Nest construction, ambient temperature and reproductive success in a cavity-nesting bird

Abstract

Nest construction is a widespread behaviour that is a critical fitness investment in many taxa. Nests provide stable environments for offspring production, development and at times adult survival. Avian nest structure and composition has been linked to insulative properties and the reduction of energetic requirements for incubating females. However, it is unclear how and why nest structure varies across landscapes within and between species, especially in cavity-nesting species. Here we examined nest size in a secondary cavity nester, the mountain chickadee, Poecile gambeli. Nests were measured across two years at two elevations varying in ambient temperature to test whether variation in nest size was associated with local ambient temperatures and internal nest cavity microclimate. Despite both elevations having high variation in ambient temperature during nest building in both years, there were no significant relationships between multiple nest measurements and temperature. Nest size was highly consistent between years within females, suggesting that individual females are the best predictor of nest size. Large variation in nest size, internal nest cavity microclimate temperature and ambient temperature during development in one year was not associated with significant differences in reproduction; but fluctuating asymmetry, a measure of developmental stress, was significantly lower in fledglings at the higher-elevation site independent of temperature. However, there were no significant differences between elevations in the second year for any reproductive parameter. Overall, our results suggest that chickadees do not adjust nest size in response to large differences in ambient or microclimate temperature and that large variation in nest size, both across and within sites, is a result of consistent individual preferences, which do not seem to have clear fitness consequences.