Provost, J.L. 1990. Biology of sandhill cranes on breeding and fall staging areas in northwestern Minnesota. M.S. Thesis, University of North Dakota. 111 pp.
Sandhill cranes (Grus canadensis) were studied on breeding and fall staging areas in northwestern Minnesota from 1 April 1989 to 21 October 1990. Principle objectives including documenting 1) location, population size, and density of breeding cranes on the primary study area, 2) nest habitat use and preference of nesting cranes, 3) nest success, 4) fledging success, 5) presence, numbers, and locations of nonbreeding cranes, and 6) fall migration chronology.
At least 28 pairs nested on the primary study area (PSA, 111.4 km2), resulting in a minimum density of 0.25 breeding pair/km2. Habitat characteristics recorded at nest sites and random sites included wetland classification; basin size; distance to upland, nearest shrub and tree; water depth; concealment by vegetation; plant species and density; and number of shrub clumps and stems within 1.5 m, and trees within 5 m. Except for distributions of distances to nearest shrub for nest and random sites, there were no statistically significant differences between mean values or distributions of variables measured at nest and random sites, and successful and unsuccessful nest sites.
Mean clutch size was 1.88 (error 0.332) eggs for 17 known completed clutches in 1989 and 1990. Estimated hatch date for 13 clutches in 1990 ranged from 21 May - 12 June (x = 30 May +- 6.6 days). In 1990, apparent and corrected nest successes were 73.3% (N = 15 nests) and 53.8% (N = 14 nests, respectively, and apparent hatching success was 69.2% (N = 26 eggs). At least 15 young cranes fledged on the PSA in 1990. Two chicks banded in 1989 were observed on fall staging areas in 1990.
Some of 23 territorial pairs on the PSA, not proven to be breeding, were possibly nonbreeding pairs. Other nonbreeding cranes occurred in groups of 2-59 birds and their numbers were highest in mid-May and late July. Upland habitats in which groups were frequently seen foraging included harvested grain field, bare or vegetated fallow field, and grass or alfalfa hayfield.
Staging of local cranes on the PSA and surrounding secondary study area began in early to mid-August. Migrants arrived by mid-September and roost counts revealed that numbers of staging cranes peaked in mid- to late September. Upland habitats in which flocks were frequently seen foraging included harvested grain field, bare or fallow field, and grass or alfalfa hayfield. In 1990, the percentage of juveniles among staging flocks peaked at 16.4% (N = 1602 cranes) on 15-16 September and the percentage of families with two juveniles was 24.4% (N = 623 families). The majority of cranes departed the study areas after goose hunting season began in late September.