Date of this Version
Proceedings of the North American Crane Workshop 13:13-24
We conducted aerial surveys to determine nest locations of greater sandhill cranes (Grus canadensis tabida) in central Wisconsin, 2001-2003. Helicopter flights covered 8.90 km2 of wetlands in each year, and we found 41 nests in 2001, 50 nests in 2002, and 48 nests in 2003 from 11 wetlands. Our best estimate of nest density (n = 14) included wetlands containing 5 or more nests and averaged 5.25 ± 0.36 (1 SE) nests/km2 of wetland. Maximum nest density of larger wetlands in any 1 year was 7.80 nests/km2. As some nests had likely failed by the time we completed our surveys, our measure of nest density likely under-estimated the total number of territories in each wetland. Minimum distances between nests averaged 222 ± 70 m (range 33-666 m) among all wetlands and 151 ± 41 m (range 33-571 m) for wetlands with 5 or more nests. Nest locations differed from a random distribution (P < 0.05) and were clustered within wetlands and within years. Nest locations were found more than expected in the wetland habitat type (Jacob’s Index D = 0.72 in 2001, 0.66 in 2002 and 0.76 in 2003) and less than expected in open water, open shrub, and closed shrub. No nests were found in wetland forests. Crane nests also tended to occur on the outside margins of the wetlands. Nest density in central Wisconsin was greater than any previous estimate for any other crane population yet recorded and likely represents a breeding population at carrying capacity as well as a species that utilizes both upland and wetland habitats together.