J. Field Ornithol., 59(4):361-368 NEST SITE PREFERENCES OF RED-TAILED HAWKS IN THE HIGHLANDS OF SOUTHEASTERN NEW YORK AND NORTHERN NEW JERSEY ROBERT SPEISER 73 Beam Place Haledon,New Jersey07508 USA THOMAS BOSAKOWSKI • Departmentof BiologicalSciences RutgersUniversity Newark,New Jersey07110 USA Abstract.--Sixty-one Red-tailed Hawk (Buteojamaicensis) nests were locatedin an exten- sivelyforested region of southeasternNew York stateand northernNew Jersey.Nesting occurredalmost exclusively in oak (Quercusspp.) forests.All nestswere constructedin live deciduoustrees (82% oaks), typically high in a secondarycrotch within the forestcanopy. Nest siteswere closerthan 70 random sitesto forest openingsand roads, which servedas hunting areas. Nest siteswere not closerto wetlands or other water sourcesthan random sites,but this may result from the fact that water was plentiful in the study area. Nests were on steeperslopes and higher on the slope than random sites,but never directly on ridgetops.Thus, elevationtended to be higher and more varied for random sites.Slope aspectsof nest siteswere different than random sites,with the majority occurringin the southeastquadrat. Nest siteswere not significantlyfurther from human habitationthan random sites,but no nestingwas observedin high densitysuburban development. PREFERENCIAS DE LUGAR DE ANIDAMIENTO DE BUTEO JAMAICENSIS EN LAS ALTURAS DEL SURESTE DE NUEVA YORK Y DEL NORTE DE NUEVA JERSEY Resumen.--Un total de 61 nidosde Buteojamaicensisfueron localizadosen una zona boscosa extensaen la region surestede Nueva York y norte de Nueva Jersey. Los anidamientos ocurrienroncasi exclusivamenteen bosquesde cedro (Quercusspp.). Todos los nidos se construyeronen •rboles deciduosvivos (82% cedro),tlpicamente altos en una crucetase- cundariadentro del doseldel bosque.Los lugaresde anidamientosestaban m•s cercanosa clarosen el bosquey carreterasque servlancomo freas de caza que 70 lugaresescogidos al azar. Los lugaresde anidamientono estabanmJs cerca de humedalesu otras fuentesde agua que los lugaresescogidos al azar, pero estopuede ser el resultadode que el agua es abundanteen el fircade estudio.Los nidosse encontraban en las pendientesmrs empinadas comparadoa los lugares escogidosal azar, pero nunca en la cima de las colinas. Por lo tanto,la elevaci6ntiende a sermayor y de alcancemfs amplioque los lugaresescogidos al azar. Las pendientesde los lugaresde anidamientofueron diferentesa los lugaresescogidos al azar con la mayoria ocurriendoen el cuadrantedel sureste.Los lugaresde anidamiento no quedansignificativamente mrs lejosde viviendashumanas que los lugaresescogidos al azar, pero no se encontr6nidos en freas de alta densidadde desarrollosuburbano. The Red-tailed Hawk (Buteojaraaicensis) is a widespread,familiar raptor of North America and its nestingecology has been well studied (Austing1964, Bohm 1978, Craigheadand Craighead1956, Fitch et al. 1946, Gates1972, Gilmer et al. 1983, Hagar 1957,Johnson 1975, Luttich • Currentaddress: Department of Toxicologyand Pathology,Roche Research Center, Nutley, New Jersey071 •0 USA. 361 362] R. Speiserand T. Bosakowski J.Field Ornithol. Autumn 1988 et al. 1971, Mader 1978, Orians and Kuhlman 1956, Petersen 1979, Siedenstickerand Reynolds1971, Smith and Murphy 1973). However, analysisof nestinghabitat has seldombeen undertaken.Howell et al. (1978) measured habitat variables at four nest sites in Ohio, and Titus and Mosher (1981) examined13 nestsites in westernMaryland. Similar studieswere conductedin Iowa (Bednarz and Dinsmore 1982) and Puerto Rico (SantanaC. et al. 1986). In this paper, we report on 61 nestsites from an extensivelyforested region that straddlessoutheastern New York and northern New Jerseyand comparethem to random sites. STUDY AREA The studywas conductedin the Highlands,an area of rolling, granitic hills in southeasternNew York and northernNew Jersey (Fig. 1). This range is part of the Reading Prong, a southerlyextension of the New EnglandUplands. The regionis heavilyforested and sparselypopulated, especiallyin the north and central sections.The dominant directionof relief lies southwestto northeastand elevationsvary from 507 m to nearly sealevel. The studyarea lies in the Carolinean Life Zone (Dice 1943), but is ecotonalin characterhaving a climax forestof northernhardwoods (Robichaudand Buell 1973). Forestsare a mosaicof young and mature stands;old-growth is rare. Oaks (Quercusspp.) predominate in mostareas. A more detailed descriptionof this region is presentedin Speiserand Bosakowski(1987). METHODS From 1977 to 1980, 24 nests of the Red-tailed Hawk were found during breedingbird surveys(Speiser 1981). We located47 additional nestsfrom 1981 to 1987. Although we generallyfollowed the techniques of Craigheadand Craighead (1956), no effort was made to locateall nests.Most nestswere found by methodicallysearching woodlands on foot. Particularattention was givento areaswhere adultsfrequently were seenperched or soaring,or where vigorousprotesting calls were heard. Somenests also were found incidentalto surveysof other raptor species (Bosakowskiet al. 1987, Speiserand Bosakowski1987). Additionalnests were found by scanningforests from vistasand fire observationtowers. Although some nestswere seen from roads while driving through the studyarea, intensivecar surveys(Craighead and Craighead1956) were not specificallyemployed as a nestsearching technique. Nearly all nests were locatedin March and April, prior to leaf-out. Nine variables were measured from 61 nest sites and 70 random sites using standard7.5 min USGS quadranglemaps. Computer-generated random coordinates were used to select the random sites. A similar number of random sitesand nest siteswas taken from each quadranglemap to avoid bias. Random sites were rejectedif locatedin nonforestedareas. Distances from nest sites and random sites to the nearest road, nearest forestopening (non-forested area >1 ha), nearestwetland (>0.5 ha), nearestwater source(lake, pond, stream),and nearesthuman habitation Vol.59, No. 4 Red-tailedHawk Nest Sites [363 :" "-, .? NEWYORK ß '• . :,:•-,,.- / •: .,'•. •. ßß .. ß d.ß..- ..... ...-' ... -, ,. ... •. ....." / ß '•-.'..; •.....-' .,.' ,,, ß , / .?:• ',. ,-A " ;' ß ' ' '• '-•::• <• •'• ...- .,,, ß ' .... ?,-•;.-: -'...::...... :.......:.... , < ,,'•'.'-"",•, .- x.,,,-'""' ß..'" :::•.;-'t,..: :-'.::.....--'-.--..-:-:.'...-:..:..-:-.-:.:-'--.- 'It •: >. •.,.:...-•- x..,<,,-- •' .,"_....- .'/.:,•, ,<;..':. .-'.':-'::.'-':-:.':'....;•..:¾•..:.:...:::.::..-:.'.'::--:-.--'.-:-.-.-:.... ///o>. I Zco k,,• ' .,-?,;:• .-""......• ß ... ." .'" 'o•' -.':.'.':.'.-:-:.-:-:--::..':.::.:.'.-:-'..-:..':':.'.'::.-::::?;':-[::::::::::::::::::::::::::::::::::::•:•;.?;."::•'...:'.'.....71// UJ• z •x _.."'"•?' _• :./:•... ...' ,, .¾:..!..%.:.?::.•::.::.•.:.::?.?;::.::::.::/J,z •LI.I ,_) •_."ß,' -.' _.,.,• '" ....,o,' ,x-x' ......:.•..:.:.•.....:•:....:..:..:.:....:....:•:..:.:•:•:•..:.:`:.•:.:•.:.:.•..:...?///-... '--:.'':'.'.' :::.':-':.":.' .' '.'.'.':'-'.' .'.'-'::".'.-' '• _..'.' ..c,,'""- i .,• ?::::i•i:i::i::i:::::::::::::::::::::::: :::.:':::;::.•::i:':/:.'::!;://[ ,oø' X• • •: :i::717:?::?:?:-:.''::-:::':-:::-'.':-'--:':-':':':.'.':?:':.':?' ""- '"-,,,,,,":/ /' ":?.::.:.:..:-:::i!i;i:?(:?(:i•i;•::i!.!::i:?g ß .........-'-.. .: .... ::::i:?-::i::•i:i::i?i:i::?::•:•??i:i::i•:i=======================================================================::5'::"..:..::! FIGURE1. Map of all Red-tailedHawk nestsfound in the Highlandsduring the study from 1977 to 1987. Note that the southerntip of the Highlands was lessextensively searchedand that nestsfound outside the Highlandswere not usedin the analysisand are not shown. were measuredfrom maps. Degreesof slopewas figured over a 150 m baselinethrough the nesttree or randomsite. Slope aspect was determined only for siteswith at leasttwo degreesslope. Slope location was ranked into one of four categoriesonly when slopeswere longer than 180 m: 0- no slope, 1--lower slope,2--middle slope,3--upper slope.Elevations were taken from the quadranglemaps. Nest site data and random sites were comparedstatistically on the RS/1 softwaresystem (Bolt, Baranek, and Newman, Cambridge,Massachusetts). Slope aspects were compared usinga Chi-squaretest. All other data were comparedfor homogeneity of variances(F-test). If varianceswere equal, a pooledvariance t-test was applied, otherwise,an unpooledvariance t-test was used. RESULTS AND DISCUSSION From 1977 to 1987 we found 61 nests;only 10 of which may have beenthe resultoTthe samehawk(s) in subsequentyears. No morethan two nestswere found in thesetraditional breedingareas. All nestswere in overstorycanopy trees and nest heightsof a sampleof 24 nestswere estimatedto range between7 and 24 m aboveground (Speiser1981). 364] R. Speiserand T. Bosakowski J.Field Ornithol. Autumn 1988 Most nestswere situated high-up within the forest canopy(upper one- third of trees)which agreeswith the findingsof Titus and Mosher (1981). To achievethis height, nearly all nestswere constructedin secondary crotches(53) whereasonly six nestswere built in primary crotches;two were on tree limbsaway from the trunk. In contrast,the majority (58%) of 32 Northern Goshawk(Accipiter gentilis) nests from the samestudy area were built in primary crotcheswhich resultedin nestplacement at the bottom of the canopy. Red-tailed Hawks built nestsin 10 different speciesof live treeswith the majorityin oaks(82%). We found32 nestsin Quercusrubra (52.5%), 10 in Q. prinus(16.4%), four in Q. velutina(6.6%), four in Q. alba(6.6%), three in Liriodendrontulipifera