BURROWING OWLS WINTERING IN
EO. BUTTSI conductedapproximately 15 months of intensive researchon thebiology of westernBurrowing Owls (Speotyto cuniculariahypugaea) in1970-71 in the OklahomaPanhandle,where BurrowingOwl populationswere concentratedin black-tailedprairie dog (Cynomys ludovicianus)coloniesor prairie dog towns. One objectiveof my study was to determine the wintering status of Burrowing Owls that summer in the Panhandle.The study area encompassed5114 sq km in Beaver and easternTexasCounties,Oklahoma,or approximatelythe easternthird of the OklahomaPanhandle,includingpart of the High Plains, breaks in the plains, erosional uplands, valleys, and sand dunes (U.S. Dept. Agr. 1962). Ap-proximately50 to 60% of the area is cultivated,and the remainderisusedprimarily for cattle grazing. The locality is mesothermaland semiarid, with summer temperaturesoften in the 90's and occasionallyexceeding100øF. Occasionalsubzerowinter temperatures,often combinedwith the usuallybrisk wind, sometimeslower the wind-chill index to -30to -40øF. Averageannualprecipitationis 49 cm, and meanannualsnowfall is 43 cm (U.S. Dept'. Commerce1969). Severeblizzard conditionsoccur regularly, particularly in January and February.METHODSBurrowing Owls wintering in prairie dog towns of the study area were censused11 to 16 February and 3 March 1971. All prairie dog towns except four, whichcontained 28 adult owls the previous June, were censusedwhen temperatureswerehigher than 50øF and wind velocitieslessthan 10 mph. Wintering owls were alsosearchedfor in the vicinities of five of the six nest burrows found outside prairiedog townsin 1970. Increasesin owl numbersin 11 prairie dog townswere monitoredduring March 1971 (Table 1). Approximate dates could thus be determined for theinitial appearanceof Burrowing Owls in spring.I tried to catch and band Burrowing Owls that were wintering in the study areato ascertain if they were permanent residents or migrants. Catching methods wereby hand, after excavating burrows in which owls had found shelter or soughtescape,and with weakened and padded size-0 steel traps (jaws wrapped withfoam rubber). The steel traps were concealedaround the entrance to burrowsshowingsignsof frequent owl use. Owls were marked with USFWS metal leg bandsand colored plastic leg bands.During February and early March 1971, 19 burrows were excavated in six prairiedog towns to search for inactive owls and to collect data on burrows used bywintering owls. Indicators of recent owl use, including owl feathers, droppings, or510The Auk 93: 510-516. July 1976
July 1976]511Oklahoma Burrowing OwlsTABLE1APPARENT CHANGES II BURROWING OVgL NUi'dBERS IN 11 PRAIRIE DOGTowNs, OKLAHOi'dAPANttANDLE,MARCIt 1971Number of owls seen on dates in MarchDogtownNo. overwintering891011121516232425262984--7-1215--20 -- --6-318311120 1820-TOTALSTownscheckedOwlsseenpellet%were at the entrancesof all 19 burrows. These burrows representedapproximately 75% of thoseevidently being used by wintering owls.R ,su ,TsA DD SCUSS O Winter populations.--TheBurrowingOwl populationwinteringin theapproximately688 ha of prairie dog townsin the study area in 1970-71apparently consistedof six birds. This was less than 1% of the owlpopulationinhabiting those same prairie dog towns in late July 1970,or lessthan 0.5% of the summerowl populationin the entire study area.No Burrowing Owls were known to winter outside prairie dog towns,but I made no systematicsearchfor winteringowls beyond the vicinitiesof nest burrows occupied the previous summer.Personnelof the Oklahoma CooperativeWildlife ResearchUnit haveconductedwinter surveysof BurrowingOwl populationsin prairie dogtowns of the Oklahoma Panhandle and adjacent areas since completionof my studiesand have alsofound a small numberof owls. A surveyofBurrowingOwl populationsin 396 ha of prairie dog townsin early January 1972 in Beaver and Texas Counties,including most prairie dogtownswhereowlswinteredthe previouswinter, revealedtwo and possiblythree winteringowls (Lewis pers. comm.). An estimatedsix owls winteredin 327 ha of prairie dog townsin Dallam County,Texas (approximately 100 miles southwestof my study area) in 1972-73. This was2.7% of the estimatedBurrowingOwl populationtherein late July 1972(Lewis pers. comm.).
512K : v.'raO. Bu'r'rs[Auk, Vol. 93Burrow characteristics.--Inwinter BurrowingOwls used burrowsthatvaried in structure. The ends of burrows were from 23 to 132 cm belowthe ground surface,and 14 of 19 were 90 cm or less deep. Ten of the19 tunnelswere less than 213 cm long, but one continuedan unknowndistancepast 460 cm. Only four tunnels containedturns sharper than90 degrees.One burrowcontaineda nest in 1970. Tunnels were 10 to23 cm high, averaging 14 cm, and were 10 to 20 cm wide, averaging13 cm. Characteristicsof four burrows used by Burrowing Owls in thewinter of 1971-72 in the OklahomaPanhandlewere very similar to thoseI excavated (Lewis pers. comm.).Activeprairie dogburrowswerenot excavatedto determineif burrowsusedby BurrowingOwls,eitherfor nestingor wintershelter,weretypicalprairie dog burrows. Most burrowsI excavatedwere shallowerand lessextensivethan thosecreditedto prairie dogsby other biologists(Wilcomb1954,Hendersonet al. 1969,Sheetsand Linder 1969), but Smith (1967)indicated that prairie dog burrowsvary widely, dependingon soil types,moisture, and other factors.Signsof occupancyby BurrowingOwls (pellets, droppings,prey remains) were found within 17 of the 19 burrowsexcavated.This materialwas in the first 122 cm of the tunnels, with most concentratedin thefirst75 cm.Temperatureswithin burrowswere not thoroughlyinvestigatedin thisstudy. My limited observationsand Wilcomb's (1954) studiesindicatethat in Oklahoma,where the frost line usuallyis shallow,temperaturesin prairie dogburrowsat least 150 cm from the burrowmouthand underthe frost line probably seldomfall below 40øF.Food storage and consumptionwithin burrows. Agersborg(1885)found large food caches,one consistingof 43 dead mice and several"shore" [ horned] larks, in burrowsoccupiedby BurrowingOwls inwinter in southeastern South Dakota.I found no evidence that Burrow-ing Owlshoardedlarge amountsof foodin cachesin Oklahomaduringwinter, nor did winter excavationof four owl burrowsin the OklahomaPanhandlein 1971-72revealsuchcaches(Lewispers.comm.).In three instances I found a dead rodent in the first 45 to 60 cm ofburrowsusedby winteringBurrowingOwls. Two rodents,a plainsharvestmouse(Reithrodontomysmontanus)and a hispid cottonrat (Sigmodonhispidus),were each being eaten by an owl when the owls were flushedfrom their burrowsin late eveningbefore dark. A plains harvest mousewas found at 0930 in a burrow from which an owl was flushed. All threerodentswere cold but undeteriorated.Burrows containingthe harvestmice were excavated,one immediatelyfollowing discoveryof the mouseand the other 4 days later. Neither containedother food items.
July 1976]Oklahoma Burrowing Owls513Rodent remains found in burrows representedfood items capturedrecently by Burrowing Owls and apparently were not part of a largercache. The presenceof bird remains,blood, and insect fragmentsinwinter burrows was additionalevidence that owls sometimes consumedprey in the shelter of burrows.Hibernation, torpor, or simplefasting.--I did not determineconclusively if BurrowingOwls overwinteringin my study area ever hibernatedor entereda torpid state. One BurrowingOwl I excavatedfrom a burrowduring cold weather (28øF, wind 15 mph) on 20 February 1971 wasquite inactiveand docile,much more so than other owlssimilarly handledincludingtwo that were excavatedduring comparableweather conditions.This lethargicstate was particularly interestingbecausea blizzard struckthe area the night of 20 February,depositingdrifts 3 to 6 m deep.Literature sourcesdo not describeany state of torpor or hibernationfor BurrowingOwls, althoughAgersborg(1885) indicatedthat they remain undergroundfor severaldaysduringwinter. J. D. Ligon (1968: 24)describedcomatosebehaviorfor female Elf Owls (Micrathene whitneyi)removedfrom their nest cavities soon after they had started incubating.This behaviorwas not a torpid state, but was in responseto the invader.ScreechOwls (Otus asio) removed from Wood Duck (Aix sponsa) nestboxesin winter in northernAlabama are sometimesvery lethargic,butphysiologicaltorpidity has not been verified (Atkinson pers. comm.).J. D. Ligon (1969) failed to inducephysiologicalmanifestationsof torporin WhiskeredOwls (Otus trichopsis),Elf Owls, or ScreechOwls whenhe deprived them of food for 3 to 4 days at ambient temperaturesof44 to 59øF.BurrowingOwls may be capableof fastingfor severaldays in winter.Heavy snow and ice cover during the blizzard in February 1971 madeit very unlikely that owls could have escapedtheir burrowsfor at least3 days. Yet an owl burrow excavated only hours before onset of theblizzard contained no food cache. The small owls deprived of food inJ. D. Ligon's (1969) study remained healthy in spite of 16 to 24%lossesin body weight.Migration.--Field observationsindicatedthat most BurrowingOwls inmy study area were migratory. The owl population increased from 6on 3 March to an estimated527 during early June 1971. The tremendousincreasein numbersof BurrowingOwls seenlocally during March andearly April probablyindicatedthe return of owls that winteredelsewhere,presumablyto the southward.The sporadicnature of increasesin Burrowing Owl numbersin variousprairie dog towns (Table 1), somestill without owls on 26 March, alsoprobably indicatedmigratory movements.If all owls presentin spring
514KENNET I O. Bux'rs[Auk, Vol. 93had overwintered,they presumablywould have becomeactive at approximately the same time and many more than six would have been seenduring winter.Excavationof approximately75% of the burrowsshowingevidenceofuse by wintering BurrowingOwls yielded only three owls. In addition,the mild weatherconditionsduring most of the winter census,mentionedpreviously,increasedthe likelihoodthat other owls would have been observedif they had overwintered.J. S. Ligon (1961) and Rossand Smith(1970) also found more BurrowingOwls abovegroundin winter as thetemperatureincreased.The most tangibleproof of migrationwas a band recovery. A femaleBurrowingOwl bandedas a nestingadult in Beaver County, Oklahoma,on 26 June 1970 was shotby a hunter near Zapotlanejo,Jalisco,Mexico,1 November1971.Resultsof my winter bandingeffortsindicatedthat the smallwinteringpopulationof BurrowingOwls were permanentresidentsand not migrantsfrom more northern areas. All three banded owls that definitely overwinteredand two owls banded 10 March 1971, and thus possiblywinterresidents,remainedto breed and nest in the sameprairie dog townswherethey were banded. This situation contrastswith that in the ImperialValley of southernCalifornia where Coulombe(1971) assumesat leasta part of the wintering BurrowingOwl populationconsistsof migrants.In summary,only a few BurrowingOwls are permanentresidentsinthe OklahomaPanhandle;mostmigrate. This conclusionis supportedbyotherbiologistsincludingLewis (pers.comm.),Sutton (pers.comm.),andTyler (1968).A recent comprehensivestudy by Martin (1973) involving bandedindividualsin a small populationof Burrowing Owls in central NewMexico revealed several striking similarities in the wintering status ofBurrowing Owls in our respectivestudy areas. Most of the summeringowl population apparently migrated from the area before winter withonly 1 to 3% remaining,the few winteringowlswere not migrantsfromother areas, and owl numbersincreasedtremendouslyin March, from2 to 17 between 15-21 March (Martin 1973). Martin's findings castdoubton the validity of J. S. Ligon's(1961) belief that BurrowingOwlsin northeasternNew Mexico are permanent residents. Data from otherareas adjacent to the Oklahoma Panhandle,including the Texas Panhandle(Rossand Smith 1970) and Colorado(Bailey and Niedrach1965),indicatethat mostof the summerpopulationsof BurrowingOwls migratealthough a few linger through the winter.The winteringstatusof BurrowingOwls nestingin the Dakotas mayalso, at least in timespast, have includedboth permanentresidentsand
July 1976]OklahomaBurrowing dedin the DakotasinJuneand July, 1931 through1936, were recoveredin centralTexas andadjacentpartsof OklahomaandArkansasbetween15 Octoberand 3 April(Brenckle 1936, Cooke 1941). Three BurrowingOwls bandedin thesummer in Manitoba and the Dakotas were recovered in Nebraska andKansasin late Septemberand early south(Brenckle1936,Cooke1941). Agersborg(1885) foundasmanyas 20 BurrowingOwlsin oneburrowduringwinterin southeasternSouthDakota,whichhe believedwerepermanentresidentsthat foragedwhenweatherconditionswerefavorableand retreatedintoburrowsstockedwith food during severeweather.ACKNOWLEDOi ENTSThis researchwas supportedby the Rob and BessieWe]der Wildlife Foundation,Sinton, Texas (Contribution No. 172); the Oklahoma State University ResearchFoundation;and the National ScienceFoundationunder the directionand addifionMsupport of the OklahomaCooperativeWildlife ResearchUnit. I thank AssistantUnit Leader JamesC. Lewis for his patienceand inva]uab]eassistancein aH phasesof the project and preparationof the manuscript.I appreciateJohn A. Morrison,Unit Leader, for making availableunit equipmentand facilitiesand his encouragement in the study. My wife, Shat]a, assistedin many ways and patiently enduredmany lonely weeksand nights throughoutthe project and manuscriptpreparation.SUmmARYApparentlyonly six BurrowingOwlswinteredin prairiedogtownsofthe easternOklahomaPanhandle (Sl14 sq kin) in 1970-71, or approximately 1% of the populationthere in late July 1970. Owl populationsincreasedvery sharplybut sporadicallyduring March. No evidenceofextensivewinter food cacheswas found. Althoughno evidencesuggestedthat winteringowls ever entereda state of hibernationor torpor, theymay have fasted for at least 3 days during blizzard conditionswithoutsuffering mortality.Most of the BurrowingOwls breedingin the study area migrated. Atleast one went as far as west-centrai Mexico.Results of the limited winterbanding studiesindicated that the small population of wintering owlswere permanentresidentsrather than migrants from the north.LITERATURE CITEDAO RSBORC,G. S. 1885. The birds of southeasternDakota. Auk 2: 276-289.BA LE¾,A.M., ANDR. J. I IEDRACIrI.1965. Birds of Colorado. Denver, DenverMus. Nat.I-Iist.BRE mXL ,J. F.1936. The migration of the western Burrowing Owl. Bird-Banding 7: 166-168.
516K zvzv xa O. Burrs[Auk, Vol. 93COOKS, M. T. 1941. Returns from banded birds: recoveries of some bandedbirds of prey. Bird-Banding 12: 150-160.COULO B , H. N. 1971. Behavior and population ecology of the Burrowing Owl,Speotyto cunicularia, in the Imperial Valley of California. Condor 73: 162176.I-Ir D SO , F. R., P. F. SPRIlVGI R,AlVDR. ADRIAlV.1969. The black-footedferretin South Dakota. Pierre, South Dakota Dept. Game, Fish, and Parks.Lmox, J. D. 1968. The biology of the Elf Owl (Micrathene whltneyi). Misc.Publ. Mus. Zool., Univ. Michigan 136: 24.Lmox, J. D. 1969. Some aspects of temperature relations in small owls. Auk86: 458-472.Lmox, J.S.New1961. New Mexico birds and where to find them. Albuquerque,Univ.MexicoPress.MAsrxx, D. J. 1973. Selectedaspectsof Burrowing Owl ecology and behavior.Condor75: 446-456.Ross, P. V., Z D D. J. S rxra. 1970. Notes on the ecology of the BurrowingOwl, Speotyto cunicularia,in the Texas High Plains. Texas J. Sci. 21: 479-480.S Ts,R. G., AND R. L. L Z D . 1969. Food habits of the black-footed ferret(Mustela nigripes) in South Dakota. Proc. South Dakota Acad. Sci. 48: 58-61.S rxTa, R. E. 1967. Natural history of the prairie dog in Kansas. Misc. Publ.16, Univ. KansasMus. Nat. Hist., State Biol. Survey.TYLrs, J. D. 1968. Distribution and vertebrate associatesof the black-tailedprairie dog in Oklahoma. UnpublishedPh.D. dissertation,Norman, Univ. Oklahoma.U.S. D r r vr zvr or A mu ru .1962. Soll survey of Beaver County, Okla-homa. Washington,D.C., Ser. 1959,No. 11.U.S. Drr sxavrsxr or Co r scs.U.S. Environ.1969. Climatological data.Washington, D.C.Sci. Serv. Admin.WrLCO B, W. J., Js. 1954. A study of prairie dog burrow systems and theecology of their Arthropod inhabitants in central Oklahoma. UnpublishedPh.D. dissertation,Norman, Univ. Oklahoma.OklahomaCooperativeWildlife ResearchUnit (U.S. Fish and WildlifeService,OklahomaDepartmentof WildlifeConservation,OklahomaStateUniversity,and Wildlife ManagementInstitute cooperating),OklahomaState University,Stillwater, Oklahoma. Presentaddress:Upper Mississippi River Wildire Refuge, La Crosse,Wisconsin54601. Accepted1March1975.
Burrowing Owl banded as a nesting adult in Beaver County, Oklahoma, on 26 June 1970 was shot by a hunter near Zapotlanejo, Jalisco, Mexico, 1 November 1971. Results of my winter banding efforts indicated that the small wintering population of Burrowing Owls were perma
one ASY male Burrowing Owl in June. Captive, non-breeding Burrowing Owls held under natural light also molted all flight feathers, annually during the prebasic molt. Timing varied greatly. While a SY finished in less than two months (the first week of May to 18 Jun), others (N 6)
The Burrowing Owl The calls in the US are a repetitive “chirp” sound and the young owls have an “eep” call to the adults for food and alarm. The more southern burrowing owls sound more like a songbird, with a raspy “chir chirp” repetition. Due to these birds living on the groun
Nov 01, 2013 · The burrowing owl is a small bird averaging 23 cm (9 in) in height with a mean wingspan of 26 cm (21 in). The burrowing owl spends most of its time on the ground, where its sandy brown plumage provides camouflage from potential predators. The burrowing owl lacks the ear tufts of m
As part of a broader project aimed to study the ecology of burrowing owls in the southeastern Pampas region of Argentina, we found that up to 70% of owl nests were located in patches where southern lapwings were also present (Authors’ unpubl. data). This percentage of co-oc-currence between these specie
owl you’re talking about, and there are a staggering 150 documented species of owls (possibly even more, depending on how you classify the different species). 19 species of owls are found in North America, including the following: barn owl, burrowing owl, eastern screech owl, great grey owl, spotted owl, an
owl. Upon capture, we recorded each owl's mass to the nearest gram, wing length, tarsus length, tail length, and length of exposed culmen (all to nearest 0.5 mm). We classified adult owls as females if they had well-developed brood patches. We were unable to discern sex ofyowtg owls based on a
This magazine is a great resource for elementary school children to use if they are interested in owls. In fact, when I was about 7 years old, I read from this reference as well. It is fun and interactive as well as understandable while containing a general overview on owls. Duncan, James R. 2003. Owls of the World. Firefly Books Inc., Buffalo.
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