Anthropogenic noise reduces avian feeding efficiency and increases vigilance along an urban-rural gradient regardless of species’ tolerances to urbanisation

Anthropogenic noise can adversely impact urban bird populations by
interfering with vocal communication. Less research has addressed if
anthropogenic noise masks the adventitious sounds that birds use to aid
predator detection, which may lead to increased vigilance and reduced
feeding efficiency. We test this hypothesis using a controlled playback
experiment along an urban-rural gradient in Sheffield (UK). We also test
the related predictions that anthropogenic noise has the greatest impacts
on vigilance and feeding efficiency in rural populations, and on species
that are more sensitive to urbanisation. We focus on six passerines, in
order from most to least urbanised (based on how urbanisation influences
population densities): blue tit Cyanistes caeruleus, robin Erithacus
rubeculla, great tit Parus major, chaffinch Fringilla coelebs, coal tit
Periparus ater and nuthatch Sitta europaea. We used play-back of
anthropogenic urban noise and a control treatment at 46 feeding stations
located along the urban-rural gradient. We assess impacts on willingness
to visit feeders, feeding and vigilance rates. Exposure to anthropogenic
noise reduced visit rates to supplementary feeding stations, reduced
feeding rates and increased vigilance. Birds at more urban sites exhibit
less marked treatment induced reductions in feeding rates, suggesting that
urban populations may be partially habituated or adapted to noisy
environments. There was no evidence, however, that more urbanised species
were less sensitive to the impacts of noise on any response variable. Our
results support the adventitious sound masking hypothesis. Urban noise may
thus interfere with the ability of birds to detect predators, reducing
their willingness to use food rich environments and increase vigilance
rates resulting in reduced feeding rates. These adverse impacts may
compromise the quality of otherwise suitable foraging habitats in noisy
urban areas. They are likely to be widespread as they arise in a range of
species including common urban birds.