The influence of light intensity on the nocturnal movement of avifauna

Abstract

The use of artificial light has brought about an array of advantages for human civilisations. However, the “turning night into day” phenomenon, and alteration of natural dark-light cycles that have been stable for geological time does not come without consequences. A range of ecosystems and organisms, including migratory avifauna, are known to be impacted. Bright light sources at night have an impact on the large-scale movement between breeding sites in northern Europe and wintering sites in Africa. Malta, being one of the top most light-polluted countries in the world, while concurrently lying on one of the Old World avian passage routes, makes migratory birds even more susceptible to implications from artificial light at night. Evidence of disorientation during passage, disruption of circadian rhythms, and collision with man-made infrastructure is manifest, particularly where heavily lit up area occur. This dissertation analyses the relationship between night-time light intensity and avian records over a time frame of nine years. Three selected stopovers sites, namely, the island of Comino, Għadira Nature Reserve and Simar Nature Reserve, are considered. Several species of passerines and waders are incorporated, and remotely-sensed light intensity data obtained from the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument onboard the Suomi and NOAA-20 satellites is analysed. The findings reveal positive and negative correlations in separate stopovers as well as different light intensities and avian distributions in the three study site locations. The results of this study suggest that the influence of artificial light at night on migratory birds stopping to refuel in the Maltese islands is currently not significant, but such impact is projected to increase when taking into consideration the proliferation of local infrastructural and domestic development.