Date of this Version
Ball, I. J., Austin, Jane E., and Henry, Adonia R. Sandhill crane abundance at Grays Lake, Idaho.In: Ellis, David H., ed., Proceedings of the Eighth North American Crane Workshop, 11–14 January 2000, Albuquerque, New Mexico (Seattle, Wash: North American Crane Working Group, 2001), p. 218.
We initiated a study on the breeding ecology of greater sandhill cranes (Grus canadensis tabida) in the Grays Lake basin ofIdaho in 1997. Interest in the status of crane populations at Grays Lake is high; consequently, we present preliminary information on estimated size of the population, changes since the 1970s, and potential environmental factors involved. Drewien (1973) counted an average of549 cranes in the spring and estimated 250 nesting pairs in 1970-71. Number of nesting pairs reportedly increased 33% (to 332) by 1982 in response to intensive management, then declined 40-60% by 1996 (Drewien 1997, and Homocker Wildlife Institute, personal communication). During 1998-99, spring counts averaged 736 cranes (34% increase from 1970-71). Among 44 survey units that were searched during both studies, nest densities increased in 27, decreased in 13, and remained unchanged in 4. Nest success declined from 78% in 1970-71 to 59% in 1997-99. We estimated that renesting accounted for 10% of nests in 1999. Fall staging populations were similar between the early 1970s (n = 1313) and late 1990s (n = 1370), but well below peak counts of the 1980s (often >3000). Factors potentially influencing the crane populations at Grays Lake include habitat management, climate (drought), predator populations, manipulation of marsh water levels, agricultural practices, baiting, and disturbance.