Artificial Night Lighting Affects Dawn Song, Extra-Pair Siring Success, and Lay Date in Songbirds

Abstract

Associated with a continued global increase in urbanization, anthropogenic light pollution is an important problem. However, our understanding of the ecological consequences of light pollution is limited. We investigated effects of artificial night lighting on dawn song in five common forest-breeding songbirds. In four species, males near street lights started singing significantly earlier at dawn than males elsewhere in the forest, and this effect was stronger in naturally earlier-singing species. We compared reproductive behavior of blue tits breeding in edge territories with and without street lights to that of blue tits breeding in central territories over a 7 year period. Under the influence of street lights, females started egg laying on average 1.5 days earlier. Males occupying edge territories with street lights were twice as successful in obtaining extra-pair mates than their close neighbors or than males occupying central forest territories. Artificial night lighting affected both age classes but had a stronger effect on yearling males. Our findings indicate that light pollution has substantial effects on the timing of reproductive behavior and on individual mating patterns. It may have important evolutionary consequences by changing the information embedded in previously reliable quality-indicator traits.

The effects of light pollution on biological rhythms of birds: an integrated, mechanistic perspective

“…Several songbird species have been found to modify their time of singing in light polluted areas in different geographical regions. The effect is strongest for some naturally early singing species: European robin (Erithacus rubecola) (Fuller et al 2007; Kempenaers et al 2010; Da Silva et al 2014, American robin (Turdus migratorius) (Miller 2006a ), Common blackbird (Turdus merula) (Kempenaers et al 2010; Dominoni et al 2014; Da Silva et al 2014, and Great tit (Parus major) (Kempenaers et al 2010; Da Silva et al 2014. These species sometimes sing truly at night.…”

“…These species sometimes sing truly at night. The effects are more moderate in other species, such as the song thrush (Turdus philomelos) (Da Silva et al 2014 ) and the Blue tit (Cyanistes caeruleus) (Kempenaers et al 2010; Da Silva et al 2014. While all of them have reported an earlier onset of dawn song, few have also shown a later offset of activity in the evening (Dominoni et al 2014; Da Silva et al 2014 and even singing behavior in the middle of the night (Fuller et al 2007 ).…”

“…Only a few studies have tried to overcome this limitation in the field to at least separate the effects of noise and light, while controlling for ambient temperature (Kempenaers et al 2010; Da Silva et al 2014. These have shown that light pollution can clearly alter the onset and offset of daily singing in a variety of species, and that the annual development of dawn and dusk chorus is accelerated under artificial lights (Da Silva et al 2015 ).…”

“…These have shown that light pollution can clearly alter the onset and offset of daily singing in a variety of species, and that the annual development of dawn and dusk chorus is accelerated under artificial lights (Da Silva et al 2015 ). In addition, Kempenaers and colleagues have demonstrated that artificial lights not only advance dawn song in the blue tit, but early singing associated with lights was positively correlated with the amount of extra pair offspring that males were able to sire, hinting at potential reproductive consequences of light pollution (Kempenaers et al 2010 ). Recent studies from the same group have expanded this previous work, showing that females advanced their morning onset of activity during the breeding season when their nest boxes were artificially illuminated .…”

“…Several studies have highlighted variation in daily as well as in seasonal rhythms of different bird species (Miller 2006b; Kempenaers et al 2010; Nordt and Klenke 2013; Dominoni et al 2014, although other environmental stimuli proper of urban areas might have confounded these results. Recently, quasi experimental approaches in the field (Titulaer et al 2012; Da Silva et al 2014 and controlled experiments under laboratory conditions (Schoech et al 2013; Dominoni et al 2013b ) have tested specific hypotheses about the effects of light at night on the daily and seasonal cycles of birds, which have included investigations on the physiological mechanisms underpinning the temporal responses of birds to light at night.…”