Low-frequency songs lose their potency in noisy urban conditions

TLDR

Urban noise hampers animal acoustic communication, prompting many bird species to shift to higher song frequencies to avoid masking, though this may reduce attractiveness that low frequencies normally confer. The study aims to determine whether the shift to higher frequencies in great tits compensates for noise or incurs costs by trading signal strength for detection. Researchers examined male great tits by measuring signal strength and detection across song frequencies under urban noise conditions. Results show that low‑frequency songs correlate with female fertility and fidelity, yet urban noise reduces their effectiveness, giving high‑frequency songs a relative advantage during signaling and highlighting a tradeoff between reproductive success and noise resilience.

Abstract

Many animal species communicate with their mates through acoustic signals, but this communication seems to become a struggle in urbanized areas because of increasing anthropogenic noise levels. Several bird species have been reported to increase song frequency by which they reduce the masking impact of spectrally overlapping noise. However, it remains unclear whether such behavioral flexibility provides a sufficient solution to noisy urban conditions or whether there are hidden costs. Species may rely on low frequencies to attract and impress females, and the use of high frequencies may, therefore, come at the cost of reduced attractiveness. We studied the potential tradeoff between signal strength and signal detection in a successful urban bird species, the great tit ( Parus major). We show that the use of low-frequency songs by males is related to female fertility as well as sexual fidelity. We experimentally show that urban noise conditions impair male–female communication and that signal efficiency depends on song frequency in the presence of noise. Our data reveal a response advantage for high-frequency songs during sexual signaling in noisy conditions, whereas low-frequency songs are likely to be preferred. These data are critical for our understanding of the impact of anthropogenic noise on wild-ranging birds, because they provide evidence for low-frequency songs being linked to reproductive success and to be affected by noise-dependent signal efficiency.