Male Singing Behaviour Research Articles

Robust autumn social attributes predict spring courtship skills in juvenile female brown-headed cowbirds, Molothrus ater

Individuals often show predictable variation in social tendencies over time and across contexts. In species that rely on social interaction for the development of courtship behaviours, predictable variation in juvenile social behaviour may influence the ontogeny of courtship skills by exposing young individuals to different levels of contact with conspecifics. During the autumn and winter, brown-headed cowbirds utilize a social display known as the head-down to facilitate close social interaction with others. In this study we investigated whether head-downs rates are correlated across social contexts, and thus constitute a social temperament trait, and whether variation in head-down rates predicts subsequent courtship behaviour in juvenile cowbirds. During the autumn, we used a fission–fusion perturbation on a flock of juvenile females and males, and recorded the number of approaches and head-downs across social contexts. All individuals were then followed into the breeding season, where we recorded male singing behaviour, female chatter vocalization and consort status. We found that female head-down rates were correlated across contexts during the autumn, and that females that engaged in more head-down displays received more songs from males, responded to more songs with chatter vocalizations and were more likely to be in a consortship during the breeding season. As far as we know, this study presents the first demonstration that a social temperament trait can predict competent adult-like courtship behaviour in juvenile birds, and suggests that juvenile sociability may be an important developmental mechanism in the emergence of reproductive competence. ► We observed a flock of juvenile brown-headed cowbirds during autumn and spring of their first year. ► In autumn, we performed a fission–fusion flock perturbation to examine social behaviour across contexts. ► Females showed correlated rates of affiliative head-down displays across social contexts in autumn. ► Autumn head-down rates predicted spring courtship skills in females. ► Individual social attributes may shape the development of courtship skills in female birds.

Eavesdropping parasitoids do not cause the evolution of less conspicuous signalling behaviour in a field cricket

Males of many species produce conspicuous mating signals to attract females, but these signals can also attract eavesdropping predators and parasites. Males are thus expected to evolve signalling behaviours that balance the sexual selection benefits and the natural selection costs. In the variable field cricket, Gryllus lineaticeps, males sing to attract females, but these songs also attract the lethal parasitoid fly Ormia ochracea. The flies use male crickets as hosts for their larvae, primarily search for hosts during a 2 h period following sunset and prefer the same song types as female crickets. We tested whether males from high-risk populations reduce the risk of parasitism by singing less frequently or by shifting their singing activity to a time of the night when the risk of parasitism is low. We compared male singing activity and its temporal pattern between six high-risk and six low-risk populations that were reared in a common environment. There was no effect of parasitism risk on either total male singing activity or the temporal pattern of male singing activity. Males from high-risk populations thus sang as frequently as males from low-risk populations. These results suggest that sexual selection on male singing behaviour may be substantially stronger in high-risk populations than in low-risk populations. It is possible that other traits may have evolved to reduce parasitism risk without compromising mate attraction.

Individual differences and repeatability in vocal production: stress-induced calling exposes a songbird's personality

Recent research in songbirds has demonstrated that male singing behavior varies systematically with personality traits such as exploration and risk taking. Here we examine whether the production of bird calls, in addition to bird songs, is repeatable and related to exploratory behavior, using the black-capped chickadee (Poecile atricapillus) as a model. We assessed the exploratory behavior of individual birds in a novel environment task. We then recorded the vocalizations and accompanying motor behavior of both male and female chickadees, over the course of several days, in two different contexts: a control condition with no playback and a stressful condition where chick-a-dee mobbing calls were played to individual birds. We found that several vocalizations and behaviors were repeatable within both a control and a stressful context, and across contexts. While there was no relationship between vocal output and exploratory behavior in the control context, production of alarm and chick-a-dee calls in the stressful condition was positively associated with exploratory behavior. These findings are important because they show that bird calls, in addition to bird song, are an aspect of personality, in that calls are consistent both within and across contexts, and covary with other personality measures (exploration).

The effects of estradiol on 17β-hydroxysteroid dehydrogenase type IV and androgen receptor expression in the developing zebra finch song system

Recent work in zebra finches suggests that genes and hormones may act together to masculinize the brain. This study tested the effects of exogenous estradiol (E2) on 17β-hydroxysteroid dehydrogenase type IV (HSD17B4) and the co-localization of HSD17B4 and androgen receptor (AR) mRNA. We asked three primary questions: First, how does post-hatching E2 treatment affect HSD17B4 mRNA expression in males and females? Second, is this gene expressed in the same cells as AR. Third, if so does E2 modulate co-expression? Female finches implanted with 50 μg of E2 on the third day post-hatching showed a significant increase in the density of cells expressing HSD17B4 and AR in HVC at day 25. Co-localization of AR cells that also expressed HSD17B4 was high across groups (> 81%). We found significant sex differences in co-localization in both the HVC and Area X of control animals, with males showing a higher percentage of cells expressing AR mRNA that also expressed HSD17B4 in comparison to females. However, although E2 treatments significantly increased the number of cells expressing HSD17B4 mRNA and AR mRNA in the HVC of females, the percentage of HSD17B4 cells co-expressing AR was reduced in HVC and Area X in E2-treated animals. These results lend support to the hypothesis that genes and hormones may act in concert to modulate the sexually differentiation of the zebra finch song system. Further, the data suggest that a single hormonal mechanism cannot mimic the complex development of male singing behavior and associated song nuclei.

Long-term influence of simulated territorial intrusions on dawn and dusk singing in the Winter Wren: spring versus autumn

Males of many songbird species have peaks of singing activity at dawn and dusk. Singing during those twilight periods can function in territory proclamation, and males are suggested to adjust song output to the level of intruder pressure. We used song playback during the breeding season to simulate intrusions into territories of male Winter Wrens (Troglodytes troglodytes) shortly after dawn. We then compared male singing behaviour during the dawn and dusk chorus before and 1 day after the simulated intrusion. One day after the playback, male Wrens increased their song output before sunrise, which confirms our results from a previous study on dawn singing in autumn territories. At dusk, on the evening following the playback, males slightly increased song output after sunset, but singing activity at dusk was generally very low. We found no significant changes of song output after sunrise, before sunset, and between 2 days of control without playback. These results are consistent with the hypothesis that dawn and dusk singing is important for territory defence in spring. Unlike in autumn, however, increased singing in spring at dawn and dusk could also serve to defend other resources such as fertile mates or to strengthen the pair bond after a territorial challenge. In comparison with the results on autumnal singing, male Wrens started singing earlier at dawn during the breeding season, and they generally sang more songs at dawn and immediately after playback. The increase in absolute numbers of songs sung in the morning after playback seemed greater in spring than in autumn; however, the proportional increase relative to overall song output was similar in both seasons.

Reproductive Asynchrony and the Divergence of Hawaiian Crickets

AbstractAsynchrony in reproductive behavior may contribute to reproductive isolation among sympatric species. While the 38 cryptic species of the genus Laupala are primarily distinguished on the basis of variation in pulse rate of male calling songs, additional phenotypes, such as asynchrony in reproductive behavior, may contribute to reproductive isolation in this genus. Here we document similarities and differences in the diel timing of two reproductive behaviors, male singing activity and insemination events. Asynchrony in the diel timing of male singing behavior was observed between two sympatric species, Laupala cerasina and Laupala paranigra, in the field. An interpopulational comparison within L. cerasina did not reveal variation in diel behavior patterns of singing between two locations. Asynchrony in the timing of copulation and sperm transfer between L. cerasina and L. paranigra was documented in the laboratory. The observed pattern of asynchrony in both the field and laboratory could have arisen in a number of ways. One possibility is that species diverged in sympatry because of interspecific interactions, producing a pattern of reproductive character displacement. Alternatively, the observed asynchrony in reproductive behavior may have played a role in the process of community assembly within this recently diverged cricket genus. The presence of interspecific variation and the absence of intraspecific variation revealed by our study do not support a pattern of reproductive character displacement for diel reproductive behavior, suggesting that the differences seen between species were not caused by recent species interactions.

Dawn singing reflects past territorial challenges in the winter wren

Territory defence can be seen as a dynamic long-term process that involves some learning. For example, a resident may adjust its territory proclamation behaviour depending on its prior experience with territorial intruders. We investigated whether short territorial challenges could have long-lasting effects on the singing behaviour of male birds. We used song playbacks to simulate intrusions into autumn territories of male winter wrens, Troglodytes troglodytes, shortly after dawn and compared male singing behaviour immediately before and 1 day after the simulated intrusion. As in many other bird species, unchallenged male wrens tended to sing more songs before than after sunrise. One day after a simulated intrusion, however, this pattern was much more pronounced. Males significantly increased their song output before sunrise, but maintained or even reduced song output after sunrise. This result suggests that dawn singing before sunrise is particularly important for territory defence. On the day after the intrusion, the start of dawn singing varied less between males, although the average starting time remained the same. Our findings suggest that a territorial challenge can influence singing behaviour almost 24 h after the intrusion. The amount and timing of birdsong, as a preventive territorial proclamation, can thus be adjusted to past territorial challenges.

Pulses, patterns and paths: neurobiology of acoustic behaviour in crickets

Crickets use acoustic communication for pair formation. Males sing with rhythmical movements of their wings and the mute females approach the singing males by phonotaxis. Females walking on a trackball rapidly steer towards single sound pulses when exposed to split-song paradigms. Their walking path emerges from consecutive reactive steering responses, which show no temporal selectivity. Temporal pattern recognition is tuned to the species-specific syllable rate and gradually changes the gain of auditory steering. If pattern recognition is based on instantaneous discharge rate coding, then the tuning to the species-specific song pattern may already be present at the level of thoracic interneurons. During the processing of song patterns, changes in cytosolic Ca(2+ )concentrations occur in phase with the chirp rhythm in the local auditory interneurone. Male singing behaviour is controlled by command neurons descending from the brain. The neuropil controlling singing behaviour is located in the anterior protocerebrum next to the mushroom bodies. Singing behaviour is released by injection of cholinergic agonists and inhibited by gamma-butyric acid (GABA). During singing, the sensitivity of the peripheral auditory system remains unchanged but a corollary discharge inhibits auditory processing in afferents and interneurons within the prothoracic auditory neuropil and prevents the auditory neurons from desensitisation.

Male singing behaviour and female presence in the territory in whitethroats Sylvia communis

Unmated male songbirds usually change their vocal behaviour when females enter their territories. Either the males court the females by changing the rate or pattern with which their normal long-ranging full songs are emitted, or they shift to special displays and long- or short-ranging vocalisations. In this study we quantified how female presence and behaviour affect the singing behaviour of male whitethroats. In the presence of a female the male frequently performed song flights, maybe to locate the female before it was courted, with sequences of diving-song displays. The courtship was interrupted by periods of perch songs. Female dscharp calls and short movements made the males initiate or resume courtship, whereas short horizontal jumps made the males intensify their courtship. Overall, the males changed their dual-function song activity in females' presence by emitting fewer perch songs and more flight songs. The quiet diving songs were only emitted during direct courtship of a female. The song types emitted immediately before, during, and after courtship are all highly variable, thus allowing for a quick assessment of the male's song repertoire. The courtship was also interrupted by periods of male woid calling, a call that is known to have a deterring effect on rival males. Bouts of woid calls were usually followed by song flights, again probably to locate the female that might have moved out of sight, or maybe to locate potential rival intruders. The latter was supported by an increased intrusion rate during female presence.

Convergent song preferences between female field crickets and acoustically orienting parasitoid flies

Traits that increase the attractiveness of males to females often make them more conspicuous to predators. In the field cricket (Gryllus lineaticeps), males are attacked by parasitoid tachinid flies (Ormia ochracea) that locate males through their calls. Female flies larviposit on crickets and the larvae burrow into and feed on the cricket, killing the cricket upon emergence. To determine whether traits preferred by females increase a male's risk of attracting a predator, I examined the effect of variation in male singing behavior on mate and predator attraction. Both female crickets and female flies preferred male calling songs with higher chirp rates, longer chirp durations, and higher chirp amplitudes. In addition, both female crickets and female flies preferred male calling songs with higher chirp rates and longer chirp durations, even when these songs were of lower amplitude. These results suggest that sexual selection by female choice will favor the evolution of higher chirp rates and longer chirp durations. However, call types that increase a male's attractiveness to females also appear to increase a male's risk of attracting parasitoids. Sexual and natural selection appear to have opposing effects on the evolution of male singing behavior in this species.[Behav Ecol 7: 279-285 (1996)]