Results of a Raptor Survey in Southwestern New Mexico

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 thosecrossed by 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 wasapproximately 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 raptorswere 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 techniques 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 index 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

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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). The AIP crossedseveral large drainages sup- LENGTH porting riparian deciduousforest and woodland I-L•IT^T Tye• (km) % AIP communities, particularly Animas and Palomas Plains grassland 125.6 30.0 creeksnear Truth or Consequences(Fig. 1). Sev- Semidesertgrassland 109.5 26.2 eral specieswere observedor heard in thesedrain- Chihuahuan desertscrub 96.6 23.1 ages,including Cooper'shawks (A. cooperii),sharp- Great Basin conifer woodland 49.9 11.9 shinned hawks (A. striatus), red-tailed hawks, and Pinyon-juniper/ponderosapine eco- American kestrels (Table 2). Riparian habitats tone 17.7 4.2 along the northern portion of the surveyroute in- Rocky Mountain montane conifer cluded the Tularosa River and Apache Creek, forest (ponderosapine) 8.1 1.9 where American kestrels, red-tailed hawks, ferru- Rocky Mountain montane conifer forest (mixed) 8.1 1.9 ginoushawks, and bald eagleswere observed.Bald Riparian deciduouswoodland 1.6 0.4 eagleswere also observed along the shoreline of Rocky Mountain montane grassland 1.6 0.4 Caballo Reservoirin January. Total 418.7 100.0 In addition to native habitatssurveyed along and near the AIP ROW, agricultural and urban areas were also traversedalong the surveyroute. Red- tailed hawks and American kestrels were the most niperusmonosperma) and pinyon pines (Pinusedu- frequently observed speciesin these habitats,but lis). Red-tailed hawks and American kestrels were turkey vultures, Swainson'shawks, northern harri- the mostfrequently observed species (78% of total ers, ferruginoushawks, merlins, and rough-legged observations),but turkey vultures were also fre- hawks were also seen (Table 2). quently observed(Table 2). At the ecotonewhere The overwhelmingnumber of American kestrels this communitymet plainsgrasslands, raptors were and red-tailed hawksobserved during all surveys particularly abundant. In October and January, and all seasonsindicated they were the most abun- golden eagles,ferruginous hawks, and rough-leg- dant raptorsin the region. Their combinedobser- ged hawkswere commonlyobserved at this eco- vations accounted for over 60% of individuals ob- tone. Pinyon-juniper woodlands also came into served (Table 3). Kimseyand Conley (1988) also contact with semidesertgrasslands along the AIP found American kestrels and red-tailed hawks to be ROW. At this ecotone, golden eagles were ob- the most abundant speciesin their study area in served in July, while bald eagles (Haliaeetusleuco- southcentral New Mexico. We also found Swain- cephalus)were observed in pinyon-juniper and son'shawks, northern harriers, golden eagles,fer- Ponderosapine (P. ponderosa)ecotones in January ruginous hawks, and Cooper's hawks in approxi- (Tables 2, 3). mately the samerelative abundances.The mostno- Rocky Mountain montane conifer forest ac- table difference between the two surveyswas that counted for approximately2% df the habitat no turkeyvultures were recordedduring their 4-yr crossedby the AIP ROW (Table 1). This cold tem- studyin southcentralNew Mexico. This difference perate community is generally found above 2,250 could partially be explained because,unlike our m and is dominatedby ponderosapine with lesser survey, the previous survey excluded the months areasof mixed conifer forestsof Douglas-fir(Pseu- of June andJuly. dotsugamenziesiz), white fir (Abiesconcolor), white We also observed more red-tailed hawks in the pine ( P.flexilis) , or aspen( Pt•pulustremuloides). Red- fall and winter (70%), while more American kes- tailed hawks and American kestrels were the most trels were observed in the spring and summer frequently observedraptors in theseforest habitats (76%). This suggeststhat large numbers of red- (Table 2). Several unidentified accipiters,includ- tailed hawks overwinter in the area, augmenting ing an adult northern goshawk (A. gentilis),were the residentpopulation as reported by Hubbard et observedin a potential nesting area. In January, al. (1988), and that most of the breeding kestrels severalbald eagleswere observedin areasof forest- migrated further south for the winter. Other spe- plains grassland ecotones. These parklands, or cieswhich overwinteredin the studyarea, asshown montane grasslands,are scatteredthroughout the by increasedobservations in October andJanuary, DECEMBER 1996 RAPTORS IN SOUTHWESTERN NEW MEXICO 187

Table 2. Numbers of raptors observedin habitat typesincluded in the AIP surveys,1988-89.

HABITAT TYPE a

SPECIES ppa pj PG SDG CD R A/U Turkey vulture ( Cathartes aura) 6 34 12 50 74 20 7 Golden eagle (Aquila chrysaetos) 3 14 9 34 30 2 Bald eagle ( Haliaeetusleucocephalus) 7 2 16 White-tailed kite ( Elanus caeruleus) 1 Northern harrier ( Circuscyaneus) 1 5 41 63 47 3 4 Sharp-shinnedhawk (A ccipiterstriatus) 2 1 2 Cooper'shawk (A. cooperii) 2 2 5 7 12 Northern goshawk ( A. gentilis) 1 Red-tailed hawk (Buteojamaicensis) 66 124 70 97 160 28 14 Swainson's hawk (B. swainsonG) 1 55 13 1 3 Rough-leggedhawk ( B. lagopus) 1 3 5 1 1 Ferruginous hawk (B. regalis) 3 7 19 6 4 6 4 Harris' hawk ( Parabuteo unicinctus) 4 Zone-tailed hawk ( B. albonotatus) 1 1 American kestrel (Falcosparverius) 98 128 187 66 46 35 21 Merlin (F. columbarius) 1 5 2 1 Prairie falcon (F. mexicanus) 1 1 18 12 8 a Habitat types:PP = Ponderosapine, PJ = Pinyon-juniper,PG = Plainsgrassland, SDG = Semidesertgrassland, CD = Chihuahuan desertscrub,R = Riparian woodland,A/U -- Agricultural/Urban.

included golden eagles,bald eagles,northern har- tures, ferruginous hawksand American kestrelsap- riers, rough-leggedhawks, ferruginous hawks,mer- pear to be more variable in their habitat use. lins, and prairie falcons. Turkey vultures and Hubbard et al. (1988) found red-tailed hawks Swainson'shawks appeared to be the only species and American kestrels to be more abundant in which summered in the study area and wintered southwestern New Mexico than elsewhere in the elsewhere(Table 3; Kimseyand Conley 1988). state. They reporfed an average of 2.5 red-tailed Like Kimsey and Conley (1988), we found Chi- hawks/100 km and 4.1 American kestrels/100 km huahuan desertscrubwith power lines to be an im- traveled during vehicular surveysfrom 1974-85. portant habitat type for golden eagles,Swainson's We found 13.6 red-tailed hawks/100 km and 14.1 hawks, red-tailed hawks and northern harriers, American kestrels/100 km traveled during our sur- whereas riparian habitats appear to be important veys.We suspectthese differenceswere largely due for bald eagles and Cooper's hawks.Turkey vul- to differencesin studydesign, including slowerve- 188 E•LF• ET AL. VOL. 30, No. 4

Table 3. Numbers and relative abundance (RA) of rap- tance.J. Carrion assistedwith word processing,and PJ. tors observed during the AIP surveysin southwestern Scheetzprepared the figure of the studyarea. J.L. Ganey, New Mexico, 1988-89. B.A. Millsap, B.A. Kimsey,J.P. Hubbard, J.M. Ramakka, and one anonymousreferee providedhelpful comments on earlier drafts of the manuscript. SPRING/SUMMER FALL/WINTER LITERATURE CITED SPECIES NO. RA NO. RA BROWN, D.E. [ED]. 1982. Biotic communities of the American kestrel 440 213.5 141 68.4 American Southwest--United States and Mexico. Des- Red-tailed hawk 165 80.1 394 191.2 ert Plants 4 (1-4). Turkey vulture 201 97.5 2 1.0 --AND C.H. LOWS. 1983. Biotic communities of the Northern harrier 7 3.4 157 76.2 Southwest.General Tech. Rep. RM-78. USDA Forest Golden eagle 20 9.7 72 34.9 Service,Rocky Mountain Forest and Range Experi- Swainson's hawk 73 35.4 0 0.0 ment Station, Arizona State Univ., Tempe, AZ U.S.A. Ferruginoushawk 2 1.0 47 22.8 FULLER,M.R. ANDJ.A. MOSHER.1987. Raptor survey Prairie falcon 8 3.9 32 15.5 techniques. Pages 37-65 in B.A. Giron Pendleton, Cooper'shawk 7 3.4 21 10.2 B.A. Millsap, ICW. Cline and D.M. Bird [EDS.],Raptor Bald eagle 0 0.0 25 12.1 management techniques manual. Natl. Wildl. Fed., Rough-leggedhawk 0 0.0 11 5.3 Washington,DC U.S.A. Merlin 0 0.0 9 4.4 GLINSIII, R.L., B.A. GIRON PENDLETON, M.B. MOSS, M.N. Sharp-shinnedhawk 1 0.5 4 1.9 LEFP,ANC, JR., B.A. MILLSAPAND S.W. HOFFMAN[EDs.] Harris' hawk I 0.5 3 1.4 1988. Proceedingsof the southwestraptor manage- Zone-tailed hawk 2 1.0 0 0.0 ment symposiumand workshop. Natl. Wildl. Fed., White-tailed kite 0 0.0 I 0.5 Washington,DC U.S.A. Northern goshawk 0 0.0 1 0.5 HUBBAm3,J.P.,J.W.SHIPMAN AND S.O. WILLIAMS,III. 1988. An analysisof vehicular countsof roadsideraptors in New Mexico, 1974-1985. Pages204-209 in R.L. Glin- ski, B.A. Giron Pendleton, M.B. Moss, M.N. LeFranc, hicle speeds,increased observer numbers, and the Jr., B.A. Millsap and S.W. Hoffman lEDS.], Proceed- overall focusof surveys.Hubbard et al. (1988) also ings of the southwestraptor management symposium found turkey vultures to be most abundant in and workshop. Natl. Wildl. Fed., Washington,DC southeasternNew Mexico, followed by the south- U.S.A. western portion of the state, which included our K•MSEY,B. AND M.R. CONLEY.1988. Habitat use by rap- survey area. They reported observing3.4 turkey tors in southcentralNew Mexico. Pages197-203 •n vultures/100 km traveled in southwestern New R.L. Glinski, B.A. Giron Pendleton, M.B. Moss, M N. Mexico, while we observed4.9 turkeyvultures/100 LeFranc,Jr., B.A. Millsap and S.W. Hoffman lEDS.], km. Proceedingsof the southwestraptor management symposiumand workshop.Natl. Wildl. Fed., Washing- ACKNOWLEDGMENTS ton, DC U.S.A• We thank E1 PasoElectric Companyfor funding the WOFFINDEN,N.D. ANDJ.R.MUP, PH¾. 1977. A roadsiderap- study.TJ. Hayden at The University of New Mexico, Al- tor census in the eastern Great Basin--1973-1974. buquerque, B.A. Kimsey,U.S. Bureau of Land Manage- RaptarRes. 11:62-66. ment, Las Cruces District, and the U.S. Forest Service, Gila National Forest, provided valuable technical assis- Received13 April 1996; accepted14July 1996