High temperatures reduce song production and alter signal salience in songbirds

Global climate change is causing heatwaves to increase in number, length and intensity. These extreme temperatures can reduce fitness when mating behaviours are affected. An important mating behaviour for many organisms is sexual signalling. For example, songbirds, such as the zebra finch, Taeniopyggia guttata, use song to attract mates. Here, we test how an acute period of extreme heat affects song production in male zebra finches. We then ask whether female zebra finches discriminate between songs produced at different temperatures. We find that males significantly reduce song output at temperatures that induce heat dissipation behaviours. We also find that males produce song bouts with shorter syllables when thermally challenged. Furthermore, the relative acoustic and structural consistency of songs changes with temperature. Finally, we find that female zebra finches discriminate between songs produced at different temperatures, and the strength of discrimination is associated with changes in syllable duration. Altogether, we demonstrate that heatwave-like conditions can impact communication via alterations in signaller behaviour and the signal itself. We also discuss the potential compounding effects of reduced song production and other physiological declines on fitness in free-living zebra finches, which increasingly experience these high temperatures. (c) 2021 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.