Winter Golden Eagle Populations in the Southwest

Abstract

Golden eagle (Aquila chrysaetos) populations wintering in portions of Texas and New Mexico were determined by regular aerial censuses from 1964 through 1968. Additional census flights were made in other areas of the Southwest on special occasions. Analyses of the census data do not clearly indicate marked year-to-year trends for eagles wintering in Texas; the populations here seemed relatively small and apparently stable. Within the limits of observability, densities calculated from the aerial counts indicated that there were seldom more than two eagles per 100 square miles in Texas, but in New Mexico, the midwinter eagle densities were several times greater. Eagle densities varied by month in New Mexico but no more than 18 percent of the 28, 50-mile aerial segments had densities of 16 or more eagles per 100 square miles in 1966. Overall, almost 75 percent of the transect segments had low density ratings. If we assume that eagle densities reflect a potential for livestock depredations, our data indicate that such depredations would be greater in New Mexico than in Texas. Nonetheless, measurements of eagle concentrations along aerial transects suggest that high density populations are rare and that any depredation problems that may occur in either state are local. GOLDEN EAGLE POPULATIONS * Boeker and Bolen 477 DIEM, K. L., AND K. H. Lu. 1960. Factors influencing waterfowl censuses in the parklands, Alberta, Canada. J. Wildl. Mgrnt. 24 ( 2 ): 11>133. KACZYNSKI, C. F. 1962. Comparison of aerial and ground counts of breeding waterfowl. M. S. Thesis. Michigan State Univ. 44pp. MARTINSON, R. K., AND C. F. KACZYNSKI. 1967. Factors influencing waterfowl counts on aerial surveys, 1961-66. U. S. Fish and Wildl. Serv. Spec. Sci. Rept.: Wildl. No. lOS. 78pp. MENDENHALL, W. 1968. Introduction to linear models and the design and analysis of experiments. Wadswori Publishing Company, Belmont, California. 465pp. Received for publication August 31, 1971. Eastern New Mexico and the Trans-Pecos and Edwards Plateau regions of western Texas have long been lmown as winter areas for golden eagles. A good estimate is not available of the size of these populations prior to the ban imposed in 1962 on hunting eagles from airplanes. A preliminary survey was conducted in 1963 by a team from the Bureau of Sport Fisheries and Wildlife. The results of this survey indicated that the 1 Permanently assigned to field headquarters, Forest Hydrology Laboratory, Arizona State University, Tempe. only feasible method for obtaining winter population estimates was by aerial sampling, since the wide, and often inaccessible, area made ground-census methods impractical (Baer et al. 1963). On this basis, a continuing program of aerial censusing was begun by the Bureau in 1964. This paper is based on information accumulated in the survey of golden eagle populations wintering in New A4exico and western Texas from 1964 through the spring of 1968. The contributions of C. Q. Heumier and J. M. Matlock, U. S. Fish and Wildlife SerLITERATURE CITED ADDY, C. E. 1970. 1970 winter survey, Atlantic Flyway. Migratory Bird Populations Sta. 6pp. Mimeo. ATKINSON-WILLES, G. l9S5 ( 1953-1954 ). Wildfowl counts in the British Isles. Wildfowl Trust 7:2948. 1959 ( 1957-58 ) . National wildfowl counts. Wildfowl Trust 10: 21-23. ATLANTIC WATERFOWL COUNCIL. 1964. The Atlantic Flyway Waterfowl Management Guide. 99pp. CRISSEY, W. F. 1957. Forecasting waterfowl harvest by flyways. Trans. N. Am. Wildl. Conf. 22:256-267. This content downloaded from 157.55.39.183 on Sun, 11 Jun 2017 18:35:01 UTC All use subject to http://about.jstor.org/terms tO9° 1 08' 107° 10*' 105° . . . . . . 478 Journal of Wildlife Management, Vol. 36, No. 2, April 1972 1099 108° 107° 106 tO5° 104 10337 , 1 37