J. Raptor Res. 27(2):113-116 ¸ 1993 The Raptor Research Foundation, Inc.

A THRE^T DISPL^YOF THE NORTHERNSaW-WHET (Aegoliusacadicus)

CHARLES T. COLLINS Departmentof Biology,California State University,Long Beach,CA 908d0 U.S.A.

Despite a voluminous literature on of the world by the observermoving away for a coupleof minutesand (Burton 1973, Clark et al. 1979, Mikkola 1983, Johnsgard then approachingthe owl again. 1988, Voous 1988) much remains to be learned about the DISCUSSION d•splaybehaviors of many strigids(Holt et al. 1990), par- Some componentsof the FUBB display sequencere- ticularly thoseinhabiting remote areas. I describeherein semblebehaviors noted in other owl speciesunder various a threat behaviorsequence of the Northern Saw-whetOwl conditions.The extreme upright stance(Fig. 2b), not ac- (Aegoliusacadicus) not previouslyreported in recentfield companiedby plumage fluffing, was noted many times in studiesof this species(Hayward and Garton 1984, Can- a hand-rearedcaptive juvenile EasternScreech-Owl (Otus nings 1987). asio)when inquisitiveand exploringits environment(Fig. 3). A similar upright defenseposture with feathererection OBSERVATIONS occursin the Barking Owl (Ninox connivens;Fleay 1968) The observationswere made on three captiveadult owls but that speciesalso includeswing spreadingnot noted in (Collins 1961, 1963) capturedin southernMichigan dur- Aegolius.Similarly, fluffing of the body plumage accom- ing the winters of 1960-61 and 1962-63. One femaleowl panied by sidewaysswaying and a raising and lowering was maintainedindoors in an area of high human activity of the body is part of a threat display of the Tropical and the othertwo (1 male, 1 unsexed)in an enclosedporch Screech-Owl(Otus choliba; Thomas 1977). A more gen- with little humancontact. All were tetheredon blockperches eralizedfluffing of the plumageat the approachof a person by jessesand a shortleash and fed laboratorymice (Mus or foreignobject has'been noted in severalspecies of strigids musculus). in captivity(pers. observation). When approachedwithin 2 m the owls often became Threat displaysof the Barn Owl (Tyto alba; Walker excited and exhibited the preflight fright reaction de- 1974:2, Bunn et al. 1982, pers.observation), Sooty Owl scribedby Catling (1972) for untetheredbirds. This in- (Tyrotenebricosa; Fleay 1968), Masked Owl (Tyro novae- cludedhead bobbing,head turning, foot shifting and even- hollandiae;Fleay 1968) and Asian Bay Owl (Phodilusbad- tual escapeflight. Only once, stimulatedby the calling of ius;Wells 1986) includean archingof the head forward a captivekestrel (Falco sparverius), was the extremesleeked- until the bill facesthe groundor almostbackward between feather concealingpose (Catling 1972:Fig. 1, Holt et al. the legs. In these species,this display is accompaniedby 1990) observed.On at least 15 occasions,however, each archingthe spreadwings and usuallya side-to-siderocking of the three owls exhibited a distinct fluff up, bow, buzz of the bodywith a shiftingfrom one foot to the other. In (FUBB) displaysequence in reactionto similar suchhu- Barn Owls, a high intensity expressionof this display •s man approach.The FUBB display was not observedin accompaniedby a rapidly repeated keck-keck-keck vo- newly captured individuals but only after the owls had calizationor bill snapping(pers. observation). In the Saw- been in captivity for a minimum of one week. whet Owl, there is: 1) no spreadingor archingof the wings, The sequence(Fig. 1) beganwith a generalfluffing up 2) a pronouncedforward bending of the body(Fig. 1, 2d) of the body plumage and exaggeratedupright stance.It and not just an arching forward and lowering of the head, was followedby a forward bow of the body and head. It and 3) no lateral movementof the bodyor feet. In the Bay ended with the raising of the head and a brief -like Owl, the performance is terminated by the head being buzz vocalization. In the first stage, the feathers of the flung up and forward emphasizingthe pale facial disk, upper belly and breastwere fluffed up and spreadlaterally large dark eyesand openbill (Wells 1986). In the Saw- (Fig. 2a) increasingthe apparent size of the . This whet Owl, the raising of the headis deliberaterather than was quickly followedby the extensionof the legsto raise rapid and the buzz vocalization accompaniesthis head the upright body (Fig. 2b). The wings and tail did not movement.Although FUBB displaycomponents are sim- appear to be extendedduring this sequence,nor was there ilar to parts of displaysof other tytonid and strigid owls, any apparent ptiloerectionof the dorsal body feathers, the total sequenceseems unique to Saw-whet Owls. No head, or face. In the secondstage, the body was bent similar display has been recordedto date in field studies forward until the head was facing downward and the bill of the congeneric (Aegoliusfunereus, was nearly at the levelof the perchsubstrate (Fig. 2c, d). Mikkola 1983, Hayward et al. 1987). At this point, with the body still in the near horizontal The function of this display and the context in which position,the headwas raisedso that it again facedforward it would be utilized in wild owls is unclear. It is likely to toward the intruder (Fig. 1) and the buzz vocalization be a form of threat display and the buzz componentcom- was emitted. Following this the owl returned to the normal parable to the hissing soundsreported for a number of upright stance and sometimesbegan the fright reaction speciesincluding some owls (Bent 1938, Sibley 1955, Fleay and attemptedflight. In no casewas the FUBB display 1968, Mikkola 1983, Johnsgard1988). The previously immediately repeated although it could be again elicited describedconcealing (Catling 1972) or freezing(Taylor

113 114 SHORT COMMUNICATIONS VOL. 27, NO. 2

Figure 1. The completefluff up, bow, buzz (FUBB) display sequenceof the Saw-whet Owl. From left to right, resting pose,feather fluff and upright stance,bow, and bow with raised head when buzz is emitted

Figure 2. Fluff up, bow, buzz (FUBB) displaycomponents. a) Initial fluffing of breastfeathers, b) full feather fluff and upright stance,c) start of bow, d) full bow with bill facing down. Not shown is raised head positionwhich is accompaniedby buzz vocalization. JUNE 1993 SHORTCOMMUNICATIONS 115

LITERATURE CITED BENT, A.C. 1938. Life histories of North American of prey. Part 2. Bull. No. 170, U.S. National Museum, Washington,DC U.S.A. BUNN, D.S., A.B. WARBURTON AND R.D.S. WILSON. 1982. The Barn Owl. Buteo Books, Vermillion, SD U.S.A.

ß BURTON,J.A. 1973. Owls of the world, their evolution, structureand ecology.E.P. Dutton & Co. Ltd., Lon- don, U.K. CANNINGS,R.J. 1987. The breedingecology of Northern Saw-whet Owls in southernBritish Columbia. Pages 193-198 in R.W. Nero, R.J. Clark, R.J. Knapton and R.H. Hamre [EDS.],Biology and conservationof north- ern forest owls: symposiumproceedings. Gen. Tech. Figure 3. Upright inquisitivestance of juvenile Eastern Rep. RM-142, U.S. Forest Service,Rocky Mountain Screech-Owl. Forest and Range Experiment Station, Fort Collins, CO U.S.A. CATLING,P.M. 1972. A behavioral attitude of Saw-whet and Boreal Owls. Auk 89:194-196. 1962) postureand fright reaction (Catling 1972) in Ae- goliusare morefrequently observed in approachsituations. CLARK, R.J., D.G. SMITH AND L.H. KELSO. 1979. However, there are also numerous reports of wild Saw- Working bibliographyof owlsof the world. Sci. Tech. whet Owls allowing very closeapproach by humanswith Ser. 1, National Wildlife Federation,Washington, DC the owls showing no signsof either defenseor escape U.S.A. (Wilson 1931, Bent 1938). The FUBB display may be COLLINS, C.T. 1961. Tail molt of the Saw-whet Owl. utilized in situationswhen easy escapeis not an option. Auk 78:634. This would accountfor the FUBB displaynot beingseen 1963. Notes on the feeding behavior,metabo- in newly capturedbirds but only in onesthat had adjusted lism, and weight of the Saw-whet Owl. Condor65: to captivity and their inability to escape.In support of 528-530. this, a female Saw-whet Owl cornered in a nestbox (Santee and Granfield 1939) showed the fluffed out breast feathers FLEAY, D. 1968. Nightwatchmen of bush and plain. typical of the first stageof the FUBB display;the bird Jacaranda Press,Brisbane, Australia. subsequentlyleft the box without any other FUBB com- HAYWARD,G.D. AND E.O. GARTON. 1984. Roost habitat ponentsbeing noticed.Michael and Michael (1928) re- selectionby three small forest owls. WilsonBull. 96: ported a Saw-whet Owl perchedjust inside the opening 690-692. of a nest cavity to emit a buzzing vocalizationwhich re- , P.H. HAYWARD AND E.O. GARTON. 1987. sembled"the sizzlingof water on a hot stove"when star- Movement and home range use by Boreal Owls in tled. However, this was certainly the beggingvocalization Central Idaho. Pages 175-184 in R.W. Nero, R.J. of a nestling(R.J. Cannings,pers. comm.) rather than an Clark, R.J. Knaptonand R.H. Hamre [EDS.],Biology adult vocalizationas suggestedby Michael and Michael (1928). No FUBB componentswere noticedin other cap- and conservationof northern forest owls: symposium tive Saw-whet Owls evenwhen stimulatedto the point of proceedings.Gen. Tech. Rep. RM-142, U.S. Forest attack (Schaeffer 1973). Further field studiesof wild owls Service,Rocky Mountain Forest and Range Experi- may help verify the exact function and context of this ment Station, Fort Collins, CO U.S.A. display. HOLT, D.W., R. KLINE AND L. SULLIVAN-HOLT. 1990. A descriptionof "tufts" and concealingposture in Northern Pygmy Owls. J. Raptor Res. 24:59-63. RESUMEN.--Una conducatade amenaza es descritapara JOHNSGARD,P.A. 1988. North American owls. Smith- el bfihoAegolius acadicus. La conductaincluye una postura erguidacon un aumentode volumendel cuerpopor ex- sonian Institution Press,Washington, DC U.S.A. pansi6nde las plumas,seguido por una indinaci6nhacia MICHAEL, C.W. AND E. MICHAEL. 1928. Behavior of adelantey una vocalizaci6nparecida a un zumbido. Saw-whet Owls in Yosemite Park. Condor 30:323-324. [Traducc•6ndeIvan Lazo] MIKKOLA,H. 1983. Owls of Europe. T. and A.D. Poy- ser, Calton, U.K. SANTEE,R. AND W. GRANFIELD. 1939. Behavior of the ACKNOWLEDGMENTS Saw-whetOwl on its nestinggrounds. Condor 41:3-9. I am grateful to Ann Wurdeman for her drawing (Fig. SCHAEFFER,F.S. 1973. Tactile bristlesof Saw-whet Owls 1) and to P.H. Collins, R.J. Cannings,D.W. Holt and are sensitiveto touch. Bird-Banding 44:125. K. McKeever for helpful commentson the manuscript. SIBLEY,C.G. 1955. Behavioralmimicry in the titmouse 116 SHORT COMMUNICATIONS VOL. 27, NO. 2

(Paridae) and certain other birds. WilsonBull. 67:128- WAL•CER,L.W. 1974. The book of owls. A.A. Knopf, 132. New York, NY U.S.A. TAYLOR, R.R. 1962. Fall Saw-whet Owl concentrations WELLS,D.R. 1986. Further parallelsbetween the Asian in Ontario. BlueJay 20:118-119. Bay Owl Phodilusbadius and Tyro species.Bull. Br. THOMAS,B.T. 1977. Tropical ScreechOwl nestdefense Ornithol. Club 106:12-15. behaviorand nestlinggrowth rate. WilsonBull. 89:609- WILSON,E.S. 1931. Tamenessof Saw-whet Owl (Cryp- 612. toglauxacadica acadica). Auk 48:266-267. Voous, K.H. 1988. Owls of the northernhemisphere. MassachusettsInstitute of TechnologyPress, Cam- bridge, MA U.S.A. Received1 September1992; accepted 22 January 1993

] Raptor Res. 27(2):116-118 ¸ 1993 The Raptor ResearchFoundation, Inc.

NATAL ORIGINS AND WINTER SITE FIDELITY OF ROUGH-LEGGED HAWKS WINTERING IN CALIFORNIA

BARRETT A. GARRISON WildlifeManagement Division, California Department of Fish and Game, 1416 Ninth Street, Sacramento,CA 95814 U.S.A.

PETER H. BLOOM WesternFoundation of VertebrateZoology, 439 Calle San Pablo,Camarillo, CA 93010 U.S.A.

Rough-leggedHawks (Buteolagopus) are a relatively dead August 1990 near Santa Cruz, California. The sum- commonwinter resident in California (Small 1974), but mer recoverydate for bird No. 4 is atypicalbecause it was to date there has been no information publishedon the found dead, and it is not known when the bird died. The breedingareas and movementsof California's wintering four Alaska birds were recovered at different locations in population.Therefore, we analyzedencounters of banded California (Table 1). birdsto documentnatal origins,site fidelity, and migratory Ten birds were banded in California and one bird was movementsof Rough-legged Hawks wintering in Cali- bandedin Nevada during the winter periodbetween No- fornia. vember and February; all were recoveredbetween De- All currently known banding encounters(N -- 16) in- cemberand April (Table 1). Of these 11 birds, 4 (36%, volvingRough-legged Hawks in Californiawere analyzed Nos. 9, 10, 15 and 16) were banded in California and for this study. The Bird Banding Laboratory, U.S. Fish recoveredor recapturedin the sameLat-Long blockwhere and Wildlife Service,provided 13 banding encountersof banded.Bird No. 15, bandedby P.H. Bloomas an HY in Rough-leggedHawks recoveredin California or banded December1977, was recapturedin December1978 in the in California and recovered elsewhere between 1966 and samefield where initially banded,while No. 16 was re- 1991. In addition, three recapturesof bandedbirds were capturedin January 1988 within 1.6 km of the banding usedin thisstudy. P.H. Bloomcaptured and/or recaptured locationof February 1987 (L. Spiegeland P. Detrich pers. six birds using bal-chatris (Berger and Mueller 1959) comm.). Three birds (27%, Nos. 6, 12 and 14) were re- baited with two domesticHouse Mice (Mus musculus)or coveredone Lat-Long blockfrom the initial bandingblock, one House Mouse in combination with other domestic and four birds (36%, Nos. 7, 8, 11 and 13) were banded rodentsor HouseSparrows (Passer domesticus; Bloom 1987). at different locations in California and Nevada and re- Four encounters(Nos. 1-3 and 5) were of nestling coveredat different locationsin California, Oregon, and Rough-leggedHawks banded on their natal areas and Nevada. recoveredduring the winter period in California (Table The length of time betweenbanding and recoveryfor 1). Three nestlingswere bandedin July at three different the 16 encountersaveraged 540 _+ 697 SD d. Young of locations on the Colville River, Alaska, and the fourth the year (L and HY) (N = 7) birds averaged413 _+304 nestlingwas bandedin August at Franklin, BanksIsland, SD d betweenbanding and recovery,while older birds Northwest Territories. A fifth banding encounterfrom a (AHY, SY, ASY, U) bandedon the wintering grounds natal area was an immature (HY) bird (No. 4) that was averaged640 _+903 SD (N = 9) d. The differencebetween banded September 1988 near Delta, Alaska and found recoveryperiods for youngof the year and older birdswas