City and forest great tits respond differently to artificial light at night: insights from a common garden study
- 1UiT The Arctic University of Norway
Abstract
Artificial light at night (ALAN) disrupts the natural light-dark cycle, which is the most important cue for synchronizing circadian clocks. If populations most exposed to ALAN adapt to get less disturbed by it, we expect forest and city populations to differ genetically. We tested this prediction in a common garden experiment using a songbird, the great tit (Parus major), originating from forest and city populations. We simulated ALAN exposure during the breeding season by keeping the birds in pairs under ALAN or dark nights for three months and then repeated the experiment in the following year with the same pairs under the opposite treatment. The advancement of daily onset under ALAN disappeared over time for city birds, but not for their forest counterparts. For these same birds, we measured their onset of daily activity under constant dim light and shift in activity in response to light pulses and showed that the city/forest difference in behavioural response was not reflected in any clock property measured. This indicates that city and forest birds differ genetically in the downstream behavioural response to ALAN, and not in the circadian clock. Thus, urbanization is unlikely to select for divergence in circadian clock properties in songbirds.
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BibTeX
@misc{solberg2026city,
title = {{City and forest great tits respond differently to artificial light at night: insights from a common garden study}},
author = {T. Solberg and P. van der Ham and E. Matthysen and M. Eens and K. Spoelstra and K. van Oers and M. Visser and B. Mizumo Tomotani},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.29.753716},
url = {https://www.biorxiv.org/content/10.64898/2026.09.29.753716v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - City and forest great tits respond differently to artificial light at night: insights from a common garden study
AU - T. Solberg
AU - P. van der Ham
AU - E. Matthysen
AU - M. Eens
AU - K. Spoelstra
AU - K. van Oers
AU - M. Visser
AU - B. Mizumo Tomotani
PY - 2026
DA - 2026/09/29
PB - bioRxiv
DO - 10.64898/2026.09.29.753716
UR - https://www.biorxiv.org/content/10.64898/2026.09.29.753716v1
AB - Artificial light at night (ALAN) disrupts the natural light-dark cycle, which is the most important cue for synchronizing circadian clocks. If populations most exposed to ALAN adapt to get less disturbed by it, we expect forest and city populations to differ genetically. We tested this prediction in a common garden experiment using a songbird, the great tit (Parus major), originating from forest and city populations. We simulated ALAN exposure during the breeding season by keeping the birds in pairs under ALAN or dark nights for three months and then repeated the experiment in the following year with the same pairs under the opposite treatment. The advancement of daily onset under ALAN disappeared over time for city birds, but not for their forest counterparts. For these same birds, we measured their onset of daily activity under constant dim light and shift in activity in response to light pulses and showed that the city/forest difference in behavioural response was not reflected in any clock property measured. This indicates that city and forest birds differ genetically in the downstream behavioural response to ALAN, and not in the circadian clock. Thus, urbanization is unlikely to select for divergence in circadian clock properties in songbirds.
ER -