Factors affecting nest-site selection and nest success of translocated greater sage grouse

Abstract

Translocations have been used for decades to restore or augment wildlife populations, yet more often than not, little to no data and/or arbitrary means are used for determining translocation success. The objectives of our study were to describe nesting habitat utilised by the greater sage grouse translocated into an extant population and to identify factors related to nest success, thereby demonstrating the adaptability of the birds to their new environment and producing one measure of long-term translocation success. We trapped female grouse individuals during the spring on and near leks of source populations, fitted them with radio-transmitters, and released them in the morning onto an active lek in an extant population in Strawberry Valley, Utah. We monitored translocated females for nesting activity and documented nesting attempts, nest success, clutch size and embryo viability. Data were recorded on habitat variables associated with nest sites and paired-random sites, including factors known to be important for resident females that nested successfully. We used logistic regression and an a priori information-theoretic approach for modelling nest v. paired-random sites and successful v. unsuccessful nest sites. Our analyses suggested that crown area of the nest shrub and percentage grass cover were the two variables that discriminated between nest and paired-random sites. Females that nested successfully selected sites with more total shrub canopy cover, intermediate size-shrub crown area, aspects other than NW and SE, and steeper slopes than for unsuccessful nests. After being translocated from distant sites with differing habitat characteristics, these birds were able to initiate a nest, nest successfully, and select micro-habitat features similar to those selected by resident sage grouse across the species range. Our results demonstrate the adaptability of the translocated female sage grouse individuals and produce one tangible measure of long-term translocation success.