GPS tracking for mapping seabird mortality induced by light pollution

Abstract

Light pollution and its consequences on ecosystems are increasing worldwide. Knowledge on the threshold levels of light pollution at which significant ecological impacts emerge and the size of dark refuges to maintain natural nocturnal processes is crucial to mitigate its negative consequences. Seabird fledglings are attracted by artificial lights when they leave their nest at night, causing high mortality. We used GPS data-loggers to track the flights of Cory’s shearwater Calonectris diomedea fledglings from nest-burrows to ground, and to evaluate the light pollution levels of overflown areas on Tenerife, Canary Islands, using nocturnal, high-resolution satellite imagery. Birds were grounded at locations closer than 16 km from colonies in their maiden flights, and 50% were rescued within a 3 km radius from the nest-site. Most birds left the nests in the first three hours after sunset. Rescue locations showed radiance values greater than colonies, and flight distance was positively related to light pollution levels. Breeding habitat alteration by light pollution was more severe for inland colonies. We provide scientific-based information to manage dark refuges facilitating that fledglings from inland colonies reach the sea successfully. We also offer methodological approaches useful for other critically threatened petrel species grounded by light pollution.

Factors influencing Manx Shearwater grounding on the west coast of Scotland

“…In addition, it is difficult to match some short‐term weather patterns with a specific bird grounding, as there may be a delay of several hours to even a few days between the moment when a bird was grounded and when it was spotted and recovered (Rodríguez et al . , ). Similarly, there may be some delays between a change in weather pattern and a peak in groundings; these delayed effects are difficult to include in the model.…”

“…Young petrels and shearwaters are inexperienced in flying and may be blown in the direction of a source of light, e.g. a village (Rodr ıguez et al 2014). Therefore, we predict that the wind direction coming from Rum (westerly), as well as strong winds, causes the highest fallout.…”

“…, Rodríguez et al . ). Fledglings on their first flight are often found to crash‐land in the cities and towns near their nest‐sites; this phenomenon can be termed ‘grounding’ (Le Corre et al .…”

“…Recent studies have found that seabirds are more likely to be encountered in locations with high light intensity (Le Corre et al 2002, Rodr ıguez & Rodr ıguez 2009, Rodrigues et al 2012, Troy et al 2013, Rodr ıguez et al 2015. Fledglings on their first flight are often found to crash-land in the cities and towns near their nest-sites; this phenomenon can be termed 'grounding' (Le Corre et al 2002, Rodr ıguez et al 2014 or 'fallout' (Ainley et al 2001, Troy et al 2011. Seabirds that land on the ground are often unable to take off from these urban locations due to their specialized anatomy, exemplified by legs set far back on the body to facilitate diving.…”

“…Adverse weather conditions and *Corresponding author. Email: syposzmartyna@gmail.com Twitter: @martyna_syposz moonless nights were reported to increase seabird fallout (Phillips & Lee 1966, Imber 1975, Reed et al 1985, Telfer et al 1987, Le Corre et al 2002, Rodr ıguez & Rodr ıguez 2009, Miles et al 2010, Rodr ıguez et al 2014. A study by Rodr ıguez et al (2014) also showed that strong winds blowing in the direction of areas of light pollution caused more seabirds to ground.…”