Cooperative Fish and Wildlife Research Units Program: all
Education, Research and Technical Assistance for Managing Our Natural Resources

Developing a better understanding of species responses to temperature change via behavior, and the factors affecting the extent of behavioral responses, is a critical and timely endeavor given the rapid pace at which the climate is changing. Young of altricial songbirds are particularly sensitive to temperature, and parents may modulate temperatures at nests via selection of nest sites, albeit to a largely unknown extent. We examined whether sagebrush-obligate songbirds that reproduce within an open ecosystem with wide temperature fluctuations and span a range of body sizes, selected nest sites on the basis of temperature. We further investigated whether predation risk and ambient conditions modulated temperature-based choices. We placed temperature loggers at nest sites and in unused but available niches and shrubs along a known predation-risk gradient and used nearby weather stations to determine ambient temperatures. Brewer’s Sparrows and Sagebrush Sparrows, the two smaller-bodied birds, selected nest sites that were warmer and less variable relative to available sites, whereas Sage Thrashers generally did not select nest sites on the basis of temperature. Both Brewer’s Sparrows and Sage Thrashers increased selection for cooler nest sites relative to available sites with increased ambient temperatures during the prospecting period. None of the three species altered nest-site selection with respect to temperature in response to ambient temperature variability or our index of nest predation risk. The microhabitat characteristics that most influenced temperatures at nests varied across species. Our results suggest that songbirds can modulate temperatures at nests to some extent, and such responses can vary depending on the conditions experienced prior to nest initiation. Responses varied across species, however, likely reflecting different physiological tolerances. The extent to which breeding birds will be able to continue to proximately influence temperature via nest site choices likely will depend on the extent and rate of future climatic shifts.