalic-midbrain-
cerebellar circuit. Scientific Reports. 8:1.
Harrington KJ, Pole-Evans S, Reeves M, Bechard M,
Bobowski M, et al. 2018. Seasonal micro-migration in
a farm-island population of Striated Caracaras (Phal-
coboenus australis) in the Falkland Islands. Movement
Ecology. 6:4.
Heinrich B. 1988. Winter foraging at carcasses by three
sympatric corvids, with emphasis on recruitment by the
raven, Corvus corax. Behavioral Ecology and Socio-
biology. 23:141–156.
Heinrich B. 1989. Ravens in winter. New York (NY): Simon
and Schuster.
Heinrich B, Marzluff JM, Marzluff CS. 1993. Common
Ravens are attracted by appeasement calls of food
discoverers when attacked. Auk. 110:247–254.
Kutsukake N, Clutton-Brock TH. 2006. Aggression and
submission reflect reproductive conflict between fe-
males in cooperatively breeding meerkats Suricata
suricatta. Behavioral Ecology and Sociobiology.
59:541–548.
Lorenz K. 1935. Der Kumpan in der Umwelt des Vogels
[Companions as factors in the bird’s environment].
Journal f¨
ur Ornithologie. 83:137–213, 289–413. Ger-
man.
Mayr E. 1974. Behavior programs and evolutionary
strategies. Journal of American Science. 62:650–659.
Miller R, Schiestl M, Whiten A, Schwab C, Bugnyar T.
2014. Tolerance and social facilitation in the foraging
behaviour of free-ranging crows (Corvus corone
corone;C. c. cornix). Ethology. 120:1248–1255.
Morrison J. 1999. Methods for gender determination in
Crested Caracaras. Journal of Raptor Research.
33:128–133.
Nicholson AJ. 1954. An outline of the dynamics of animal
populations. Australian Journal of Zoology. 2:9–65.
Parker GA. 2000. Scramble in behaviour and ecology.
Philosophical Transactions of the Royal Society of
London B. 355:1637–1645.
Reeves M, Crofts S, Bildstein KL. 2018. Distribution and
abundance of breeding Striated Caracaras in the
Falkland Islands (Malvinas). Journal of Raptor Re-
search. 52:309–315.
Rexer-Huber K, Bildstein KL. 2013. Winter diet of Striated
Caracara Phalcoboenus australis (Aves, Polyborinae)
at a farm settlement on the Falkland Islands. Polar
Biology. 36:437–443.
Signe P, Van Schaik CP. 2000. Dominance and communi-
cation: Conflict management in various social settings.
In: Aureli F, de Waal FBM, editors. Natural conflict
resolution. Berkeley (CA): University of California
Press; p. 77–105.
Smith SM. 1978. The ‘‘underworld’’ in a territorial sparrow:
Adaptive strategy for floaters. American Naturalist.
112:571–582.
Solaro C, Sarasola JH. 2019. Urban living predicts
behavioural response in a Neotropical raptor. Behav-
ioural Processes. 169:103995.
Strange IJ. 1996. The Striated Caracara (Phalcoboenus
australis) in the Falkland Islands. Author’s edition.
Falkland Islands.
Suh A, Paus M, Kiefmann M, Churakov G, Franke FA, et al.
2011. Mesozoic retroposons reveal parrots as the
closest living relatives of passerine birds. Nature
Communications. 2:1–7.
131Short Communications
Downloaded From: https://bioone.org/journals/The-Wilson-Journal-of-Ornithology on 03 Nov 2021
Terms of Use: https://bioone.org/terms-of-useAccess provided by University of Ottawa