Microhabitat Selection of Brood-Rearing Sites by Greater Sage-Grouse in Carbon County, Wyoming

Declines in Greater Sage-Grouse (Centrocercus urophasianus, hereafter sage-grouse) populations could be attributed to low chick survival, which may be influenced by the availability of food and cover at sites used by females rearing broods. Habitat attributes important to broods may vary regionally; thus, it is necessary to understand factors affecting regional sage-grouse brood-rearing site selection, especially when estimating the impacts of development. We monitored brood-rearing female sage-grouse equipped with solar Argos Global Positioning System Platform Transmitter Terminals from 2011 to 2013 to assess microhabitat selection by broods in Carbon County, Wyoming. We measured vegetation and arthropod characteristics at diurnal sites used by broods (n = 42 in 2011, n = 31 in 2012, n = 32 in 2013) and at 3 paired-random sites associated with each used site (n = 315), located 50 m, 250 m, and 500 m from the used site. We fit conditional logistic models within an information-theoretic framework to identify vegetation and arthropod characteristics associated with microsite selection of brood-rearing sites. Sage-grouse selected brood-rearing sites with greater visual obstruction (0–45.7 cm in height), higher numbers of arthropods in the order Diptera, and lower numbers of arthropods in the order Coleoptera. There was an interaction effect between the number of arthropods in the order Hymenoptera and the canopy cover of broad-leaf forbs; the relative probability of selection increased with increasing number of Hymenoptera when there was low cover (20%). We also found a quadratic relationship between selection of brood-rearing sites and total vegetation canopy cover; the relative probability of selection increased until approximately 75% cover and then decreased with increasing cover. Sage-grouse rearing broods selected a diverse array of vegetation types, but greatest use occurred within mesic communities. Our results could be used to identify vegetation communities with high relative probabilities of use by sage-grouse rearing broods, which will help guide management decisions and provide reference conditions for future research that evaluates the effects of wind energy development on sage-grouse.