Anthropogenic noise affects male house wren response to but not detection of territorial intruders

Abstract

Anthropogenic noise decreases signal active space, or the area over which male bird song can be detected in the environment. For territorial males, noise may make it more difficult to detect and assess territorial challenges, which in turn may increase defense costs and influence whether males maintain territory ownership. We tested the hypothesis that noise affects the ability of male house wrens ( Troglodytes aedon ) near active nests to detect intruders and alters responses to them. We broadcast pre-recorded male song and pink noise on territories to simulate intrusions with and without noise, as well as to noise alone. We measured detection by how long males took to sing or approach the speaker after the start of a playback. To measure whether playbacks changed male behavior, we compared their vocal responses before and during treatments, as well as compared mean vocal responses and the number of flyovers and attacks on the speaker during treatments. Noise did not affect a male’s ability to detect an intruder on his territory. Males altered their responses to simulated intruders with and without noise compared to the noise-only treatment by singing longer songs at faster rates. Males increased peak frequency of songs during intrusions without noise compared to noise-only treatments, but frequency during intruder plus noise treatments did not differ from either. When confronting simulated intruders in noise, males increased the number of attacks on the speaker compared to intruders without noise, possibly because they were less able to assess intruders via songs and relied on close encounters for information. Although noise did not affect intruder detection, noise affected some aspects of singing and aggressive responses, which may be related to the challenge of discriminating and assessing territorial threats under elevated noise.

Anthropogenic noise affects female, not male house wren response to change in signaling network

“…Units were pre‐programmed to begin recording 1 hr before to 4 hr after sunrise (Eastern Standard Time, EST) in 30‐min recording increments. Playbacks took place between sunrise and 1100 (EST) on days with minimal wind speed and no precipitation and followed the same procedure used by Grabarczyk and Gill (2019a). Briefly, we created 28 playbacks from recordings of male house wrens breeding in southwest Michigan during 2015–2016.…”

“…Males sing with eventual variety, repeating the same terminal section several times before gradually transitioning to a new song type (Kroodsma, 1977; Rendall & Kaluthota, 2013). Therefore, to mimic natural singing patterns, a single song type was repeated every 15 s for 10 min, similar to typical rates of singing (Grabarczyk & Gill, 2019a). From the collection of 28 exemplars used in Grabarczyk & Gill, 2019a, 16 were randomly selected for use in the present study (two playbacks were used twice, one in 2016 and one in 2017).…”

“…Therefore, to mimic natural singing patterns, a single song type was repeated every 15 s for 10 min, similar to typical rates of singing (Grabarczyk & Gill, 2019a). From the collection of 28 exemplars used in Grabarczyk & Gill, 2019a, 16 were randomly selected for use in the present study (two playbacks were used twice, one in 2016 and one in 2017). For noise playbacks, we created a pink noise signal in Avisoft SASLab Pro v5.2 (R. Specht, Glienicke/Nordbahn, Germany).…”

“…Male house wren song consists of two parts, a low‐amplitude introduction section that is structured for short‐distance transmission, followed by the high‐amplitude terminal section capable of transmitting beyond the typical boundaries of a male's territory under low‐noise conditions (Figure 1, Video S1; Grabarczyk & Gill, 2019a). On recordings, we used Avisoft to mark the terminal section of all songs recorded for each male with section labels on the spectrogram window (Flat top window, 512 FFT length, 93.75% overlap, 0.725 ms time resolution).…”

Singing under glass: rapid effects of anthropogenic habitat modification on song and response behaviours in an isolated house sparrow Passer domesticus population

“…Fewer studies have investigated the perception and response behaviours of target receivers to songs from different noise‐habitats (Mockford and Marshall , Ripmeester et al , Luther and Magnotti , LaZerte et al ). However, recent work has shown that while birds do not necessarily respond less strongly to songs in elevated noise‐habitats (Phillips and Derryberry , Grabarczyk and Gill ) they often respond less strongly to songs from habitats with noise levels that differ from their own habitat (Mockford and Marshall , Luther and Derryberry ).…”