Data from: Stressful city sounds: glucocorticoid responses to experimental traffic noise are environmentally dependent

A major challenge in urban ecology is to identify the environmental
factors responsible for phenotypic differences between urban and rural
individuals. However, the intercorrelation between the factors that
characterise urban environments, combined with a lack of experimental
manipulations of these factors in both urban and rural areas, hinder
efforts to identify which aspects of urban environments are responsible
for phenotypic differences. Among the factors modified by urbanisation,
anthropogenic sound, particularly traffic noise, is especially detrimental
to animals. The mechanisms by which anthropogenic sound affects animals
are unclear, but one potential mechanism is through changes in
glucocorticoid hormone levels. We exposed adult house wrens, Troglodytes
aedon, to either traffic noise or pink noise. We found that urban wrens
had higher initial (pre-restraint) corticosterone than rural wrens before
treatment, and that traffic noise elevated initial corticosterone of
rural, but not urban, wrens. By contrast, restraint stress-induced
corticosterone was not affected by noise treatment. Our results indicate
that traffic noise specifically contributes to determining the
glucocorticoid phenotype, and suggest that glucocorticoids are a mechanism
by which anthropogenic sound causes phenotypic differences between urban
and rural animals.