Effects of early-life noise exposure on the spatial learning and memory in the zebra finch (Taeniopygia guttata)

Anthropogenic noise is almost omnipresent. Consequently, birds are constantly exposed, with studies documenting impacts on important processes such as reproduction. But a notable gap in the literature relates to how anthropogenic noise could impact early avian development and specifically behavioural development. To investigate this, zebra finch (Taeniopygia guttata) eggs were exposed daily to either traffic noise or bird song, for the last 5 days of incubation in artificial incubators. Post-hatch from days 4 to 12, nestlings were again exposed to the acoustic treatments in a balanced 2x2 full factorial design. Once adult, the spatial memory of the experimental subjects was tested over a series of trials to test the ability to learn and remember the location of a food source. I predicted that compared to control birds, adult birds with early-life exposure to noise would perform less well in the spatial memory task. I observed that among females with prenatal exposure to noise, fewer individuals learned the position of their baited feeder and needed more trials to learn than females with prenatal exposure to song. Although no treatment effect was observed in females in their latency to find the baited feeder, all female subjects improved in their latency regardless of treatment, demonstrating their capacity to learn the task. No significant treatment effects were observed in males in their spatial learning abilities. However, males with postnatal exposure to noise were more exploratory when introduced to a novel environment. To my knowledge, this is the first documented evidence in any species that exposure to anthropogenic noise can directly cause developmental effects which subsequently impair spatial learning abilities. These results suggest that birds developing in urban environments may have long term impacts on their spatial memory and thus potentially their fitness. Future studies should focus on what mechanisms lead to these developmental effects and how they can affect fitness.