Results from a new study reveal that artificial light sources associated with urban areas can disrupt the natural movement patterns of birds migrating at night across the UK. Using a combination of passive acoustic monitoring devices and the latest computing approaches, researchers Simon Gillings and Chris Scott were able to determine that calling rates of migrating Blackbirds, Song Thrushes and Redwings were significantly higher over brightly lit urban areas, most likely a consequence of the birds being attracted by the artificial lighting.
Migrant birds face many challenges, and those that migrate at night may be subjected to additional impacts. Approximately 80% of UK summer migrants migrate at night and vast numbers of individuals may be involved; for example, an estimated 40–150 million birds cross the North Sea at night during the autumn migration period. There is growing evidence, mostly from North America, that nocturnal migrants can be affected by artificial light at night (termed ‘ALAN’ by researchers), becoming disoriented and, in some cases, flying into structures such as lighthouses, oil platforms and tall buildings. Mass mortality of nocturnal migrants, notably those attracted to illuminated tall buildings, is a recognised problem in North America. While UK and other European cities tend to have fewer tall buildings, there is an urgent need to establish the possible impacts of light pollution on migrant birds here.
The present study, which took place in Cambridgeshire between late September and mid-November 2019, used passive acoustic monitoring devices to capture the presence of nocturnally migrating thrushes passing over gardens located along a gradient from the brightly lit city of Cambridge to the darker countryside that surrounds it. The audio recordings captured were then processed and analysed using the latest neural network computing approaches. These involved training an artificial neural network to identify the calls of the target species, before being given the collected recordings to analyse.
Full paper: Gillings, S & Scott, C (2021) Nocturnal flight calling behaviour of thrushes in relation to artificial light at night. Ibis. https://doi.org/10.1111/ibi.12955
Posted On: 06/05/2021