Female song rates in response to simulated intruder are positively related to reproductive success

Abstract

Bird song is well studied in males as a sexually selected behavior. However, although song is also common among females, it is infrequently examined and poorly understood. Research suggests that song is often used as a resource defense behavior and is important in female-female competition for limited resources, e.g., mates and territories. If so, song should be positively related to fitness and related to other resource defense behaviors, but this possibility has rarely been explored. Here we examine fitness estimates in relation to spontaneous song rates and song rates in response to a simulated intruder (playback), in the superb fairy-wren (Malurus cyaneus), a cooperatively breeding songbird. We also determine how song rates relate to other territorial defense behaviors. Song rate in response to playback, but not spontaneous song rate, was positively related to nest success and the number of fledglings produced by successful females. Further, response song rate was also correlated with other territorial defense behaviors (latency to respond and flights). This evidence supports the hypothesis that female song may be used in the context of female-female competition to improve access to limited reproductive resources, and suggests that song may provide direct fitness benefits.

Elaborate Mimetic Vocal Displays by Female Superb Lyrebirds

“…Like other species with female song, lyrebirds are non-migratory (Price, 2009;Logue and Hall, 2014), and do not experience the seasonal extremes associated with the absence of song in females of northern hemisphere species (Slater and Mann, 2004). Our findings support the idea that complex song by females is more commonly associated with intra-sexual competition for ecological resources than with mate attraction (Cooney and Cockburn, 1995;Hall and Peters, 2008;Illes and Yunes-Jimenez, 2009;Cain et al, 2015, see also Tobias et al, 2012, but contradict suggestions of an association with convergent sex roles (Slater and Mann, 2004). Indeed, our study suggests that elaborate female vocal displays can evolve even in species with strong selection for male extravagance.…”

“…Identifying the ecological and life-history correlates of female song requires detailed study of song, particularly in species that diverged closest to the ancestral node (Odom et al, 2014). At present, little is known about female song in other early diverging species, with the exception of the Maluridae (Cooney and Cockburn, 1995;Hall and Peters, 2008;ColombelliNégrel et al, 2010;Dowling and Webster, 2013;Cain et al, 2015). Therefore, it is not yet clear what aspects of song in lyrebirds have been retained since their ancestor diverged from the main branch of the oscines, and what features have since evolved.…”

Female Song Rate and Structure Predict Reproductive Success in a Socially Monogamous Bird

“…This contrasts somewhat with other studies where female territorial defense behavior in response to a simulated female intruder (but not spontaneous song), predicts reproductive success (Cain et al, 2015), and where higher rates of female song at the nest increases predation risk (Kleindorfer et al, 2016). It is known that female song in bellbirds has an important role in female competition (Brunton et al, 2008b) and here we found that higher female song rate during both incubation and chick-rearing were positively correlated with male provisioning rate (Figure 2).…”

“…If characteristics of female song reflect competitive ability, then we predict an association between female song rate and reproductive success and a positive association between aspects of song performance and female fitness. To our knowledge, just one study has examined female song rates and fitness (Cain et al, 2015), and it found a positive relationship between defense responses to song playbacks during territory establishment and the probability of successful nesting. No study has yet examined how female song complexity and song rate during breeding relates to reproductive success.…”

Female in-nest chatter song increases predation

“…However, there is growing focus on the occurrence [3] and functions of female song [4], mostly using the perspective of life history and social selection theory. Female song is widespread and ancestral in songbirds, and females sing across 71% of extant species spanning 32 families [5].…”