<I>Milvago Chimango</I>&Rpar; Feeding on Common Lesser Toads
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LETTERS j RaptorRes. 38(2):190-191 ¸ 2004 The Raptor ResearchFoundation, Inc. OBSERVATIONOF THE CHIMANGO CARACARA(A/IILVAGO CHIMANGO) FEEDING ON COMMON LESSER To•s ( BUFOFERNANDEZAE) The Chimango Caracara (Milvago chimango)is a member of Falconidae that occurs throughout southern South America: Argentina, Chile, Uruguay, Paraguay,and southern Brazil (Olrog 1995, Las AvesArgentinas, Editorial E1 Ateneo, BuenosAires, Argentina). Variousstudies have describedthe ChimangoCaracara as an opportunisticpred- ator and scavenger.Its diet has been reported to include arthropods,gastropods, worms, vertebrates, vegetables, and carrion (Barros Valenzuela 1960, Rev. Univ. 44-45:31-37, Nufiez and Yafiez 1981, Not. Mens.Mus. Nac. Hist. Nat. Chile 25.5-9, Nufiez et al. 1982, Bol. Mus. Nac. Hist. Nat. Chile 39:125-130, Cabezas and Schlatter 1987, An. Mus. Hist. Nat Valparaiso18:131-141). On 5 November 2001, from a distanceof ca. 50 m, we observeda Chimango Caracarafeeding upon a dead adult common lessertoad (Bufofernandezae). We made this observationin Los Porterios(34ø53'45"S, 58ø05'02'%V), a sub- urban region of La Plata city (BuenosAires Province,Argentina), where land usesinclude cattle ranching,floricul- ture, and horticulture. At the time of our observation,the caracarawas perched on a fence post 1 m in height, which was located in a pasture. This fence post was situated 20-m south of a small, temporary pond where the common lesser toad breeds (pers. obs.) and ca. 30-m south from the caracara'snest. The nest was in a eucalyptustree (Eu- calyptussp.) located along the edge of the pond. The caracarawas pecking at the toad's belly and swallowingpieces torn from the frog's visceraand foreleg muscles.This observationconstitutes the first report of the common lesser toad in the Chimango Caracara'sdiet. Between September 2001 and February 2002, once a wk, we visited the site and examined the ground around fence postsin a fence line that passedwithin 200 m of the caracara'snest. During our visits,we frequently sawthe caracaraperched on this fence line. We found 15 carcassesof the common lessertoad, remainsof a RufousHornero (Furnariusrufus), a mouse (unknown species),and bones of a criolla frog (Leptodactylusocellatus) around theseperch- 1rigsites. Toad carcassesfound at perching sitestypically had been evisceratedthrough a ventral hole. The skeleton and dorsalskin remained intact and in somecases the carcasseswere without legs.All toad carcassesfound were deposited at the herpetologicalcollection of the Instituto de Limnologia Platerise"Dr. Rat1 A. Ringuelet" under the number ILPLA A 491. Snout-ventlength of the toad carcassesaveraged 60.1 mm (---4 mm [SD], range = 55.6-68 mm, N = 16). The common lessertoad, along with other speciesof Bufo, has a very thick and glandular-dorsalskin and two prominent post-cephalicglands in a dorso-lateralposition (parotoid glands). These glandssecrete substances that are noxiousor toxic to somepredators (Duellman and Trueb 1986, Biologyof Amphibians,The JohnsHopkins Univ. Press,Baltimore, MD U.S.A.). Despite this fact, severalbirds have been reported to feed on the common lessertoad including the Red-backedHawk (Buteopolyosoma), Burrowing Owl (Athenecunicularia), American Kestrel (Falcosparv- enus;Gallardo 1974, Antibios de losAlrededores de BuenosAires, Editorial Universitaria de BuenosAires, Argentina) and Cattle Egret (Bubulcusibis; Torres et al. 2000, Cuad.Herpetol. 14:81). Contrary to Gallardo's(1974) field reports,Huertas and Vallejo (1988, Bol.Soc. Zool. Urug., 2 øgpoca, 4:46-49), based on laboratory observations,reported that the American Kestrel, which typicallykills and eats a variety of non-bufonid anuran species,does not kill and eat the common lessertoad (including small-juveniletoads which have more toxins than adults), perhapsbeing unable to avoid irritation causedby the secretionof the toad's dorsalglands. Corn (1993,Herpetol. Rev. 24:57) and Brothers(1994, Herpetol. Rev. 25:117) reported that the AmericanCrow (C0rvus brachyrhynchos)and Common Raven (Corvuscorax) fed on the congeneric,and also toxic, boreal toad (Bufo boreas), ewsceratingthem from the ventral side, as describedabove. Speciesthat feed successfullyon the common lessertoad and other bufonids may be able to do so by making ventral holes in the frog's bodies.This method of consumption may help the predator avoid the noxious substances. We captured and weighed severalcommon lessertoads in order to assesstheir potential energetic value to the caracara.The toad's small body size (i = 15.62 g __-4.28 g SD, range = 10.26-24.88 g, N = 9) along with its toxicity suggestslittle energeticbenefit relative to handling cost,for the caracara(body massca. 300 g). However,during the breeding season,when rainfall is high, toadsare numerousand are often observedconcentrated around ponds (pers. 190 JUNE 2004 LETTERS 191 obs.). This seasonalabundance of the common lessertoad might compensatefor what might otherwisebe a marginal resource. We thank G. Finarelli for her assistancewith fieldwork and J.L. Morrison and three anonymousreviewers for their commentson earlier versionsof the manuscript.--LeandroAlcalde (e-mail address:[email protected]) and Sergio D. Rosset,Contribuci6n Cientifica n ø 750 del Institutode LimnologlaPlatense "Dr. Rafil A. Ringuelet"(ILPLA), CC 712 (1900) La Plata, Argentina. Received 15 April 2002; accepted 21 December 2003 AssociateEditor: Joan L. Morrison j. RaptorRes. 38(2):191 ¸ 2004 The Raptor ResearchFoundation, Inc. CONSUMPTIONOF A RINGED KINGFISHER(MEGAC•RYLE TORQUATA) BY A WHITE-TAILEDHAWK (BUTEOALBICAUDATUS) IN SOUTHEASTERN BRAZIL The White-tailed Hawk (Buteoalbicaudatus) is a poorly known speciesranging from southern Texas to northern Argentinean Patagonia (Farquhar 1992, The Birds of North America, No. 30, Washington, DC U.S.A.). Few data are reported on its diet, which comprisesinsects, rodents, reptiles, and birds (Farquhar 1992, Sick 1993, Birds in Brazfi: a natural history.Princeton Univ. Press,Princeton, NJ U.S.A.). Virtually no data are publishedon its ecologyin South America. We observeda feeding event by the White-tailedHawk in the 2300 ha Itirapina EcologicalStation (22ø12'S, 47ø54'W),State of S5oPaulo, Brazil. On 23 April 1998,at 1300 H, while drivinga car throughthe savannahgrassland, we observedan adult White-tailedHawk feeding on dead Ringed Kingfisher (Megaceryletorquata). The fresh kingfisher remainswere in a small tree, ca. 2 in abovethe ground. As we approached,the hawk flew awayand the remains fell to the ground. Only the complete cranium, cervicalvertebrae, ulna, metacarpals,phalanges, and somerectrices were left by the hawkwhen we inspectedthe carcass.The Ringed Kingfisheris a piscivorousand semiaquaticbird associated with rivers, ponds, lakes, and reservoirs,occurring from extreme southern Texas to southernmostSouth America (del Hoyo et al. 2001, Handbook of the birds of the world. Lynx Edicions,Barcelona, Spain). The nearest aquatic environment, a reservoir,was located ca. 2 km away from the observationsite. It is possible,therefore, that the kingfishercould have been passingover the grasslandsavannah when captured. This may have been the caseas the White-tailedHawk is known to kill and consumeprey in or nearby the site of predation (M.A.M. Granzinolli pers. obs.). The Brazilian subspecies,B. a. albicaudatus,has a massranging from 850-884 g (del Hoyo et al. 1994.) The Ringed Kingfisherbody massranges from 305-341 g (Sick 1993). Therefore, the kingfisherrepresented 34.5-40.1% of adult massof the hawk. Other authorshave reported consumptionof birds by White-tailedHawks, but few with a massof more than 300 g (seeFarquhar 1992). However,43 of 259 pelletsfrom the State of Minas Geraisin southeast Brazil containedbirds and, exceptfor one individualwith a massof 72 g, all the otherswere lessthan 40 g (M.A.M. Granzinolli and J.C. Motta-Juniorunpubl. data). According to the latter study,which evaluatedthe hawk's diet over a 1-yr period, birds are relativelyuncommon prey, totaling 11.1% of consumedbiomass of this species.Thus, the present observationsuggests that this hawk subspeciescan also prey upon larger birds occasionally.Also, we note that White-tailedHawks are known to scavengeon dead animals (Farquhar 1992) and that the kingfishercarcass we found may not have been captured and killed by the hawk.Nonetheless, we suggestthat the feeding eventwe observed was the result of predation and our record documentsthe consumptionof a relativelylarge bird in the diet of the White-tailed Hawk. We thank Funda•5o de Amparo a Pesquisado Estado de S5o Paulo for financial support and Denise Zanchetta from Instituto Florestal de S5o Paulo for the license to conduct studiesin the Ecological Station. C. Farquhar and Adriana A. Bueno made suggestionson the manuscript.This is publication No. 16 of the project "Ecology of the Cerradosof Itirapina."--Jos(• CarlosMotta-Junior (e-mail address:[email protected]) and Marco Antonio Monteiro Granzinolli, Departamento de Ecologia,Instituto de Bioci•ncias, Universidade de Silo Paulo, 05508-900, Silo Paulo, SP, Brazil. Received 11 June 2003; accepted 18 December 2003 .