Interpopulation variation in nest architecture in a secondary cavity-nesting bird suggests site-specific strategies to cope with heat loss and humidity

Abstract

© 2017 American Ornithological Society. Nest morphology can affect the breeding success of birds. Thus, birds inhabiting different environments may experience divergent selection for nest structure and composition that results in intraspecific geographic variation in nest architecture. We describe interpopulation differences in nest architecture among Thorn-tailed Rayaditos (Aphrastura spinicauda) in 2 contrasting environments near the species' distribution limits: a temperate and very humid environment in north-central Chile (the forest relicts of Fray Jorge National Park; 30°38′S, 71°40′W) and a cold and windy sub-Antarctic environment in the south of Chile (Isla Navarino; 55°4′S, 67°40′W). We collected a total of 62 nests from Fray Jorge and 61 nests from Navarino in 2013 and 2014, measured their dimensions, and quantified their constitutive materials. We tested the nests' thermal properties (simulating heat loss by convection and conduction) and hygroscopic features (water absorpti