Noise Exposure in Egg Stage Harms Bird Development, Fitness

Eggs and nesting baby birds exposed to moderate levels of anthropogenic traffic noise experience large, direct, and additive adverse effects on long-term development and fitness, according to a new study. The findings underscore the disruptive properties of noise on physiology, development, and reproduction, leading to lifelong fitness reduction, and call for a reassessment of the threat posed by anthropogenic noise and the need for noise mitigation measures. Noise pollution has become a global issue of concern, even in Earth's most remote places. Adverse impacts of exposure to anthropogenic noise pollution on animals are well documented, including effects on acoustic communication and behavior. More recently, studies have started to show negative effects on physiology, reproduction, and development across a range of animal species, as well as in humans. Despite this growing body of evidence, little is known about how noise impairs development and fitness. It's unknown whether noise sound waves are intrinsically harmful for developing young or simply disturbs and/or alters parental behaviors. To better understand these impacts, Alizée Meillère and colleagues investigated the fitness impact of developing wild zebra finch birds in a moderately noisy environment. Meillère et al. found that noise doesn't just alter adult behavior but had direct impacts on bird growth and fitness when only eggs are exposed to noise. In their experiment, the authors exposed soon-to-be-hatching eggs and postnatal nesting birds to specific acoustic environments – namely recordings of traffic noise (at levels that birds routinely encounter in an urban environment), zebra finch songs, or silence. According to the findings, birds exposed to moderate anthropogenic traffic noise in the egg experienced long-term impacts, including impaired nesting growth, shorter telomere length, and reduced fitness as adults. "The study of Meillère et al. on zebra finches reinforces the notion of negative noise impact on chicks as they develop in the egg, an effect that extends to pre-natal exposure to noise in other species, including humans," writes Hans Slabbekoorn in a related Perspective. "The findings suggest that the acoustic environment of breeding birds in cities and along highways should be better managed, and that the acoustic comfort in hospital environments for pregnant mothers and babies warrants special attention."