]. Raptor Res. 25(3):94-95 ¸ 1991 The Raptor ResearchFoundation, Inc.

JUVENILEURBAN-HACKED PEREGRINE FALCONS (galcoperegrinus) HUNT

AT NIGHT

ANNIE

WENDT

Wisconsin PeregrineSociety,P.O. Box 7748,Milwaukee,WI 53207-7748 GREG SEPTON

Milwaukee Public Museum, 800 W. Wells St., Milwaukee, WI 53233

JEFF MOLINE

7202CountryClub,Apt. 7, SantaTeresa,NM 88008 Although PeregrineFalcons(Falcoperegrinus)are considereddiurnal raptors,they have taken bats in the dim light of dawn and dusk (Stager 1941, Ratcliffe 1980). Beebe(1960) reportedthat Peale'speregrines(F. p. pealeO hunted nocturnal seabirds"so late in the evening,or so early in the morning,as to be almostnocturnal."Nelson (1970) found that peregrinesnestingin murrelet colonies did not hunt during the day until mostof the murrelets had movedoffshore.Here we report nocturnalhuntingby young peregrinesreleasedin Milwaukee, Wisconsinin 1987.

We released14 captive-produced peregrinesby hacking, describedby Sherrodet al. (1982). The releasesite was on the top-floorledgeof the First WisconsinCenter, 178 m above street level. We

colormarked

the falcons with

fluorescentpaint and releasedfive of them on 27 July, five on 6 August,and four on 9 August.We watchedthem from the "411 Building"locatedtwo blockswest,arriving each morning beforefirst light and stayinguntil dark. We fed the falconsby tying Coturnix Quail (Coturnix spp.) to two hack boards:one board was attachedto the hack box and the other to the roof of the 12-storyNorthwestern Mutual Life InsuranceBuilding (NML) across thestreetandto thenorth.Everyevening,afterdark (about 2030-2100 H) from27 July throughtheendof September, we removedthe uneatenfoodand tied enoughfresh quail

many ledgesand was a favored roostingplace for the falconsbothday and night. From duskto midnight,spotlights mountedon the ledgespoint up againstthe brick walls,illuminatingthe building.As we left the NML after resupplyingthe hackboards,we couldseeas many as six peregrinesat a time circling the Gas Co., chasingeach otherand dartingaboutrather recklessly, lit from below by the spotlights. We first found cached,night-killed prey on the "411" roof the morningof 8 September.Each night thereafter, we removedall prey remainsbeforeleavingthe building. Each morning,beforefirst light, we returnedand found the bodiesof birds that the falconshad cachedon the 411, NML, and Gas Co. buildings. The falconsfed on these

cachedbirds during the day, ignoring the quail on the hack boards.From 8-16 Septemberwe found a total of 38 Yellow-billedCuckoos(Coccyzus americanus), oneBlackbilledCuckoo(C. erythropthalmus), andoneRose-breasted Grosbeak (Pheucticusludovicianus),with a maximum of

13 birdson 13 September.Many of the cachedbirds had their bodies"raked" open or had their heads removed, both consistent with peregrinekills. On 17 September,the weatherchangedabruptly from warm, sunny,and breezy,to cooland rainy for 1 wk. We found few new kills, and the falconsonceagain ate the quail we provided. Once the weather cleared after 22 to the boards to ensure that each falcon could eat its fill September,the falconsstoppedrelying on the quail on a the next day.The falconsfirst startedcatchinglarge,flying daily basis.We foundan averageof 1-2 new kills per day, insects(i.e., dragonflies,butterflies)on 7 Augustand birds and saw the falcons retrieving cachedfood from other on 27 August.We sawthem huntingdowntownand along buildings.By 29 September,all the falconshad stopped the shoreof Lake Michigan, which is about four blocks usingthe hack board and we closedthe site for the season. east of the release site. Ten of the youngfalconssurvivedto independence; the Severalthingssuggested that the youngperegrineswere otherfour were killed or crippledwithin 1 wk of release. activeat night. We often heard them calling as they flew The falcons'increasedhunting proficiencyapparently pastwhile it was still too dark for us to see.At daybreak, corresponded with an influx of cuckoosinto the area. The we found falcons on the NML roof, where none had been city lights probably encouragedthe nocturnalhunting; perchedthe night before.They often had full crops,or D.M. Bird (pers. comm.) has seenAmerican Kestrels(F. were just finishinga quail they had managedto remove from the hack board. sparverius) huntinglarge, flying insectsat night underthe On at leastsix nightsin August,we saw the peregrines lights of Montreal's Olympic Stadium. It is possiblethat flying at night. The WisconsinNatural Gas Company wild peregrinesalso take night-migratingbirds, particuBuilding (Gas Co.), acrossthe streetfrom the NML, has larly when the moonis full. 94

FALL 1991

SHORT COMMUNICATIONS

RESUMEN.--Halcones Peregrinos(Falcoperegrznus) jCvenes,que fueron sueltosen Milwaukee, Wisconsinen 1987, estuvieronactivosy cazarondurante la noche.Desde el 8

95

NELSON,R.W. 1970. Someaspectsof the breedingbehavior of Peregrine Falconson Langara Island, B.C. M.S. thesis,University of Calgary, Calgary, Alberta,

Canada. al 16 de septiembre, encontramos 38 cuclillosde la especie RATCLIFFE,D.A. 1980. The Peregrine Falcon. Buteo Coccyzus americanus,1 de la especieC. erythropthalmus, y Books, Vermillion, SD. 1 picogordode la especiePheucticus ludovicianus, que habian sido cazadosen la noche; con un m5ximo de 13 aves SHERROD, S., W. HEINRICH,W. BURNHAM,J. BARCLAY ANDY. CADE. 1982. Hacking: a methodfor releasing el dla 13 de septiembre.Muchas de las avescapturadas PeregrineFalconsand other birds of prey. The Pertenian los cuerposabiertosy decapitados, lo que es consistenteen las vlctimasde HalconesPeregrinos. egrineFund, Inc., Ithaca, NY. [TraducciCnde Eudoxio Paredes-Ruiz] STAGER, K.E. 1941. A groupof bat-eatingDuck Hawks. ACKNOWLEDGMENTS

Condor 43:137-139.

We thank David Bird, Fran Hamerstrom, R. Wayne Nelsonand ClaytonWhite for reviewingthis manuscript. LITERATURE

CITED

BEEBE,F.L. 1960. The marine peregrinesof the Northwest Pacific Coast. Condor 62:145-189.

Received30 November 1990; accepted31 May 1991