Data from: Early-life exposure to artificial light at night elevates physiological stress in free-living songbirds

Artificial light at night (ALAN) can disrupt adaptive patterns of
physiology and behavior that promote high fitness, resulting in
physiological stress and elevation of steroid glucocorticoids
(corticosterone, CORT in birds). Elevated CORT may have
particularly profound effects early in life, with the potential for
enduring effects that persist into adulthood. Research on the
consequences of early-life exposure to ALAN remains limited,
especially outside of the laboratory, and whether light exposure
affects CORT concentrations in wild nestling birds
particularly remains to be elucidated. We used an experimental
setup to test the hypothesis that ALAN elevates
CORT concentrations in developing free-living birds, by exposing
nestling great tits (Parus major) to ALAN inside nest boxes. We
measured CORT in feathers grown over the timeframe of the experiment (7
nights), such that CORT concentrations represent an integrative
metric of hormone release over the period of nocturnal light
exposure, and of development. We also assessed the relationships
between feather CORT concentrations, body condition, nestling
size rank and fledging success. In addition, we evaluated the relationship
between feather CORT concentrations and telomere length.
Nestlings exposed to ALAN had higher feather CORT concentrations than
control nestlings, and nestlings in poorer body condition and
smaller brood members also had higher CORT. On the other hand,
telomere length, fledging success, and recruitment rate were not
significantly associated with light exposure or feather CORT
concentrations. Results indicate that exposure to ALAN elevates CORT
concentrations in nestlings, which may reflect physiological
stress. In addition, the organizational effects of CORT are known to
be substantial. Thus, despite the lack of an effect on telomere
length and survivorship, elevated CORT concentrations in
nestlings exposed to ALAN may have subsequent impacts on later-life
fitness and stress sensitivity.