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Home , Barred owl, Strix (bird)

THE JOURNAL OF RAPTOR RESEARCH A QUARTERLY PUBLICATION OF THE RAPTOR RESEARCH FOUNDATION, INC.

VOL. 29 SEPTEMBER 1995 NO. 3 f RaptorRes. 29(3):151-157 ¸ 1995 The Raptor ResearchFoundation, Inc.

SPATIAL OVERLAP AND HABITAT ASSOCIATIONS OF BARRED AND GREAT HORNED OWLS IN SOUTHERN

KIM J. LAIDIG1 ANDDAVID S. DOBKIN2 Departmentof Biology,Rutgers University, Camden, NJ 08102 U.S.A.

A•sT•CT.--Barred owls ( varia) are closelyassociated with relativelyundisturbed mature forest,in contrastto greathorned owls (Bubo virginianus) which are characteristicallyassociated with highly fragmented landscapesof forestsand fields.The two speciesare potentialcompetitors, and greathorned owls may prey upon barredowls. We assessedthe relativeabundance and distributionof both speciesin areasof known barredowl abundanceby usingtaped playback of conspecificvocalizations. Estimated relative abundances of the two owls were virtually identical,and estimatedhome rangesoverlapped extensively between the two spedes,although our data suggestthat temporalpartitioning may have reducedactual overlap. Barred owls were associatedwith cedarswamp-pitch lowland habitat and dependedon mature hardwoodswamp forestfor sites,but suitablenesting habitat was extremelylimited and occurredonly in small patches. Forestfragmentation is likely responsiblefor the extraordinarydegree of spatialoverlap found between the two speciesin southernNew Jerseyand posesa continuingthreat to the integrityof the region'sbarred population. KEY WORDS: Barredowl; Bubo virginianus;great ; spatialoverlap; Strix varia; temporaloverlap; vocalresponsiveness.

Sobreposici6nespacial y asociadonesde hfibitatde Strix variay Bubovirginianus en el sur de New Jersey RgsvMv_•.--Strixvaria estfiestrechamente asociada a bosquesmaduros relativamente no perturbados,en contrastea Bubo virginianus caracterisficamente asociado a paisajes de bosques y campos altamente fragmentados. Ambasespecies son potencialmente compefidoras, incluso B. virginianuspuede predar sobre S. varia.Medimos la abundandarelativa y distribud6nde ambas espedes en fireasde conocidas abundancias de S. varia, realizando "playbacks"con vocalizaciones conespecificas. Las abundanciasrelativas estimadas para los dos bfihos fueron virtualmenteidgnticas. Los rangosde hogarestimados se sobreponianextensamente entre ambasespecies, aunquenuestros datos sugieren que la partici6ntemporal puede haber reducido la actualsobreposici6n. Strix variaestaba asociado a hfibitat de fierras bajas pantanosas y con pendiente, dependla de bosques lefiosos madufos paraubicar sus nidos. Pero este propicio tipo de hfibitat era extremadamente escaso y se daba s61o en pequefios parches.Probablemente, el fen6meno de la fragmentaci6ndebosques es el responsabledel extraordinario grado de sobreposici6nespacial entre ambas especies de bfihos,en el sur de New Jerseyy planteauna continua amenazaa la integridadde la poblaci6nde S. variade la regi6n. [Traducci6nde Ivan Lazo]

The barredowl (Strix varia) is widely distributed acrossCanada to BritishColumbia (Clark et al. 1987, throughoutNorth Americaeast of the Rockiesand Johnsgard1988). In recentyears, the spedeshas ex- pandedits westernmost range into northwestern Mon- • Present address:The Pinelands Commission, P.O. Box 7, tana and northernIdaho, southeasternAlaska, much New Lisbon,NJ 08064 U.S.A. of westernBritish Columbia, and souththrough the 2 Presentaddress: High DesertEcological Research Institute, Cascadesof ,, and northernCal- 15 S.W. ColoradoAvenue, Suite 300, Bend, OR 97702 U.S.A. ifornia (Johnsgard1988, Verner et al. 1992).

151 152 KIM J. LAir)It ANDDAVm S. DOBKIN VOL. 29, NO. 3

The broad geographicrange of barred owls belies in the state'sthree southernmost counties (Cape May, Cum- a distributionthat is often highly localizedbecause of berland,and Atlantic), and focused on BelleplainState Forest and adjacentstate wildlife managementareas, Great Cedar their closeassociation with mature and old-growth ,Bear Swamp, and Mays Landing.Each survey route forest(Johnsgard 1988), and the owl's relativeintol- consistedof 10 broadcaststations at 1-km intervals.Taped eranceof anthropogenicdisturbance (Bosakowski et al. territorial vocalizations(Peterson 1983) were broadcastat 1987, Bosakowski1989). For example,barred owls in eachstation using a Uher 4000 ReportMonitor setat full New Jerseyhave been extirpated from many partsof volume.Each broadcastconsisted of six repetitionsof a 10- secset of callsfollowed by 50 secof silence.The taperecorder the state(New JerseyDepartment of Environmental speakerwas rotated180 degreesbetween each 10-secset of Protection1985), and presentlyoccur in substantive vocalizationsto providebroadcast into the foreston bothsides numbersonly in the extremenorthwest (Bosakowski of the roadway. Completionof eachbroadcast was followed et al. 1987, 1989a) and south(Sutton and Sutton1985, by a 10-min responsetime. broadcastsconsisted of a singleindividual followed by a pair of owlsemitting the Sutton 1988)--the only regionsthat still provideex- "standard" vocalization. broadcasts con- tensivetracts of relativelyundisturbed broad-leaved or sistedof an individualemitting the six- to eight-syllablecall mixed forest. that is typical of this spedes. Successfulmanagement of small,disjunct barred owl Surveyperiods were separatedby 6-8 wk; within each populationsrequires a clear understandingof popu- period,surveys for eachspecies on a routewere separated by 1-2 wk. Samplingorder for eachspecies was alternated lation distributionand habitat dependency.Although betweensurvey periods. Surveys were conductedbetween portionsof the area inhabitedby the southernNew sundownand sunrisewhen wind speedwas low and predp- Jersey population are protectedfrom development itationnegligible. At eachbroadcast station, presence/absence within the PinelandsNational Reserve,much of south- datawere collected based on vocalresponses or visualcontacts. ern New Jerseyremains subject to intensedevelopment This surveytechnique assumes that an owl'sresponse indi- catesintrusion by a conspecificinto its breedingterritory or pressure(Collins and Russell 1988). In addition,forest homerange (Fuller and Mosher 1981). fragmentationas a resultof clearcutting,firewood har- To simplifyhabitat quantification, we approximatedan- vest,and deer management(as elsewherein eastern nual home rangesof owls (Nichollsand Fuller 1987) by )routinely create openings within con- circularplots superimposed onU.S. Fishand Wildlife Service National Inventory(NWI) vegetationmaps, with tiguousforest. Such forestry practices bring the more eachbroadcast station as the centerpoint. Our goalwas not disturbance-tolerantgreat hornedowl (Bubovirgini- to preciselydelimit owl homeranges or to determinecenters anus),with its regionallyexpanding population (Har- of activity,but ratherto characterizeconservatively the rel- wood 1988, Bosakowskiet al. 1989b), into contactwith ativehabitat composition within areas likely utilized by owls. the more reclusive,forest-dwelling barred owl (Bosa- To facilitatecomparisons, we usedcircular plots representing a homerange of 369 ha for eachspecies, based on radio- kowskiet al. 1987, 1989a,b).Great hornedowls pose telemetrytracking studies conducted in otherparts of their a potentialthreat to barred owls as predatorsof both ranges(Nicholls and Warner 1972, Fuller 1979, Petersen adultsand young (Bent 1938, Grant 1966,Fuller 1979, 1979,Elody and Sloan1985). Although 369 ha approaches Bosakowskiet al. 1989c),and as potentialcompetitors the documentedupper limit for barredowl homeranges, we selectedthis value because (1) it approximatedthe mid-range with considerableprey overlap(Johnsgard 1988, Bo- of great hornedowl home-rangesizes, (2) within , sakowskiand Smith 1992). avianhome ranges tend to be largerin habitatscharacterized The objectivesof our studywere to (1) assessthe by low biologicalproductivity (as found on the New Jersey relative abundances and distributions of barred owls coastalplain [Woodwell 1979]), and (3) roadsgenerally were and great hornedowls in southernNew Jersey,and locatedin uplands,hence larger plots were necessary to coun- ter underestimationof wetlandhabitat types. Circular plots (2) examinehabitat associations of the two species. of this size spacedat 1-km intervalsensured sampling of habitatsat spatial scalesappropriate to known movement METHODS AND STUDY AREAS distancesby thesespecies. Barred owls and great hornedowls were sampledsepa- As notedby Bosakowski(1987), responses less than 2 km rately during sevensurvey periods from May 1988 through apartshould be evaluated cautiously toconsider whether owls May 1989, usingtape playbackof conspecificvocalizations. belongto the sameor adjacentterritories. We conservatively This techniqueis particularlyeffident for detectingbarred assessedthe spatial and temporal distribution of owlresponses owls,which are reliablyand highly responsiveto tape play- to tapedvocalizations in combination with mappedestimated backor vocalimitation (McGarigal and Fraser 1984, 1985, homeranges to determinethe maximumnumber and dis- Bosakowski1987). tributionof owl homeranges on eachsurvey route. (Sona- Six surveyroutes traversing areas with the greatestpoten- graphicanalysis of tapedvocal responses for individualiden- tial numbersof barredowls were selectedbased on previous tiffcation of barred owls confirmed that at least some indi- roadsidesurveys conducted in southernNew Jersey(Sutton vidualsresponded from adjacent stations [Dobkin and Laid•g and Sutton1985, Sutton1988). Surveyroutes were located unpubl.data].) We placedbroadcast stations at relatively SEPTEMBER1995 BARREDAND GREATHORNED OWLS IN NEW JERSEY 153

Table 1. Number of stations(N = 10 per route) yieldingbarred owl/great hornedowl responseson eachsurvey, and estimatedtotal number of home rangesfor each specieson each survey route in southernNew Jersey, May 1988 to May 1989.

SURVEYMONTH/YEAR ESTIMATEDHOME ROWrE 5/88 6/88 8/88 11/88 1/89 3/89 5/89 RANGES Belleplain 2/1 0/1 2/3 4/2 2/0 2/1 3/1 3/3 Buckshutem 2/0 1/2 4/1 0/0 0/4 1/2 4/0 3/3 Cedar Swamp 1/0 0/0 1/0 0/1 1/3 0/2 1/0 1/1 Mays Landing 1/0 1/3 1/0 0/1 0/0 0/0 0/0 1/1 Port Elizabeth 3/1 0/4 1/2 0/0 2/1 0/3 2/0 2/2 Steelmantown a 1/0 3/1 3/2 1/1 0/0 3/1 3/2 Total 13/12 a Not surveyed. short,1-km intervalsto increasethe probabilityof owl de- ticityin thedata. Owl responseswere analyzed by chi-square tectionsthat might otherwisebe misseddue to (1) variation and binomial tests. Habitat differences between stations with in owl locationwithin its home range at the time of tape andwithout owls were examined by Mann-WhitneyU-tests. broadcast,and (2) variationin effectivetransmission distance Frequenciesof owl occurrencein relationto percentcoverage of broadcastsand detectabilityof owl vocalresponses. of differenthabitats were assessedwith Spearmanrank cor- Habitats at each broadcast station were determined from relations,but thesetests were not performedon the shrub- theNWI maps,which delimit 19 habitattypes in thevicinity scruband emergent-openwater habitattypes to avoiddis- of thesurvey routes. We condensedthese habitat types to five tortionand possiblespurious correlations due to the large categories:(1) upland -pineforest (UP) dominatedby numberof zerosin the dataset (Ludwig and Reynolds 1988). relativelyshort, small-diameter trees, (2) hardwood-mixed hardwoodswamp (HMS) usuallydominated by large de- RESULTS ciduousoverstory trees and frequentlywith denseundersto- ries,(3) cedarswamp-pitch pine lowland (GSPP) consisting RelativeAbundances and Vocal Responsiveness. of Atlanticwhite cedar (Chamaecyparis thyoides) or pitchpine We obtaineda total of 53 barredowl and 44 great (Pmusrigida), respectively; lowland pine understories usually hornedowl responses(Table 1). Routesthat weremost werequite dense, (4) shrub-scrub(SS) of low woodygrowth productivefor barred owls also were the most pro- that often resultedfrom clearcuttimber harvest,fire, or aban- donedcranberry bog succession, and (5) emergent-openwater ductivefor great hornedowls. Conversely,routes that (EMOW) of shallow pondsor marsheswith a producedthe fewestresponses from barred owls also notable absence of trees and shrubs. More detailed accounts were the leastproductive for greathorned owls (Table of floristiccomposition are providedby McGormick(1979). 1). Barredowls and greathorned owls each responded Goverageby eachhabitat within the plotswas quantified with a Numonicselectronic planimeter. at 31 of 60 stationssurveyed (Table 2), with each We used nonparametricstatistics (Siegel and Gastellan speciesresponding exclusively at 16 of 31 stations. 1988) to avoidproblems of nonnormalityand heteroscedas- Hence, over the duration of the entire study,neither

Table 2. Spatial overlapof barred owls (B) and great hornedowls (G) basedon responsesa to playbackof tape- recordedconspecific vocalizations along surveyroutes in southernNew Jersey, May 1988 to May 1989.

BROADCAST STATION NUMBER

ROWrE 1 2 3 4 5 6 7 8 9 10

Belleplain BG -G -G BG B- -G BG B- BG BG Buckshutem BG BG BG B- B- BG BG B .... G Cedar Swamp -- -G -- B- BG -G ...... Mays Landing B- -G -G -G ...... B- -- Port Elizabeth -G B- BG B- -- B- -G -G -G -G Steelmantown B- B- BG BG B- B- B- -G BG -G

and G indicateat least one responseat a stationover the courseof the entire studyperiod; - indicatesno response. 154 KIM J. LAIDIGAND DAVID S. DOBKIN VOL. 29, NO. 3

Table 3. Percent coverageof habitat types in 369-ha Table 4. Spearmanrank correlationcoefficients for barred circularplots centered on owl surveystations (N = 60) in owl and great hornedowl occurrencewith percentcoverage southern New Jersey. by habitat type in estimatedhome ranges centered on each survey station (N = 60) along routes in southernNew

HABITAT Jersey, May 1988 to May 1989. TYPEa MEAN (SD) MINIMUM MAXIMUM HABITAT UP 71.6 (19.0) 16.8 97.6 TYPE a BARRED OWL GREAT HORNED OWL HMS 22.8 (16.9) 0.9 79.5 CSPP 2.0 (2.1) 0.0 13.1 UP -0.14 0.00 SS 2.1 (3.2) 0.0 12.9 HMS 0.21 -0.08 EMOW 1.5 (4.8) 0.0 32.6 GSPP 0.30 b -0.08 a UP = upland oak-pine forest, HMS = deciduoushardwood- a UP = upland oak-pine forest, HMS = deciduoushardwood- mixed hardwoodswamp, CSPP = cedarswamp-pitch pine lowland, mixedhardwood swamp, CSPP = cedarswamp-pitch pine lowland SS = shrub-scrub,EMOW = emergent-openwater. b p = 0.05. positivenor negativeinterspecific association could be Habitat Associations.Nearly 95% of thetotal hab- detectedamong stations. Of the 15 stationswhere both itat acrossthe 60 stationsconsisted of uplandoak-pine speciesresponded, however, only four instanc•esoc- forestand mixed hardwood swamp (Table 3), although curredin which bothspecies responded from the same the latter comprisedless than 25% of the total habitat. stationwithin the samesurvey period (even though However, the percentcoverage by each habitat type surveysfor eachspecies were separatedby 1-2 wk). rangedwidely amongindividual stations (Table 3). This suggestsa possibleavoidance or spatiotemporal Barredowls were associated positively (rs = 0.30,P partitioningof areasbetween the two specieswhere -- 0.05, Table 4) with cedarswamp-pitch pine lowland home rangesoverlapped extensively (z = 1.56, P = habitat,but no other significant relationships were found 0.06). in testingeither frequency of owl occurrence(Table Viewed overthe courseof the entirestudy, adjacent 4) or absoluteowl occurrence(all testsP > 0.10) in stationsfrequently yielded responses from singlein- relationto percentcoverage of habitattypes. dividuals,but mostoccurred on differentsurvey dates and were evokedin responseonly to playbackat the DISCUSSION neareststation. Hence, we view many of theseas re- sponsesfrom the sameindividual. A conservativein- RelativeAbundances and Vocal Responsiveness. terpretationof the responsedata combinedwith map- Our estimateof barredowl homeranges for all of the ping of estimatedhome ranges results in remarkably surveyroutes combined is considerablysmaller than similar estimatesof homerange numbers for eachspe- the numbersreported by Sutton(1988) in his survey cieson eachsurvey route (Table 1), for a total of 13 of someof thesesame routes. Our estimatesrepresent barred owl and 12 great hornedowl home ranges. a moreconservative approach based on surveydata in Neither speciesexhibited seasonal differences in re- combinationwith mappingof estimatedhome ranges sponsivenessto taped vocalizations in comparisonsbe- over time, and supplementedwith vocalizationanal- tweenbreeding (March to June) andnonbreeding sea- yses.Sutton (1988) viewedresponses from adjacent sons(barred owls, x 2 = 0.13, df = 1, P > 0.35; great stationsat differentsurvey times as distinct individuals. horned owls, X2 = 0.49, df = 1, P > 0.20), or between We consideredresponses clustered around several ad- spring/summer(March to August)and fall/winter jacentbroadcast stations as representinga singlepair (barredowls, )/2 = 0.42, df = 1, P > 0.25; greathorned of unlessvocalization analyses indicated other- owls, X2 = 0.32, df = 1, P > 0.25). We recordedthe wise. Even allowingfor differencesin estimationbe- mostbarred owl responsesin May and August,the tweenthe two surveys,our resultsindicate that fewer fewestresponses in March andJune, and intermediate barred owls occurin southernNew Jerseythan as- levelsin the winter months(Table 1). Great horned sumedpreviously (Sutton 1988). owlsresponded in relativelyuniform numbers across Other studiesthat examined habitat overlap between all monthssurveyed, except for a markedreduction in barredand greathorned owls generally found distinct responsivenessin May surveys(Table 1). habitatseparation, with overlapoccurring only along SEPTEMBER1995 BARREDAND GREAT HORNED OWLS IN NEW JERSEY 155 forestmargins or where open fields and be obscuredby combiningresponsiveness data on a wereinterspersed (Fuller 1979,McGarigal and Fraser seasonal basis. 1984, Bosakowskiet al. 1989a). We foundvirtually Marked seasonalityin responsivenessto taped play- completeoverlap of occupiedareas, with only two of backreportedly also characterizes great hornedowls, 13 estimatedbarred owl homeranges not extensively which were notedas mostresponsive from December overlappedby estimatedgreat horned owl ranges.We throughMarch (Emlen 1973, Smith et al. 1987), but •nfer that the extraordinarydegree of spatialoverlap we foundno evidence of seasonality.The onlyapparent demonstratedin our study(1) resultsfrom the small- deviationfrom relative uniformity acrossall months scale,but pervasivefragmentation created by narrow, surveyedwas the marked decrease seen in May surveys forest-dividingcorridors (Rich et al. 1994), , of both years,which correspondsto the beginningof and deliberateecotonal development for deer manage- the fledglingperiod for great hornedowls in New ment in southernNew Jerseyforests, and (2) reflects Jersey(Bosakowski et al. 1989c),and is consistent with the patchydistribution of maturehardwood and cedar low responsivenessby barredowls during their early swampwoodlands relative to the extensiveoak-pine fledglingperiod. forest (Forman 1979). Habitat Associations.Barred owls usually nest in Although spatial overlap was extensive,our data the interiorof contiguousforests with matureand de- suggestthat temporalpartitioning may havereduced cadenttrees of sufficientsize to providecavities for nest actualoverlap of the two species,as demonstratedby sites(Dunstan and Sample1972, Elody 1983, Allen Fuller (1979) with severalinstances of radio-tagged 1987), preferablyin standswith trees >51 cm dbh barredowls that exhibitedapparent spatial avoidance (Devereux and Mosher 1984). Of the habitats avail- behaviorin responseto greathorned owls. Fuller (1979) ablein our studyarea, only mature hardwood foundthat while someannual home ranges of the two providedtrees that were suitablefor nest sites.The speciesoverlapped considerably, very little home range only old-growthforests in southernNew Jersey are overlapwas evident when examined on a weeklybasis. hardwoodswamps that escapedlogging by virtue of Similarly,although 16 stationsyielded both species in their relativeinaccessibility. The high commercialval- our study,few overlapswere notedwithin individual ue of Atlanticwhite cedarresulted in essentiallycom- surveyperiods. plete (and repeated)harvest of cedarstands over the Other studieshave reporteddistinct seasonal vari- past 300 yr (Collinset al. 1988). abilityin barredowl responsivenessto taped playback We believe that the association between barred owls of vocalizations(Bosakowski 1987). In northern New and cedar swamp-pitchpine lowlands (which com- Jersey, Bosakowskiet al. (1987) found barred owl prisedonly 2% of the total mappedarea) indicatesthe responsivenessto be greatestin the breedingseason importanceof this habitat for roostingand foraging. from March to June, with relativelyfew responses Cedar standsprovide and shelteras roost outsideof thesemonths. Smith (1978) recordedhigher sites(Applegate 1975, Fuller 1979), especiallywhen barredowl responserates in Connecticutin late spring deciduoustrees are leafless,and likely providethermal (May to July), and Elody(1983) foundhigh response refugiain summer(Havens 1979). Cedarswamps also ratesin northern in summermonths. supportsubstantial populations of volesand Incubationby barredowls in New Jerseyoccurs in (Craigand Dobkin 1993)--the primaryprey of barred March and early April with mostegg datesfalling owlsin the region(Rusling 1951, Devereuxand Mo- between17 and 29 March (Johnsgard1988). Barred sher 1984, Bosakowskiet al. 1987). owl incubationrequires 28-33 d and fledgingaverages Not surprisingly,great hornedowls were not as- 42 d posthatching(Ehrlich et al. 1988). Hence, we sociatedwith anyparticular habitat in ourstudy, which found maximum responsivenessduring the nestling is consistentwith the view that this speciesis a habitat and early dispersalperiods, and found minimal re- generalist(Fuller 1979,Petersen 1979, McGarigal and sponsivenessduring incubation and earlyfledgling pe- Fraser 1984, Bosakowskiet al. 1989a) acrossthe spec- riods.This patternis consistentwith very low calling trum of foresthabitats found in southernNew Jersey. ratesrecorded during incubation in westernMaryland Increasedforest fragmentation as a resultof habitat (Devereux and Mosher 1984). Overall, the data sug- manipulationto increasedeer populations(creation of gestthat maximumresponsiveness occurs during spe- "wildlife openings"),logging operations, and the pro- cificportions of the annualcycle (which happen pro- liferationof utilityrights-of-way (Rich et al. 1994)will gressivelylater at higherlatitudes), a patternthat can continueto createhabitat conditions that are likely to 156 KIM J. LAIDIG AND DAVID S. DOBKIN VOL. 29, NO. 3 benefitgreat horned owls, but negativelyaffect barred CI,•ax, R.J., D.G. SMITH AND L. KELSO. 1987. Distri- owls. Thus, the barred owl populationin southern butional status and literature of northern forest owls. New Jerseycannot be consideredsecure. At the very Pages47-55 in R.W. Nero, R.J. Clark, R.J. Knapton least, land managementactivities should not be un- and R.H. Hamre [EDS.],Biology and conservationof dertaken that will further diminish suitable barred owl northernforest owls. USDA For. Serv.Gen. Tech. Rep. RM-142, Fort Collins, CO U.S.A. habitat in the region. COLLINS,B.R. aND E.W.B. RUSSELL[EDS.]. 1988. Pro- ACKNOWLEDGMENTS tecting the New Jersey Pinelands:a new directionin The authorsthank Tom Bosakowski,Andy Carey, Ralph land-usemanagement. Rutgers Univ. Press,New Bruns- Good,Fabian Jaksi•, Mark Morgan,Thomas Morrell, Lar- wick, NJ U.S.A. ry Niles,Adam Rich, Don Stearns,and Clay Suttonfor --, N.F. GOODAND R.E. GOOD. 1988. The landscape helpfulcomments on various versions of thismanuscript. We of the New JerseyPine Barrens.Pages 3-33 in B.R. aregrateful to RobertZampella of the New Jersey Pinelands Collinsand E.W.B. Russell[EDS.], Protecting the New Commissionfor providingthe useof mapsand electronic JerseyPinelands: a new directionin land-usemanage- planimeter,and to the Endangeredand NongameSpedes ment.Rutgers Univ. Press,,NJ U.S.A Programof the New JerseyDivision of and Wildlife forfinandal support. K. Laidigis especiallygrateful to Rob- Cw•a%L.J. aNDD.S. DOBKIN.1993. Communitydynam- erta Laidigfor her steadfastencouragement throughout the icsof smallmammals in matureand logged Atlantic white project.This paperis basedin parton a thesissubmitted by cedarswamps of the New JerseyPine Barrens.New the seniorauthor in partialfulfillment of the requirements York StateMus. Bull. No. 487, Albany,NY U.S.A. for the M.S. degreeat RutgersUniversity. DEWREUX,J.G. aNDJ.A. MOSHER. 1984. Breedingecol- Lrr•R•TU•E CITED ogy of barredowls in the centralAppalachians. Raptor Res. 18:49-58. ALLF_Xq,A.W. 1987. Habitatsuitability index models: barred DUNSTaN,T.C. aNDS.D. SAMPLE.1972. Biologyof barred owl. USDI Fish Wildl. Serv.Biol. Rep. 82(10.143). owls in . Loon 44:111-115. APPLEGATE,R.D. 1975. Co-roostingof barredowls and EHRLICH,P.R., D.S. DOBKINaND D. WHEYE. 1988. The commongrackles. -Banding 46:169-170. birder'shandbook: a field guideto the naturalhistory of BENT, A.C. 1938. Life historiesof North American birds North Americanbirds. 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