3J0 



Interior West — Our /./iv/ii; Rcsoiinex 



For further inrurniation: 



Charles van Riper III 



National Biological Service 



Colorado Plateau Research Station 



PO Box 5(1 1 4 



Northern Arizona University 



Flagstaff, AZ 8601 1 



frequent this region if annual spawning trout are 

 present. 



Bald eagle counts along the Colorado River 

 coiTidor during the winters of 1990-94 mirrored 

 the bald eagle numbers at Nankoweap Creek. 

 Their numbers peaked during late February and 

 early March and varied greatly among years. 

 Higher concentrations of bald eagles noted in 

 other areas of the southern Colorado Plateau, 

 when lower numbers were recorded along the 

 Colorado River, suggest widespread eagle 

 movements over the region. Bald eagles appear 

 to concentrate in areas that have the most abun- 

 dant and available food resources, and these 

 locations change annually. 



References 



Brown. B.T. S.W. Carothers. and R.R, Johnson. 1987. Grand 

 Canyon birds; historical notes, natural history, and ecolo- 

 gy. University of Arizona Press, Tucson. 302 pp. 



Brown, B.T, R. Mesta, L.E, Stevens, and J. Weisheit. 1989, 

 Changes in winter distribution of bald eagles along the 

 Colorado River in Grand Canyon. Arizona. Journal of 

 Raptor Res. :.V11()-I13. 



Jenkins, J.M. 1992. Ecology and behavior of a resident popu- 

 lation of bald eagles, Ph.D. dissertation. University of 

 California, Davis. 18.3 pp. 



Leibfried, W.C. and W.L. Montgomery. 1993. Regulated 

 flows, trout spawning, and abundance of bald eagles on the 

 Colorado River, Grand Canyon National Park. Pages 37-48 

 in PG. Rowlands, C. van Riper III, and M.K. Sogge, eds. 

 Proceedings of the First Biennial Conference on Research 

 in Colorado Plateau National Parks Transactions and 

 Proceedings Series NPS/NRNAU/NRTP-q3/10, U.S. 

 Department of the Interior. Washington. DC. 



McClelland. B.R. 1973. Autumn concentrations of bald 

 eagles in Glacier National Park. Condor 75:121-123. 



McCfelland, B.R., L.S. Young, D.S. Shea. PT McClelland, 

 H.L. Allen, and E.B. Spettigue. 1982. The bald eagle con- 

 centration in Glacier National Park, Montana: origin, 

 growth, and variation in numbers. Living Bird 21:133-155. 



Southern. WE. 1963. Winter populations, behavior, and sea- 

 sonal dispersal of bald eagles in northwestern Illinois. 

 Wilson Bull. 75:42-55- 



Spencer. DA., ed. 1976. Wintering of the migrant bald eagle 

 in the lower 48 states. National Agncultural Chemicals 

 Association, Washington, DC. 170 pp. 



Stalmaster, M.V. 1987. The bald eagle. Universe Books, New 

 York. 227 pp. 



Steenhof, K. 1978. Management of wintenng bald eagles. 

 U.S. Fish and Wildlife Service FWS/OBS-78/79. 59 pp. 



Mexican 

 Spotted Owls 

 in Canyonlands 

 of the Colorado 

 Plateau 



by 



David W. Willey 



National Biological Sen'ice 



Fig. 1. Distribution of Mexican 

 spotted owls in the southwestern 

 United States. 



In response to perceived threats to critical 

 nesting habitat and lack of adequate protec- 

 tive regulations, the Mexican spotted owl {Stri.x 

 (iccidcntiilis lucida) was officially listed as a 

 threatened species under the Endangered 

 Species Act in 1993 (Federal Register 1993). 

 Limited information is available on the distrib- 

 ution of Mexican spotted owls inhabiting arid 

 canyonlands throughout the southwestern 

 United States (Ganey and Balda 1989). Though 

 widely distributed, the Mexican spotted owl 

 apparently occurs in isolated populations 

 restricted to habitat islands (Fig. 1 ). Here 1 

 report findings from spotted owl surveys con- 

 ducted throughout the northwest portion of the 

 Colorado Plateau in Utah, 



The Colorado Plateau Physiographic 

 Province consists of extensive sandstone 

 canyons interspersed by eroded valleys, 

 upwarped plateaus, and isolated mountain ranges 

 (Thonibury 1965), Prolonged erosional dissec- 

 tion produced a maze of complex watersheds 

 within the Colorado Plateau region (Youngblood 

 and Mauk 1985). Agency lands encompassed by 

 the Colorado Plateau include extensive U.S. 

 Department of Agriculture national forests and 

 U.S. Department of the Interior Bureau of Land 

 Management (BLM) areas, seven National Park 

 Service national parks, two national recreation 

 areas, several national monuments, and state- 

 administered lands, all in the Four Comers 

 region (Arizona, New Mexico, Colorado, and 

 Utah) of the southwestern United States. 



These lands may function as biological refu- 

 gia, providing dispersal corridors and habitat 

 islands joining occupied and potentially suit- 



Mevican spotted owls (5;//.v occidentalis lucida) roosted in 

 canyonlands in southern Utah. 



able spotted owl habitat. In the Four Comers 

 region, spotted owls are associated with rocky 

 canyon terrain (i.e., canyonlands) and could be 

 negatively affected by such activities as timber 

 harvesting, mining, and recreation (Ganey 

 1988), Long-term study of spotted owl distribu- 

 tion and habitat use is necessary to provide 

 information on the potential effects of human 

 activities and to develop ecologically based 

 conservation plans (Gutieirez 1989), 



Surveys 



Information on Mexican spotted owl distrib- 

 ution within canyonlands of the Colorado 

 Plateau was gathered by using published 

 species accounts and conducting field surveys. 



During the field surveys, individuals and 



