j. RaptorRes. 30(4):183-188 ¸ 1996 The Raptor ResearchFoundation, Inc. RESULTS OF A RAPTOR SURVEY IN SOUTHWESTERN NEW MEXICO W•t)E L. EAKLE 1 Dames& Moore,Environmental Services Group, 7500 NorthDreamy Draw Drive, Suite145, Phoenix,AZ 85020 U.S.A. E. LINWOOD SMITH Dames& Moore,Cambric Corporate Centeg, 1790 EastRiver Road, Suite E-300, Tucson,AZ 85718 U.S.A. STEPHEN W. HOFFMAN HawkWatchInternational, PO. Box 660, Salt Lake City, UT 84110 U.S.A. DALE W. STAHLECKER EagleEcological Services, 30 FondaRoad, Santa Fe, NM 87505 U.S.A. RUSSELL B. DUNCAN SouthwesternField Biologists,8230 East Broadway,Suite W-8, Tucson,AZ 85710 U.S.A. A•STRACT.--Eightroadside surveys for raptorswere conductedin southwesternNew Mexico from May 1988-January1989 to examineseasonal abundance and habitatuse. Of the 17 speciesobserved, Amer- ican kestrels(Falco sparverius), red-tailed hawks (Buteojamaicensis), turkey vultures (Cathartes aura), and northern harriers (Circuscyaneus) were most common and occurred along the entire surveyroute in all habitats.Bald eagles(Haliaeetus leucocephalus) were recordedless frequently only in Januaryin riparian habitats and pinyon-juniper and Ponderosa pine ecotones,and Swainson'shawks (B. swainsoni)were infrequently observedin mesquite grasslandsand Chihuahuan desertscrubin May and July. Golden eagles (Aquila chrysaetos),ferruginous hawks (B. regalis),prairie falcons (E mexicanus),and Cooper's hawks(Accipiter cooperii) were alsorecorded infrequently but occurredwidespread along the surveyroute. KEYWORDS: southwesternNew Mexico,distribution, relative abundance, habitat use, raptor roadside survey. Resultadosde rutas de estudio de rapacesen el suroestede New Mexico RESUMEN.--Ochoestudios de ruta para rapacesfueron ejecutadosen el suroestede New Mexico desde mayo de 1988 a enero de 1989, con el fin de examinar abundanciaestacional y uso de hfibitat. De las 17 especiesobservadas, Falco sparverius, Buteo jamaicensis, Cathartes aura y Circuscyaneus fueron las mils comunescon presenciaa lo largo de todaslas rutas y hfibitats.Haliaeetus leucocephalus, fue registrada con menor frecuenciasolamente en diciembreyen ciertoshfibitat y Buteoswainsoni fue poco observado en praderasen mayo y julio. Aquila chrysaetos,Buteo regalis, Falco mexicanus y Accipitercooperii fueron registradosinfrecuentemente pero se presentabanmuy dispersosa lo largo de la ruta de estudio. [Traducci6n de Ivan Lazo] E1 Paso Electric Company initiated construction mental review process,we conducted eight raptor of the Arizona Interconnection Project (/kiP), a surveysalong roads parallel to or near the trans- 345 kv transmissionline between Deming and Red mission line right-of-way (ROW). Our objectives Hill, New Mexico in 1988. As part of the environ- were to: (1) compile a specieslist, (2) determine the distribution of raptors along the transmission • Present address:U.S. Army Corps of Engineers, San line ROW, (3) document habitat use by raptors, FranciscoDistrict, Regulatory Branch, 333 Market Street, and (4) estimate the relative abundance of raptor San Francisco, CA 94105-2197. speciesobserved. 183 184 E•act•}•ET AL. VOL. 30, No. 4 STUDY AREA AND METHODS RESULTS AND DISCUSSION The AIP crossesseven major biotic communitiesor bi- Of the 43 raptor speciesfound in New Mexico, omesbetween Red Hill and Deming (Fig. 1). Nearly80% 29 are falconiformsand 14 are strigiforms(Glinski of the area traversedis grasslandor desertscrub(Table 1). We followed the classificationsystem described by et al. 1988). We observed 17 of the falconiform Brown (1982) to determine habitat typesalong the sur- speciesduring our surveys.Interestingly, Kimsey veyroute, and Brownand Lowe (1983) to further identify and Conley (1988) observed only 11 speciesin habitat typestraversed during our surveys. their 4-yr studyof raptor habitat use near Las Cru- The survey route we selected provided accessalong ces, slightlysouthwest of our studyarea. many portions of the AIP ROW and crossedhabitats rep- resentativeof those crossedby the AIP where accesswas Plains grasslandaccounted for the largest per- limited. The route followed ixnprovedand unimproved centage of habitat crossedby the AIP, approxi- surface roads, as well as the AIP corridor whenever pos- mately 30% (Table 1). This cold temperateplant sible.The length of the route wasapproximately 515 kin, community is characterized by essentiallyopen whereasthe length of the AIP corridor wasapproximate- ly 419 km. landscapesof either sod-formingshort grassesor Surveysalong the route were scheduledin May 1988 tall grassspecies. American kestrels(Falco sparver- to coincide with nesting, in July 1988 to coincide with ius), red-tailed hawks (Buteojamaicensis), and fledging, in October 1988 to coincidewith fall migration, northern harriers (Circus cyaneus)were the most and in January 1989 to coincidewith wintering. Each sea- frequentlyobserved species, followed by prairie fal- sonalsurvey was conducted by two teamsof two observers each. One team began at Red Hill in the north and the cons (E mexicanus), ferruginous hawks( B. regahs), other near Deming in the south.Each team surveyedthe and turkey vultures (Cathartesaura) (Table 2). entire route by vehicleover a 5-6 d period, simultaneous- Golden eagles (Aquila chrysaetos)and merlins (E ly and independently of the other team. For example, columbarius)were infrequentlyobserved. Nearly all Surveys1 and 2 were conducted concurrently from 2-7 of the sightingsof northern harriers in grasslands May 1988, Surveys3 and 4 from 11-15July 1988, Surveys 5 and 6 from 26-30 October 1988, and Surveys7 and 8 were in October andJanuary, indicating that plains from 24-28 January 1989. Surveyswere conducteddur- grasslandhabitat may be important to migratory ing variable weather conditions,but were alwaystermi- and wintering populationsof this species(Table 3). nated during periods of precipitation (rain or snow). Semidesertgrassland accounted for the second Each surveyteam drove the route at 17-40 kin/hr. largest percentage of habitat crossedby the AIP When raptors were observed,vehicles were stoppedmo- ROW (26%, Table 1). This warm temperategrass- mentarily to identify the birds. Periodic stopswere also made to scanfor distant raptors.All raptor observations land community, sometimes called "mesquite were recorded on data forms and mapped. Data record- grassland,"is a highly diverseassemblage of peren- ed for each observation included date, time, location, nial bunch grasses,woody perennial shrubs, leaf species,age, sex,number, habitat, activity,and perching succulents,and cacti. Large numbers of several substrate,if applicable.Weather conditions and vehicle mileage were also recorded. Surveyswere initiated be- specieswere observedin these grasslandsduring tween 0600-0900 H Mountain Standard Time (MST) and all seasons (Tables 2, 3). American kestrels and were terminated between 1600-1900 H MST. red-tailed hawks were recorded during every sur- The surveyroute was treated as a line transectto esti- vey while turkey vultures and Swainson'shawks (B. mate the relative abundance of each speciesof raptor. swainsoni)were observedonly in May andJuly and Line transects are considered to be one of the best tech- niques for estimatingraptor relative abundance(Fuller golden eagles only in July, October, and January. and Mosher 1987). We used the index of relative abun- Northern harriers and prairie falconswere com- dance developedby Woffinden and Murphy (1977) for monly seen, especiallyin October and January. diurnal raptors in the eastern Great Basin of Utah that Other fall and winter observations included fer- is basedon km traveledduring roadsidesurveys. The in- dex is calculated as follows: ruginous hawks,rough-legged hawks (B. lagopus), and merlins (Table 3). Relative Abundance Chihuahuan desertscrubaccounted for approx- imately23% of the habitatcrossed by the AIP ROW Number of speciesobserved = X 1000 (Table 1). This warm temperate vegetation type is Number of km traveled frequently characterizedby creosotebush(Larrea tridentata), tarbush (Flourensiacernua), mesquite To examine seasonaldifferences, we pooled the data from Surveys1-4 to calculate a Spring/Summer relative (Prosopisspp.), and other shrubs.Large numbersof abundance index and the data from Surveys5-8 to cal- severalspecies were recordedin thesehabitats dur- culate a Fall/Winter index. ing all seasons(Table 2). Turkey vultures and DECEMBER 1996 RAPTORS IN SOUTHWESTERN NEW MEXICO 185 / ClBOLA '•'•-• / • I--•LNATIONAL / J'• "i FOREST I / i i I I / I / / / • / / / ClBOLA / NATIONAL FOREST I / / ILLI...... / / NATIONAL "' / FOREST / / / o / z / / / / / I / I / I / AI.•UQE•RQUœ i, / NEW IdœXl½O GILA I...' •,t I. NATIONAL I ,,FOREST TRUTH OR JCONSr'QUœNCœS • ' LEGEND: I CRUCES/ / SURVEY ROUTE .--- ..... TRANSMISSION LINE ............. PASO Fzgure1. Raptor surveyroute along the AlP corridor in southwesternNew Mexico, 1988-89. Swainson'shawks were observedin May and July, Great Basinconifer woodland accountedfor ap- red-tailed hawksand American kestrelsfrom May proximately12% of the habitat crossedby the AIP to January, golden eaglesand prairie falconsfrom ROW (Table 1). This cold temperate, dry, mid-ele- July to January, and northern harriers and ferru- vational biome, often referred to as pinyon-juniper ginous hawksin October and January (Table 3). woodland, is dominated byjunipers (primarilyJu- 186 E^i•}• ET AL. VOL. 30, NO. 4 Table 1. Habitats along the AIP transmissionline right- northern portion of the AIP ROW (Fig. 1, Table of-way.Habitat typesfollow Brown (1982). 2).