BREEDING ECOLOGY OF BARRED IN THE CENTRAL APPALACHIANS

ABSTRACT- Eight pairs of breedingBarred Owls (Strix varia) in westernMaryland were studied. Nest site habitat was sampledand quantifiedusing a modificationof theJames and Shugart(1970) technique (see Titus and Mosher1981). Statisticalcomparison to 76 randomhabitat plots showed nest sites werb in moremature forest stands and closer to forest openings.There was no apparent association of nestsites with water. Cavity dimensions were compared statistically with 41 randomlyselected cavities. Except for cavityheight, there were no statistically significant differences between them. Smallmammals comprised 65.9% of the totalnumber of prey itemsrecorded, of which81.5% were members of the familiesCricetidae and Soricidae. accounted for 14.6%of theprey items and crayfish and insects 19.5%. We also recordedan apparentinstance of juvenile cannibalism. Thirteennestlings were produced in 7 nests,averaging 1.9 young per nest.Only 2 of 5 nests,where the outcome was known,fledged young.

The Barred (Strix varia) is a common noc- STUDY AREA AND METHODS turnal raptor in forestsof the easternUnited States, The studywas conducted in Green Ridge State Forest (GRSF), though few detailedstudies of it havebeen pub- Allegany County, Maryland. It is within the Ridge and Valley lished.Most reportsare of singlenesting occurr- physiographicregion (Stoneand Matthews 1977), characterized by narrowmountain ridges oriented northeast to southwestsepa- encesand general observations(Bolles 1890; Carter rated by steepnarrow valleys(see Titus 1980). 1925; Henderson 1933; Robertson 1959; Brown About 74% of the countyand nearly all of GRSF is forested 1962; Caldwell 1972; Hamerstrom1973; Appel- Major foresttypes were describedby Brushet al. (1980).Predom- gate 1975; Soucy 1976; and Wright 1977; inant tree speciesinclude white (Quercusalba), red oak (Q. Leder and Walters 1980). Habitat was described rubra),chestnut oak (Q.prinus), scarlet oak (Q. coccinea),red (Acerrubrum), and pignut and mockernut (Carya glabra qualitativelyby Nicholls and Warner (1972) and and C. tomentosa).Predominant understory include flow- Fuller (1979). food habits were re- ering dogwood(Cornus florida), sassafras(Sassafras albidum), ser- ported by Cahn and Kemp (1930), Errington viceberry( spp.), and saplingsof the dominanttrees. (1932), Errington and McDonald (1937), Wilson The studyarea wassystematically searched for activenests from late Februarythrough May in 1981and 1982.During 1982,tape (1938), Mendall (1944), Hamerstrom and recorded Barred Owl calls were broadcast in order to elicit re- Hamerstrom (1951), Blakemore (1960) LeDuc sponsesand help localizenesting pairs. (1970),and Korschgenand Stuart(1972). The food Nest siteswere plottedon 7.5 rain USGStopographic maps and habits studied, however, were all from midwestern County Soil ConservationService maps. A nestsite was defined as states,except Mendali's (1944) study from Maine. a 0.4 ha plot (11.3 m radius) centered on the nest tree. This size plot was consideredmore time and field efficient than either Dunstanand Sample(1972) reported the number smalleror largersize plots when making quantitative estimates of of fledglingsfrom 1 cavityeach year for 5 years,but the vegetation(Lindsey et al. 1958,James and Shugart1970). provided no other productivity information. Nestswere checkedperiodically each season to obtainnesting Clutch sizesin variousgeographic regions can be chronologyand productivity information. At the same time, re- gurgitatedpellets found in the cavitieswere collected and anyprey found in Bent (1961) and Murray (1976). remains were noted. This study was conducted in an area where 4 At the end of the nestingseason, vegetation at eachactive nest diurnal raptor species,the Red-shoulderedHawk sitewas sampled using a modificatonof the Jamesand Shugart (Buteolineatus ), Broad-wingedHawk (B.platypterus ), technique (1970), as describedby Titus and Mosher (1981). Thirty-four variableswere measuredor derived at eachsite (Table Red-tailed (B. jamaicensis)and Cooper's 1). The type of cavityin whicha pair nested(hollow tree stub,hole Hawk (Accipitercooperi), were alsounder study(see from disease,excavated hole, or hole from broken limb) and Titus and Mosher 1981,Janik and Mosher 1982). successionalstage of the cavitytree (Fig. 1) were recorded. Our objectiveswere to quantitativelydescribe veg- Height to cavityentrance was measured with a meter tape for etation structure at Barred Owl nest sites and com- treesclimbed, otherwise height measurementsand percentslope weremeasured with a Hagaaltimeter. Percent canopy, understory pare it with surrounding habitat, measure and and ground coverswere basedon 40 ocular tube readings, 10 comparedimensions of cavitiesused by them with alongeach of 4 transectsstarting at the nesttree and extendingin those from randomly selectedcavities, describe eachof the compassdirections. their food habitsfor this geographicregion, and We comparednest site data with random habitat samplescol- lected by Titus and Mosher (1981) to determine if vegetation determinetheir breedingchronology and produc- structure around nest trees differed from surrounding habitat. tivity. Variablesmeasured at random plotsare listedin Table 1 except

49 RAPTORRESEARCH 18(2):49-58 50 DEVERE^UX AND MOSHER VOL. 18, NO. 2

Table 1. Quantativehabitat variables and cavitycharacteristics used in analysisof Barred Owl nest site habitat

1. ALTITUDE Altitude of plot in meters;taken from U.S.G.S.7.5-min. quadrangles 2. SOIL Soil-woodssuitability; measures suitability for tree productivity;class 1 indicateshigh produc- tivityand class6 indicateslow productivity(Stone and Matthews1977) 3. SITINDX Siteindex; based on SOIL and thetree speciespresent in the plot (Stoneand Matthews1977)

4. WATER Distance to water in meters

5. DISFOROP Distanceto the nearestforest opening in meters;measured to the nearestbreak in forest continuity,such as created by trail, road, field, etc. 6. PERSLOP Percentslope of plot 7. CANHT Canopyheight of the plotin meters;the meanof 5 measurementstaken to the top of the canopy 8. CANEVER Percentageevergreen canopy cover 9. CANTOT Percentagetotal canopy.cover 10. UNDEVER Percentageevergreen understorycover 11. UNDTOT Percentagetotal understorycover 12. GRNDEVER Percentageevergreen ground cover 13. GRNDTOT Percentagetotal ground cover 14. SHRUBDEN Shrubdensity (James and Shugart1970, James 1978)

15. SHRUBIND Shrub index (Titus 1980) 16. NOSPTREE Number of speciesof overstorytrees in the plot 17. NOSPSHRB Numberof speciesof shrubsand saplingsin the plot 18. NOTREES Number of overstorytrees in the plot 19. UND14 Numberof understorystems 1-4 cm diameterin the plot 20. UND58 Number of understorystems 5-8 cm diameterin the plot 21. UNDGT8 Numberof understorystems greater than 8 cm diameterin the plot 22. DBHLT26 Number of overstorytrees less than 26 cm dbh in the plot 23. DBH2650 Number of overstorytrees 26-50 cm dbh in the plot 24. DBHGT50 Number of overstorytrees greater than 50 cm dbh in the plot 25. BASAL Basalarea in m2/hatbr overstorytrees 26. DBH* Diameter at breastheight of nest tree 27. TREEHT* Height of cavitytree in meters 28. CAVHT* Height to lowestpoint of cavityentrance in meters 29. %CAVHT* Percentagecavity height; calculated as: (GAVHT/GANHT) (100) = %GAVHT 30. TREEDIAM* Diameter of cavitytree at cavityheight 31. HORIZONT* Horizontal length of cavityopening in cm 32. VERTICAL* Vertical length of cavityopening in cm (Table 1 continued) SUMMER 1984 APPALACHIAN BARRED OWLS 51

(Table 1 concluded) 33. CAVDIAM* Insidediameter of cavityin cm;measured from insideof entranceto backwall; for hollowtree stubs,the largestdiameter is recorded 34. CAVDEPTH* Cavitydepth in cm; measuredfrom lowestpoint of cavityentrance to baseof cavity.

(* = variablesunique to cavitiesand cavity trees). for the cavityand cavitytree specificvariables. (Siegal 1956) tested for similarity betweennest site habitat and Dimensionsof 41 randomlyselected, unoccupied cavities were random habitatplots, and nest site cavityand random cavityd•- measuredand compared with nest cavities to providea measureof mensions.Spearman rank correlation coeffidents (Siegal 1956) cavitysizes availble to BarredOwls and assesscavity selection. The were calculatedto determine the extent of correlation among random samplingof cavitieswas stratified. Transects, approxi- structural features of habitat and among cavity characteristics mately100 m apart, 1.6km longextending on bothsides of a road X 2 goodness-of-fittests were usedon pooledsamples of nestsite running the lengthof the studyarea, were randomlychosen. A and randomcavities to determineif differencesexisted among the coin flip determined which side of the road the transectwas numberof eachcavity type found and numberof cavitytrees •n walked. Every third cavityencountered was measuredbut no eachsuccessional stage. Test results were considered significant if morethan 3/transectto avoidmeasuring too many within a single P < 0.05. habitattype. The criteriaibr acceptinga randomcavity was that it be at least2 m from the groundand haveat leasta 15cm diameter RESULTS AND DISCUSSION opening,or, fbr a hollowtree stub,a 25 cm dbh. Minimum sample sizeswere calculatedfbr each variable to Habitat. -- Eight-Barred Owl nestswere located. determineif random samplingwas adequate. Sample sizes were The 4 found in 1981 were not reused in 1982. Nest consideredadequate if they met the criteria of remaining within 20% of the mean for 95% of the samples.Twenty of 25 variables sitehabitat and random habitatplots were signific- pertainingto habitatstructure met thiscriteria with < 76 samples. antlydifferent betweengroups for 7 of 25 variables Sevenof 9 cavityand cavitytree variablesmet this criteria with (Table 2). Nest siteswere found significantlycloser samplesizes of • 41. to forest openings than random sites,in habitats Habitat data were subjected to nonparametric statistical analysesconducted on the StatisticalPackage for the SocialSci- with well developed understories.Percent under- ences(SPSS) computer program (Nie et al. 1975, Hull and Nie storycover and the number of stemsgreater than 8 1981). Two setsof Kruskall-Wallis one-way analysisof variance cm diameter, both positivelycorrelated with each

Table 2. Means+_ standard deviations and rangesof habitatvariables at BarredOwl nestsites and randomhabitat plots, and resultsfi'om Kruskal-Wallisone-way ANOVA (chi-squarestatistic) testing for significantdifferences betweengroups.

Barred owl Random Kruskal- Habitat nest sites sites Wallis variablea (N -- 8) (N = 76) X 2 value

ALTITUDE 1239 +_ 517 1356 +_ 613 0.084 (820- 2420) (560- 2860)

SOIL 3.6 +_ 1.4 3.9 _+ 1.3 (1 - 6) (1 - 6) 0.093

SITINDX 65 +_ 11.7 61.4 _+ 12.5 0.410 (45 - 85) (40- 90)

WATER 218 +_ 222 320 +_ 243 1.860 (15 - 675 (35 - 1050)

(Table 2 continued) 52 DEVER•AVX AND MOSHER VOL. 18, NO. 2

(Continuation of Table 2)

Barred owl Random Kruskal- Habitat nest sites sites Wallis variablea (N = 8) (N = 76) X z value

DISFOROP 85 _ 116 221 _ 209 7.481'* (4- 350) (8 - 1110)

PERSLOP 9.4 + 12.9 21.6 _ 13.3 0.107 (0 - 40) (3 - 80)

CANHT 23.5 + 3.3 20.6 _ 4.5 2.991 (19- 28) (10 - 31)

CANEVER 7 _ 13 6 _+ 14 0.019 (0 - 32) (0 - 53)

CANTOT 68 + 21 75 _+9 0.230 (30 - 98) (43 - 90)

UNDEVER 0 2 +7 0.535 (0 - 37)

UNDTOT 67_+ 14 53 _+ 14 5.120' (50 - 90 (17 - 80)

GRNDEVER 0 .5 0.059 (0 - 30)

GRNDTOT 43 _ 13 38 + 16 0.893 (23 - 68) (10 - 75)

SHRUBDEN 23 _ 19 24 +11 1.074 (5 - 68) (3 - 64)

SHRUBIND 42 _ 23 50 +21 1.220 (10 - 83) (14 - 115)

NOSPTREE 4.5 _ 1.7 4.6 _+ 1.8 0.046 (3 - 7) (1 - 10)

NOSPSHRB 11.4 _ 2.8 10.1 _ 2.9 1.395 (8- 16) (5 - 17)

NOTREES 10.9 _ 3.6 19.5 + lO) 7.315'* (4- 17) (7 - 48)

UND14 69.8 _+ 34.9 74.3 _+ 33.3 0.245 (28- 131) (9 - 154)

UND58 17.5 + 8.8 12.7 + 8.7 2.874 (3 - 33) (1 - 45)

(Table 2 continued) SVMMER 1984 APPALACHIANBARRED OWLS 53

(Table 2 concluded)

Barred owl Random Kruskal- Habitat nest sites sites Wallis variablea (N = 8) (N = 76) X 2 value

UNDGT8 9.5 _+ 3.7 5.9 _ 3.6 5.870* (4- 16) (0 - 14)

DBHLT26 5.1 _ 3.2 14.7 _+ 11.6 6.554** (0- 10) (0 - 48)

DBH2650 3.9 _ 2.2 4.6 _+ 2.8 0.665 (2- 8) (0- 12)

DBHGT50 1.8 _+ 1.2 0.2 __ 0.6 12.714'** (0 - 4) (0 - 3)

BASAL 28.4 _+ 5.8 20 -+ 5.5 11.755'** (21.7 * 40.1) (3.9 - 34.2)

aMnemomc names defined in Table 1. (* = P "0.05; ** = P ,•- 0.01; *** = P < 0.001). other (r = 0.24, P = 0.03, N = 84), were signific- 1975, Soucy1976), perhapsbecause such areas are antly higher at nest sites.There were fewer over- often inacessibleor too wet to be logged,thereby story trees, becauseof fewer trees in the < 26 cm providingold growthtimber and abundantnesting dbh sizeclass. There were significantlymore trees cavities.We found no differencein the proximityto > 50 cm dbh at nest sites(45/ha vs 5/ha at random water betweennest sitesand random habitat plots. sites),itnd greaterbasal area. The averagedistance to waterwas 218 m with only 1 Theseresults' fire in •'•/i•al agreementwith the nest located on a stream "floodplain". Further- qualitativehabitat descriptionsprovided by previ- more, Nicholls and Warner (1972) and Fuller ous authors (i.e., Barred Owls utilize forest stands (1979), both radiotelemetrystudies, reported that mature enough to provide suitablenesting cavities). Barred Owls utilized oak-upland habitat more fre- Craigheadand Craighead(1969) suggestedone of quentlyand consistentlythan anyother habitattype the reas6nsBarred Owls were absentfrom part of including white cedar (Thuja occidentalis)swamps, their study area was a lack of mature basswoods alder (A!nusspp.) swamps,and marshes.Nicholls (Tilia sp.)and a lackof heart rot fungusin woodlots and Warner (1972) suggestedthat owls used up- that had mature trees. However, owls are known to land sitesbecause of more suitable nest sites,abun- nest in old hawk or nests,as did 1 pair in dance of hunting perches,open understory for this study, and 23 of 38 pairs reported by Bent hunting,and the opportunityto hear prey betterin (1938). Bent suggestedthat they choosealternative dry areas. nests becauseof lack of cavities. Hilden (1965) and Bent (1938) reported that distributionof Barred Temple (1977) indicatedthat birds may shift from Owls in southern New England coincides with their traditional nesting sitesby imprinting on the Red-shoulderedHawks and noted they are often type of nestsfrom whichthey fledge. If this occurs found in the samewoodlot. In this study, forest in Barred Owls, thoseraised in old hawk or squirrel structure around Barred Owl nest sites was similar nests may subsequentlyuse these nest types re- to that of sympatricRed-shouldered , both gardlessof cavityavailability. speciesutilizing old growth timber for nesting.Six Much literature on Barred Owls indicatesan ap- of the 7 significantvariables listed in Table 2 were parent associationwith wet areas (Carter 1925, Er- also significant for the Red-shouldered Hawk rington and McDonald 1937,Bent 1938,Appelgate (Titus and Mosher 1981). Apparent differences 54 DEvEm•^ux AND MOSUEa VOL. 18, NO. 2 between them were that Red-shouldered Hawk other 3 types (X2 = 54.17, 3 df, P < 0.05). nestswere no closerto forest openingsthan ran- Twenty-three percent were holes,resultingfrom dom habitat plots, but were significantlycloser to brokenlimbs and 8% were holescreated by disease. water, and there wasa higher shrubdensity at Red- No excavated holes were found that met the criteria shoulder occupiedsites. to be includedin the randomcavity sample. Four of Cavities.-- Six Barred Owl nestswere in the top the 7 nestingcavities were in trees in the second of hollowtree stubs,1 in a cavitycreated by disease successionalstage (see Fig. 1) and 1 each in the and 1 in an old stick nest. The high incidenceof third, fourth and fifth stages.There wasno statisti- hollowtree stubsas nest sites is probablya reflection caldifference in the total numberof cavitytrees in of cavity type availabilityin this area. Sixty-nine each of the 5 successionaltree stages(X 2 = 9.29, 4 percent of the total number of cavitiesmeasured df, P < 0.05). were hollow tree stubs,significantly more than the There was a significantdifference between ran-

Table 3. Means_+ standard deviation and rangesof cavityand cavitytree dimensionsfor Barred Owl nestsite cavities and random cavities,and resultsfrom Kruskal-Wallisone-way Anova (chi-squarestatistics) testing for similaritybetween groups.

Kruskal- Wallis Cavity Nest site Random X2square variable a cavities N cavities N value

DBH 61 _ 15 7 53 _+ 13 41 1.652 (42 - 88) (26 - 90)

TREEHT 15.4 _+ 5.8 7 12.9 _+ 7.1 41 1.137 (10 - 25) (3 - 24)

CAVHT 9.1 _ 2.9 7 6.3 _ 3.1 41 5.5999* (4- 14) (2- 17)

%CAVHT 39 _ 11 7 30 _ 14 41 2.724 (17 - 50) (10 - 71)

TREEDIAM 46 _+ 8 4 48 _ 11 33 0.048 (36 - 54) (25 - 69)

HORIZONT 15 _+ 0 1 21 + 8 12 2.571 (12 - 40)

VERTICAL 45 _ 0 1 49 _ 35 12 2.571 (20- 140)

CAVDIAM 33 _+ 8 6 30 _+ 10 33 0.985 (22 - 41) (11 - 60)

CAVDEPTH 54 _+ 44 6 167 _+ 203 33 0.767 (3 - 130) (0 - 800) aMnemonic namesdefined in Table I. (* = P •.. 0.05). SUMMER APPALACHIANBARRED OWLS 55

,•.•...?,,?,.,,,:.,.;• ,•:_:,.-:.•o•_,;,•5•e: ..:../..,,•½;,,,.!• ;'..•:...,•g .....:,?.?.? •

1. LIVE 2. DECLINING 3. DEAD; 4. DECOMPOSING; 5. DECOMPOSING; NO APPARENT EARLY STAGE LATE STAGE DECOMPOSITION

Figure1. Successionalstages for describing Barred Owl cavity trees: 1. LIVE- treeis apparently healthy except for cavity;2. DECLINING- treeis obviously declining; losing leaves; some dead branches; 3. DEAD;NO APPARENT DECOMPOSITION - no leaves;tree stillhas all or mostof bark; somebranches may be broken;no apparentrotting of wood;4. DECOMPOSING;EARLY STAGE - manybroken branches; bark falling off; woodbecoming soft in spots; 5. DECOMPOSING;LATE STAGE- littleor nobark on tree;very soft wood; broken tree stub is often all thatremains domand nestsite cavity dimensions for only 1 of 9 cent occurrenceof mammalsand birds is fairly typi- variables(Table 3). Cavitiesused by owlsaveraged 3 calof whathas been reported in the literature.Fish, m higherthan random cavities. Cavity depth of nest reptiles, amphibians,and arthropods have also site cavitieswas highly variable,ranging from 3 - beenrecorded as prey itemsbut are probablymore 130 cm. Bent (1938) recordeda depth for 1 Barred importantto individualowl pairsthan to a regional Owl cavityof 244 cm. population.The majorityof crayfishrecorded as The cavitydata suggest that mostcavities, given preyin thisstudy, for example,were from 2 nests. certainminimum dimensions,may be suitablefor Jaksic(1982) hypothesizedthat temporal segre- nesting.Nest trees generally have at leasta 25 cm gationsof falconiformand strigiform raptorsmay dbh and those with cavities 9 m or more above not reduce competition for food between groups. groundmay be preferred.Most reported dimen- However, his data for Barred Owls revealed little sions(Bent 1938; Allin 1944; LeDuc 1970;Dunstan dietary overlap with falconiform species,except and Sample1972; Soucy1976 Leder and Walters with the American Kestrel (Falcosparverius). We 1980) are lessthan the maximum cavitydimensions also observed little overlap. Sciuridae we found. Fewdata exist on the lengthand/or width were clearlythe major prey for the 4 hawkspecies of cavity openings.Hamerstrom (1972) recom- on the studyarea (Janikand Mosher 1982), while mended a 20 cm dia openingwhen constructinga Cricetidaeand Soricidaespecies, which accounted nestbox for this speciesbut did not indicatethe for 81.5% of the mammals and 53.7% of the total basis for this measurement. Forsman (1975) re- number of prey items,were the predominant prey porteda rangeof cavityentrance widths of 15.2 - for owls. Furthermore, Flying and 55.9 cm for 10 cavitiesused by the closelyrelated Crayfish,both nocturnaland not recordedas prey SpottedOwl (Strixoccidentalis ). itemsfor the hawks,comprised 8.5% and 12.2%of Food Habits. -- Barred Owl food habits in the the total number of prey items recorded, respec- GRSFregion are summarizedin Table 4. The per- tively. 56 DEVEREAUX AND MosI-n;a VOL. 18, No. 2

Table4. Foodhabits of BarredOwls in the CentralAppalachians a.

Prey Species Occurrence

Mammals

SouthernFlying Squirrel(Glaucomys volansi) 7 Shorttail Shrew (Blarina brevicauda) 7 Peromyscnsspp. 5 MeadowVole (Microtnspennsylvanicus) 4 EasternChipmunk (Tamiasstriatns) 2 Red Squirrel (Tamiasciurushudsonicus ) 1 Unidentified Cricetidaesp. 16 Unidentified Soricidaesp. 12 Total 54 65.9

Birds

ScarletTanager (Pirangaolivacea ) 3 EasternPhoebe (Sayornis phoebe) 2 (Cyanocittacristata ) 1 Unidentified 6 Total 12 14.6

Arthropods Crayfish (Cambarussp.) 10 Unidentified insects 6 Total 16 19.5

Total Items 82 100.0 aBasedon prey remains and analysis ofpellets from seven nests.

One nestling,about 28 d old, wascannabilized by begin nesting about 1 wk before Red-tails (Janik its sibling.Most of itsbody was eaten; legs, and skin 1980), the earliestnester of the hawk speciesfor this and feathers of the back were all that remained. area. Based on growth measurementsbeing taken every Average clutchsize/nest was 2.3, slightlyhigher 3 to 4 d, both nestlingsappeared healthy and were than the 2.0 reported by Murray (1976) for Barred of relativelyequal sizeat 27 d old. The causeof Owls in this region and latitude. A total of 13 nestl- death wasunknown but fratricide in raptors usually ings were produced in 7 nests, averaging 1.9 occursshortly after the secondyoung hatches (Stin- young/activenest. The outcome of 5 nests was son 1979) and amongnestlings of considerablesize known. Of these,only 2 fledged young. The eggs difference (Ingram 1959), neither of which were rolled out of 1 nestand the nestlingsin the other 2 the casein this incident.Juvenile cannibalism is not were preyed upon, perhapsas a result of human an uncommon occurrence among raptors, but to activityat the nestsites. our knowledge has not previously been The 2 young in successfulnests emerged from documented for Barred Owls. their cavities when 31 + 1 d and 30 + 1 d old, NestingChronology and Productivity.-- Nesting respectively.At thisage, Barred Owlsare essentially chronologyand productivityparameters are sum- flightless.Primary remigesand rectricesof these2 marized in Table 5. Hatch dateswere fairly consis- owlswere only 50 and 12% of adult size, respectively, tent amongnests, 5 out of 6 hatchingwithin 7 d of within 2 d of fledging. Bent (1938) alsoreported each other. Mean egg dates indicate Barred Owls nestlingBarred Owlsclimbing out of their cavities SUMMER1984 APPALACHIANBARRED OWLS 57

Table 5. Nestingchronology and productivityof Barred Owls in the central Appalachians,1981-1982 (# of nestsin parentheses).

Meanegg date a (6) 20 March Mean hatch date (6) 10 April Mean nestdeparture date (2) 24 May

Mean clutch size (7) 2.3 Totaleggs producted b (8) 19.0 % hatchingsuccess (8) 68.4 # of nestlingsper activenest (7) 1.9 Total number fledged (5) 2.0 # fledged/successfulnest attempt (2) 1.0 % nestingattempts successful (2/5) 40.0 aEggdates based on back dating from hatch dates using a 28-dayincubation period (Bent 1938) bMinimalnumber ofeggs produced based on# ofhatchlings and/or eggs found innests at 28-35 d old. Forsman (1975) reported Spotted CONCLUSIONS Owls leaving their cavitiesat 34-36 d old. Dunstan Secondary cavity nesting birds, including the and Sample(1972) and Soucy(1976), however,re- Barred Owl, cannot choose a location within a ported Barred Owls not leavingnests until about 49 habitat to "place" their nests.They are limited to d old. The ageat whichowls emerge may be a factor what is already available. The data indicate that of cavitysize. Those in small,cramped cavities, un- differences exist between Barred Owl nest site ableto spreadand exercisetheir wings,may emerge habitat and surrounding habitat, but do not indi- at an earlier age. cate whether cavities are selected based on those Leaving the nest early is a disadvantagefrom a differences.Further studyis needed to answerthis developmentstandpoint because additional energy question. is required to compensatefor that lost to environ- mental stress and increased activity. This was ACKNOWLEDGEMENTS suggestedby measurementsof 1 of the owls that We thank J. Coleman, L. Garrett, M. Kopeny, D. Lyons, F. weighedthe same2 d after leavingthe nestas 2 d Presley,R. Whetstoneand K. Titus for their time and assistance We alsothank S. Postupalskyfor commentson an earlier version before leaving. However, mobility vs sitting in the of the manuscript.This studywas supported, in part, by grants nest may be advantageousin terms of predator from SigmaXi, the MarylandOrnithological Sodety, and the U.S avoidance.Birds in cavitiesare especiallyvulnera- Fish and Wildlife Service(FWS 14-16-0009-80-007). This is Scien- ble to becausethere is usually only 1 tific SeriesNo. 1549-AEL of the AppalachianEnvironmental escaperoute. Young Barred Owls that do leave Laboratoryand TechnicalReport-10 of the CentralAppalachian Raptor EcologyProgram. nests at a preflight stage are not totally helpless. Adult Barred Owls will continue to feed and defend LITERATURE CITED their young throughout the summer, even after they can (Henderson 1933, Bent 1938, Dunstan ALLIN,A.E. 1944. Nestingof the barred owl (Strixvaria) and Sample 1975, Bird and Wright 1977). Also, in . Can. Field Nat. 58:8-9. young Barred Owls have the ability to climb trees APPELGATE,R.D. 1975. Co-roostingof barred owlsand using their beaksand talons(Dunstan and Sample commongrackles. Bird Banding42:169-170. BENT, A.C. 1938. Life histories of North American birds 1972). Thus, they are able to move about, first by of prey.Part II. U.S. Natl. Mus.Bull. 170.Washington, gliding or fluttering to the ground, then climbing a D.C. 482 pp. nearby tree. Tree climbing has alsobeen reported BIRD, D.M, ANDJ. WRIGHT. 1977. Apparent distraction for Great-horned Owl (Bubovirginianus), Screech displayby a barred owl. Can.Field Nat. 91:176-177. Owl (Otusasio) (Dunstan and Sample 1972) and BLAKEMORE,L.A. 1960. Barred owl food habits in Glen- SpottedOwl (Forsman 1975). wood Park, Minneapolis,Minnesota. Flicker 12: 21-23. 58 DEVEREAUXAND MOSHER VOL. 18, No. 2

BOLLES,F. 1890. Barred owls in captivity.Auk 7:101- of raptorsin the centralAppalachians. Raptor Research 114. 16:18-24. BROWN,W.H. 1962. Parentalcare by a barred owl.Iowa KORSCHGEN,LJ. ANDH.B. STUART.1972. Twentyyears Bird Life 32:58. of avianpredator-small relationships in Mis- BRUSH,G.S., C. LENKAND J. SMITH. 1980. The natural souri.J. Wildl.Manage. 36:269-282. forestsof Maryland: an explanationof the vegeta- LEDER,J.P. ANDM.L. WALTERS.1980. Nestingobserva- tional map of Maryland.Ecol. Monogr. 50:66-92. tions for the barred owl in westernWashington. CAHN,A.R. ANDJ.T. KEMP. 1930. On the food of certain Murrelet: 110-112. owls in east-central Illinois. Auk 47:323-328. LEDuc,P. 1970. The nestingecology of somehawks and CALDWELL,L.D. 1972. Diurnal huntingby a barredowl. owls in southeastern Minnesota. Loon 42:48-62. Jack Pine Warbler 50:93-94. LINDSEY, A.A., S.D. BARTONAND S.R. MILES. 1958. Field CARTER,J.D. 1925. Behavior of the barred owl. Auk efficienciesof forest samplingmethods. Ecology 42:443-444. 39:428-444. Craighead,J.J. and F.C. Craighead,Jr. 1969. Hawks, MENDALL,H.L. 1944. Foodof hawksand owls in Maine. owls,and wildlife. Dover Publ, Inc. . J. Wildl. Manage.8:198-208. DunstanT.C, and S.D. Sample1972. Biology of barred MURRAY,G.A. 1976. Geographicvariation in the clutch owlsin Minnesota.Loon 44:111-115. sizesof sevenowl species.Auk 93:602-613. ERRINGTON,P.L. 1932. Food habitsofsouthern Wiscon- NICHOLLS,T.H. AND D.W. WARNER. 1972. Barred owl sin raptors. Part I. Owls.Condor 34:176-186. habitatuse as determined by radiotelemetry.J. Wildl. ANr• M. MCDONALr•. 1937. Conclusions to Manage. 36:213-224. the foodhabits of thebarred owl in Iowa.Iowa BirdLife NIE, N.H., C.H. HULL,J.G. JENKINS,K. STEINBRENNER, 7:47-49. ANI•H. BENT(eds.). 1975. Statisticalpackage for the FORSMAN,E. 1975. A preliminary investigationof the social sciences.McGraw-Hill Book Co., New York. spottedowl in oregon.M.S. thesis,Oregon StateUniv. ROBERTSON,W.B. 1959. Barred owl nesting on the 127 pp. ground. Auk 76:227-230. FULLER, M.R. 1979.Spatiotemporal ecology of four SIEGEL,S. 1956. Nonparametricstatistics for the be- sympatric raptor species.Ph.D. dissertation,Univ. havioral sciences.McGraw-Hill Book Co., New York. Minnesota.220 pp. SoucY, L., JR. 1976. Barred owl nest. North Am. Bird HAMERSTROM,F. 1972. Birdsofprey of Wisconsin.Wisc. Bander 1:68-69. Dept. Nat. Res. STINSON,C.H. 1979. On the selectiveadvantage of frat- 1973. Diurnal sleep rhythm of a young ricide in raptors.Evolution 33:1219-1225. barred owl. Auk 90:899-900. STONE,K.M. ANDE.D. MATTHEWS.1977. Soil survyof HAMERSTROM, F.N., JR. AND F. HAMERSTROM. AlleganyCounty, Maryland. USDA, Soil Cons.Ser- 1951. Foodof youngraptors on the Edwin S. George vice. 234 pp. Reserve. Wilson Bull. 63:16-25. TEMPLE,S.A. 1977. Manipulatingbehavioral patterns of HENDERSON, G. 1933. Boldness of barred owls when endangered birds. A potential management dangerthreatens young. Wilson Bull. 45:143. technique.Pp. 435-443 In S. A. Temple (ed.), En- HILDEN, O. 1965. Habitat selection in birds. Annals Zool. dangered birds. Managementtechniques for pre- Fenn. 2:53-75. servingthreatened species.Univ. Wisc. Press,Madi- HULL,C.H. ANDN.H. NIP (eds). 1981. SPSSupdate 7-9. son. McGraw-Hill Book Co., New York. 402 pp. TITUS,K. 1980. Nestsite habitat selection by woodland INGRAM, C. 1959. The importance of juvenile can- hawks in the central Appalachians. M.S. thesis, nibalismin the breeding biologyof certain birds of FrostburgState College, Maryland. 67 pp. prey.Auk 76:218-224. ANr•J.A. MOSHER. 1981. Nest site habitat JAKSIC,F.M. 1982. Inadequacyof activitytime asa niche selectionby woodlandhawks in the centralAppalac- difference: the caseof diurnal and nocturnalraptors. hians. Auk 98:270-281. Oecolo•a52:171-175. WILSON, K.A. 1983. Owl studies in Ann Arbor, Michi- JAMES,F.C. 1978. On understandingquantitative sur- ganAuk 55:187-197. veysof vegetation.Amer. Birds 32:18-21. ANDH.H. SHUGART,JR. 1970. A quantita- Cooperative Wildlife Rsh. Lab, Southern Illinois Univ. Carbon- tive methodof habitatdescription. Audubon Field Notes 24:727-736. dale, IL 62901. Addressof secondauthor: AppalachianEn- vironmentalLab, Univ. of Maryland, FrostburgState College JANIK,C. 1980. Nestingbiology and behaviorof wood- Campus, Frostburg, MD 21532. Present addressof secondau- land raptors in western Maryland. M.S. Thesis, thor: SavageRiver Consulting,Box 71, Frostburg,MD 21532. FrostburgState College, Maryland. 87 pp. ANDJ.A. MOSHER.1982. Breeding biology Received8 March 1983; Accepted10 May 1984.