Birds living near airports do not show consistently higher levels of feather corticosterone.

Noise represents a threat to human and wildlife health, triggering physiological and behavioral challenges to individuals living close to sources of extreme noise. Here, we considered airport environments as sources of potentially stressful stimuli for birds and tested if those living near airports are under higher physiological stress than birds living in quiet sites. We used measurements of CORT in feathers (CORT_f) as a proxy of chronic stress. We evaluated 14 passerine and 1 non-passerine species, living near three Brazilian airports. We found that, across species, individuals with a better body condition had lower CORT_f concentration. At the species level, we found that CORT_f concentration was not consistently affected by airport noise. Comparing individuals living in quiet sites with those living near airports, we found that 2 species had higher and 2 had lower CORT_f concentrations near airports, while 11 species presented no significant differences between sites. At the population level, model selection indicated that the direction and strength of these differences are weakly related to species' song frequency (peak frequency), as lower-frequency singers tended to present higher CORT_f levels at airport-affected sites. In summary, we were unable to find a consistent response among species, probably due to species-specific differences in their response to anthropogenic disturbances. Instead, we found that species might be affected differently according to their singing spectral frequency and that individuals in good body condition show lower CORT_f, suggesting that this measure is consistent with lower physiological stress.