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ORNITOLOGIA NEOTROPICAL 14: 541–543, 2003 © The Neotropical Ornithological Society

PREDATION ON BY THE WHITE ( ALBICOLLIS)

Oliver Komar

Natural History Museum and Biodiversity Research Center, and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045, USA. E-mail: [email protected]

Depredación de aves por el Aguililla Blanca (Leucopternis albicollis). Key words: Mist netting, , Blue-crowned Motmot, Momotus momota, Swainson’s Thrush, Catharus ustulatus, , Leucopternis albicollis.

The White Hawk (Leucopternis albicollis) and mation of White Hawk specimens in museum other members of its are considered to collections. specialize on reptilian prey (Slud 1964, Brown I captured birds with mist nets and made & Amadon 1968, Zhang & Wang 2000). The field observations during December 2001 White Hawk’s diet also includes , , to February 2002 in Parque Nacional birds, , , and (Slud El Imposible, southwestern El Salvador 1964, Brown & Amadon 1968, Haverschmidt (13°51’N, 89°59’W). Mist nets measured 12 m & Mees 1994, Draheim 1995). prey items x 2.6 m, with 36 mm mesh. Museums sur- identified in the literature include several spe- veyed for stomach content information on cies of toucans (Brown & Amadon 1968, specimen tags included the Natural History Skutch 1971, Sick 1993, Draheim 1995), a Museum and Biodiversity Research Center of tinamou (Lamm 1974), two of , the University of Kansas (Lawrence, and a wren (Draheim 1995, Draheim et al. in KUNHM), the Field Museum of Natural His- press). Draheim et al. (in press) reported that tory (Chicago), the Peabody Museum of Nat- of 210 prey items delivered to incubating ural History, Yale University (New Haven), White Hawk adults or nestlings in Guatemala, and the Museum of Natural Science, Louisi- 5.7% (12) were birds. The closely related ana State University (Baton Rouge). Gray-backed Hawk (Leucopternis occidentalis) During the late afternoon of 13 February has been observed preying on crakes, jays, 2002, a White Hawk entangled itself in a mist doves, and domestic chickens, and 10% of net placed across a streambed. Fifty centime- prey items delivered to nests were avian (Var- ters away, an almost completely defeathered gas 1995). Here I present several incidents of body of a recently killed Blue-crowned Mot- White attacking birds, and report find- mot (Momotus momota) lay on a small boulder ings from a search for stomach content infor- in the middle of the stream. All of the mot-

541 KOMAR mot’s flight and most of its contour The observations reported herein docu- feathers had been removed. Many feathers ment specific avian prey items of the White were strewn across the ground 10–15 m away, Hawk. They establish that, at least occasion- suggesting that the hawk had defeathered the ally, White Hawks will completely defeather a bird in a tree above the stream. The skin was medium sized avian prey item before con- mostly intact, but had been ripped on the suming it, or before bringing it to a nest or a breast, and showed puncture wounds consis- dependent juvenile. The motmot weighed tent with talons on the back. The defeathered about 16–18% of the body weight of a White motmot weighed 122 g and was preserved in Hawk, and thus should be able to provide formalin and alcohol (KUNHM 94085). most, if not all, of the daily food needs for the Although the mist net was not torn, and no hawk (Thiollay 1994). The hawk may not eat motmot feathers were in the net itself, I can- motmots or thrushes on a regular basis, if not rule out the possibility that the hawk had these were prey items only because they had plucked the motmot from the mist net. been trapped in the mist net. Perhaps White Also entangled in the mist net, and within Hawks prey on birds opportunistically, attack- a few centimeters of the hawk, was a live ing birds when they are injured or trapped. Swainson’s Thrush (Catharus ustulatus). I sup- The genus Leucopternis belongs to the pose that the White Hawk was attracted to , and many genera of the the net by the struggling thrush, and subse- Accipitridae family contain species that prey quently became entangled. Apparently the upon a large variety of vertebrates and inver- hawk had already defeathered the motmot tebrates (Thiollay 1994). A generalist feeding when it discovered the thrush, and probably strategy may be ancestral in the accipitrid landed on the boulder with the motmot, and clade, in which case Leucopternis species would then attempted to jump onto the thrush, but be expected to have a diverse diet that instead became entangled in the net. includes birds. White Hawks have been observed on other occasions attacking birds caught in mist ACKNOWLEDGMENTS nets. A. T. Peterson (pers. com.) observed a White Hawk feeding on several passerine I thank Cullen Hanks, Brian J. O’Shea, and A. birds (Pipra mentalis, Manacus candei) from mist Townsend Peterson for comments and con- nets in the Chimalapas region, Oaxaca, south- tributions to the manuscript, and curators and ern . Several other passerines in adja- collections managers who permitted access to cent nets were mortally wounded by hawk museum collections. Jean-Marc Thiollay, Rus- attacks that same week, perhaps by the same sell Thorstrom, and Dave Whitacre reviewed individual that had been seen near the nets. the manuscript and provided constructive Apart from literature reports of observa- criticism. SalvaNATURA and the Ministry of tions of predation on birds summarized Environment and Natural Resources of El above, there is little documentation of bird- Salvador provided logistical assistance for eating by White Hawks. Several literature field work. accounts of stomach contents for the species, summarized in Draheim et al. (in press), do REFERENCES not report birds as prey items. Of 60 White Hawk specimens in the museum collections I Brown, L., & D. Amadon. 1968. , hawks, and consulted, only one included stomach content of the world. Volume 2. Country Life information ( remains) on the label. Books, Feltham, Middlesex, UK.

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Draheim, G. S. 1995. Breeding biology and habitat Florida Press, Gainesville, Florida. requirements of the White Hawk (Leucopternis Slud, P. 1964. The birds of Costa Rica: distribution albicollis) in Guatemala. M. Sc. Thesis, Boise and ecology. Bull. Am. Mus. Nat. Hist. 128: 1– State Univ., Boise, Idaho. 430. Draheim, G. S., D. F. Whitacre, A. M. Enamorado Thiollay, J. M. 1994. Family Accipitridae (hawks Guzmán, O. A. Aguirre Barrera, & A. E. and eagles). Pp. 52–105 in del Hoyo, J., A. Hernández Córdova in press. White Hawk Elliott, & J. Sargatal (eds.). Handbook of the (Leucopternis albicollis). Pp. – in Whitacre, D. F. birds of the world. Volume 2: New World vul- (ed.). Raptors of the Maya : ecology of a tures to guineafowl. Lynx Edicions, Barcelona, Neotropical raptor community. Cornell Univ. Spain. Press, Ithaca, New York. Vargas, H. 1995. Food habits, breeding biology, Haverschmidt, F., & G. F. Mees. 1994. Birds of and status of the Gray-backed Hawk (Leucopter- Suriname. VACO N. V. Uitgeversmaatschappij, nis occidentalis) in western . M. Sc. The- Paramaribo, Suriname. sis, Boise State Univ., Boise, Idaho. Lamm, D. W. 1974. White Hawk preying on the Zhang, S., & L. Wang. 2000. Following of brown Great Tinamou. Auk 91: 845–846. capuchin monkeys by White Hawks in French Sick, H. 1993. Birds in : a natural history. Guiana. 102: 198–201. Princeton Univ. Press, Princeton, New Jersey. Skutch, A. F. A naturalist in Costa Rica. 1971. Univ. Accepted 28 January 2003.

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