How does night-time light pollution affect parental care and provisioning behaviour in Herring Gulls Larus argentatus?

Abstract

Conflict between humans and wildlife has been long documented and is continuing to proliferate. As human populations grow and expand into the remaining natural spaces, the impact of urbanisation is likely to increase. Wildlife that inhabits urban areas are exposed to artificial lighting at night (ALAN) and may exhibit life history and/or behavioural shifts as a result. In recent years, research regarding the ecological impacts of ALAN has been accelerating to catch up with rates of urbanisation and lighting evolution, and a key part of this research is understanding the link between light environment and wildlife behaviour. In this thesis, I investigated the differences in the light environment experienced by breeding herring gulls (Larus argentatus) on rural and urban nests, and the effects of ALAN on gull behaviour. To do this, I deployed custom-built light sensors and motion- activated trail cameras near urban rooftop nests and in a rural colony in Cornwall. I found that the light environment at urban herring gull nests had higher values of light intensity and a smaller ratio of both blue to green and green to red wavelengths of light. Furthermore, gulls exposed to higher maximum nightly lux were observed performing sitting behaviour for a smaller proportion of time. This significant result supports some of the previous literature that suggest light environment can influence behaviours at the nest. Conversely, the non-significant models raise further questions about the intricacies of the urban environment and the reliability of our experimental design. Further understanding of the ways in which the light environment can differ and behavioural differences this causes may guide us towards the discovery and use of lighting sources less disruptive to natural light routines.