Ingrained city rhythms: flexible activity timing but more persistent circadian pace in urban birds

TY - JOUR

T1 - Ingrained city rhythms

T2 - flexible activity timing but more persistent circadian pace in urban birds

AU - Tomotani, B.M.

AU - Timpen, Fabian

AU - Spoelstra, K.

N1 - Data archiving: data in DataverseNL

PY - 2023/5/30

Y1 - 2023/5/30

N2 - Urbanization dramatically increases the amount of light at night which may disrupt avian circadian organization. We measured activity patterns of great tits breeding in the city and forest, and subsequently measured two clock properties of these birds under controlled conditions: tau (endogenous circadian clock speed) and after-effects (history-dependency of the clock relative to previous conditions). City and forest birds showed a high repeatability of activity onset (0.60 and 0.41, respectively), with no difference between habitats after controlling for date effects. Activity duration and offset showed more variance, without a difference between birds from the two habitats. Tau did not differ between city and forest birds, however, city birds showed stronger after-effects, taking more days to revert to their endogenous circadian period. Finally, onset of activity was correlated with clocks speed in both habitats. Our results suggest that potential differences in activity timing of city birds is not caused by different clock speeds, but by a direct response to light. Persistence in after-effects suggests a reduced sensitivity of the clock to light at night. Urbanization may select for clock properties that increase the inertia of the endogenous circadian system to improve accuracy of activity rhythms when exposed to noisier lighting cues.

AB - Urbanization dramatically increases the amount of light at night which may disrupt avian circadian organization. We measured activity patterns of great tits breeding in the city and forest, and subsequently measured two clock properties of these birds under controlled conditions: tau (endogenous circadian clock speed) and after-effects (history-dependency of the clock relative to previous conditions). City and forest birds showed a high repeatability of activity onset (0.60 and 0.41, respectively), with no difference between habitats after controlling for date effects. Activity duration and offset showed more variance, without a difference between birds from the two habitats. Tau did not differ between city and forest birds, however, city birds showed stronger after-effects, taking more days to revert to their endogenous circadian period. Finally, onset of activity was correlated with clocks speed in both habitats. Our results suggest that potential differences in activity timing of city birds is not caused by different clock speeds, but by a direct response to light. Persistence in after-effects suggests a reduced sensitivity of the clock to light at night. Urbanization may select for clock properties that increase the inertia of the endogenous circadian system to improve accuracy of activity rhythms when exposed to noisier lighting cues.

KW - Animals

KW - Circadian Clocks/physiology

KW - Circadian Rhythm/physiology

KW - Cities

KW - Passeriformes/physiology

KW - Urbanization

KW - great tit

KW - after-effects of entrainment

KW - free-running period

KW - incubation

KW - artificial light at night

KW - urbanization

UR - https://doi.org/10.34894/8KYFYO

U2 - 10.1098/rspb.2022.2605

DO - 10.1098/rspb.2022.2605

M3 - Article

C2 - 37192668

SN - 0962-8452

VL - 290

SP - 20222605

JO - Proceedings of the Royal Society B: Biological Sciences

JF - Proceedings of the Royal Society B: Biological Sciences

IS - 1999

ER -