Owls on the Cape May Peninsula

J. Raptor Res. 27(4):210-213 ¸ 1993 The Raptor Research Foundation, Inc.

ROAD MORTALITY OF SAW-WHET AND SCREECH-OWLS ON THE CAPE MAY PENINSULA

GEORGE LOOS AND PAUL KERLINGER CapeMay Bird Observatory,New JerseyAudubon Society, P.O. Box 3, CapeMay Point,NJ 08212 U.S.A.

ABST•t^CT.--Duringa 10-yr study in southernNew Jersey, 250 road-killed raptors of six owl and six hawk specieswere foundduring 145 km of roadtravel between mid-October and early April. Northern Saw-whet Owls (Aegoliusacadicus) and Eastern Screech-Owls(Otus asio) accounted for 45% (N = 114) and 36% (N --- 91) of all road kills, respectively.A large percentageof the saw-whet(79%) and screech- owls (88%) found were lessthan 1 yr old. More than 87% of road-killed saw-whetowls and 71% of EasternScreech-Owls were found betweenNovember and January. Slightly lessthan one-half of all roadkills of thesetwo speciesoccurred within the southernmost15 km of the CapeMay peninsula.We concludethat southernNew Jersey,especially the southernCape May peninsula,hosts a large number of wintering and migrating saw-whet owls and residentscreech-owls, and that collisionswith automobiles kill a significantnumber of theseowls.

Mortalidad en caminosde la Penlnsulade Cape May de Aegoliusacadicus y Otusasio RESUMEN.--Enun estudiode 10 aftosen el sur de New Jersey, se encontr6un total de 250 rapaces muertaspor accidentescarreteros, que incluyeronseis especies de bfihosy seisespecies de halcones.Los ejemplaresfueron encontrados a lo largo de una carreterade 145 km, entre mediadosde octubrey los primerosdias de abril. E1 45% de losejemplares muertos correspondlan a Aegolius acadicus (N = 114) y el 36% a Otusasio (N = 91). Un gran porcentajede los ejemplaresde A. acadicus(79%) y O. asio(88%) colectadostenlan menos de un afio.E1 87% de A. acadicusy el 71%de O. asiocolectados fueron encontrados entrenoviembre y enero.La mayorlade las muertescarreteras de estasdos especies ocurrieron 15 km al surde la PeninsulaCape May. Seconcluye que el surde New Jersey,especialmente al sur de la Peninsula de Cape May, hospedaa un gran nfimerode migrantesinvernales de A. acadicusy del residenteO. asio, y que las colisionescon autom6viles matan a un nfimerosignificativo de estosbfihos. [Traducci6n de Ivan Lazo]

Raptors and other birds are being killed in large with the Garden StateParkway (Fig. 1). The studyroute numbersby automobiles(Hodson and Snow 1965, waschanged slightly in 1987 when the startingpoint moved from North Cape May to a location24 km northwardon Hernandez 1988). To better understandthe mag- the Parkway, althoughthe entire route was doneevery nitude of automobilemortality on Northern Saw- day. Cruisingspeed during the studywas between80 and whet Owls (Aegoliusacadicus), Eastern Screech-Owls 88 km/hr. (¸tus asio),and other raptors,we report the results When a dead raptor was seenon the road, its location of a 10-yr studydone in southernNew Jersey.In was notedas the nearestone-tenth mile roadmarker along with the date and species.Birds that were not damaged addition to quantifying raptors killed on the road, badly were collected,and sex was determinedby exam- we present information on the abundance,distri- ining gonads.Age was determinedby plumagecharacters, bution, seasonalincidence of road kills and the age the presenceof two or moreprimary or secondaryfeathers compositionof thoseroad kills. of differentages indicated birds greaterthan 1-yr of age as opposedto birds lessthan a year old whoseprimary and secondaryfeathers were all the sameage. METHODS RESULTS Every weekday from 1980-1990, a 145 km route was drivenby GL (Fig. 1) betweenthe North CapeMay Ferry A total of 250 road-killedraptors representing six Terminal and Atlantic City in southernNew Jersey.The owl and six hawk specieswere foundalong the Gar- drive was part of the route to (starting at about dawn) den State Parkway and other roadsduring the 10- and from (ending near dusk) work. The route includes year study period (Table 1). Owls predominated two countyroads and a state road from the ferry terminal in North Cape May to the beginningof the Garden State (88% of all raptors)with Northern Saw-whetOwls Parkway; the Garden State Parkway; and the Atlantic and Eastern Screech-Owlsbeing most numerous. City Expresswayfor about 5 km east of its intersection Saw-whet owls accounted for 52% of all owls and

210 DECEMBER 1993 ROAD-KILLED RAPTORS 211

.ew

Delaware Bay Atlantic Ocean

Forry..• Terminal pe May Figure 1. Map of CapeMay peninsula,New Jersey,showing the roadswhere road kills werecollected.

screechowls for 42%. The number of road kills per year averagedabout 25, although numbersvaried Table 1. Summaryof road mortalityof hawksand owls greatly from year to year. The smallestnumber of during the study period, 1980-1990, in southernNew saw-whetowls found in one year was one in 1984- Jersey.The numbersreflect raptors found on the regular 1985 and the largestwas 34 in 1988-1989. route and other roadsduring the study period. Of the 68 saw-whet owls for which age was determined,54 (79%) were birdsin their firstyear and NUMBER the remainder were older than 1 yr. The sex ratio SPECIES FOUND was almost even, with 20 (49%) of 41 owls for which gonadswere checked,being female. Among the 32 Sharp-shinnedHawk (Accipiterstriatus) 7 Cooper'sHawk (Accipitercooperii) 1 screechowls for which age was determined,only Red-shouldered Hawk (Buteo lineatus) 1 13% were older than 1 yr. Males outnumberedfe- Broad-wingedHawk (B. platypterus) 6 males almost two to one (11 males, 6 females), al- Red-tailed Hawk (B. jarnaicensis) 7 though the sample size was too small to analyze American Kestrel (Falcosparverius) 9 statistically. Common Barn Owl (Tyro alba) 1 More than 87% of the road-killed saw-whet owls Eastern Screech-Owl(Otus asio) 91a,b were foundfrom November-January,with Decem- Great Horned Owl (Bubovirginianus) 9 ber accountingfor 41% of all road kills (Fig. 2). Barred Owl (Strix varia) 3 Five percentof road kills were found in the months Long-earedOwl (Asiootus) of October, March, and April. For screech-owls, Northern Saw-whet Owl (Aegoliusacadicus) 114c November-January also accountedfor a majority Includes73 foundon regular route and 18 found on other roads (72%) of road kills. in Cape May County. The ratioof redto graymorph owls was 2.15. The distribution of saw-whet and screech-owls Includes109 foundon regular route and 5 found on other roads along the study route was not uniform. A much in Cape May County. 212 GEORGELOOS AND PAUL KERLINGER VOL. 27, NO. 4

Saw-whet Owl the distributionof screech-owlsappeared to be uniform.Although north of the EggHarbor River,very N ß 114 few were found.

DISCUSSION 40 N u Our data suggestthat a large numberof saw-whet b ß 3O owlsmigrate into and winter in the Cape May pen- r insula and other portionsof southernNew Jersey.

2O Our observations,together with recentlydiscovered 0 saw-whetowl roostsin other parts of SouthJersey (E. Manners,T. Bailey,and W. Daseypers. comm.) $ 10 and the large numbersbanded during autumn mi- gration at Cape May Point (Duffy and Kerlinger

OCT NOV DEC JAN FEB MAR APR 1992), suggestthat saw-whetowls may winter in greaternumbers in this area than in any other area in North America. Screech Owl The averageof 25 road-killed raptorsper year seemsto be a large number consideringthat this studywas done by one personover a small portion N ß 91 of the peninsula.Furthermore, we know of no other N 40 North Americanstudies that report suchlarge num- u bers of road kills. The fact that most saw-whet owls b ß 30 wererecovered after autumnmigration suggests that r thesebirds remain in the peninsulafor the winter.

20 The preponderanceof Eastern Screech-Owlsfound 0 during November-Januaryand the factthat a large proportionof immature males were in the sample, 8 10 suggeststhat this classmay be particularly vulner- able to road injuries, especiallywhile dispersing. o OCT NOV DEC JAN FEB MAR APR Road-killedowls are commonplacein the CapeMay Month of Road-kill Recovery peninsula.During the same10-yr period,more than Figure 2. Seasonal distribution of the occurrenceof 50 other road-killed raptors,mostly owls, were ac- Northern Saw-whet Owl and Eastern Screech-Owl road quired by the Cape May Bird Observatory.None kills in the Cape May peninsula,New Jersey,during the of thesewere included in the study.The actualnum- period 1980-1990. ber of saw-whetowls killed on SouthJersey road- ways is impossibleto access,but in areas such as GloucesterCounty, where communal-type roosts oc- greater percentageof road kills of both saw-whet cur,road kills are common(E. Mannerspers. comm.). and screech-owlswere foundnear the tip of the Cape More than 700 saw-whet owls were banded in May peninsulathan farther north on the Parkway. Cape May Point during the autumns of 1980 to The southernmost 10 km of the Garden State Park- 1990 (Duffy and Kerlinger 1992). Four of these way and the road betweenthe ferry terminal and birds, all bandedin November,were recoveredby the baseof the Parkway accountedfor nearly one- GL from 4-8 km up the peninsulafrom the banding half (53 of 111, 47.7%) of all saw-whet owls and sites. Of these birds banded in November, one was 41.2% of all screech-owls found dead. Smaller num- recoveredin April the next year, one in November bersof owlswere foundon the Parkwayin the region of the sameyear, and two in Decemberof the same of two stoplights(16-19 km from the end of the year. This may indicatethat an appreciablenumber Parkway), near the toll booth (32 km)--where cars of the owlsthat migrateinto CapeMay Pointremain slow down, and near the bridge over the Great Egg on the peninsulafor the winter. Harbor River (46 km) and its associatedtoll booth. The fact that such a large number of Northern North of mile-marker 6 (10 km) on the Parkway, Saw-whet Owls, Eastern Screech-Owls, and other DECEMBER 1993 ROAD-KILLED RAPTORS 213 raptorswere killed by automobilesdemonstrates the reviews.Finally, we thank the membersof the Cape May magnitudeof the threat. It is probablyfortuitous for Bird Observatoryfor financialsupport during the analysis and writing of this paper. the owls and many other birdsthat traffic in autumn and winter is much less than in warmer, tourist LITERATURE CITED months. With recent suburban developmenton the DUFFY, K. AND P. KERLINGER. 1992. Autumn owl mi- peninsula,habitat has become more limited and local gration at Cape May Point, New Jersey. WilsonBull traffic hasincreased. This couldpose an evengreater 104:312- 320. threat to somewintering raptors. HERNANDEZ,M. 1988. Road mortality of the Little Owl ACKNOWLEDGMENTS (Athenenoctua) in Spain.J. RaptorRes. 22:81-84. We thank C. Loos for tolerating the time GL spent HODSON, N.L. AND D.W. SNOW. 1965. The road deaths searchingfor road kills. K. Duffy and P. and C. Sutton enquiry, 1960-1961. Bird Study 12:168-172. providedGL with encouragementduring the study. K. Bildstein, K. McKeever, and Jo Olsen providedhelpful Received11 January 1993; accepted16 August 1993