Prey partitioning between mates in breeding booted eagles (Hieraaetus pennatus)

2005·1.9 MB·English

by  J E Martinez

June 2005 Short Communications 159
Departamento de Ordenacion del Territorio yMedio ductive output of potentially competitive Long-eared
Ambiente. 2001. El medio ambiente en la comunidad Owls and Tawny Owls. Ornis Scand. 15:176-182.
autonoma del Pais Vasco. Servicio editorial del Go- Palomares, F. and T.M. Caro. 1999. Interspecific killing
bierno Vasco, Vitoria-Gasteiz, Spain. among mammalian carnivores. Am. Nat. 153:492-508.
Herrera, C. and F. Hiraldo. 1976. Food-niche relation- Saurola, P. 1995. Owls of Finland. Hiijayhtyma Oy, Hel-
ships among European owls. Ornis Scand. 7:29-41. sinki, Finland.
Jaksic, F. 1988. Trophic structure of some nearctic, neo- Sergio, F, L. Marches:, and P. Pedrini. 2003. Spatial re-
tropical and palearctic owl assemblages: potential fugia and the coexistence of a diurnal raptor with in-
roles of diet opportunism, interspecific interference traguild owl predator./. Appl. Ecol. 72:232-245.
and resource depression./. Raptor Res. 22:44—52. ScHOENER, TW. 1974. Resource partitioning in ecological
AND H.E. Braker. 1983. Food-niche relationships communities. Science 185:27-39.
Taylor, 1994: Barn Owls: predation-prey relationships
and guild structure of diurnal birds of prey: compe- I.
and conservation. Cambridge University Press, Cam-
tition versus opportunism. Can.]. Zool. 61:2230-2241.
bridge, U.K.
Kostrzewa, a. 1991. Interspecific interference competi-
Venier, L.A. and L. Fahiug. 1996. Habitat availability
tion in three European raptor species. Ethol. Ecol. Evol.
causes the species abundance-distribution relation-
5:127-145.
ship. Oikos 76:564—570.
Marti C.D., K. Steenhof, M. Kochert, and Marks.
1993. Community trophic structure: the rolJe.s of diet, Zuberogoitia, I. 2002. Ecoethology of the Bizkaia’s owls
Ph.D. dissertation, Univ. Pais Vasco, Leioa, Spain.
body size and activity in vertebrate predators. Oikos67:
AND L.F Campos. 1998. Censusing owls in large
fi-18
. areas: a case study. Ardeola 45:47-53.
Martinez,J.A. and I. Zuberogoitia. 2002. Factors affect- AND J.A. MartInez. 2000. Methods for surveying
ing the vocal behaviour ofEagle Owl Bubo bubo: effects Tawny Owl Strix aluco populations in large areas. Biota
of sex and territorial status. Ardeola 49:1-9. 1:137-146.
, , J. Colas, andJ. Macia. 2002. Use of re- AND . 2001. The Little Owl in the “Proy-
corder calls for detecting Long-eared Owls Asio otus. ecto Noctua.” Pages 103-108 mJ.C. Genot, J.M. La-
Ardeola 4Q:^7—101. pios, P. Lecomte, and R.S. Leigh, [Eds.], Chouette
Mikkoia, H. 1983. Owls ofEurope. T. & A.D. Poyser, Gal- cheveche et territorie. Actes du colloque de Champ-
ton, U.K. sur-Marne, Paris, France.
Newton, I. 1979. Population ecology ofraptors. T. &A.D.
Poyser, Hertfordshire, U.K. Received: 31 December 2003; accepted 22 February 2005
Nilsson, I. 1984. Prey weight, food overlap, and repro- Associate Editor:James R. Belthoff
/. RaptorRes. 39(2):159-163
© 2005 The Raptor Research Foundation, Inc.
Prey Partitioning between Mates in Breeding Booted Eagles (Hieraaetuspennatus)
Jose E. Martinez and Jose F. Calvo^
Departamento de Ecologia e Hidrologia, Universidad de Murcia, Campus de Espinardo, 30100 Murcia, Spain
Keywords: Booted Eagle, Hieraaetus pennatus; foodpar- breeding adults (Mueller and Meyer 1985, Massemin et
titioning, forest; prey provisioning, reversed size dimorphism al. 2000, Simmons 2000). However, no explanation has
(RSD). gained universal acceptance (Bildstein 1992). One ofthe
most popular explanations is the prey-partitioning hy-
Reversed sexual-size dimorphism (RSD) is widespread pothesis or female supplementary feeding hypothesis
m
raptors and owls, with females being larger than males (Reynolds 1972, Korpimaki 1985), which suggests that
(Newton 1979). Several researchers have proposed that RSD is advantageous because it allows females to hunt
this trait is driven by different selective forces acting on larger prey, widening the prey base available for the pair
and reducing intersexual competition for food (Snyder
and Wiley 1976, Andersson and Norberg 1981, Massemin
^ Email address: [email protected] et al. 2000). Several authors (e.g., Snyder and Wiley 1976,
160 Short Communications VoL. 39, No. 2
Newton 1979, Simmons 2000) have noted that the degree assess temporal differences in the type and mass of the
ofRSD among raptor species shows a strong relationship prey captured.
We used Morisita’s index (Krebs 1999) to assess over-
with the proportion of birds in the diet. Nonetheless,
lap in the prey species caught by male and female eagles.
studies addressing differential prey-size choice between A linear mixed-effects model was employed to evaluate
sexes have been equivocal (Opdam 1975, Collopy 1984, differences in the mean mass of prey captured by each
Kennedy andJohnson 1986, Boal and Mannan 1996). mate. Nest was considered as a random factor to avoid
Between 1998 and 2000, we conducted a study on a pseudoreplication and the temporal factor was included
breeding population of Booted Eagles {Hieraaetuspenna- as a fixed effect. The proportions of each prey type and
tus) in southeastern Spain. This species is a medium-sized size were also assessed by the analysis offour-way contin-
raptor showing a moderate degree of reversed size di- gency tables using Poisson log-linear models and likeli-
morphism {x male body mass = 709 g, female = 975 g; hthoeodeffreacttisootfesstex,(Vneensta,blaensdannedstRiinpglpeeyri2o0d02a)s etxopleaxnaamtionrey
del Hoyo et al. 1994, Balbontin et al. 2001). Although factors. Statistical analyses were performed with the Rsta-
the Booted Eagle is a common bird of prey of the forests tistical package (Maindonald and Braun 2002).
and woodland areas of the Iberian Peninsula (Veiga and
Vihuela 1994), little is known about its diet. Earlier stud- Results
ies in Europe and South Africa describe it as a small- and We
identified to the species level 117 of 127 preyitems
medium-sized bird hunter, also preying on lizards and
delivered to nests (Table 1). Birds made the bulk of the
mammals (Steyn and Grobler 1985, Veiga 1986, Martinez
Booted Eagle diet (65.35%), followed by ocellated lizards
et al. 2004). (Lacerta lepida\ 26.77%), and mammals (7.87%). Females
Here, our objective was to analyze the prey items de-
brought 40 prey items (31.50%) and males 87 (68.70%).
livered to the nest by male and female Booted Eagles,
Of these, 54 were delivered directly by the male, and 33
examining differences in the kind and body mass ofprey
were previously transferred and then delivered by the fe-
between the genders.
male. The prey-provisioning rate was 0.24 prey items/hr
(0.08 for females and 0.16 for females).
Methods
A moderate degree of dietary similarity between the
We carried out the study between 1998—2000 in central sexes was found (Morisita’s index = 0.67). However, the
Murcia (southeastern Spain; 38°00'N, 1°45'W). The study mean mass of prey captured by males and females dif-
marea included about 10 000 ha and ranges from 550—1521 fered significantly (Tj iiy = 11.50, P< 0.001). The tem-
above sea level, with a topography characterized by poral factor and its interaction with the gender were not
rugged slopes dominated by pine forests {Pinus halepen- significant (Ti ng ~ 0.20, P = 0.66 and Tj j^g = 0.19, P =
sts) interspersed with traditional agroecosystems (cereal
0.59, respectively).
plots, vineyards, and olive and almond groves).
The analysis of the prey-type contingency table re-
Dietary differences between males and females were
assessed from observations of prey deliveries at five dif- vealed that sex, nesting period, and nest factors signifi-
= P <
ferent nests. Prey items were identified from blinds lo- cantly influenced prey type (sex: 25.42, 0.001;
m = P < =
cated 30—50 away from the nests using a spotting scope nesting period: x^ 23.79, 0.001; nest: x^ 72.40,
P<
and binoculars. One nest was observed in 1998, two in 0.001;). Based on the Poisson model, males delivered
1999, and other two in 2000. Observations were con- greater proportions of small birds, nesdings, and reptiles
ducted every 4-8 d from the early nestling stages (late than females (Table 2) Both sexes captured similar pro-
.
May) until 5-7 d after fledging (early August). Nest ob- portions of large adult birds and mammals.
servations started at 1100 H, lasted until 1900 H, and
continued the following day from 0700-1100 H. In total, Discussion
509 hr ofdirect observation were made, duringwhich we
recorded visually all prey deliveries. A prey item was as- Our results show that differences in provisioning rates
sumed to have been captured by the male when: (1) we between sexes was moderate and similar to those report-
observed the male delivered prey to the nest or (2) the ed by Simmons (1986), Manosa (1994), and Gronnesby
prey captured by the male was delivered to the nest by and Nygard (2000) for a variety of small and medium-
the female after a food transfer involving characteristic sized forest raptors. The Morisita’s index points to a mod-
vocalizations. A prey item was assumed to have been cap- erate dietary similarity between sexes, a finding which
tured by the female when she delivered it and no food differs from those of Kennedy and Johnson (1986) and
transfer was observed. Boal and Mannan (1996) for Cooper's Hawk {Acdpiter
Biomass of prey was estimated based on data reported
by Van den Brick and Barruel (1972) and Manosa cooperit) and Northern Goshawk {Accipitergentilis), respec-
(1994). Mass data was log transformed for analysis. Prey tively. These workers found extensive niche overlap be-
Items were also assigned to the following categories: tween the sexes in these species that also exhibit substan-
mammals, large adult birds (>200 g), small adult birds tial sexual dimorphism.
(<200 g), nestlings (<100 g) and reptiles. We also con- Our study suggests prey-size partitioning between pair
sidered two nesting periods (early, until the chicks were members of Booted Eagles during the chick-rearing
ca. 30 d old, and late, until the end of observations), to stage. Previous studies have reported a similar tendency
June 2005 Short Communications 161
qqqqqqqqqq qqqqqi>qqqqq
O
00 O CM o> OOJ inoioincoococooco odooooooooo q q q
irj 1—i CO iri GO 00
CM I— CO t-
(
h qqqqqqqqqqqqqqqqoqmooq
2u; QD o oo ir: q lo CMt^dtPcMOinindddcMddcMCMcBdcMddd q q
o in CM iri CM tP i>
Pi GO rto 00
Pi
Ph
GmO
0to Q CM o CM m i-HOOOmi—lOCMCMOTfO^OO^rHOO^OO CM GO GO +1
d 00 nr
2
rto
o GO
o
0
CM
00I
01 qqqqqqqqqcMqq
oi q q q q in O O q q q m o o o
O d d d O O O O O O O d d
CM hH i-h CD CM CM in rto rH rH GmO
GO GO GO
a,
c
V
H
COc/3J3 2to; DQ q GO Oo J> dO Od Tfi J> (D Od GO Od oCoMi^—i^i’—(coMoC-O^GTOfCiMeoCoModoCoMoCoMootdD q q
CM CM in GO 00 in CM m in in
GO GO
Q
O to
c/3 Ph 2:
u
tOo p
d Q CM r-H CM O in OOOOCD^m'sfOCMOCMrH,—iCMOOGOGMCMOCMCMi-iHn 1GO1 1GO1 I0'0r -}-I
<D 2 00
I'
w
T3
u
-M ooooomoomooooooomooooo
0 o o o o
o o oO m m m ooi>oini>oair-iooJ>j>'^-Gficr>in-^incDCM om
rt CM rH CM <0 GO CM Tto t-H rto rto
V CM
"3
<+<
T
3
fl
ci
J
a;
>-
a 8 -I ou;
s I O.
S
8 T3
-i-< ou;
!!ZU1 |l >3 •04 >
Cl o
O .6 u
ou;
-o a
(U c?'<S +HS 53 0
CC>-Ji g .is =+-(
t«Irj3H XJ X5 a ^S l1i/3 tt3o bO
a N JJ
P((h-U1 Pcni PPni! tP Itt0Joo acBS Xd! CQJp 0
w0VOonw0VoOnr'pPlUaiS c?0CnST-32„§ X_stio O0 ODO0 cn O fVtCOzoIJih Q'ttOdOooJJ' Xtot3oo X§3 Os ^bPPoJD CIDwcG XA2SC«d
cn Ji -C u
162 Short Communications VoL. 39, No. 2
Table 2. Estimated probabilities from the main effects log-linear model applied to the prey-type frequency table.
Probabilities from the hve nests are summed.
Earia Nestling Period Late Nestling Period
Prey Type Males Females Males Females
Mammals 0.43 0.27 0.07 0.22
Large adult birds (s200 0.20 0.10 0.28 0.44
g)
Small adult birds (<200 g) 0.53 0.22 0.16 0.11
Nestlings (<100 0.67 0.07 0.22 0.05
g)
Reptiles 0.69 0.04 0.22 0.04
in raptors and owls (Simmons 1986, Mahosa and Cordero valuable comments on the manuscript. This work was
1992, Overskaug et al. 1995), although several authors funded by Spanish Ministry of Science and Technology
found only weak evidence of prey partitioning between (project REN2002-01884/GLO, partially hnanced by
FEDER
funds).
sexes during the nestling period (Widen 1984, Toyne
1998, Delannoy and Cruz 1999). Males in our study, on
Literature Cited
average, delivered smaller prey items than females. The
taking of smaller prey by males could be related to their Andersson, M. and A. Norberg. 1981. Evolution of re-
smaller body size and greater agility, which would favor versed sexual size dimorphism and role partitioning
the search, pursuit, and hunting of such prey (Temeles among predatory birds, with a size scaling of flight
1985) and reduce the costs of handling prey (Villaran performance. Biol. Linn. Soc. 15:105-130.
J.
2000). Females may reduce competition for food with BALBONTiN, M. Ferrer, and E. Casado. 2001. Sex de-
J.,
males by taking larger prey; Booted Eagle females weigh termination in Booted Eagles {Hieraaetuspennatus) us-
27% more than males on average (del Hoyo et al. 1994), ing molecular procedures and discriminant function
which is consistent with theories concerning the selective analysis. Raptor Res. 35:20—23.
advantage of RSD (Andersson and Norberg 1981, Te- J.
Bildstein, K.L. 1992. Causes and consequences of re-
meles 1985). In summary, our findings suggest that in-
versed sexual-size dimorphism in raptors: the head
tersexual prey-size partitioning may be related to the sex-
start hypothesis. /. Raptor Res. 26:115-123.
ual dimorphism of this species.
Boat, C.W. and R.W. Mannan. 1996. Prey sizes of male
and female Northern Goshawks. Southwest. Nat. 41.
Captura Diferencial de Presas for Machos y Hembras
355-358.
DE Hieraaetuspennatus
COLLOPY, M.W. 1984. Parental care and feeding ecology
—
Resumen. Entre 1998 y 2000 estudiamos la dieta de ma- of Golden Eagle nestlings. Auk 101:753-760.
chos y hembras de Hieraaetus pennatus, mediante el con- DEL Hoyo, J., A. Elliott, and J. Sargatal. 1994. Hand-
trol visual de cinco nidos en una zona forestal del sureste book of the birds of the world, Vol. 2. Lynx Edicions,
de Espaha. Machos y hembras capturaron respectiva- Barcelona, Spain.
mente el 69% y el 31% del total de las presas aportadas Delannoy, C.A. and A. Cruz. 1999. Patterns of prey
a los nidos. La tasa de aporte fue de 0.24 presas/hora, abundance and use by male and female Puerto Rican
siendo las aves la dieta predominante de los polios Sharp-shinned Hawks. Caribb. J. Sci. 35:38-45.
(65%). Encontramos un moderado nivel de similitud en- Gronnesby, S. and T. Nygard. 2000. Using time-lapse vid-
tre las capturas de machos y hembras, pero la biomasa eo monitoring to study prey selection by breedinggos-
media y las frecuencias de los diferentes tipos de presas hawks Accipiter gentilis in central Norway. Ornis Fenn
capturados fueron significativamente distintos entre am-
77:117-129.
bos sexos. Nuestros resultados sugieren la existencia de Kennedy, P.L. and D.R. Johnson. 1986. Prey-size selec-
diferencias entre la dieta de ambos sexos, probablemente tion in nesting male and female Cooper's Hawks. Wil-
relacionadas con el dimorhsmo de tamaho.
son Bull. 98:110-115.
[Traduccion de los autores]
Korpimaki, E. 1985. Diet of the kestrel Falco tinnunculus
Acknowledgments in the breeding season. OrnisFenn. 62:130-137.
anWdeM.thCaanrkreS.teOvfiodrioh,elCp. iGnartchiea,heMl.dCwloermke.ntWee, Ra.reRuailzs,o Krejbsa,miCn.J/.Cu19m9m9i.ngEcso,loMgeinclaolPmaertkh,odCoAloUg.yS,.A2,nd Ed. Ben-
indebted to M.A. Sanchez, Rodriguez, and C. Sobrado Maindonald, j. and j. Braun. 2002. Data analysis and
J.
for their assistance in the identihcation of several prey graphics using R. Cambridge Univ. Press, Cambridge,
remains. J. Balbontin, J.C. Senar, and E. Cerezo made U.K.
June 2005 Short Communications 163
Manosa, S. 1994. Goshawk diet in a Mediterranean area . 2000. Harriers of the world: their behavior and
of northeastern Spain. Raptor Res. 28:84-92. ecology. Oxford Univ. Press, Oxford, U.K.
J.
AND P. Cordero. 1992. Seasonal and sexual vari- Snyder, N.F.R. and J.W. Wiley. 1976. Sexual size dimor-
ation in the diet of the Common Buzzard in north- phism in hawks and owls of North America. Ornithol
eastern Spain. Raptor Res. 26:235-238. Monogr. 20:1-96.
J.
Martinez, J.E., M. Cremades, I. Pagan, and J.F. Calvo. Steyn, P. andJ.H. Grobler. 1985. Supplementary obser-
2004. Diet of Booted Eagles in southeastern Spain. vations on the breeding biology of the Booted Eagle
Pages 593-599 in R.D. Chancellor and B.-U. Meyburg in southern Africa. Ostrich 56:151-156.
[Eds.], Raptors worldwide. World Working Group on Temeles, E. 1985. Sexual size dimorphism of bird-eating
Birds of Prey & Owls. MMD/BirdLife, Hungary, Bu- hawks: the effect of prey vulnerability. Am. Nat. 125
dapest. 485-499.
Massemin, S., E. KorpimAki, andJ, Wiehn. 2000. Reversed Toyne, E.P. 1998. Breeding season diet of the goshawk
sexual size dimorphism in raptors: evaluation of the Accipitergentilis in Wales. Ibis 140:569-579.
hypotheses in kestrels breeding in a temporally Van den Brick, FH. and P. Barruei,. 1972. Guia de cam-
changing environment. Oecologia 124:26-32. po de los mamiferos salvajes de Europa occidental.
Mueller, H.C. and K. Mever. 1985. The evolution of re- Omega, Barcelona, Spain.
versed sexual dimorphism in size: a comparative anal- Veiga, J.P. 1986, Food of the Booted Eagle (Hieraaetus
ysis of the Falconiformes of the western Palearctic. pennatus) in central Spain. Raptor Res. 20:120-123.
Pages 65-101 in R.F. Johnston [Ed.], Current orni- AND ViNUELA. 1994. Booted Eagle Hieraaetuspen-
J.
thology. Plenum, New York, NYU.S.A. natus. Pages 182-183 in G.M. Tucker and M.F Heath
Newton, I. 1979. Population ecology ofraptors. T. ScA.D. [Eds.], Birds in Europe: their conservation status.
Poyser, Berkhamsted, U.K. BirdLife International, Cambridge, U.K.
Opdam, P. 1975. Inter- and intraspecific differentiation Venables, B.D. and W.N. Ripley. 2002. Modern applied
with respect to feeding ecology in two sympatric spe- statistics with S, 4th Ed. Springer, New York, NY
cies of the genus Accipiter. Ardea 63:30-54. U.S.A.
OvERSKAUG, K., E. Kristiansen, and P. Sunde. 1995. Sex- VillarAn, a. 2000. Analisis comparativo de la dieta de
specific diet analysis of the Tawny Owl {Strix aluco) in ambos sexos en el carabo comun Strix aluco en la Pen-
Norway./. RaptorRes. 29:137-140. insula Iberica. Ardeola 47:203-213.
Reynolds, R.T. 1972. Sexual dimorphism in Accipiter Widen, P. 1984. Activity patterns and time budgets in the
hawks; a new hypothesis. Condor 74:191-197. goshawk Accipitergentilis in a boreal forest area ofcen-
Simmons, R.E. 1986. Ecological segregation of the Red- tral Sweden. Ornis Fenn. 61:109-112.
breasted Sparrowhawk Accipiter rufiventris and six co-
existing Accipitrine raptors in southern Africa. Ardea Received 6 May 2004; accepted 22 March 2005
74:137-149. Associate Editor:JuanJose Negro
J RaptorRes. 39(2);163-166
© 2005 The Raptor Research Foundation, Inc.
Predation of Small Mammals by Rufous-legged Owl, Barn Owl, and Magellanic
Horned Owl in Argentinean Patagonia Forests
Daniel E. Udrizar Sauthier,^ Analia Andrade, and Ulyses Pardinas
F.J.
Centro National Patagonico, Casilla de correo 128, 9120 Puerto Madryn, Chubut, Argentina
Key Words: Magellanic Horned Owl; Bubo magellanicus; reflect foraging inside forested habitats. For the southern
Rufous-legged Owl; Strix rufipes; Bam Owl; Tyto alba; diet, cone of South America, including Argentina and Chile,
stgmodontine rodents. only a few contributions have addressed this topic (Mar-
tinez andJaksic 1996, 1997, Ramirez-Llorens 2003, Trejo
Despite the large number of forest owls in the Neo- and Ojeda 2004).
tropics, there are few data available on their diets that The Rufous-legged Owl {Strix rufipes) inhabits dense
and old-growth temperate forests in southern Argentina
^ Email address: [email protected] and Chile (Straneck and Vidoz 1995, Martinez andJaksic