Greater Sage-Grouse (Centrocercus urophasianus) Habitat Selection in Northwestern Wyoming and Stable Isotope Analysis of Fecal Material.

摘要

Dramatic range-wide declines in Greater Sage-Grouse populations have prompted efforts to determine habitat characteristics that are selected by sage-grouse for foraging, nesting and brood-rearing areas in an effort to conserve this species. Managers at Heart Mountain and Y U Bench in northwestern Wyoming expressed the need to quantify various habitat characteristics and to determine key use areas at both study sites. Data were collected on a variety of habitat variables in spots selected by grouse for foraging, nesting, and brood-rearing activities. These variables were compared to the same variables measured at random points at both study sites. Significant differences existed between foraging/nesting habitat plots selected by sage-grouse and random habitat plots at both sites. Areas used most by sage-grouse for lekking, nesting, and brood-rearing were identified at both study locations. Data analyses indicated sage-grouse at Heart Mountain were choosing foraging and nesting areas dominated by junegrass while grouse at YU Bench were choosing foraging sites dominated by junegrass and nesting sites dominated by needle and thread grass.;Stable carbon and nitrogen isotope ratios were used to determine diet compositions of adults and chicks using avian fecal matter instead of tissue. Sage-grouse produce two different kinds of fecal material: intestinal droppings and cecal tars. Both types of fecal matter as well as various insect and plant species were collected at both field sites. Isotope analyses combined with mixing model analyses indicated that adult grouse at both sites were relying more on C3 grasses than either forbs or sagebrush in the summer months compared to what has been previously reported. Mixing model results confirmed that insects were the main food item for chicks at these two locations but these results also indicated that chicks are consuming more C3, C4 and CAM plants than has been previously reported.