Nest Site Characteristics and Factors Affecting Nest Success of Greater Sage-grouse

Nesting success of greater sage-grouse (Centrocercus urophasianus) influences annual reproductive success and population dynamics. To describe nesting habitat and measure the effects of vegetation characteristics on nesting out- comes, we sampled 87 sage-grouse nests during 2004 and 2005 in the Montana Mountains of northwestern Nevada. Within a 78.5-m 2 circular plot surrounding each nest, we quantified sagebrush canopy cover and grass cover. We used Akaike's Information Criterion to rank competing models describing potential relationships between vegetation character- istics at and surrounding sage-grouse nests and to determine those characteristics associated with nest success. Nest initia- tion rate was high (90.0%) and apparent nest success was 40.2%. We used a Mayfield estimation to determine a probabil- ity of nest success (hatch >1 chick) of 36%. Grass cover within a 3-m 2 area centered on the nest had a positive effect on nest success (odds ratio: 1.03, 95% CI: 1.005 - 1.059). We also found weak support for a positive effect on nest success of sagebrush cover at the nest (odds ratio: 1.02, 95% CI: 0.993 - 1.043). Our results are similar to previous findings and con- firm the importance of sagebrush cover and herbaceous understory for nesting. To manage sagebrush communities for successful nesting by greater sage-grouse, we recommend providing sufficient grass and sagebrush cover.