DOI: 10.5061/dryad.748rk
title: Data from: Singing from North to South: latitudinal variation in timing of dawn singing under natural and artificial light conditions

description: 1. Animals breeding at northern latitudes experience drastic changes in
 daily light conditions during the breeding season with decreasing periods
 of darkness, whereas those living at lower latitudes are exposed to
 naturally dark nights throughout the year. Nowadays, many animals are also
 exposed to artificial night lighting (often referred to as light
 pollution). 2. Animals strongly rely on variation in light levels to time
 their daily and seasonal behaviour. Previous work on passerine birds
 showed that artificial night lighting leads to earlier onset of dawn song.
 However, these studies were carried out at intermediate latitudes with
 more limited seasonal changes in daylength, and we still lack an
 understanding of the impact of artificial night lighting in relation to
 variation in natural light conditions. 3. We investigated the influence of
 natural and artificial light conditions on the timing of dawn singing in
 five common songbird species in each of three regions in Europe that
 differed in natural variation in daylength (northern Finland, 65°N;
 southern Germany, 48°N; southern Spain, 37°N). In each region, we selected
 five peri-urban forest sites with and five without street lighting, and
 recorded dawn singing at the beginning of the local breeding season. 4.
 Our results show that the earliest natural singers, i.e., European robins
 (Erithacus rubecula) and common blackbirds (Turdus merula), started dawn
 singing earlier along with the natural increase in night brightness in
 Finland, with no additional effects of artificial night lighting. In
 contrast, the later singers, i.e., great tits (Parus major), blue tits
 (Cyanistes caeruleus), and chaffinches (Fringilla coelebs), showed similar
 onsets of dawn song relative to sunrise across the season and similar
 effects of artificial night lighting at all latitudes. 5. Artificial night
 lighting affected great tits, blue tits and chaffinches even in northern
 Finland where nights became very bright. Proximate factors such as
 differential light sensitivities may explain why early singers showed more
 plastic behavioural responses to naturally and artificially bright nights.
 The maintenance of rhythmicity in the late singers during bright northern
 nights and under artificial night lighting may also be an adaptive
 response to predation risk or costs of sleep loss.
description: Latitudinal variation in
 timing of dawn singing under natural and artificial light
 conditionsRegion = country of
 recording (Spain, Germany, Finland) Location = name of the site (see Table
 S2) Longitude = longitude of each location in ºE Latitude = latitude of
 each location in ºN Treatment = type of location (lighted or control) Mean
 intensity at 0m = mean intensity at each location in lux, measured under
 the street lights, with the lux meter held 2m from the ground Mean
 intensity at 5m = mean intensity at each location in lux, measured 2
 meters from the street lights, with the lux meter held 2m from the ground
 Mean intensity at 10m = mean intensity at each location in lux, measured
 10 meters from the street lights, with the lux meter held 2m from the
 ground Date = date of recording (DDMM) Calendar date = date starting from
 1 = 1 January Lay date = date standardized according to the great tit mean
 lay date of each region Sunrise = time of sunrise at each location on each
 day in HH:MM Extraction = name of the person who extracted the recording
 data (David =David Diez-Méndez / Satu = Satu Tolvanen) Temperature =
 temperature at sunrise at each location on each day in degrees Celsius
 Rain = presence of rain during the recording (yes/no) Robin onset =
 European robin start of dawn singing at each location on each day in
 minutes before sunrise Blackbird onset = Common blackbird start of dawn
 singing at each location on each day in minutes before sunrise Great tit
 onset = Great tit start of dawn singing at each location on each day in
 minutes before sunrise Blue tit onset = Blue tit start of dawn singing at
 each location on each day in minutes before sunrise Chaffinch onset =
 Common chaffinch robin start of dawn singing at each location on each day
 in minutes before sunriseData_JAE_ADS.xls