Survival of Gunnison sage-grouse Centrocercus minimus in Colorado, USA
Amy J. Davis, Michael L. Phillips, Paul F. Doherty
Gunnison sage-grouse Centrocercus minimus has declined from their historic range and recent monitoring has provided evidence that some populations are continuing to decline. The evaluation of long-term, population-specific survival rates is important to assess population stability, and is necessary for conservation of this species of concern. We evaluated adult and yearling survival in two dynamically different populations of Gunnison sage-grouse (a relatively large, more stable population and a small, declining population). Our goal was to examine the relationship between annual survival and population, and test hypotheses with regards to temporal effects (across years and within year) and individual effects (sex and age). We also evaluated the effects of snow depth on sage-grouse survival. We tracked 214 radiomarked birds in the large population from 2005–2010 and 25 birds in the small population from 2007–2010. We found no evidence for a difference in survival between yearlings and adults nor did we find an influence of snow depth on survival. Males had the lowest survival during the lekking season (March–April); females had lower survival during the nesting and chick rearing season (May–July) and late-summer and fall (August–October). The annual survival rate was 0.61 (SE 0.06) for females and 0.39 (SE 0.08) for males. Survival was constant across years and between the populations suggesting observed population changes during this time period are not a result of changes in adult survival.