Abstract

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Maxson, S.J., and M.R. Riggs. 1996. Nest habitat selection and nest success of greater sandhill cranes in northwestern Minnesota. Report submitted to the Minnesota Department of Natural Resources. 18+ pp.

Abstract:

We studied Greater Sandhill Cranes (Grus canadensis tabida) in northwestern Minnesota to document nest habitat selection and nest success, and to determine whether nest success was related to nest habitat characteristics. We located 62 crane nests. At each nest and a matched random site in the same wetland, we recorded 15 habitat characteristics. We used multiple conditional logistic regression to determine whether habitat characteristics differed between matched pairs of nests and random sites. Only the low height concealment index and sedge (Carex spp.) stem density predicted whether a location was a nest site. The odds of a location being a nest site (vs. a random site) decreased 2.8 times for each 10% increase in concealment score and increased 3.1 times for each unit decrease in ln (sedge stem density). Overall nest success was 39.6% (95% CL = 23.4%, 51.7%). Nests initiated in April were less likely to be depredated than those initiated in May (P = 0.03). All but one of 23 depredated nests appeared to have been destroyed by mammalian predators. Nests in large wetland basins (>2.2 ha) were not more likely to hatch than those in small basins (< 2.2 ha) (P = 0.29). The dominant vegetation within a 5 m radius of the nest did not differ significantly between hatched and depredated nests (P = 0.63). We tested for an association between 10 other habitat variables and the probability that a nest would be depredated by fitting an unconditional logistic regression model to data from the 62 nest sites. Only low height concealment score, water depth, and their interaction were statistically significant. The odds of depredation at nests in shallow water (< 9.7 cm) were 3.7 times greater than at nests in deeper (> 9.7 cm) water regardless of the low height concealment score. At deeper water nest sites, the odds of depredation increased 1.2 times for each 10% decrease in concealment score.


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