Sleepless in Town – Drivers of the Temporal Shift in Dawn Song in Urban European Blackbirds

Abstract

Organisms living in urban environments are exposed to different environmental conditions compared to their rural conspecifics. Especially anthropogenic noise and artificial night light are closely linked to urbanization and pose new challenges to urban species. Songbirds are particularly affected by these factors, because they rely on the spread of acoustic information and adjust their behaviour to the rhythm of night and day, e.g. time their dawn song according to changing light intensities. Our aim was to clarify the specific contributions of artificial night light and traffic noise on the timing of dawn song of urban European Blackbirds (Turdus merula). We investigated the onset of blackbird dawn song along a steep urban gradient ranging from an urban forest to the city centre of Leipzig, Germany. This gradient of anthropogenic noise and artificial night light was reflected in the timing of dawn song. In the city centre, blackbirds started their dawn song up to 5 hours earlier compared to those in semi-natural habitats. We found traffic noise to be the driving factor of the shift of dawn song into true night, although it was not completely separable from the effects of ambient night light. We additionally included meteorological conditions into the analysis and found an effect on the song onset. Cloudy and cold weather delayed the onset, but cloud cover was assumed to reflect night light emissions, thus, amplified sky luminance and increased the effect of artificial night light. Beside these temporal effects, we also found differences in the spatial autocorrelation of dawn song onset showing a much higher variability in noisy city areas than in rural parks and forests. These findings indicate that urban hazards such as ambient noise and light pollution show a manifold interference with naturally evolved cycles and have significant effects on the activity patterns of urban blackbirds.

Dark Matters: The Effects of Artificial Lighting on Bats

“…For instance, early singing may be a signal of male quality in songbirds and increases the rate of extra-pair copulations, which are usually higher in older males. In territories affected by artificial light, males of several songbird species start singing earlier at dawn and thereby gain access to about twice as many extra-pair mates (Kempenaers et al 2010;Nordt and Klenke 2013;Dominoni et al 2014). The effect of artificial light on paternity gain is even stronger in yearlings than in adults, and so street lights might result in maladaptive mate choice of females by artificially increasing the extra-pair success of yearlings (Kempenaers et al 2010).…”

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

“…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.…”

PRELIMINARY STUDY ON Eidolon helvum (Kerr, 1792) POPULATION DYNAMIC IN CÔTE D’IVOIRE, WEST AFRICA

“…Counting has been performed on Saturdays, except from football match days in Felix Houphouët-Boigny stadium adjoining the study zone. In fact, the spectators cry during football matches bring out a massive flight of bats (Mann et al, 2002;Hayes et al, 2009;Nordt & Klenke, 2013). That counting was done in 16 roosting sites (Figure 1), before the waking up and the massive agitation of bats, by counting the perched bats on branches of each tree, from its base towards the extremity whatever the age and the sex, usually counting carried out manually but some time help of the binoculars was also taken (Kunz, 2003;O'Shea et al, 2003;Krebs, 2006;Hayes et al, 2009;Hayman et al, 2012;.…”