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Austin, Jane E., Ball, I. J., and Henry, Adonia R. Nesting ecology of sandhill cranes 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. 221.
We examined the nesting ecology of greater sandhill cranes (Grus canadensis tabida) at Grays Lake, Idaho during 1997-99 to detennine the effects of nest-site characteristics and land use on crane nest success. These are preliminary results from 3 years of a 4-year study. Crane nests were located in portions of the Grays Lake basin from early May through late June each year (n = 131 in 1997; n = 131 in 1998; n = 143 in 1999). Apparent nest success varied among years (54% in 1997, 71% in 1998, and 53% in 1999; overall average of 59%). We estimate that 10% of nests found in 1999 were renests. Most crane nests were located in baltic rush/spikerush (Juncus balticus/Eleocharis sp.; 46% of nests), semi-wet meadow (19%), and bulrush/cattail (Scirpus sp./Typha sp.; 19%) plant communities; 62% of nests during early May were in:;; 12 cm of water. As indicated by plant community, water depths at nests, and nest isolation rankings, nest success tended to be higher where nests were in relatively deep water (ca. >40 em) and were relatively isolated from access by mammalian predators. Nest success rates during 1997-99 were lower than those recorded in 1950-51 (90%, n = 107; Steel 1952) and 1970-71 (78%, n = 308; Drewien 1973). A variety offactors likely contribute to lower nest success, including changing predator communities over the past 30-40 years. Differences among years in our study may be affected by changing availability of alternate prey. Small mammal populations and crane nest success were the highest in 1998. Water-level management, relating to cranes and other waterbird populations, plant communities, and ecosystem function, is an emerging issue for land managers in the Grays Lake basin.