SHORT COMMUNICATIONS

Observationsof Nesting Northern Pygmy-

DEriVER W. HOLT ^r•D WILLI^M D. NORTOr•

On 18 April 1981, nests of a Northern Pygmy- Prey information was difficult to obtain. Pellets are (Glaucidiumgnoma) and Northern Saw-whetOwl (Aegoliua small(average 17.5 x 9.6 ram; N = 26), roostingareas of acadicus)were discovered in the same tree in Missoula the male difficult to locate,and the owlsdid not deposit County, Montana (Norton and Holt 1982). We know of pelletsbelow the nestingcavity. Of the nineteen prey only one reported (Holman 1926) observationof nesting items identified, ten were mammals and nine were Noi•thernPygmy-owls in .The purposeof (Table 1). this paper is to summarizeour observationsand provide During one observationat dusk,the female pygmy-owl information on a little known North Americanspecies. attacked and killed a Red Squirrel (Tamiasciurushud- The nestwas visited daily 4 April - 21June ! 981. Obser- sonicus)on the ground and fed there. Similarly,in Feb- vationswere madeusing binoculars and a variablepower ruary 1982,we observedtwo other Northern Pygmy-owls spottingscope from distancesof 15-50 m. The owlswere preying on Bohemian Waxwing (Bombycillagarrulus) and observedfrom the onsetof their activityin late afternoon cachingand feeding on them on the ground and under until activityceased in the evening.Pellets and prey re- bushes.Apparently, Northern Pygmy-owlsare capableof mainswere collectedfrom the nestfor analysisafter the killinglarge prey, but someprey maybe too heavyto fly nestlingsfledged. Prey itemswere identified by cranial, with and mustbe eatenor partiallyeaten on the ground. dental and feather characteristics.Three prey itemswere Tail switchingbehavior by the adult owlswas displayed retrievedafter the male wasobserved caching them. Two only when we approachedclosely. The tail was switched otherswere observedin possessionof the female. These from sideto sidewith a quick,jerky motion.The distance observationsare in addition to prey deliveriesfrom male betweenthe observersand the tail switchingowl wasnot to femalereported by Norton and Holt (1982). measured; however, the behavior occurred whether or The adult femalepygmy-owl was observed each day at not the owl had prey. We observedthe samebehavior in the cavity'sentrance. These observations,and observa- wintering Northern Pygmy-owls.A description of the tionsthat the male never entered the cavity,indicate the nest,nest tree and habitattype has been reported (Norton femaleas the soleincubator and brooder.Each evening at and Holt 1982). dusk,the male called(a hollow, slowtoot-toot) at approxi- Kellomaki(1977) labelledthe site of prey exchange matelyone secintervals until the female camefrom the between the male and female European Pygmy-owl nestcavity to the area in whichhe wasperched. Appar- (Glaucidiumpasserinum) as the "sojourningsector", an area entlythis call solicited the femaleto receiveprey from the of prey deliverygenerally 10 - 30 m in front of the nest. male. Prey was exchangedin a small tree located ap- We refer to this area as the "prey exchangearea". Prey proximately10 m in front of the cavityentrance. A soft exchangebetween adults continueduntil the nestlings twitteringvocalization was made by one or both owlsdur- fledged, although the female began to hunt nine days ing the exchange,followed by the departure of the male. afterthe eggs hatched. Kellomaki (1977) reported that the The female either ate partsof the prey or returned to the femaleEuropean Pygmy-owl did not beginto hunt until cavitywith it. A softwhistling sound was produced by the the end of the nestlingperiod. wingsas each owl took flight. Mikkola (1983) reported laying intervalsof every sec- Six eggshatched on 13 May. On 25 May we heard what ond day for the EuropeanPygmy-owl. Scherzinger (1970) webelieved were food begging calls of the nestlingsfor the and Kellomaki(1977) reportedincubation periods of the first time. The cheepingcall occurred when the female EuropeanPygmy-owl to be 28-30d. Steyn(1979) reported enteredthe nestcavity, whether or not shehad prey. The the incubationperiod of the Pearl-spottedowl (Glaucidium nestlingswere quiet when the female was absent.This perlatum)to be 29 d. Scherzinger(1970) and Steyn(1979) behaviorcontinued until the nestlingsfledged on 5 and 6 statedthat incubationdoes not begin until the clutch is June. complete.Scherzinger (via Heimo Mikkola, pers.comm.) We never observedthe male enter the nestcavity. On proved synchronoushatching in captive European one occasionthe femalefailed to emergefrom the cavity Pygmy-owls.Norton and Holt (1982) alsoreported syn- for 11 min asthe male calledwith prey. Shethen flew to chronoushatching in Northern Pygmy-owls.However, a the male and receivedthe prey. The latesttime at which female Northern Pygmy-owlfrom Montana sent by the the malewas recorded to callwas 2207 H. We stayeduntil authors to the Owl Rehabilitation Research Foundation, after 2400 H on severalnights. Vineland,Ontario, Canada, layed eggs in captivitywhich

39 40 SHORTCOMMUNICATIONS VOL. 20, No. 1

Table 1. Preyremains from one pair of breedingNorthern Pygmy-owlsin MissoulaCounty, Montana, 4 April - 21June 1981. Preyitems were identifiedfrom thirty-sixpellets, debris from the nest,cached prey and observations.

PREY TYPE NUMBER METHOD OF DETECTION

Birds

Empidonaxspp. 1 from debris in nest Hammond'sFlycatcher (Empidonax hammondii) 1 cache located Parusssp. 1 from debris in nest Red-breasted Nuthatch (Sittacanadensis) 1 from debris in nest Townsend'sSolitaire (Myadestes townsendi) 1 from debris in nest Cassin'sFinch (Carpodacuscassinii) 1 from debris in nest Unid. Passeriformbirds (mandibles only) 3 from debris in nest and pellets

Mammals

Sorexspp. 1 from debris in nest Red Squirrel (Tamiasciurushudsonicus) 1 observation Deer Mouse (Peromyscusmaniculatus ) 1 from debris in nest Northern Red-backedVole (Clethrionomysgapperi) 1 cache located Unid. Microtine spp. 1 from debris in nest House Mouse (Mus musculus) 4 pellets,cache located WesternJumping Mouse(Zapus princeps) 1 observation

Totals 19

hatchedasynchronously (Kay McKeever,pers. comm.). thus may indicate excitementor a threat display. The Obviously,hatching in this genuswarrants further inves- behavior needs further observation. tigation. Nestlings of European Pygmy-owlsusually Reportson the foodhabits of Northern Pygmy-owlsare fledge on the sameday, do not return to the nest,and scanty.To our knowledge,Holman (1926) recordedthe nestlingsthat do not fledgeat thistime are left behindby only accountof food habitsduring the breeding season the adults.(Heimo Mikkola, pers.comm.). prior to the accountsof Norton and Holt (1982). Holman Assuming that the Northern Pygmy-owl, European (1926) observednineteen prey exchangesbetween the Pygmy-owland Pearl-spottedOwl havesimilar incubation male and female in . Prey identified included periods,(28 days,Scherzinger 1979; 30 days,Kellomaki eight lizards, five birds and six mammals.Fisher (1893) 1977;29 days,Steyn 1979, respectively), we extrapolated examined6 stomachsof Northern Pygmy-owlsand found that the eggsin thisstudy were laid between3 April and 15 1 to contain a , 1 contained a mouse, 1 contained April 1981, and incubationbegan approximately 15 Ap- lizards,1 containedan insectand 2 stomachswere empty. ril. The incubationperiod wascalculated to be approxi- Other reports(Pierce 1921; Burleigh 1929;Brooks 1930; mately28 d, and the nestlingperiod was 23 d. The fledg- Clabaugh1933; Castle 1937; Farley 1937; Brock 1958; lings were observedon six occasionsbetween 7 and 14 and Gashwiler1960) included few prey itemsof Northern June. The owls were not locatedafter 14 June, and the Pygmy-owlsat varioustimes of the year. studywas terminated. Other interestingreports of Northern Pygmy-owlprey Observedtail switchingbehavior has been previously includeincidental observations; Walker (1924)reported a reported. Mailiard (1926) observeda bathing Northern Northern Pygmy-owlkilling a young chicken (Gallus Pygmy-owljerking its tail from sideto side,but he con- domesticus).Keck (1925) observeda Northern Pygmy-owl cludedthat it wassimply shaking off water.Steyn (1979) eating a chipmunk in YosemiteNational Park. Kimball reportedthat "tailjerking" accompaniedby headbobbing (1925) in Arizona and Balgooyen(1969) in California wasa behaviorlinked to excitementin the Pearl-spotted recorded Northern Pygmy-owlskilling Gambel'sQuail Owl. We believethat tail switchingwas a direct conse- (Callipeplagambelii) and California Quail (C. californica), quenceof our approachto Northern Pygmy-owlsand respectively.In California, Michael (1927) observeda SPRING 1986 SHORT COMMUNICATIONS 41

Northern Pygmy-owlto entera woodpeckerhole and take MICHAEL,C.W. 1927. : The little demon. out a fully featherednestling. Condor 29:161-162. Though Mikkola (1970) collectedpellets and prey re- MIKKOLA,H. 1970. On the activity and food of the mainsfrom below the nest of EuropeanPygmy-owls in PygmyOwl (Glaucidiumpasserinure) during breeding. Finland, we did not locateany pelletsor prey remains Ornis Fenn. 47:10-14. below our Northern Pygmy-owlnest site, nor could we MIKKOLA,H. 1983. Owls of Europe. Buteo Books,Ver- find any further indicationin the literaturethat Northern million, South Dakota. Pygmy-owlsdeposit pellets or prey remainsbelow their NORTON, W.D. AND D.W. HOLT. 1982. Simultaneous nests.Apparently the female at our nestdeposited pellets nestingof Northern PygmyOwls and Northern Saw- and prey remainsaway from the nestsite, and few remains whet Owlsin the samesnag. Murrelet 63:94. were found in the cavityafter the nestingperiod. PXERCE,W.M. 1921. California Pygmy Owl from We thankDale Becker, Gwilym Jones, Jeff Marks,Riley Cucamonga Canyon, Southern California. Condor McClelland, Heimo Mikkola and Ian Nisbet for review, 33:96. criticismsand suggestionson earlier drafts of the manu- SCHERZINGER,W. 1970. Zum Aktionssystemdes Sper- script.We thank R.J. Clark and Brian A. Millsap for lingskauzes(Glaucidium passerinure L.). Zoologica41:1- commentson the final draft. Kay McKeeverprovided 130. captivebreeding information. We thank her and the Owl STEYN, P. 1979. Observationsof Pearl-spotted and Rehabilitation Research Foundation. We are thankful to Barred Owls. Bokmakierie 31:50-60. DianeBoyd for photographyand field assistance.Philip WALKER,A. 1924. Noteson someOregon birds.Condor L. Wright and RichardHutto from the Universityof 26:181. Montana patientlyanswered our endlessquestions and provided ideas and encouragement.We thank them Department of Zoology, University of Montana, Missoula, greatly.Finally, we are gratefulto NancyClaflin and the Montana 59812. Present address of first author: 2513 Les- girlsfor providingfinancial support and faith in two un- ter Street, Missoula, Montana 59801. Address of second dergraduates. author: P.O. Box 5353, l•ozeman, Montana 59719. Received15 August 1985; Accepted1 January 1986. LITERATURE CITED BALGOOYEN,T.G. 1969. Pygmy Owl attacksCalifornia Quail. Auk 86:358. BROCK,E.M. 1958. Somepreyof the PgymyOwl. Condor 60:338. BROOKS,A. 1930. The PygmyOwl. Murrelet11:7-9. BURLEIGH, T.D. 1929. Birds of northwestern An Unusual Incident with the Bald Eagle Washington.Auk. 46:512. (Haliaeetus!eucocephalus ) CASTLE,G.B. 1937. The RockyMountain Pygmy Owl in Montana. Condor 39:132. JERRYOLSEN CLABAUGH,E.D. 1933. Food of the Pygmy Owl and Goshawk. Condor 35:80. On 20 July 1969, I watched2 immatureBald Eagles(Haliaeetus FARLEY,F.L. 1937. The Pygmy Owl. Can. Field Nat. leucocephalus)feeding on the eastshore of Lake Lebarge,Yukon 51:86-87. Territory, Canada (oppositeRichthofen Island - 61ø10'N, 135ø FXSHER, A.K. 1893. Hawks and Owls of the United 05'W). The eagleswere about 350 metres away from me and flushedwhen I walkedtowards them to investigate.I sawthat the States.Bull. U.S. Dept.of Agric.3:1-210. eagleshad been feeding on the body of a man lying half sub- GASHTILER,J.S. 1960.Hunting behavior of a PygmyOwl. mergedin the water.The bodywas fully clothed,and one trouser Murrelet 41: 12-13. leg wasripped and the calf of that leg had been partly eaten. HOLMAN,F.C. 1926. Nesting of the California Pygmy I notified the Royal Canadian Mounted Police (RCMP) who Owl in Yosemite. Condor 28:92-93. collectedthe body. The RCMP informed me that the man had KECK,D.D. 1925. PygmyOwl eats chipmunk. Yosemite apparentlybeen killed in Whitehorse,Yukon Terrtory, and had Nat. Notes 4:84. drifteddown the YukonRiver from there.The bodyprobably had been submergedfor about a month before rising and being KELLOMAKI,E. 1977. Food of the Pygmy Owl washed ashore. (Glaucidiumpasserinure) in the breedingseason. Ornis. I know of no other reportsof eagles(as opposedto vultures) Fenn. 54:1-29. eatinghuman flesh. KIMBALL,H.H. 1925. PygmyOwl killing a quail. Condor 27:209-210. R.M.IL 1705, Sutton, New South Wales, AUSTRALIA 2620 MAILIARD,J.1926. A CaliforniaPygmy Owl bathes.Con- dor 28:171. Received25 July 1985; Accepted 1 August 1985