Sunrise in the city: disentangling drivers of the avian dawn chorus onset in urban greenspaces

Abstract

Urban systems are known to have a number of effects on avian richness, density, and morphological and behavioral traits. However, no study to date has simultaneously examined the wide range of urban variables in relation to the avian dawn chorus, a complex behavioral phenomenon. Previous studies investigating adjustments of the dawn chorus onset in urban settings have mainly been confined to relationships with noise and light levels. In addition to noise and light levels, in this study we included other potentially related environmental characteristics describing vegetation structure, urban infrastructure, and human activity, all of which have been shown to be drivers of bird diversity in urban areas. We conducted dawn chorus surveys at 38 Los Angeles urban greenspaces and used a classification and regression tree analysis to identify specific urban scenarios that best explained timing differences in the dawn chorus onset. Our results show that light level was the most important variable related to the dawn chorus onset time, in which, counter-intuitively, bird communities in greenspaces with higher light levels had later onsets. In addition, noise was an important factor for the chorus onset in greenspaces with higher light levels. Although our results differ from those of previous studies, these findings highlight the importance of noise and light levels in explaining dawn chorus onset variation, indicating the need for further research in untangling this complex and ecologically important phenomenon.

Variation in Diurnal Patterns of Singing Activity Between Urban and Rural Great Tits

“…For neither of these studies, it is clear whether there was a shift or an extension of activity, as data were not collected for the full day. Another recent study in urban greenspaces (Lee et al, 2017) also reported an impact of both light and noise on dawn chorus timing, with a larger role for artificial light at night, but with an opposite effect from the studies above. Traffic noise appears to be correlated to advancing dawn chorus in tropical bird species as well, where artificial light has apparently less of an effect, probably due to little variation in day length at their latitude (Dorado-Correa et al, 2016;Marín-Gómez and MacGregor-Fors, 2019).…”

“…Traffic noise and street lightening are two of the most prominent pollutants that are put forward as causing changes in avian rhythms (Nordt and Klenke, 2013;Lee et al, 2017). American robins (Turdus migratorius), for example, initiated their dawn chorus during the night, especially in areas with elevated artificial light levels (Miller, 2006).…”

“…They found that redwinged blackbirds (Agelaius phoeniceus) sang more at dawn and dusk at the rural sites and more during midday at the urban sites. Traffic noise and street lightening are two of the most prominent pollutants that are put forward as causing such divergence in avian rhythms (Nordt and Klenke, 2013;Lee et al, 2017), with sometimes sound put forward as most prominent factor (e.g., Fuller et al, 2007) and sometimes light (e.g., Da Silva et al, 2014).…”

Dawn chorus interpretation differs when using songs or calls: the Dupont’s Lark Chersophilus duponti case

“…Despite the prevalence of dawn-singing in birds and the numerous studies focused on that topic, its origin, evolution and causes remain unclear and seem to be context-dependent, differing among species, populations and studies (e.g., Staicer, Spector& Horn, 1996 ; Catchpole & Slater, 2008 ; Zhang, Celis-Murillo & Ward, 2016 ). This could be explained in part because researchers have indistinctly analysed or have even pooled calls and songs ( Poesel, Foerster & Kempenaers, 2001 ; Grava et al, 2013 ; Stanley et al, 2016 ; Lee, MacGregor-Fors & Yeh, 2017 ) to elucidate dawn chorus function (but see LaZerte, Otter & Slabbekoorn, 2017 ). Nonetheless, the bulk of dawn chorus studies have been focused on singing activity (e.g., Gil, Graves & Slater, 1999 ; Amrhein, Korner & Naguib, 2002 ; Liu, 2004 ).…”

Peer Review #3 of "Dawn chorus interpretation differs when using songs or calls: the Dupont’s Lark Chersophilus duponti case (v0.1)"

“…Staicer et al, 1996;Catchpole & Slater, 2008;Zhang et al, 2016). This could be explained in part because researchers have indistinctly analysed or have even pooled calls and songs (Poesel et al, 2001;Grava et al, 2013;Stanley et al, 2016;Lee et al, 2017) to elucidate dawn chorus function (but see LaZerte et al, 2017).…”