Age of Sexual Maturity of Sandhill Cranes from Mid-Continental North America

Abstract

Juvenile (n = 393) sandhill cranes (Grus canadensis) from mid-continental North America were marked with neckbands from 1975 to 1980; we obtained 110 observations of marked cranes from 1980 to 1986. We classified each observed crane as alone, paired, or parent. Cranes paired as early as age 3, but more commonly at 5-6; they raised young to 9 months as early as age 5, but 76% of recruitment was from cranes ->8 years old. Our data emphasized the value of controlling harvest age structure and the need for agespecific survival rates to better understand effects of harvest. J. WILDL. MANAGE. 53(1):43-46 Age structure and age-related productivity are important variables affecting recruitment in populations of long-lived species of migratory birds (Raveling 1981). Knowledge of age-specific survival and productivity is fundamental to understanding population dynamics of longlived species, and can lead to better harvest management strategies (Raveling and Lumsden 1977). The need to understand population dynamics becomes critical when hunted populations exhibit low recruitment rates (Miller et al. 1972, Johnson 1979). Sandhill cranes from mid-continental North America (MCNA) are long-lived, exhibit low recruitment rates, and are hunted in 8 Central Flyway states, Mexico, Canada, and Alaska (Tacha and Vohs 1984). These characteristics, and concern about potential overharvest (Miller et al. 1972, Johnsgard 1983), suggest the need for understanding age-related survival and recruitment that could lead to improved harvest management. We document relationships between age, pair formation, and recruitment for sandhill cranes from MCNA. We thank C. M. Boise for access to her records of crane banding at Clarence Rhode National Wildlife Refuge, G. C. Iverson and D. C. Martin for field assistance, and W. D. Klimstra, F. Schitoskey, and A. W. Tipton for administrative support. T. J. Dwyer, D. H. Johnson, W. D. Klimstra, 0. E. Maughan, H. W. Miller, and M. C. Tacha reviewed the manuscript. J. C. Lewis, H. W. Miller, and O. E. Maughan were instrumental in maintaining funding for this project. The Oklahoma Cooperative Fish and Wildlife Research Unit has the Oklahoma Department of Wildlife Conservation, Oklahoma State University, U.S. Fish and Wildlife Service, and Wildlife Management Institute cooperating. Funding was provided by U.S. Fish and Wildlife Service contracts 14-16-008-2133, 14-16-000981-047, 14-16-0009-84-966, and 14-16-00091545 work order 82620-01.