Welcome to the American Ornithological Society 2018 Annual Conference. We are pleased to have you join us at the lovely Hilton El Conquistador Resort in Tucson, AZ.
Songbird nests are critical life-history components with the potential to influence fitness correlates such as nestling development and nest survival by moderating nest microclimate and camouflage, respectively. Nest characteristics should co-vary with prevailing environmental and ecological conditions, providing a buffered environment for offspring to develop and preventing predator detection for several weeks. For an alpine population of ground-nesting Horned Larks (Eremophila alpestris) in northern British Columbia, Canada, we investigated the influence of three nest characteristics (substrate, lining, and decoration) on microclimate using explicit measures of nest temperature, as well as associated fitness consequences (i.e. nestling size traits, nest survival). Substrate use decisions may reflect a trade-off between microclimate and nest survival as nests placed in heather had the coldest microclimate compared to grass and bare-ground substrates, but also the greatest nest survival (68\% compared to 37-44\%). Nests that were lined with willow (Salix sp.) seed-down were associated with larger, heavier nestlings, while nest decoration placed in front of the nest (e.g. stones) was associated with warmer nest microclimates, providing support for a thermoregulatory function for both nest traits. Nest decoration greatly increased building effort, varying in mass from 5.3 g to 186.6 g and requiring up to 163 extra building trips. We discuss the potential for nest decoration to also function as an extended female phenotypic signal. High phenotypic flexibility in all nest characteristics (61-88\% within-female variation) suggests the capacity to respond to at least some of the anticipated changes of climate change through nest placement and characteristics decisions.
