Data from: Does urbanization cause stress in wild birds during development? insights from feather corticosterone levels in juvenile house sparrows (Passer domesticus)

Urban landscapes are associated with abiotic and biotic environmental
changes that may result in potential stressors for wild vertebrates. Urban
exploiters have physiological, morphological and behavioral adaptations to
live in cities. However, there is increasing evidence that urban
exploiters themselves can suffer from urban conditions, especially during
specific life-history stages. We looked for a link between the degree of
urbanization and the level of developmental stress in an urban exploiter
(the house sparrow, Passer domesticus), which has recently been declining
in multiple European cities (e.g. London, UK). Specifically, we conducted
a large-scale study and sampled juvenile sparrows in 11 urban and rural
sites to evaluate their feather corticosterone (CORT) levels. We found
that juvenile feather CORT levels were positively correlated with the
degree of urbanization, supporting the idea that developing house sparrows
may suffer from urban environmental conditions. However, we did not find
any correlation between juvenile feather CORT levels and body size, mass,
or body condition. This suggests either that the growth and condition of
urban sparrows are not impacted by elevated developmental CORT levels, or
that urban sparrows may compensate for developmental constraints once they
have left the nest. Although feather CORT levels were not correlated with
baseline CORT levels, we found that feather CORT levels were slightly and
positively correlated with the CORT stress response in juveniles. This
suggests that urban developmental conditions may potentially have
long-lasting effects on stress physiology and stress sensitivity in this
urban exploiter.