Date of this Version
Ivey, Gary L., and Eric J. Scheuering. Mortality of radio-equipped sandhill crane colts at Malheur National Wildlife Refuge, Oregon. In: Urbanek RP, Stahlecker DW, eds. 1997. Proceedings of the Seventh North American Crane Workshop, 1996 Jan 10-13, Biloxi, Mississippi. Grand Island, NE: North American Crane Working Group. pp. 14-17.
We radio-equipped 142 greater sandhill crane (Grus canadensis tabida) colts at Malheur National Wildlife Refuge, Oregon, during 1991-95 to document prefledging mortality factors. Fates of 19 colts were undetermined. A total of 23 colts survived to fledge (19% of known fates). Evidence collected from the carcasses and death sites indicated that predators were responsible for the largest number of colt deaths (64), followed by unknown causes (13), parasitic gapeworms (Cyastoma spp.) (8), drowning (7), intraspecific aggression (5), study-related mortality (I), roadkill (I), and hay swather (1). Of 64 colts killed by predators, 26 were lost to mink (Mustela vison), 10 to great horned owls (Bubo virginianus), 9 to golden eagles (Aquila chrysaetos), 7 to unidentified predators, 5 to coyotes (Canis latrans), 5 to unidentified raptors, 1 to a northern harrier (Circus cyaneus), and 1 to a raccoon (Procyon lotor). Because mink were the most significant predator, we initiated an experimental mink control program in 1993. Losses from mink in 1993 were reduced to 9%, compared with 36% and 27% in 1991 and 1992, respectively. We concluded that an integrated approach involving habitat management and predator and parasite control could be used to enhance crane productivity.