J. Raptor Res. 27(4):180-184 ¸ 1993 The Raptor Research Foundation, Inc.

LIVE PREY TO YOUNG RAPTORS--INCIDENTAL OR ADAPTIVE ?

WALTER R. SPOFFORD Aguila-Rancho,Portal, AZ 85632 U.S.A.

DEAN AMADON AmericanMuseum of Natural History, Central Park West, New York, NY 7002d U.S.A.

ABSTR^CT.--Raptorssometimes bring prey that is still alive to their nests,or potentialprey may blunder into raptor nestsor result from competitionfor a nest. Such delivery of live prey seemsincidental or accidentaland non-adaptive:the live prey sometimesescapes. When live prey is a nestlingbird it may be "adopted"and even reared, thus providinginsights into parental behaviorand to similar behavior amongcaptives. Raptors that catchflying prey oftendrop prey near their fledgedyoung, which the latter catchor attemptto catchin midair. In one ,the PeregrineFalcon (Falcoperegrinus), such dropped prey regularly includessome living .

Presasvivas para rapacesjuveniles--accidental o adapativo? RwSUMWN.--Algunasveces las avesrapaces 11evan presas afin vivasa susnidos, estas pueden constituir un desprop6sitoen los nidosde las rapaceso generaruna competenciapor el nido. Tal liberaci6nde la presaviva pareceaccidental y no adaptativa:la presa algunasveces escapa. Cuando la presaviva es un polluelo,este puede ser adoptadoy hastacriado, proveyendo conductas parentales entre los cautivos.Las rapacesque capturanpresas voladoras a menudodejan caer la presacerca de susjuveniles, las que mils tarde captufa o intenta capturar en el aire. En Falcoperegrinus, regularmente las presasincluyen algunas aves vivas. [Traducci6n de Ivan Lazo]

Scatteredobservations exist of raptors bringing competefor the samenest and broodmix-ups occur. live prey to their nestlings.All classesof prey are Mikkola (1983:164) wrote: "Even if a female Ural representedexcept mammals, perhaps because the Owl (Strix uralensis)has already laid her eggsin her latter mightbite and injure bothadult and immature chosennest, she remains highly vulnerableto the raptors. We have not found instancesfor owls but attentionsof a nest-huntingGoshawk ( gen- their nocturnalhabits and frequent use of cavities tilis)." One nest containedthree eggsof the for nestingmake observationsdifficult. and one of the owl. All four were incubatedby the Live prey may be in raptor nestsfor diverserea- goshawk."On 23 May the nest containeda newly sonsor under varying circumstances.Our objective hatchedUral Owl chickand three eggsof the (then) was to enumerate these reasons,give examplesof real owners ... the owlet soondisappeared and on each,and discusswhether any of them are adaptive the 8th June the nestcontained only three goshawk to raptors.Instances of live prey being"adopted" by nestlings." raptorsare alsoevaluated. Presentation of prey,alive S.K. Sherrod(pers. comm.)was told by Russian or dead, to fledgedraptors is also considered. naturalist, R. Pfeifer, of finding a young Northern Raven (Corvuscorax) in the nest of a Golden Eagle OBSWRV^TIOSS (Aquilachrysaetos). Both specieshad showninterest Adventitious Occurrences. Potential living in the nest and Pfeifer assumed that the ravens had prey--, birds, mammals--may occasionally laid eggs before being evicted, one of which was blunder into a raptor'snest. Weaver finches(Passer) hatchedby the eagle. Or perhapsone of the eagles and grackles(Quiscula) sometimes breed in the base had brought the raven to the nest (see below). of large hawk nests;their youngmight flutter into Instances Involving Insects and Lower Ver- the raptor's nest. Occasionallytwo raptor species tebrates.After intensivestudy of Mauritius Kestrels

180 DECEMBER 1993 L•VE PREY TO YOUNG RAPTORS 181

(Falcopunctatus) in the field and captivity, C.G. a Black Kite (Milvus migrans) and an Australian Jones(pers. comm.) wrote: "We now haveabout 10 Kestrel (Falcocenchroides). Both were pinned down recordsof kestrelsdelivering live or twitching prey by the Black-breastedKite and fed to her chicksbut to the nest. All that I can recall were when the not until after the youngkestrel had repulseda kite kestrelswere rearing well-grown young.I have seen nestlingby raking it with its talons(but seebelow). many hundredsof prey items deliveredto the nest Gossettand Smith (1993) found a living, unin- duringthe incubatingphase and if my memoryserves jured passerinechick in a nest of the Ferruginous me correctly,none of these(geckos, Phelsuma) were Hawk (Buteoregalis), which containedtwo young alive. Large insects,such as locustsand dragonflies, Ferruginous more than a week old. The are not usually deliveredto the nestlingsuntil their hawks' nest was on a metal tower and the observers last week or so in the nest. Some of these insects are thoughtthat the passerinemust have been brought verymuch alive when they are broughtto the nest." thereby oneof the hawks.The next day they found At a nest of the Chanting Goshawk (Melierax only a wing quill of the foreign nestling. canorus)the male brought a live agamalizard" . . . Living Birds Brought as Prey but Receiving which he depositedon the nestwhere it lay feigning Parental Care. On 3 June 1960, one of us (WRS) death. When the female leant forward to pick it up watcheda female Golden Eagle incubatingher sin- a while later, the agamacame to life and divedover gle egg at a nest in Maine. The following day she the nestedge, pursued by the female,but it escaped" wasmoving restlessly and oftenpeered into the nest. (Steynand Myburgh 1992). Probablythe chickwas cheepingwithin the egg.At Tenneson(1992) statedthat living snakesare not 0515 H the next morning the female eagle was at- •nfrequentlybrought to the "nest" of the ophioph- temptingto feeda nestling,a partly featheredAmer- agousLaughing (Herpetotherescachinnans) ican Crow (Corvusbrachyrhynchos), which she later but also found that surplussnakes are draped over moved back under her when it tottered across the boughsat the nestsite. Obviously these could nest. The eaglet was hatching. A week later the not be alive. This falcon promptly dispatchesven- eagletwas there alongwith a few black feathers, omoussnakes, which comprisea substantialportion presumablyfrom the haplesscrow. The nearestsite of its food. It is possible,therefore, that the living snakes observed were "more dead than alive." Poi- for AmericanCrows was a valley about7 km away. The following remarkable eventswere observed kilothermicvertebrates may flap or writhe for some and photographedat nestsof the Black-breastedKite time after "death," so a precisedistinction is some- (Cupper 1977, Cupper and Cupper 1981). On 8 times impossible.Fish sometimesflop over the side Octoberone attendednest was empty, two others of a Bald Eagle's(Haliaeetus leucocephalus) nest, or turtles walk over its rim (Palmer 1988:215). In such heldeggs. On 7 Novemberthe previouslyempty nest cases,failure to kill the prey resultsin its loss. held two chicks.Although the time interval seemed Live Birds Brought to Raptor Nests without too shortto lay and hatch a clutchof eggs(and the Receiving Parental Care. A Cooper'sHawk (Ac- chickswere very small),it was assumedthe young czpitercooperii) brought two living, nestlingScarlet musthave been kites. Food remains in the nestproved Tanagers(Piranga olivacea) to its nest(Meng 1959). to be legs of Australian Kestrels. On the next visit One of three quelea finches(Quelea) brought to a 20 dayslater, a youngkestrel with somedown on its brood of Taita (Falcofasciinucha) was alive head fluttered about the baseof the nesttree; a second (Hartley et al. 1993). fledgling flew down from the tree and gave a dis- At several nests of the Australian Square-tailed tractiondisplay. The next day,along with the female Kite (Lophoictiniaisura), food brought to the kite kite, there were four young kestrelsof varying ages nestlingsconsisted entirely of nestlingbirds. A fri- in the nest; later three more flew in. An adult kite, arbird (Philemonsp.) was alive when deliveredby presumablythe male, arrived with another young the male; the female kite seizedit at onceand began kestrel, this one dead. The chicks fed on it. The next to feed it to her chicks(Cupper and Cupper 1981). day the kites were broodingand feedingtheir adopt- In the relatedbut larger Black-breastedKite, (Hami- ed kestrelsof variousages. Evidently the male Black- rostramelanosternon), the foodincludes large breastedKite had formeda searchimage on kestrels. and somenestling birds, both living and dead. Two He brought in many youngones, some dead, some living prey were chicksof other speciesof raptors: alive. The female kite began to feed and rear the 182 WALTER R. SPOFFORDAND DEAN AMADON VOL. 27, No. 4

youngkestrels, and there was no indicationthat she pursuit. Dropping of live prey has beenobserved at ever laid eggs. least twice in the New Zealand Falcon (Falco no- Over a period of years,Watson et al. (1993) ex- vaeseelandiae;Lawrence and Gay 1991). After its amined more than 600 nestsof Bald Eagles in the younghave fledgedthe Eurasian Sparrowhawk (Ac- Puget Sound area. Three of them (two at the same cipiternisus) drops birds for them to catch,but very nest in alternateyears) each contained a living nest- rarely doesone of theseprey itemsshow signs of life ling Red-tailedHawk (Buteojamaicensis)and in two (Newton 1986:208). In the relatedCooper's Hawk, of thesethe young hawks fledged;it was not deter- H. McElroy (pers.comm.) saw an adult carryinga mined how the young hawks fared after fiedging. fly in amongthe branchesof a tree where its The observationswere from a helicopter, but pho- brood were perched. It dropped a live bird which tographswere taken. The hawkswere alwaysyoun- fluttered down at an angle and was caughtby one ger than the eagletsin the samenest, and the ob- of the iramatures. More observations are needed to servers concluded that the hawks must have been be sure that such use of living birds is established brought to the nest by one of the eagles.A nest of behavior in accipitersor other speciesof somewhat the Bald Eagle in Michigan alsocontained a healthy, similar habits. recentlyfed Red-tailed Hawk chickabout a month Bent (1937:155) quotesa correspondentwho re- youngerthan two eagletsin the nest.A photograph ported a Red-tailed Hawk droppinglive mice to its showsthe hawk at one side of the nest; the eaglets young;they attemptedto catchthem in midair "with at the other. No further observationswere possible fair success."This requiresconfirmation. and the outcome was not known (Stefanek et al. 1992). DISCUSSION In one astoundingincident, a pair of American As indicated,the deliveryof living prey to raptor Kestrels (Falcosparverius) lost their brood in a nest nestlingsis so rare as to suggestthat it is incidental box, apparently to a mammalian predator (Tlusty and non-adaptive.Living prey sometimesescapes. and Hamerstrom 1992). The kestrels then trans- Nestling raptors havenever beenseen to manipulate ferred their attentionto a box 1.1 km away which living prey as do the young of a few kinds of mam- contained a brood of young European Starlings mals, such as cats (Felidae). To do so in an elevated (Sturnusvulgaris). The kestrelsrepulsed the parent nestmight result in someof the youngraptors falling starlingsand adoptedand fed the youngstarlings on to their death. The Mauritius Kestrel may be an mice and other items, entering the nest box to tear exception.It brings living insectsto its young only the prey to pieces. when they are well grown. The speciesis a cavity Living Birds Brought to Raptor Fledglings.In nester so the danger of the young falling from the several speciesadults fly near young which have nest would be lessthan in an open nest. fledgedor are aboutto, carrying prey conspicuously All the recordsof living birds brought as prey to presented.The fledglingsoften fly out and seizesuch raptor nestswere nestlings.This might suggestthat prey or attempt to catch it in midair if the adult if adults were brought, they would escapeor be drops it. The next step would be the similar pre- quicklykilled. Nestlingbirds are incompletelyfeath- sentation of living, perhaps incapacitated, prey. ered.They neednot be deplumedbefore taking them Sherrod (1983) who spentdays observingrecently to the nest and in the processkilled and often de- fledgedPeregrine Falcons (Falco peregrinus) found capitatedas are adult prey. I. Newton (pers.comm.) that living birds, as well as dead ones,are indeed concludedthat not infrequently birds captured by dropped for the young to pursue. If a flying prey the Eurasian Sparrowhawkare still alive at the time escapesthe sallies of the fledglings,an adult may the hawk arrives with them at its plucking post. recaptureit, carry it aloft again, and releaseit still Nestlings,on the other hand, may be taken directly alive. Living birds thus presentedare mostly small to the nest. speciesbut range up to the size of the Rock Dove When large, vigorousand sometimespotentially ( Columbalima). dangerousprey is caught, "Cooper'sHawk--like Pursuit of living prey must acceleratethe acqui- other (and hawks in general)--will re- sition of foragingtechniques in theseyoung falcons. spondto movementof the prey by stronglygrasping Probably similar behaviorwill be found in other it, then relaxing their grip, then clamping down speciesof the genusFalco that catchbirds in midair again" (Palmer 1988:350). Nestlingswill be lessapt DECEMBER 1993 LIVE PREY TO YOUNG RAPTORS 183 to trigger suchkilling reactions.Still, it doesseem field (Winkler 1992). Raptorsare a group in which remarkable that Bald Eagles on four known occa- observationsand experimentscan be carriedout both sionshave brought small, nestling Red-tailed Hawks in captivity and in the field, and in which there is a to their nest alive. wide range of behavior. S.K. Sherrod (pers. comm.) makes the further interestingsuggestion that if nestling raptors per- ACKNOWLEDGMENTS ceive an approachingwinged predator as a parent For valuable commentson the manuscript we are in- and begin to vocalize, it might set up conflicting debted to W.W. Bowman IV, T.J. Cade, S.K. Shetrod and D.E. Vatland. As will be evident from the text, a stimuli causingthe predatorto carry off one of the number of individuals have providedus with unpublished young without killing it. All of the young hawks in notesor observations;we are grateful to all of them. Joe Bald Eagle nestswere Red-tailed Hawks but this is Schmutzhas given pivotal supportthroughout, above and a large conspicuousspecies which often nests in beyondhis editorial responsibilities. somewhat exposed sites. Red-tailed Hawk chicks LITERATURE CITED (and adults?)do occasionallyappear as prey items in Bald Eagle nests(W.S. Clark pers.comm.). BENT, A.C. 1937. Life histories of North American birds of prey. U.S. Nat. Mus. Bull. 67:1-409. After fledging, young raptors are no longer in CUPPER,J. 1977. Black-breasted Buzzards rearing and danger of falling. Yet the regular presentationof preying on Kestrels simultaneously.Australian Bird living prey, even at that stage,has been established Watcher 7:69-73. as yet only in the PeregrineFalcon. Many raptors -- AND C. CUPPER. 1981. Hawks in focus.Jaclin secure most of their food, such as , on the Enterprises, Mildura, Australia. ground. Nevertheless,none of them are known to GOSSETT,D.N. ANDJ.D. SMITH. 1993. Live passerine provideliving prey to their fledglingson the ground nestling found in Ferruginous Hawk nest. J. Raptor as do a few mammals.Probably this is becausein- Res. 27:125-126. experiencedhawks conspicuouslyengaged with liv- HARTLEY, R.R., G. BODINGTON, A.S. DUNKLEY AND A. ing prey might attract larger predators. When a GROENEVALD.1993. Notes on the breedingbiology, hunting behavior and ecologyof the Taita Falcon in trained falcon brings its quarry to the ground and Zimbabwe. J. Raptor Res. 27:132-141. struggleswith it, falconersdash to savetheir bird as LAWRENCE, S.B. AND C.G. GAY. 1991. Behaviour of they know it may be killed by other predators.The fledging New Zealand Falcons. Notornis8:173-182. presentationof living prey to raptor fledglingson MENG, H. 1959. Food habitsof nestlingCooper's Hawks the ground could thus be maladaptive. and Goshawksin New York and Pennsylvania.Wilson Although the delivery of living birds as prey to Bull. 71:169-174. raptor nestlingsis probably incidental, it assumes MIKKOLA,H. 1983. Owls of Europe. Books,Vet- someinterest when the prey is a young bird which million, SD U.S.A. begsfor foodand is "adopted,"fed, and evenreared NEWTON,I. 1986. The Sparrowhawk.T. andA.D. PoT- to fledging.Hawks do not always recognizetheir set, Calton, U.K. PALMER, R.S. [Ed.]. 1988. Handbook of North Amer- own young.Recently fledged Ospreys (Pandion hal- ican birds, Vols. 4, 5: .Yale Univ. Press, zaetus),for example,sometimes visit neighboring Os- New Haven, CT U.S.A. prey nestsand successfullybeg for food,sometimes POOLE,A.F. 1989. Ospreys, a natural and unnatural intimidating younger Ospreysin doing so (Poole history. Cambridge Univ. Press, Cambridge, U.K. 1989:111).The sameapparently occurs in the Eur- SHERROD,S.K. 1983. Behavior of fledgling Peregrines. asianSparrowhawk (Newton 1986:210). That Bald Peregrine Fund, Ithaca, NY U.S.A. Eagleshave reared both their own youngand young STEFANEK,P.R., W.W. BOWERMANIV, T.G. GRUBBAND Red-tailed Hawks, a third or a quarter of the size J.B. HOLT, JR. 1992. Nestling Red-tailed Hawk in of the eaglets,indicates how indiscriminatethe in- occupiedBald Eagle nest. J. Raptor Res. 26:40-41. stinct to feed a beggingchick may be. Extensive STEYN,P. AND N. MYBURGH. 1992. Observationson the breedingof a Pale Chanting Goshawk (Nlelierax cano- studieson captive breeding of manyraptors has shown rus). Birding in SouthernAfrica 44:80-83. that whenphysiologically prepared for breeding,they TENNESON,M. 1992. The dance of death. Am. Birds 46: oftenreadily adoptalien chicks,sometimes even halt- 197-203. ing incubationand perhapsinhibiting egg-laying to TLUSTY, M.F. AND F. HAMERSTROM. 1992. American do so. Kestrels(Falco sparverius) adopt and fledgeEuropean Researchon parental care is presently an active Starlings(Sturnus vulgaris). J. Raptor Res. 26:195. 184 WALTER R. SPOFFORDAND DEAN AMADON VOL. 27, NO. 4

WATSONJ.W., M. DAVISONAND L.L. LWSCHN•.R.1993. parentalcare" by T.H. Glutton-Brock.Condor 94:1035- Bald Eaglesrear Red-tailed Hawks. ]. RaptorRes. 27: 1036. 126-127. WINKLER, D.W. 1992. Review of: "The evolution of Received22 June 1992; accepted24 June 1993

REQUEST FOR INFORMATION

Dieter Schmidt is preparinga bookon the Red-napedShahin (Falco pelegrinoides babylonicus) also called the Russett- headedFalcon (F. pelegrinusbabylonicus) or Desert PeregrineFalcon (F. peregrinusbabylonicus). Schmidl requests the following informationon the species:literature mentioningthis falcon, e.g., from handbooks,checklists, expedition reports,etc.; publishedor unpublishedmanuscripts with observationsof, for example,breeding records and sightings; addressesof institutionsor personsengaged in the study of this falcon; and information on museum specimens.All contributionswill be acknowledgedand contributorswill be informedabout publicationdate of the book.--Dieter Schmidt, Max-Ptanck-Institut, D-82319 Seewiesen,Germany. FAX (8157)-29209.