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searchCouncil, the Canadian Wildlife Service, the St. LOKEMOEN, J. T., H. F. DUEBBERT,AND D. E. SHARP. Francis Xavier University Council for Research and 1990. Homing and reproductive habits of mal- the Nova Scotia Department of Lands and Forests. lards, gadwalls,and blue-wingedteal. Wildl. Mon- ogr. 106. p. 28. LITERATURE CITED POSTON,H. J.. 1974. Home range and breeding bi- BARTONEK,J. C., AND C. W. DANE. 1964. Numbered ology of the Shoveler. Can. Wildl. Serv. Rep. Ser. nasal discs for waterfowl. J. Wildl. Manaae. 28: No. 25. p. 49. 688-692. REED, A. 1970. The breeding ecology of the black BISHOP,R. A., D. D. HUMBURG,AND R. D. ANDREW% duck in the St. Lawrence estuary. D.Sc. thesis. 1978. Survival and homina of female mallards. Univ. Laval, Quebec. p. 175. J. Wildl. Manage. 42: 192-196. RINGELMAN,J. K., J. R. LONGCORE,AND R. B. OWEN, BLOHM.R. J. 1978. Mierational homine of male Gad- JR. 1982. Breeding habitat selection and home walls to breeding &unds. Auk 95763-766. rangeof radio-marked black ducks(Anus rubripes) COULTER,M. W., AND W. R. MILLER. 1968. Nesting in Maine. Can. J. Zool. 60:241-248. biology of black ducks and mallards in northern SEYMOUR,N. R., ANDR. D. TITMAN. 1978. Changes New England. Vermont Fish Game Dep. Bull. 68- in activity patterns, agonistic behavior, and ter- 2. p. 73. ritoriality of black ducks (Anus rubripes)during DWYFR,T. J., S. R. DERRICKSON,AND D. S. GILMER. the breeding seasonin a Nova Scotia tidal marsh. 1973. Migrational homing by a pair of Mallards. Can. J. Zool. 56:1773-1785. Auk 901687. SEYMOUR,N. R., ANDR. D. TITMAN. 1979. Behavior EVRARD,J. 0. 1990. Male philopatry in Mallards. of unpaired male black ducks(Anus rubripes)dur- Condor 92:247-248. ing the breeding season in a Nova Scotia tidal GREENWOOD,P. S. 1980. Mating systems,philopatry marsh. Can. J. Zool. 57:2421-2428. and dispersal in birds and mammals. Anim. Be- SOWLS.L. K. 1955. Prairie Ducks. Wildlife Manage- hav. 28: 1140-l 167. ment Institute, Washington, DC. LESSELS,C. M. 1985. Natal and breeding dispersalof TITMAN, R. D. 1983. Spacing and three-bird flights Canada Geese (Brunta can&ens@. Ibis 127:3l- of Mallards breeding in pothole habitat. Can. J. 41. Zool. 61:839-847. LINCOLN,F. C. 1934. The operation of homing in- stinct. Bird-Banding 5: 149-l 5 5.

The Condor93:191-193 0 The Cooper Ornithological Society I99 I

UNDESCRIBED BOWING DISPLAY IN THE COOPER’S HAWK’

ROBERTN. ROSENF~ELD* Department of Zoology, North Dakota State University,Fargo, ND 58105

JOHN BIELEFELDT Park Planning, Rucine County Department of Public Works, Sturtevant, WI 53177

Key words: Coopers’ Hawk; Accipiter cooperii; when Cooper’s Hawks typically begin daily nest build- bowingdisplay; nest building. ing activities. On nine occasions immediately following the ap- As part of a lo-year study of the nesting ecology of pearanceof a mated pair at the nest site at dawn, we Cooper’s Hawks (Accipitercooperii) in Wisconsin, we saw a bowing display in eight marked males and one obtained data on pre-incubation behavior of 47 mated female. The display never exceeded 60 set and in no pairs during 1986-89. Here we describean unreportd casedid both members of the pair exhibit the behavior Bowing display,seen 10 times among nine birds during simultaneously.Displaying birds assumeda horizontal the me-laying period, and discussits function. standingposition from which “bursts” of quick bowing All displays were seen in Waukesha County, south- movements (3-10) occurred,each bow was interrupted eastern Wisconsin (42”53’N, 88”29’W) (Rosenfield by very short (< 1 set) pauseswith the forebody at the 1990). All observations save one occurred at dawn, horizontal plane (Fig. 1). The legs did not bend no- ticeably during bows and thus only the upper body tipped downward. Wings and tail were not spreadand I Received 2 July 1990. Final acceptance24 October the tail moved up only as the head and chest were 1990. lowered (Fig. 1). In at least one male, the tail under- 2 Current address: College of Natural Resources, coverts were spread. Two males were silent; six males University of Wisconsin, Stevens Point, WI 5448 1. gave several kik calls during this behavior. At other 192 SHORT COMMUNICATIONS

FIGURE 1. Bowing display.

times, males use this note to “announce” their arrival in Pelecaniformes probably evolved from nest-build- at the nesting area with prey (Meng 1988). Both sexes ing movements. commonly give this same vocalization at dawn in the Bowing displays have been reported in many avian pre-incubation period (pers. obs.) and we believe it orders, including Falconiformes (Sherrod et al. 1981, servesprimarily to signala bird’s location. During one Cade 1982), and may have evolved for different rea- display that was seen more clearly than the others, a sons in different orders and species. Sherrod (pers. male appearedto tuck his head toward his chestwhile comm.) believes that male raptors bow to convey their bowing the forebody (the head was thus below the “submissiveness”to their larger,dominant mates when “normal” plane of the body) and he uttered kik calls the birds are perched close to each other. This expla- only between bows, when the body was horizontal, The nation is not incompatible with ours. Bowing as sym- single female seen bowing gave a single kik at the be- bolic nest building by male Cooper’s Hawks could also ginning of display. Male-to-female distancesduring this function as or extend the function of “appeasement.” behavior ranged from 1 to 41 m (X = 22 m). It is possible that the bowing display in Cooper’s All bowing displaysoccurred just prior to nest build- Hawks occurs more frequently during pair formation ing, and except for a singleafternoon instance,bowing or in new pairs, as in other species(Green-backed Her- occurred only in the morning- the time of peak daily on [B. s. sundevalli],Kushlan 1983; Ring Dove [Strep- building (Rosenfield 1990). Bowing might function as topelia risoria], Erickson and Morris 1972; Peregrine demonstrative nest-building that signalsa bird’s readi- Falcon [F&o peregrinus],Sherrod, pers. comm.). Of nessto engagein actualbuilding. Cooper’s Hawks build the 10 times we observed this behavior, seven were nests by shoving twigs into the structure, repeatedly early in the pre-incubation stage(from 3 1 to 2 1 days grabbingthe sticksat different points along their length before the first eggswere laid in these pairs). The other and pushingthem into the existing base.Such repeated three occasionswere about two weeksbefore eggswere grabbing resultsin body and head movements similar laid. At least five of the 10 pairs in which bowing was to those seen in bowing. Bowing behavior was seen seen included a new mate. mainly in males, the sex that does most of the building We thank K. L. Bildstein, J. W. Grier, and S. K. (Rosenfield 1990). Sherrod for helpful comments on this manuscript, and Many bird specieshave incorporated some elements J. M. Papp for drawing the figure. of nest building behavior into courtshipactivities. This ranges from “symbolic” holding of nest materials in LITERATURE CITED the beak during courtship displaysto males’ construc- tion of entire nestsused to attract females (Collias and CADE,T. J. 1982. Falcons of the world. William Col- Collias 1984). The male Green-backed Heron (Buto- lins Sons, London. ridesstriatus) attracts the attention of other heronswith COLLIAS,N. E., AND C. C. COLLIAS. 1984. Nest build- loud calls and a Snap display in which he extends his ing and bird behavior. Princeton Univ. Press, neck forward and down and snaps his mandibles to- Princeton, NJ. gether to produce an audible click. The display resem- ERICKSON,C. J., ANDR. L. MORRIS. 1972. Effects of bles movements of nest-building, and Meyerriecks mate familiarity on the courtshipand reproductive (1960) consideredit to be ritualized twig-grasping.Van successof the -Ring Dove (Streptopeliarisoria). Tets (1965) suggestedthat courtship bowing displays Anim. Behav. 20:341-344. SHORT COMMUNICATIONS 193

KUSHLAN, J. A. 1983. Pair formation behavior of the cipiter cooperii [Bonaparte]). Ph.D. diss. North GalanaaosLava Heron. Wilson Bull. 95: 118-12 1. Dakota State Univ., Fargo. MENG, HI K. 1988. Cooper’s Hawk: voice, p. 327- SHERROD,S. K., W. R. HEINRICH,W. A. BURNHAM,J. 328. In R. S. Palmer [ed.], Handbook of North H. BARCLAY,AND T. J. CADE. 1981. Hacking: a American birds, vol. 4, part 1. Diurnal raptors. method for releasingPerearine Falcons and other Yale Univ. Press, New Haven, CT. birds of prey. The P&egrine Fund, Inc., Fort Col- MEYERRIECKS,A. J. 1960. Comparative breeding be- lins, CO. havior of four speciesof North American herons. VAN TETS,G. F. 1965. A comparative study of some Publ. Nuttall Omithol. Club, No. 2. Cambridge, social communication patterns in the Pelecani- MA. formes. Omithol. Monogr. No. 2. American Or- ROSENFIELD,R. N. 1990. Pre-incubation behavior nithologists’ Union, Washington, DC. and paternity assurancein the Cooper’s Hawk (Ac-

The Condor93119%197 0 The Cooper Ornithological Society 199 I

THE DIET OF PEREGRINE FALCONS IN RANKIN INLET, NORTHWEST TERRITORIES: AN UNUSUALLY HIGH PROPORTION OF MAMMALIAN PREY ’

MARK BRADLEY Department of RenewableResources, G.N. W. T., Awiat. N. W.T. XOC OEO, Canada LYNN W. OLIPHANT Department of Anatomy, WCVM, Universityof Saskatchewan,Saskatoon, SaskatchewanS7N 0 WO, Canada

Throughouttheir virtually world-wide range,Peregrine METHODS Falcons (Falco peregrinus)rely almost completely on The study area surroundsthe Inuit hamlet of Rankin the aerial capture of other birds (Cade 1960, Radcliffe Inlet (Keewatin Region, Northwest Territories, Can- 1980). Moreover, the Peregrine’s reliance on a wide ada) on the northwest coast of Hudson Bay. The area range of stable avian prey populations is believed to is tundra interspersedwith rocky outcrops that form be responsiblefor the great stability of their breeding the cliffs used for nesting. July mean high and low density and reproductive output (Newton 1979, Rat- temperaturesare 13.1”C and 4S”C. Peregrine Falcons cliffe 1980). arrive in late May and leave again in late September In our study area near Rankin Inlet, Northwest Ter- or early October. Laying is usually in the first 10 days ritories, Canada, however, Peregrine Falcons are not of June, eggshatch in mid-July, and young fledgefrom very stable in either breeding density or reproductive mid to late August. A complete descriptionof the study output. The number of successfulpairs rose from a area and the natural history of the population has been three-year mean of 13 to 2 1 and production of fledg- given elsewhere(Court et al. 1988a, 1988b). lings nearly doubled in conjunction with a 1985 peak During the nestling period, we collected pellets (the in microtine rodent density (Court et al. 1988a, 1988b). regurgitated,indigestible body parts of prey) and prey The authorsspeculated that the microtine increasepro- remains once each week from three nests in 1986, and vided an abundant food resource that the Peregrine from five nests in 1987. We made collections every Falcons exploited to their reproductive advantage. A three days from an additional two nests in 1986. We subjective appraisal of prey use during the microtine removed all prey remains prior to the first collection, peak year indicated that both microtine rodents and and after each subsequentcollection to prevent count- arctic ground squirrels were being eaten (Court et al. ing prey individuals twice. 1988a). Analysis of remains was similar to methods used by We wanted to determine if mammals were a normal Mollhaaen et al. (1972). We examined remains and prey speciesfor the Rankin Inlet PeregrineFalcon pop- dissectedpellets from eachcollection, and recordedthe ulation. Therefore, in this paper, we quantitatively de- number of each kind of identifiable body part. The scribe the diet of Peregrine Falcons of Rankin Inlet minimum number of animals was equal to the greatest during two years of non-peak microtine abundance. number of identical bones per taxon. If no countable items were found from a species,then we counted one individual for findina the hair or bodv feathers. Ju- ’ ’ Received 10 July 1990. Final acceptance6 Novem- venile plumagesenabled us to distinguishbetween age ber 1990. classesof most passerinesand shorebirds.