Mud acts as a noise dampener in Australian passerine nests

Research into the effects of anthropogenic noise on birds has revealed that individuals are susceptible to negative impacts of noise at all life stages. Scientists are particularly concerned about the effects of noise on embryos and nestlings, because of potential survival and fitness consequences. However, almost nothing is known about how background anthropogenic noise is experienced within nests. Many natural materials and shapes are effective noise dampeners, thus we would expect that nest inhabitants may be subject to differing levels of environmental noise than those detected by researchers outside of a nest. Similarly, noise levels may vary between nests of different shapes and materials. A test was conducted on 250 museum nest specimens to discover whether these properties might contribute to the detectable levels of noise inside the nest. Most nests were generally ineffective at dampening environmental noise. Strikingly, however, mud nests showed major differences in detectable noise levels compared with all other nest types, with levels being up to 6 dB lower than control conditions. This insight will hopefully inform future studies into the effects of noise on birds and provide valuable information regarding how this extended behavioural phenotype might contribute to a species’ resilience against harmful environmental conditions.