Effect of air movement on the thermal insulation of avian nests

Capsule: Air movement over a nest increases the rate of cooling within the nest cup but the walls provide good thermal insulation. Aims: This study compared nests of six bird species of the families Fringillidae and Motacillidae to investigate the insulative properties in still and moving air treatments. It was hypothesized that differences in nest size and moving air would differ between species and would have a significant effect on insulatory values of the nests. Methods: Nest dimensions were measured for a total of 35 nests from six species. Thermal properties of the nests were recorded using temperature loggers within nests placed in a wind tunnel under still and moving air conditions. Results: Insulatory values and internal nest cooling rates were significantly increased by moving air. There was no significant difference between species for the thermal properties of nests but nest mass correlated with greater insulatory values and a lower rate of cooling within the nest cup. Nest wall thickness had no significant effect on the thermal characteristics of the nests. Conclusion: The use of a constructed nest mitigated the effects of air movement but the differences between species reflected difference in nest mass rather than wall thickness