Male House Wrens Research Articles

Song structure of male Northern House Wrens and patterns of song production and delivery across the nesting cycle

Song structure of male Northern House Wrens and patterns of song production and delivery across the nesting cycle

Song structure of male Northern House Wrens and patterns of song production and delivery across the nesting cycle

Song structure of male Northern House Wrens and patterns of song production and delivery across the nesting cycle

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

AbstractVocal signals mediate social relationships, and among networks of territorial animals, information is often shared via broadcast vocalizations. Anthropogenic noise may disrupt communication among individuals within networks, as animals change the way they vocalize in noise. Furthermore, constraints on signal transmission, including frequency masking and distance, may affect information exchange following a disruption in social networks. We tested the hypothesis that signaling interactions within networks of breeding male and female house wrens (Troglodytes aedon) depend on distance, ambient noise, and receiver nesting stage. We used playback experiments to simulate territorial intrusions with and without noise playbacks on the territories of established males and simultaneously recorded the vocal responses of neighbors. To examine whether intrusions impacted interactions between males, we used randomization tests to determine whether treatment, distance, noise, or nesting stage affected vocal coordination between challenged and neighboring males. We also quantified singing patterns to explore whether intrusions on territories of challenged males affected singing by males and females on neighboring territories. Males sang at the lowest rates and were less likely to overlap songs with the challenged male when their partner was laying, compared to males during early and late nesting stages. Noise and distance did not affect vocal coordination or male singing rates. Fewer females sang during the intruder‐only treatment compared to the control and intrusions with noise. Added noise in the territories of challenged males may have masked signals, and as a result, females only changed their behavior during the intruder‐only treatment. Our results suggest that the fertility of breeding partners may be more important to males than short‐term changes on rival male territories. Elevated noise did little to alter male responses to threats within networks. Females appeared to eavesdrop on interactions involving neighboring males, but noise may have prevented detection of their interactions.

Social context and noise affect within and between male song adjustments in a common passerine

AbstractAcross populations, animals that inhabit areas with high anthropogenic noise produce vocalizations that differ from those inhabiting less noisy environments. Such patterns may be due to individuals rapidly adjusting their songs in response to changing noise, but individual variation is seldom explored. Therefore, we tested the hypothesis that male house wrens (Troglodytes aedon) immediately adjust their songs according to changing noise and that social context further modifies responses. We recorded songs, quantified noise, and defined social context within pairs as female fertile status and between males as number of conspecific neighbors. We used a reaction-norm approach to compare song trait intercepts (between-male effects) and slopes (within-male effects) as a function of noise. Individuals immediately adjusted song duration in response to changing noise. How they achieved adjustments varied: some sang shorter and others longer songs with greater noise, and individuals varied in the extent to which they adjusted song duration. Variation in song duration could be affected by competition as between-male noise levels interacted with number of neighbors to affect syllable duration. Neither within- nor between-male noise effects were detected for frequency traits. Rather, males with fertile mates sang lower-frequency songs and increased peak frequency with more neighbors. Among males, social context but not noise affected song frequency, whereas temporal structure varied between and within individuals depending on noise and social factors. Not all males adjusted signals the same way in response to noise, and selection could favor different levels of variation according to noise.

Anthropogenic noise and social context affect vocal plasticity in a common urban passerine

Vocal communication shapes animal social networks, connecting individuals over space and time via information, facilitating mate attraction and resource defense. Despite evidence that both the physical and social environment affect signaling behavior, few studies consider variation in individual responses to environmental change within a social context. We test the hypothesis that male House wrens (Troglodytes aedon) plastically adjust songs and song sections structured for short-and long-distance transmission in response to change in their immediate noise environment, but that both social context and noise affect singing patterns at the population level. We recorded paired males prior to clutch initiation, quantified ambient noise in the moments before singing, and define social context within pairs as female fertile status and between males as number of conspecific neighbors. Among males, adjustment patterns varied depending on transmission properties, social context, and noise. In response to immediate change in noise, males plastically adjust some, but not all, song traits. We show that not all males adjust signals in the same way, and that consideration of social context and signal function are crucial for understanding variation in signal structure. This is an essential step towards understanding how both the social and physical environment may drive selection on vocalizations.

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

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.

Social factors, not anthropogenic noise or artificial light, influence onset of dawn singing in a common songbird

AbstractWith worldwide increases in artificial light and anthropogenic noise, understanding how these pollutants influence animals allows us to better mitigate potential negative effects. Both light and noise affect the timing of daily activities, including the onset of dawn song in birds, yet the influence of these pollutants compared with social factors that also influence song onset remains unknown. We investigated the onset of dawn song, testing hypotheses aimed at understanding the influences of light and noise pollution as well as male competition, pairing status, and breeding stage on timing of dawn singing by male House Wrens (Troglodytes aedon). Overall, models with social factors fit song onset data better than models with abiotic factors of noise and sky glow, and the highest ranking model included nesting stage, number of male neighbors, and temperature. Males began singing earlier when they were building nests and when mates were fertile than during later nesting stages. Males also sang earlier as the number of male neighbors increased. The timing of dawn song by male House Wrens appeared unaffected by day-to-day variation in light and noise pollution, with social factors having larger effects on the onset of daily behavior in this species.

Perceived threat to paternity reduces likelihood of paternal provisioning in house wrens.

Biparental care is a critical and, occasionally, unequally shared obligation that ensures that young survive to maturity. Such care may be complicated in systems in which one parent, typically the male, is unsure of his genetic relatedness to the young. Males may reduce paternal provisioning when full paternity is not assured, as occurs in mating systems in which females engage in extrapair copulations. Moreover, other factors independent of extrapair matings, such as male personality traits, likely also affect the level of paternal care. In this study, we determined the effect of a paternity threat event (i.e., a conspecific or a heterospecific territory intrusion) and male personality (i.e., the level of aggressiveness) on provisioning effort by male house wrens (Troglodytes aedon). Males were more likely to attack a conspecific intruder than a heterospecific intruder. Males that were exposed to a conspecific intruder were less likely to provision young at all. Of those males that did feed the young in their nest, male aggressiveness did not relate to feeding effort. These findings suggest that the likelihood of paternal care is reduced by perceived threats to paternity but that the costs of not feeding potentially multisired young are high and feeding efforts are unrelated to male personality.

When to change your tune? Unpaired and paired male house wrens respond differently to anthropogenic noise

In response to anthropogenic noise, many bird species adjust their song frequency, presumably to optimize song transmission and overcome noise masking. But the costs of song adjustments may outweigh the benefits during different stages of breeding, depending on the locations of potential receivers. Selection might favor unpaired males to alter their songs because they sing to attract females that may be widely dispersed, whereas paired males might not if mates and neighbors are primary receivers of their song. We hypothesized male house wrens (Troglodytes aedon) respond differently to noise depending on their pairing status. To test our hypothesis we synthesized pink noise, which mimics anthropogenic noise, and played it at three intensities in territories of paired and unpaired focal males. We recorded their songs and analyzed whether song structure varied with pairing status and noise treatment. To validate our study design, we tested whether noise playback affected measurement of spectral song traits and changed noise levels within territories of focal males. Consistent with our predictions, unpaired males sang differently than paired males, giving longer songs at higher rates. Contrary to predictions, paired males changed their songs by increasing peak frequency during high intensity noise playback, whereas unpaired males did not. If adjusting song frequency in noise is beneficial for long-distance communication we would have expected unpaired males to change their songs in response to noise. By adjusting song frequency, paired males reduce masking and produce a song that is easier to hear. However, if females prefer low frequency song, then unpaired males may be constrained by female preference. Alternatively, if noise adjustments are learned and vary with experience or quality, unpaired males in our study population may be younger, less experienced, or lower quality males.

Female house wrens value the nest cavity more than exclusive access to males during conflicts with female intruders

AbstractIndividuals should fight hardest when they stand to lose the most. Whereas males frequently compete for fertile females, females more often compete for high quality males, male care, or resources required to breed. We asked whether established, territorial female house wrens (Troglodytes aedon) challenged by simulated female intruders fight as if they place more value on retaining (1) their nesting cavity or (2) exclusive access to other benefits offered by males. We randomly assigned house wren pairs to receive one or three nest boxes and then assayed female aggression. The relative costs to losing differed between box treatments. For one-box females, the risk of losing the cavity and territory was higher. For three-box females, the risk of losing the cavity may be lower because intruders may be able to settle as secondary females in the supplemental boxes. In this situation, females would lose exclusive access to males and their territories but would still retain the male’s assistance rearing offspring since male house wrens favour their oldest brood. We found that one-box females were significantly more aggressive. This response may be adaptive, as females that switched territories between broods were significantly more likely to lose their entire nest prior to hatching than females that retained the same territory. We interpret our results to mean that female house wrens value the nest cavity more than other benefits from exclusive access to males and their territories. This work contributes to a body of evidence that females often compete for resources required to breed.

House Wren (Troglodytes aedon) provisions nestlings of Northern Cardinal (Cardinalis cardinalis)

ABSTRACT Cases of interspecific parental care are rare and pose an evolutionary puzzle. We report a male House Wren (Troglodytes aedon) regularly provisioning Northern Cardinal (Cardinalis cardinalis) nestlings in a nest located near his own. The male wren continued to provision the cardinal nestlings after his own nestlings hatched, and provisioned the cardinal nestlings more than his own nestlings during the time that their nestling periods overlapped. The adult cardinals also provisioned their own nestlings. After the cardinal chicks fledged, the male wren provisioned only his own nestlings. This is most likely a case of nonadaptive misdirection of parental behavior on the part of the wren. That the wren provisioned both nests while both were in the nestling stage, but provisioned only the wren chicks as fledglings, may suggest that kin recognition in House Wrens is mutable rather than fixed. However, this behavior is also congruent with observations of polygynous male House Wrens transferring parental...

Male House Wrens provide more parental provisioning to nests with a brighter artificial egg

ABSTRACT Recent research suggests that male birds could use eggshell color as a signal of the quality of their offspring to decide how much parental care to provide. Previous studies have found support for this hypothesis in bird species that lay blue eggs, but it has not been as thoroughly tested in species that lay brown eggs, such as House Wrens (Troglodytes aedon). In this species, brighter eggs are associated with greater female investment. We tested whether males responded to this potential cue. We experimentally manipulated clutch brightness by randomly adding a white or brown plastic egg to nests during incubation and then compared the male provisioning rates between those two treatment groups. Male House Wrens whose nests had received a white egg provisioned their nestlings at significantly higher rates than males whose nests had received a brown egg. These results suggest that male House Wrens pay attention to female investment when deciding how much energy to spend on nestling provisioning. Thi...

Aggressive displays by male House Wrens are composed of multiple components that predict attack

Aggressive signals should predict whether the sender of the signal will attack the receiver, yet this criterion has been little studied. We conducted experiments with male House Wrens (Troglodytes aedon) in north-central Illinois in 2009 to test the hypothesis that rates of song delivery and wing-quivering (putative aggressive signals) signal aggressive intent. We simulated a conspecific territorial intrusion by combining playback of male song with a male taxidermic mount, predicting that these signals would be related to a male's likelihood of attacking a conspecific. All males (N = 37) sang in response to the intrusion. Males attacking the mount sang at significantly higher rates and performed significantly more wing quivers than males that did not attack. In addition, all males that attacked the mount performed wing quivers (9/9), whereas only 53.6% (15/28) of males that did not attack did so (P = 0.011). Our results are consistent with the hypothesis that both song and wing quivering indicate a signaler's aggressive intent and that these signals are likely components of a multi-component, hierarchical display. Los despliegues agresivos de la Ratona Común están compuestos por múltiples componentes que predicen el ataque Las señales de agresividad deberían predecir si el emisor de la señal atacará al receptor, aún así este criterio ha sido poco estudiado. Realizamos experimentos en la Ratona Común (Troglodytes aedon) en el centro norte de Illinois en 2009 a fin de poner a prueba la hipótesis de que la tasa de emisión del canto y de temblor de alas (señales putativas de agresividad) señalizan la intención agresiva. Simulamos la intrusión territorial de un conespecífico al combinar playback de un macho con un ejemplar taxidermizado, prediciendo que estas señales estarían relacionadas a la probabilidad de un macho de atacar a un conespecífico. Todos los macho (N = 37) cantaron en respuesta a la intrusión. Los machos que atacaron el ejemplar taxidermizado realizaron más temblores de alas que los machos que no atacaron. Adicionalmente, todos los machos que atacaron realizaron temblores de alas (9/9), mientras que solo el 53.6% (15/28) de los machos que no atacaron lo realizó. Nuestros resultados son consistentes con la hipótesis que tanto el canto como el temblor de alas indican la intención agresiva del emisor, y que estas señales probablemente sean componentes de un despliegue jerárquico y de múltiples componentes.

Are Androgens Related to Aggression in House Wrens?

AbstractElevated circulating testosterone levels are hypothesized to allow male animals to direct resources into territorial and mating behaviors at the expense of reducing paternal care of offspring. For this hypothesis to apply, testosterone must facilitate territorial/mating behaviors and have antagonistic effects on paternal care, but this pattern has only been supported in some, not all, species. I tested whether androgens correlate with aggressive behaviors in male house wrens ( Troglodytes aedon), a double‐brooded species where paternal and aggressive behaviors overlap temporally. House wrens may therefore benefit from having a hormonal mechanism that allows males to rapidly change behavioral states. However, I found no evidence that androgens (testosterone and 5α‐dihydrotestosterone) relate to aggression in house wrens: Androgens did not increase in response to playback, and endogenous‐circulating androgens were not correlated with how aggressively males responded to those playbacks. Moreover, androgen levels were low during the pre‐breeding stage of the second brood, when many males establish new territories and attract new mates. This study adds to a growing body of the literature suggesting that the relationship between circulating androgens and aggressive behavior is more complex than originally thought.

Aggressiveness, Boldness and Parental Food Provisioning in Male House Wrens (Troglodytes aedon)

AbstractBehavioural syndromes have been identified in a large number of species, yet our understanding of them in an ecological context remains poor. Specifically, there are few data that relate behavioural syndromes to other biologically important behaviours and, ultimately, to reproductive success. In this field study, we examined the aggressiveness and boldness of free‐living male house wrens (Troglodytes aedon) and found a statistically significant positive relationship between these two behaviours (i.e. a behavioural syndrome). When we examined the two axes of this behavioural syndrome in relation to the male's share of provisioning, we found a negative relation between a male's aggressiveness and his provisioning rate, but no relationship between male boldness and provisioning behaviour. These differences in provisioning behaviour among males with different levels of aggression may reflect differences in reproductive strategies or different life‐history trade‐offs among males. Moreover, these results indicate that while some behavioural traits may be correlated, this does not mean that traits that compose the behavioural syndrome cannot evolve independently of one another.

Reproductive allocation in female house wrens is not influenced by experimentally altered male attractiveness

The differential allocation hypothesis proposes that females mated to attractive males should invest more resources in their offspring than those mated to less-attractive males, whereas the compensation hypothesis posits that females mated to less-attractive males should invest more resources in their offspring to compensate for lower-quality young. We tested these hypotheses by manipulating attractiveness of male house wrens (Troglodytes aedon) prior to female arrival by adding extra nest sites to territories of some males while leaving control males with only a single nest site. Females laid their eggs sooner in the nests of attractive males, and attractive males were more likely to retain their territory over successive broods and were marginally more likely to obtain a mate for a second brood later in the season than were control males, thereby confirming the effect of our manipulation on male attractiveness. Experimentally enhanced attractiveness also led to increased hematocrit in males. However, there were no consistent differences in the number, size, or quality of eggs laid by females mated to attractive and control males, nor were there any differences in the size, health state, or immune function of nestlings produced from these eggs. There was also no effect of treatment on the number of nestlings surviving to fledging. Collectively, these results are inconsistent with both the differential allocation hypothesis and the compensation hypothesis. Future studies should consider the possibility that the criteria used by females in selecting a mate may vary temporally and be more flexible than generally thought.

Male quality influences male provisioning in house wrens independent of attractiveness

Female reproductive investment can vary according to their mate’s attractiveness, and males may differentially invest according to their own attractiveness. Thus, when studying female parental investment, male investment must also be considered. We tested the hypothesis that the attractiveness of male house wrens (Troglodytes aedon) influences their investment independent of their own intrinsic quality by manipulating the number of nest sites (one ¼ control; 4 ¼ attractive) in each male’s territory. Treatments (attractive or control) were applied prior to (natural state) or after (imposed state) male settlement, and male investment was determined twice during the nestling stage by the number of trips males made to the nest to provision their nestlings. Males that settled in the attractive territories were significantly older than those that settled in control territories in the natural state. There was a significant interaction effect between state and treatment on male provisioning. Provisioning rates of attractive and control males in the imposed state did not differ, but attractive males in the natural state provisioned at a lower rate than control males late in the nestling stage. Thus, provisioning by males is influenced more by their intrinsic quality than their attractiveness. Key words: attractiveness, house wren, mate choice, provisioning, reproductive allocation, Troglodytes aedon. [Behav Ecol]

Addition of arthropod cocoons to house wren nests is correlated with delayed pairing

Males in the cavity-nesting house wren (Troglodytes aedon) frequently add arthropod cocoons to their nests during building, possibly as an ornamental cue for female choice. We tested this hypothesis by comparing the time to pairing for males that did and did not add cocoons to their nests and for males in whose nests we manipulated the number of cocoons prior to pairing. We also tested the hypothesis that females acquire fitness-related benefits by selecting mates based on their use of cocoons. The use of cocoons by males was not consistently related to habitat, but the number of cocoons added per nest increased during the course of the breeding season. Contrary to prediction, the time to pairing for males adding cocoons was significantly longer than that for males without cocoons in their nests at both unmanipulated and experimental nests. There was also no consistent fitness-related benefit for females related to the use of cocoons by their mates. Therefore, we conclude that females did not prefer males that added cocoons to their nests, and that the increased time to pairing for males that add cocoons likely results in fitness-related costs brought about by delayed breeding. Nonetheless, male house wrens routinely use cocoons, and why they do so remains unknown.

Males achieve greater reproductive success through multiple broods than through extrapair mating in house wrens

In polygynous species, it is unclear whether extrapair matings provide a better reproductive payoff to males than additional social mates. Male house wrens, Troglodytes aedon, show three types of social mating behaviour: single-brooded monogamy, sequential monogamy (two broods) and polygyny. Thus, male reproductive success can vary depending on the number of mates, the number of broods and the number of extrapair fertilizations. We used microsatellite markers to determine the realized reproductive success (total number of young sired from both within-pair and extrapair fertilizations) of males in these three categories. We found that polygynous males were more likely to be cuckolded than monogamous males; however, half of the polygynous males had a third brood, which resulted in similar reproductive success for sequentially monogamous and polygynous males. Despite the paternity gained from extrapair fertilizations by single-brooded males, males were more successful when they produced multiple broods during a season, either sequentially (monogamy) or simultaneously (polygyny). In our population, multibrooded males were more likely to have prior breeding experience and arrived earlier in the season, which provided a better opportunity to obtain more than one brood and, thus, produce more young.

Increased cuckoldry as a cost of breeding late for male house wrens (Troglodytes aedon)

One factor hypothesized to influence the reproductive behavior of individuals is the degree to which reproductive efforts are synchronized with others in the population. We asked whether the timing of a pair’s breeding cycle, relative to cycles of pairs on neighboring territories, affected rates of extrapair mating over 2 years in a Wyoming population of house wrens (Troglodytes aedon). Extrapair young (identified using 5 microsatellite loci) occurred in 74% of nests of 19 pairs whose cycles began later than cycles of one or more neighbors compared to only 26% of nests of 27 pairs whose cycles began earlier than, or simultaneously with, cycles of all neighbors. Extrapair offspring occurred in 65% of 17 nests belonging to males who initially settled and began nesting early relative to neighbors but who were forced to renest late after we removed their first mates. Rates of cuckoldry were not significantly different for forced-late and naturally late males. Our experimental approach controlled for possible effects of male quality, clearly demonstrating an effect of timing of breeding on extrapair mating activity. Key words: breeding synchrony, extrapair mating, house wrens, Troglodytes aedon. [Behav Ecol 13:670–675 (2002)]