Nest site characteristics and nest success of translocated and resident greater sage grouse at Clear Lake National Wildlife Refuge

Thesis (M.S.)--Humboldt State University, Natural Resources: Wildlife, 2011Translocation has been used to augment declining Greater Sage Grouse (Centrocercus urophasianus, hereafter sage grouse) populations for several decades. However, little or no data are available directly comparing translocated and resident sage grouse reproduction. I monitored translocated and resident (birds that had not been translocated) sage grouse during 2009-2011 at Clear Lake National Wildlife Refuge in Modoc County, California to examine vegetation characteristics associated with nest success and nest site selection. In addition, I identified nest predators to obtain information on nesting productivity and factors influencing nest success in this population. I monitored 17 translocated and 16 resident radio marked sage grouse females for a total of 63 nests and measured vegetation characteristics at nest sites and paired sites. I monitored 42 of the 63 nests using continuous videography to identify nest predators. I examined factors influencing the proportion of females that nested. In addition, I assessed the biotic and abiotic variables that influenced nest site selection, and examined daily nest survival using the nest survival model in program MARK. The highest ranked model (AICc weight = 0.60) describing nest initiation indicated that translocated sage grouse were less likely to nest in their first year than resident hens or translocated hens after their first year (post-translocated). The best supported model of daily nest survival (AICc weight = 0.53) included greater nest shrub diameter and grass height, but lower grass cover and shrub height. The second ranked model included the translocation status of the hen (translocated vs.post-translocated and resident). Nest success for this population (45%) was similar to other sage grouse populations (47%). The best model distinguishing nest sites from paired sites was strongly supported (AICc weight = 0.962) and included greater shrub diameter, grass cover, and shrub height and lower grass height at nest sites than paired sites. I found little support for the hypothesis that translocated hens used nest sites with different vegetation characteristics than resident hens. Of the six nest predations events I captured on video, five were coyotes and one was a badger. The relatively high proportion of females that attempted to nest and high nest success of the studied population suggests that nest productivity was not limiting the population. My results confirm that translocation can be an effective management tool for augmenting small or declining sage grouse populations. However, translocated hens may initiate nests at a lower frequency in their first year than resident hens. I recommend nesting habitat management focus on promoting larger sagebrush and increasing herbaceous cover