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

ABSTRACT

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 outcomes, we sampled 87 sage-grouse nests during 2004 and 2005 in the Montana Mountains of northwestern Nevada. Within a 78.5-m₂ 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 characteristics at and surrounding sage-grouse nests and to determine those characteristics associated with nest success. Nest initiation rate was high (90.0%) and apparent nest success was 40.2%. We used a Mayfield estimation to determine a probability of nest success (hatch ≥ 1 chick) of 36%. Grass cover within a 3-m₂ 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 confirm 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.

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