Female House Wrens may Use a Low‐Amplitude Call as an Aggressive Signal

Abstract

The majority of work on aggressive signaling has focused on male–male contests. Although females in many species compete over important resources, female signals are understudied. In house wrens (Troglodytes aedon), females compete with other females to protect nesting cavities and eggs. We suggest that a high‐pitched, low‐amplitude call, hereafter abbreviated as ‘HI’, may be an aggressive signal used by female house wrens. Using playback of simulated female intruders, we found that females used HI calls significantly more often during playback of female house wrens compared to playback of heterospecifics. Additionally, HI calls were given significantly more often in the minute preceding physical attack. In comparison, song rates did not predict future attacks. Finally, we present pilot data that suggest listening females may respond more aggressively to female playback containing HI calls compared to playback containing only songs. This suggests the reliability of HI calls could be maintained by a receiver retaliation rule. HI calls bear a striking resemblance to the low‐amplitude songs of many male songbirds, in terms of both acoustic structure and social context. This is one of the few reports of a putative low‐amplitude aggressive signal in a female songbird. However, the nature of female competition may make low‐amplitude signaling an underappreciated signaling form in female animals.

Female bird song rates do not covary with population density in a North American species

“…This difference could be an honest signal of aggression that results from the higher abundance of canyon wrens in Arizona, or it may be a non‐functional geographic difference that results from genetic or cultural drift (Lynch, 1996). If the difference is functional, low‐frequency songs might indicate higher aggression in Arizona, as they do in males and females of other species (Benedict et al, 2012; Geberzahn et al, 2010; Krieg & Burnett, 2017). Future playback experiments using song stimuli with different frequencies could test for this type of aggressive functionality.…”

“…In temperate North America, house wrens ( Troglodytedes aedon ), winter wrens ( Troglodytes hiemalis ), cactus wrens ( Camphylorhynchus brunneicapillus ), and canyon wrens ( Catherpes mexicanus ) all have female songs that are used less frequently than male song (Billerman et al, 2020; Odom & Benedict, 2018). Despite that, some have very well‐described functions; house and canyon wren females use songs to defend territories against conspecifics, particularly other females (Hathcock & Benedict, 2018; Krieg & Burnett, 2017; Krieg & Getty, 2016). Canyon wren female songs are distinct in form from male songs, creating the possibility for conspicuous sex‐specific signaling (Benedict et al, 2013; Figure 1).…”

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

“…Females produce a variety of signal types, but overall sing at lower rates than males (Johnson & Kermott, 1990). Female wrens sing to coordinate with breeding partners during early stages of breeding, including occasionally during incubation (Johnson & Kermott, 1990), and give high‐frequency, low‐amplitude signals in response to territorial intruders of both sexes (Krieg & Burnett, 2017; Krieg & Getty, 2016). Consequently, noise pollution on territories may affect both within‐pair and among‐neighbor signaling interactions.…”

Anthropogenic noise, song, and territorial aggression in southern house wrens

“…The experiments have three consecutive stages: pre‐playback, playback, and post‐playback (Cramer 2013a, Krieg and Burnett 2017). The duration of the pre‐playback stage varied from 41 s to 2 min (mean = 100.5 s) before the playback of lure or song stimulus (when there was no lure playback).…”