Impacts of anthropogenic pollution on cognition and sleep in an urban bird

© 2020 Charles Farley ConnellyThe world is rapidly urbanizing, transforming Earth’s natural habitats. While the loss of these habitats is the most visible impact of urban expansion, human population growth has also brought associated phenomena that have the capacity to negatively impact non-human animals. Two key anthropogenic phenomena associated with urban environments have become almost inescapable: anthropogenic noise and artificial light at night. Anthropogenic noise can now be heard in some of the most remote protected areas in the world, while, in the US alone, half of all land mass is exposed to unnatural levels of light at night. There is growing evidence that these environmental ‘pollutants’ have negative impacts on the behaviours and fitness of urban wildlife. In this thesis, I focus on the potential of these anthropogenic pollutants to disrupt cognitive processes and sleep in an urban-adapted species, the Australian magpie (Cracticus tibicen). Wild magpies occupying territories across suburban Melbourne that were exposed to varying levels of urban noise performed similarly on cognitive tasks. Variation in cognitive performance was best explained by age rather than the amplitude of noise to which birds were exposed on a daily basis. I found some evidence that higher sound levels may impair cognitive development, but the effect was observed in only one of four cognitive tasks presented. In captivity, the performance of magpies on similar cognitive tasks was compared under two conditions (experimental exposure to realistic traffic noise, compared to a quiet control). I again found no difference in cognitive performance in the presence or absence of noise. They did, however, perform better on tasks the second time they experienced them, regardless of noise. Finally, I explored the effect of urban noise and two different colours (blue-rich and blue-reduced) of artificial light at night on sleep in magpies. Magpies exposed to a 24-hour recording of urban noise spent more time awake and less time in non-rapid eye movement (non-REM) and REM sleep throughout the night. Likewise, magpies exposed to artificial light at night spent less time asleep, and their sleep was more fragmented. In addition, blue-rich lighting had a greater effect on sleep than did blue-reduced lighting. My findings shed light on some of the putative pathways by which anthropogenic noise and artificial light can affect key biological processes in suburban wildlife, but also illustrate that not all processes are necessarily detrimentally affected