A meta-analysis of greater sage-grouse Centrocercus urophasianus nesting and brood-rearing habitats.

摘要

The distribution and range of the greater sage-grouse Centrocercus urophasianus have been reduced by 56% since the European settlement of western North America. Although there is an unprecedented effort to conserve the species, there is still considerable debate about the vegetation composition and structure required for nesting and brood-rearing habitat. We conducted a meta-analysis of vegetation characteristics recorded in studies at nest sites (N=24) and brood habitats (N=8) to determine if there was an overall effect (Hedge's d) of habitat selection and to estimate average canopy cover of sagebrush Artemisia spp., grass and forbs, and also height of grass at nest sites and brood-rearing areas. We estimated effect sizes from the difference between use (nests and brood areas) and random sampling points for each study, and derived an overall effect size across all studies. Sagebrush cover (d< sub>++=0.39; 95% C.I.: 0.19-0.54) and grass height (d< sub>++=0.28; 95% C.I.: 0.13-0.42) were greater at nest sites than at random locations. Vegetation at brood areas had less sagebrush cover (d< sub>++=-0.17; 95% C.I.: -0.44-+0.18), significantly taller grasses (d< sub>++=0.31; 95% C.I.: 0.14-0.45), greater forb (d< sub>++=0.48; 95% C.I.: 0.30-0.67) and grass cover (d< sub>++=0.17; 95% C.I.: 0.08-0.27) than at random locations. These patterns were especially evident when we examined early (<6 weeks post hatching) and late brood-rearing habitats separately. The overall estimates of nest and brood area vegetation variables were consistent with those provided in published guidelines for the management of greater sage-grouse.