The impact of the Jacques Cartier bridge illumination on the food chain: from insects to predators

摘要

Artificial light at night can impact numerous diurnal species by influencing their distribution and habits. In this study, artificial lights placed on the Jacques Cartier bridge in Mont real, Canada were evaluated to determine their impact on insects, insectivorous birds and peregrine falcons. The impact was measured the year the illumination begun and the year following (two years in total). Insect distribution and abundance at three different sites around the bridge was measured. Insectivorous bird abundance and activity were evaluated by observing the cliff swallow as a proxy. Peregrine falcon presence and nesting behavior at the bridge was measured. Insects (aerial and aquatic) were found to be more abundant closer to the illuminated part of the bridge and particularly in the year following the illumination's beginning. Similarly, cliff swallows were more abundant at the bridge the year following the start of the illumination and their activity was more important closer to the illuminated section. Peregrine falcons were only present at the bridge in the year following the beginning of the illumination and specifically at the illuminated part of the bridge. No nesting was detected. These three groups are connected to each other through a food chain in which insect abundance impacts insectivorous bird abundance, which in turn impacts peregrine falcon presence. The illumination therefore positively impacts these three groups separately and together through their food chain. This research highlights the importance of monitoring bird and insect population close to the bridge and further continuation of these observations are necessary to determine if the observed tendency will continue to develop throughout the years.