Factors affecting mortality of shearwaters stranded by light pollution

Abstract

Every year and across the world, thousands of fledglings of different petrel species crash into human structures because they are disorientated by artificial lights during their first flights. As this phenomenon is rather predictable, rescue campaigns are organized to help birds to reach the ocean, but unfortunately, a low proportion gets hurt or dies. Despite the huge number of affected individuals, and the fact that the problem was detected a long time ago, little is known on this source of mortality. We have studied the factors (i.e. body condition, plumage development, fledging date and sex) influencing the mortality of Cory's Shearwater Calonectris diomedea fledglings stranded inland due to light pollution in Tenerife (Canary Islands) during two consecutive breeding seasons (2009 and 2010). Late fledglings showed lower values of a body condition index than early ones. No sex biases were detected, neither considering stranded birds overall, nor for recovery dates or in the body condition of rescued fledglings. Our results indicate that late birds stranded by lights showing abundant down are more susceptible to fatal collisions and that the lights do not selectively kill birds with lower body condition indices. An enhancement of veterinary care should be done during the last part of the fledging period when more fatal collisions occur, especially focused on fledglings with abundant down. More research to determine why some individuals end up disoriented around artificial lights and others do not is urgently needed to minimize or prevent fallouts. bs_bs_banner Animal Conservation. Print

Using observed seabird fallout records to infer patterns of attraction to artificial light

“…Although rescue efforts for downed fledglings appear to save many birds annually, it is estimated that some birds still perish due to fallout because they are never found (Ainley et al 2001). Furthermore, it is unknown whether the experience of fallout leaves rescued fledglings unscathed enough to survive their first few weeks of pelagic life (Ainley et al 2001, Le Corre et al 2002, Rodriguez & Rodriguez 2009, Rodriguez et al 2012a. Thus, while the continuation of these rescue and light reduction efforts is crucial, populations could still be declining due to the effects of anthropogenic light despite these measures, albeit at a slower rate.…”

Artificial light alters natural regimes of night-time sky brightness

“…The impacts of direct artificial light include navigational disorientation of birds1415, turtles1617 and invertebrates1819, the displacement and concentration of selected foraging habitat in bats2021 and birds22, the extension of foraging times in birds222324, and changes to the composition of invertebrate communities25. Added to this, the potential effects of sky glow include artificially increasing the amount of ambient light and time available for foraging2627, interfering with celestial light patterns used in navigation28, and the disruption of temporal activity patterns linked to daily, monthly and annual lunar rhythms in sky brightness29303132.…”

Melatonin: a possible link between the presence of artificial light at night and reductions in biological fitness

“…The ecological consequences of the increasing presence of artificial LAN are well documented in animals although the evidence from natural populations, in particular, is frequently correlational [2,4,5]. Behaviourally, LAN is linked to an increase in the observed number of bird strikes and subsequent deaths [6,7] and changes in the foraging capacity and activity patterns of vertebrates [8][9][10][11][12] and invertebrates [5,13]. At the population level, animals living in well-lit urban environments are observed to shift the timing and structure of their mating calls [14][15][16][17] and the commencement of breeding [15,18].…”