SHORT COMMUNICATIONS 533

The Condor 88533-534 0 The Cooper Ornithological Society 1986

EXTRA AND HELPERS AT THE NESTS OF RICHARDSONS’ MERLIN ’

PAUL c. JAME.+AND LYNN W. OLIPHANT Department of VeterinaryAnatomy, Universityof Saskatchewan, Saskatoon,Saskatchewan S?N 0 WO, Canada

Key words: Merlin: Falco columbarius; helpers;extra a House Sparrow (Passerdomesticus). The yearling flew birds;Saskatoon; breeding behavior. to the perched male and the sparrow was transferred to him in the same way as usual heterosexualfood transfers. Cooperative breeding in birds is a widespread phenome- The yearling then flew to a nearby tree, where he cached non, yet its occurrencein raptors is much less common the kill. Severalminutes later, the adult male retrieved the in comparisonwith other taxa (Skutch196 1, Rowley 1976). sparrow, ate approximately half of it, and then flew to the In only two speciesdo breedinggroups occur regularly.In perched yearling where the food was again transferred. the GalapagosHawk ( galaoanoensis).these arouus This time the yearling flew to the nest, gave the half spar- are composedof severalmales and one female and appear row to the female and left. A similar food transfer between to be polyandrous (Faaborg et al. 1980); in the Harris’ the males was observed the following day. However, on Hawk ( unicinctus),groups are dominated by this occasion,the yearling ate the entire kill provided by males and may include extra females, but only the alpha the adult. The yearling was not seen killing his own food, male copulateswith the breeding female (Bednarz 1985, despite the fact that he would accompany the adult male Dawson and Mannan 1985). In addition, extra birds have on hunting forays. been recorded at the nests of the Mississippi Rite (Ictinia The yearlingwas alsoseen defending the nest areaagainst mississippiensis;Parker and Ports 1982), Red Rite (Milvus potential nest predators.For example, during the morning milvus;Davies and Davis 1973), Bald (Haliaeetus of 14 June, he vigorously attacked two American Crows leucocephalus;Sherrod et al. 1976, Fraser et al. 1983) (Corvusbrachyrhynchos), and later a Black-billed Magpie BateleurEagle (Terathopius ecaudatus: Brown 1952, 1953), that had approachedthe vicinity ofthe nest.Both incidents Red-tailed Hawk (B. iamaicensis:Wilev - 1975. Santanaet occurredwhile the adult male was absent and the female al. 1986),and American Kestrel (Falco sparverius;Wegner was at the nest. 1976). These and other studies have shown that raptor Other more casualobservations made in Saskatoonfrom helpers can be of either sex, with the majority of cases 1975 to 1984 suggestthat the above behavior may not be involving adults. We report here the first evidence of help- a uniqueincident. We have noted extra Merlins on at least ing at the nest in Richardson’s Merlins (F. columbarius 22 other occasionsthroughout the breeding seasonat 14 richardsonii),as well as document the regular occurrence out of 103 nesting attempts. All but one have involved of extra birds on Merlin breeding territories. birds in brown plumage, and at least 15 of these (71%) The most consistent observations (total ca. 600 min) were identified as males by their size and vocalizations. were made at a nestin the city of Saskatoon,Saskatchewan, The interaction of these birds with the resident pairs var- where an expanding Merlin population has existed since ied. The extra was supplantedfrom a perch on only about 1971 (Oliphant and Haug 1985). The nest, originally two occasions.No other negative reactions by resident made by a Black-billed Magpie (Picapica), was discovered birds have been noted. Extra birds have aiven the Coo- on 14 May 1985 approximately 13 m high in a maple ulation Chutter (Feldsine and Oliphant 1985) on five oc- (Acer spp.) tree. Our attention was initially drawn to the casions. When used by adult males, this call generally site by the vocal activitv of the Merlins. Based on this. indicatesa desireto copulate(Feldsine and Oliphant 1985). and the plumage/sizedifferences of the birds (Temple 1972; On two of these instances,the resident female then solic- Feldsine and Oliphant 1985), it was apparent that three ited to the extra male by bowing deeply and fanning her birds were in attendance: an unbanded adult male, an tail, but no copulation ensued.On one other occasion,the unbandedfemale, and a yearlingmale. The latter had been resident female copulatedwith the extra male. In addition banded as a nestling,and later recapturedon 5 November to the 1985 observations above, extra birds have been 1984 when it had been weighed, measured, and marked seen bringing prey into breeding territories on three oc- with a colored plastic leg jess (Warkentin 1986). We are casions, of which two involved food transfers to the fe- almost certain that the recipients of the help were not the males. An extra bird has also previously been seenaccom- parents of the helper. He was fledged from a nest located panying the resident adult male on a hunting foray. 2.6 km from the 1985 site, and both his parents in 1984 At first, we interpreted these observations solely as an were banded. Neither of the adults he helped in 1985 were unavoidable consequenceof the high Merlin nesting den- banded. Relatedness,however, is not essentialfor helping sity within the city of Saskatoon(Oliphant and Haug 1985). to be favored by natural selection (Reyer 1980). However, the constancyof extra bird sightings,their tol- Repeated visits to the site showed that the yearling re- erance by resident pairs, and their observed participation mained with the pair until the end of June. when he left in copulation,prey delivery, and nest defensesuggests that the area following the failure of the nesting’attempt. The the behavior could be more regular in occurrence. adults displayed no aggressiontowards him at any time. Nest defenseand food provisioning are two helper roles His interaction with them during this period is illustrated that have been describedin other raptors (de Vries 1973. by the following observations:on the morning of 14 May, Mader 1975, 1979, Wiley 1975, Wegner 1976, Faaborget the adult male was seen returning from hunting carrying al. 1980. Parkerand Ports 1982. Santanaet al. 1986). Their potential contribution to elevated breeding successand survivorship of the recipients is self evident. In return, a I Received 28 January 1986. Final acceptance6 May male helper can benefit from helping by being related to 1986. the brood helped, either directly by copulating with the 2Present address: Department of Biology, University of female (de Vries 1973, Faaborget al. 1980), or-indirectly Calgary, 2500 University Drive N.W., Calgary, Alberta, by helping his own parents (Woolfenden 1975). He could T2N lN4, Canada. also benefit by learning and practicing behavior that he 534 SHORT COMMUNICATIONS may subseauentlvuse (Brown 1978), or bv channellina SHOUGH. 1983. Three adult Bald Eaglesat an active fooh energ; towards himself as in the 1985-example (see nest. Raptor Res. 17:29-30. also Verbeek and Butler 1981). Whereas few Merlin heln- MADER,W. J. 1975. Extra adults at Harris’ Hawk nests. ers have been seen copulatingwith resident females, they Condor 77~482-485. could potentiallyfertilize eggs.At leastsome yearling males MADER,W. J. 1979. Breedingbehavior of a polyandrous are known to be able to breed successfully(Temple 1972), trio of Harris’ Hawks on southern Arizona. Auk 96: and 2 out of 18 successfulSaskatoon pairs in 1985 had 776-788. yearlingsas the only male present. In addition to the op- OLIPHANT,L. W., AND E. HAUG. 1985. Productivity, tions of regular breeding or helping, some yearlings ap- population density and rate of increaseof an expand- parently do neither. The factors underlying these alter- ing Merlin population. Raptor Res. 19:56-59. natives are unclear, although we do not believe that lack PARKER,J. W., ANDM. PORTS. 1982. Helping at the nest of nestinghabitat is important. The Saskatoonpopulation by yearling Mississippi Kites. Raptor Res. 16:14-17. is still expanding and much apparently suitable habitat REYER,H-U. 1980. Flexible helper structureas an eco- remains vacant. logical adaptation in the Pied Kingfisher, Ceryle rudis rudis. Behav. Ecol. Sociobiol. 6~219-227. We thank J. Faaborg, J. K. Schmutz, and J. W. Wiley for their comments on the manuscript, and J. Polson and ROWLEY,I. 1976. Cooperative breeding in birds. Symp. No. 10. Proc. XVI Int. Omithol. Congr. (1974):657- A. Schmidt for their observationson extra birds. The Mer- 693. lin researchwas supportedby University of Saskatchewan SANTANA,E. C., R. L. KNIGHT,AND S. A. TEMPLE. 1986. President’s NSERC and NSERC PostdoctoralFellowshins Parental care at a Red-tailed Hawk nest tended by to the senior author. three adults. Condor 88:109-l 10. LITERATURE CITED SHERROD.S. K.. C. M. WHITE. AND F.S.I. WILLIAMSON. 1976. Biology of the Bald Eagleon Amchitka Island, BEDNARZ,J. C. 1985. The breeding systemof the Harris’ Alaska. Living Bird 15:143-182. Hawk: cooperative polyandry? Abstr. 103rd AOU SKUTCH,A. F. 1961. Helpers among birds. Condor 63: meeting, Tempe, AZ. 198-226. BROWN, J. L. 1978. Avian communal breeding systems. TEMPLE,S. A. 1972. Sex and age characteristicsof North Annu. Rev. Ecol. Syst. 9: 123-155. American Merlins. Bird-Banding 43: 191-196. BROWN,L. H. 1952, 1953. On the biology of the large VERBEEK,N.A.M., AND R. W. BUTLER. 1981. Coopera- birds of prey of Embu District, Kenya Colony. Ibis tive breeding of the Northwestern Crow Corvuscaur- 94:577-620, 95174-l 14. inus in British Columbia. Ibis 123:183-l 89. DAVIES,P. W., AND P. E. DAVIS. 1973. The ecologyand VRIES,T. DE. 1973. The GalapagosHawk: an eco-geo- conservationof the Red Kite in Wales. Br. Birds 66: graphical study with the special reference to its sys- 183-224, 241-270. tematic position. Free Univ. Press, Amsterdam. DAWSON,J. W.,ANDR. W. MANNAN. 1985. Composition WARKENTIN,I. G. 1986. Successfulrelease of rehabili- and behavior of breeding groupsof Harris’ Hawks in tated Merlins (Falco columbarius).Can. J. Zool. 64: Arizona. Abstr. 103rd AOU meeting, Tempe, AZ. 262-264. FAABORG,J., T. DE VRIES, C. B. PATTERSON,AND C. R. WEGNER,W. A. 1976. Extra-parental assistanceby male GRIFL~N. 1980. Preliminary observationson the oc- American Kestrel. Wilson Bull. 88:670. currenceand evolution of polyandry in the Galapagos WILEY,J. W. 1975. Three adult Red-tailed Hawks tend- Hawk (Buteo galapagoensis).Auk 97:58 l-590. ing a nest. Condor 77:480-482. FELDSINE,J. W., AND L. W. OLIPHANT. 1985. Breeding WOOLFENDEN,G. E. 1975. Florida Scrub Jay helpers at behavior of the Merlin: the courtship period. Raptor the nest. Auk 92:1-15. Res. 19:60-67. FRASER,J. D., L. D. FRENZEL,J. E. MATHISEN,AND M. E.