Troglodytes Aedon Research Articles

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.

Continent-wide patterns of divergence in acoustic and morphological traits in the House Wren species complex

ABSTRACT Phenotypic traits are important for assessing differences between populations, especially in groups with poorly resolved taxonomy. One such group, the House Wren complex, presents extensive taxonomic controversy and is thought to comprise many independent evolutionary units. Although the songs and morphological features of House Wrens (Troglodytes aedon) show extensive variation, differences between populations have not been quantified. We assessed variation in acoustic and morphometric traits within this complex and compared patterns of variation with currently recognized subspecies boundaries. First, we compared songs and morphology among eight recognized subspecies (T. a. aedon, T. a. parkmanii, T. a. cahooni, T. a. brunneicollis, T. a. nitidus, T. a. musculus, T. a. beani, and T. a. rufescens), controlling for significant effects of latitude. Second, we used variation in male song, a trait with an important role in mate choice and male–male competition, to assess divergence among subspecies. ...

Condition-dependent sex difference in nestling House Wren (Troglodytes aedon) response to phytohaemagglutinin injection

Adult male and female birds typically respond differently to immunological challenges, but whether this difference is present in altricial nestlings is not well-documented. Furthermore, the timing of the development of different axes of the immune system might vary in nestlings and also be affected by differences in condition and health state. We tested for sex-related differences in the immune response of nestling House Wrens (Troglodytes aedon Vieillot, 1809) to the injection of phytohaemagglutinin (PHA) and in the bacteria-killing capacity of their plasma. Based on prior work, we predicted that if there were sex-related differences in immune responsiveness, they would most likely occur when the sexes differed in some measure of condition or health state. Female nestlings had a stronger response to the injection of PHA than males in the one of three breeding seasons in which the condition of nestling females exceeded that of males, suggesting that the response to PHA injection is condition-dependent rather than sex-dependent. The sexes, however, did not differ in bactericidal activity, suggesting that different axes of the immune system may not be affected to the same degree by differences in sex or in condition.

Sexual differences in risk-taking behaviour of the Southern house wren during the nestling rearing stage

When faced with a predator near the nest, breeding birds faced a dilemma: to continue providing parental care to their offspring exposing themselves to risk or to desert the nest for a brief period of time, exposing their offspring to harm due to the suspension of parental brooding and feeding. In this study, we analysed the response of nesting Southern house wrens (Troglodytes aedon musculus) to a predator model placed near the nest. The experiment was performed in 56 nests when nestling were 3–4 or 10–12 days old. The model (a plastic decoy of the Great Horned Owl Bubo virginianus) was placed at 3 m from the nest. Parent risk-taking was measured as the time elapsed for males and females to resume parental activities during the exposition to the model. We found that males and females delayed parental visits when exposed to the predator model, but females resumed them faster than males, irrespectively of the nesting stage. We also found that males refused to enter to the nest more frequently than females when exposed to the predator model. No effect of breeding experience or nesting stages was noted in the risk taking behaviour of adults. We suggest that sexual differences detected in this species reflect the higher ability of females to cope with the nestling needs and its lower lifetime expectancy.

Offspring sex ratio varies with clutch size for female house wrens induced to lay supernumerary eggs

Theory predicts that a mother’s ability to produce high-quality offspring should influence whether she produces sons or daughters. We tested this hypothesis in house wrens (Troglodytes aedon) using a within-clutch design in which we induced females to produce more eggs (8–10 eggs) than they normally would (6 or 7 eggs) to determine whether maternal effort and the allocation of resources to supernumerary eggs (those laid beyond the usual number) influence the offspring sex ratio. At the clutch level, we predicted that high-quality females, as defined by their ability to produce supernumerary eggs in response to egg removal, would overproduce sons relative to females treated the same way but producing fewer eggs. At the level of the egg, we predicted that supernumerary eggs would more likely contain daughters than sons. As predicted, females producing extralarge clutches overproduced sons and those producing smaller clutches produced relatively more daughters. Last-laid eggs were also more likely to contain daughters than earlier-laid eggs although there was no difference in the mass of eggs containing males and females. These results suggest that mothers adjust the sex of their offspring strategically to maximize fitness.

Song organization and variability in Northern House Wrens (Troglodytes aedon parkmanii) in western Canada

ABSTRACT. Detailed descriptions of song structure are critical to understanding the ontogeny, evolution, and function of bird song, particularly for species with large song repertoires. We provide a first detailed characterization of song organization and variability in a migratory population of House Wrens (Troglodytes aedon) breeding in western Canada, using a sample of 15,608 songs from 15 males. Males sang with high intensity in protracted bouts prior to pairing and often resumed high-intensity singing later in the breeding cycle to attract a second mate. The high-amplitude terminal portion of songs comprised rapid trills of frequency-modulated notes organized into discrete syllable types with a mean of 10 syllables and 4 syllable types per song. The population syllable repertoire was large (n = 27) and mostly shared but was used to produce much larger repertoires of song types, most of which were unique. Individual males sang up to 194 different song types, with no evidence of a ceiling. However, mal...

Measuring consistency: spectrogram cross-correlation versus targeted acoustic parameters

Several recent studies indicate that the consistency of song or syllable repetitions signals male quality. However, the comparability and efficacy of different measurement methods is not known. Here, I compared two approaches to measuring the consistency of syllable repetitions within the trills of House Wren (Troglodytes aedon) songs. In the first approach, I calculated the coefficient of variation (CV) in standard time–frequency measurements within each trill. In the second approach, I used spectrogram cross-correlation (SPCC), which measures the maximum pixel-by-pixel similarity of two spectrograms. The two approaches gave correlated estimates of trill consistency, but SPCC was more strongly related to two putatively biologically relevant traits: specifically, SPCC differed more strongly between age classes, and more variation in SPCC could be attributed to individual differences. CV-based measures complemented SPCC measures by clarifying some of the specific acoustic features whose consistency changed with age. Although additional comparisons between measurement approaches would be useful to assess generality, it appears that researchers interested in song or trill consistency should consider using an SPCC, or a combined SPCC- and CV-based, approach.

No evidence that sperm morphology predicts paternity success in wild house wrens

Postcopulatory sexual selection (PCSS) in internally fertilizing vertebrates is a topic of great interest, yet relatively little is known about the characteristics of sperm and ejaculates that confer an advantage in PCSS. In this study, we investigated several measures of sperm morphology that potentially contribute to fertilization success under PCSS. We tested whether sperm morphology related to success in PCSS (via extra-pair paternity) in house wrens (Troglodytes aedon). We found no evidence that sperm morphology differed between extra-pair sires and the within-pair males they cuckolded, nor that sperm morphology correlated with the proportion of within-pair offspring sired, the number of extra-pair offspring sired, or the total annual reproductive success. Male behavioral strategies may affect the probability that their sperm compete with other males’ sperm and that their sperm succeed under competition. Effects of these behavioral strategies, as well as differences between males in sperm number, could mask the effects of sperm morphology on the outcome of PCSS. Despite moderate levels of extra-pair paternity, selection on sperm may be relatively weak in house wrens. Further work is needed to understand general patterns in how sperm morphology relates to fertilization success within species.

Do sex ratio and development differ in sexually size-dimorphic shiny cowbirds (Molothrus bonariensis) parasitizing smaller and larger hosts?

Fil: Tuero, Diego Tomas. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Ecologia, Genetica y Evolucion de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecologia, Genetica y Evolucion de Buenos Aires; Argentina

Host manipulation via begging call structure in the brood-parasitic shiny cowbird

Young brood-parasitic birds must solicit provisions from other species, their hosts. The acoustic structure of the begging call has been proposed to help parasites secure host care in cases where they mimic the host's call, on the basis that parents respond best to their own species' call type. We investigated whether nonmimetic calls can also manipulate host provisioning in the parasite's favour. Nestlings of the generalist brood-parasitic shiny cowbird, Molothrus bonariensis , produce ‘tremulous’ calls comprising repeated syllables, wholly unlike the ‘chip’ calls of a common host, the house wren, Troglodytes aedon . We broadcast both call types, matched for call rate and amplitude, at unparasitized wren broods and found that parents provisioned more during broadcast of cowbird calls than those of their own species' young. Further experiments showed that (1) tremulous calls function akin to a rapid call rate, with each syllable of the cowbird's call eliciting a provisioning response equivalent to a single wren call, and thus that (2) cowbird calls exploit a provisioning rule common among birds; when we repeated our experiments in a species naive to parasitism, the great tit, Parus major , we found their responses closely resembled those of house wrens. Shiny cowbirds therefore show us an alternative route by which a parasite's begging call structure may be tailored to optimize host care. Aptly for a generalist, cowbird calls may well act as a highly effective stimulus of provisioning across a range of hosts whose own calls are structurally simpler.

Parental Risk-Taking Behaviour and Nest Defence During the Nestling Rearing Stage in Northern House WrensTroglodytes aedon

Abstract Risk-taking behaviour of short lived nesting birds is often explained in relation to the reproductive value of offspring (the reproductive value hypothesis) and the harm that the absence of parental care can cause to nestlings (risk of harm-to-offspring hypothesis). The reproductive value hypothesis predicts that the risk assumed by adults should increases with nestling age, whereas the risk of harm-to-offspring hypothesis predicts the opposite pattern. We assessed the risk-taking behaviour of nesting males and females Northern House Wrens, Troglodytes aedon, faced with a predation threat (plastic owl model) when rearing 3–4 and 10–12 days old nestlings. We used the time elapsed until parents first entered the nest-box as a measure of risk-taking behaviour and alarm calling rate as a proxy of nest defence. Females resumed sooner parental activities when exposed to the model when nestlings were young, supporting the risk of harm-to-offspring hypothesis. In contrast, the time lasted to resume paren...

Urban noise influences vocalization structure in the House WrenTroglodytes aedon

Urban habitats are noisy and constrain acoustic communication in birds. We analysed the effect of anthropogenic noise on the vocalization characteristics of House Wrens Troglodytes aedon at two sites with different noise levels (rural and urban). We measured in each song and song trill the frequency bandwidth, maximum amplitude, highest and minimum frequency, and trill rate. In noisy urban environments, there was a reduction in bandwidth and an increase in trill rate relative to quieter, rural environments. The whole song of birds from both populations increased in minimum frequency as noise increased, improving song transmission.

Sibling Cooperation Influences the Age of Nest Leaving in an Altricial Bird

In altricial birds, siblings raised within a nest usually leave the nest within hours of each other, despite often differing considerably in age. The youngest members of the brood are typically underdeveloped at this time and less likely than their older siblings to survive outside the nest, yet they risk abandonment if they do not fledge with their older siblings. Nest leaving is usually initiated by the older offspring, which may delay this process to provide more time for their younger siblings to mature, increasing the younger siblings' postfledging survival and their own inclusive fitness. We tested this hypothesis in a population of house wrens Troglodytes aedon and found that broods with broad age spans among siblings had longer nestling periods than broods with narrow age spans and that delayed fledging improves the survival and reproductive prospects of younger siblings, although at a potential cost to future siblings. We also manipulated age spans through cross-fostering and found that older foster nestlings postponed fledging when raised with younger broodmates, as predicted if the age of younger nestlings determines the time of fledging. Our results support kin-selection theory and demonstrate that the exact time of fledging is attributable, in part, to sib-sib interactions.

Antiparasitic defenses in hosts of South American cowbirds

The cowbirds (Molothrus, Icteridae) are a monophyletic group that includes five extant brood-parasitic species. The Screaming (M. rufoaxillaris), Giant (M. oryzivorus) and Shiny (M. bonar- iensis) cowbirds range mostly in South America. Screaming and Shiny cowbirds are the ancestral and most recent species of the clade, respectively, therefore, differing in how long they have coevolved with their hosts. We present new experimental data on egg-rejection in a host of the Shiny Cow- bird, the House Wren (Troglodytes aedon), review different lines of antiparasitic defenses in hosts of Screaming, Giant and Shiny cowbirds and assess whether hosts of different parasites differ in the type and extent of defenses. Hosts of all three parasites ejected non-mimetic eggs. Most hosts of Giant and Shiny cowbirds were grasp ejectors, whereas the main host of the Screaming Cowbird (the Baywing, Agelaioides badius) ejected parasitic eggs using its feet. Hosts smaller than Shiny Cowbirds neither ejected cowbird eggs nor deserted nests following parasitism. Some hosts also reacted more aggres- sively towards the parasite. The main host of Screaming Cowbird discriminated against non-mimetic chicks. Our results show that most hosts, regardless of the presumed evolutionary time of interaction with the parasite, have evolved some type of antiparasitic defense.

Physically challenging song traits, male quality, and reproductive success in house wrens.

Physically challenging signals are likely to honestly indicate signaler quality. In trilled bird song two physically challenging parameters are vocal deviation (the speed of sound frequency modulation) and trill consistency (how precisely syllables are repeated). As predicted, in several species, they correlate with male quality, are preferred by females, and/or function in male-male signaling. Species may experience different selective pressures on their songs, however; for instance, there may be opposing selection between song complexity and song performance difficulty, such that in species where song complexity is strongly selected, there may not be strong selection on performance-based traits. I tested whether vocal deviation and trill consistency are signals of male quality in house wrens (Troglodytes aedon), a species with complex song structure. Males’ singing ability did not correlate with male quality, except that older males sang with higher trill consistency, and males with more consistent trills responded more aggressively to playback (although a previous study found no effect of stimulus trill consistency on males’ responses to playback). Males singing more challenging songs did not gain in polygyny, extra-pair paternity, or annual reproductive success. Moreover, none of the standard male quality measures I investigated correlated with mating or reproductive success. I conclude that vocal deviation and trill consistency do not signal male quality in this species.

House Wrens Alter Nest Architecture to Compensate for Cavity Vulnerability

Abstract We compared House Wren (Troglodytes aedon) nests in nest boxes with either small (28 mm) or large (38 mm) entrance holes. Spring clutch size did not differ between wrens using boxes with large and small holes. Nests in boxes with large holes had a significantly taller ‘berm’ of sticks between the box entrance and the nest cup than did nests in boxes with small holes. This was true even when the same wren pairs were given boxes with different-size holes for spring and summer nests. We compared the difficulty of touching the eggs when we removed the frontplate of the nest box as an alternative measure of nest vulnerability to predators and brood parasites. There was a significant association between hole size and accessibility: boxes without the protection of a small entrance hole were far more likely to be categorized as ‘inaccessible.’ We found a similar relationship between berm height and nest architecture: nests with tall berms were generally less accessible than were nests with shorter berms....

Sexual Differences in Life History Traits ofPhilornis seguyi(Diptera: Muscidae) Parasitizing House Wrens (Troglodytes aedon)

AbstractWe studied life history traits of Philornis seguyi García, 1952 (Diptera: Muscidae) parasitizing house wrens, Troglodytes aedon (Vieillot) (Passeriformes: Troglodytidae), and analyzed sexual differences in the size of larvae, pupae, and adults, as well as in the length of larval and pupal stages and in adult survival. Males were larger than females at the larval, pupal, and adult stages, but there were no sexual differences in the length of larval and pupal stages, or in the time adults survived. Larvae developed in 5–6 d and started the larval-pupal molt within 24 h after abandoning the host. Pupal stage lasted for 9 d and its length was positively associated with size of the pupa. The size of the pupa was positively associated with that of the larva and the size of the adult with that of the pupa. In laboratory conditions, 86% of the larvae pupated and 75% of the pupae emerged as adults. In natural conditions, the proportion of unsuccessful pupae increased by the end of host's breeding season. The proportion of males and females that survived until the adult stage did not differ from random. Our results show that P. seguyi has a relatively short generation time, which would allow it a rapid population growth during the host breeding season, and indicate that intrasexual selection may have selected for large body size in P. seguyi males.

WOODEN VERSUS INSULATED METAL NESTBOXES: A COMPARISON OF REPRODUCTIVE SUCCESS AND USE BY SONGBIRDS

ABSTRACTWe compared reproductive success of Tree Swallow (Tachycineta bicolor) and House Wren (Troglodytes aedon) nests in wooden nestboxes to insulated metal nestboxes to determine if a new insulated metal nestbox design is a safe alternative to wooden nestboxes. We also examined the preference of four species of cavity-nesting birds to nest in wooden versus metal nestboxes. No significant differences were found among clutch size, hatching success, and the number of fledglings produced in Tree Swallow and House Wren nests between the two types of nestboxes. Therefore, insulated metal nestboxes appear to be a safe alternative to wooden nestboxes. Metal nestboxes were preferred by Tree Swallows to wooden nestboxes (χ2 = 6.5, n = 25, p = 0.01). However, wooden nestboxes were preferred to metal nestboxes as a first choice for nesting 77.1% of the time for all four species. House Wrens, Eastern Bluebirds (Sialia sialis), and House Sparrows (Passer domesticus) all preferred wooden to metal nestboxes (Fisher's Exact Tests, all p < 0.001). Thus, insulated metal boxes are safe, but may not attract desirable species, such as Eastern Bluebirds, when compared to traditional wooden Peterson-style boxes.

Vocal deviation and trill consistency do not affect male response to playback in house wrens

Signals that require a high degree of skill to produce are expected to honestly indicate signaler quality. In trilled birdsong, 2 parameters that likely reflect performance difficulty are vocal deviation (how rapidly sound frequency is modulated) and trill consistency (how precisely syllables are repeated). These parameters function as intra- and intersexual signals in most bird species tested to date, but they may not adequately capture song performance difficulty in all species. I used 2 playback protocols to test whether males respond differently to songs that differ in vocal deviation and trill consistency in house wrens (Troglodytes aedon). Despite large sample sizes, male responses did not depend on playback treatment. Males sang each trill type at a range of pitches, and the vocal deviation of the trill depended strongly on the pitch at which it was sung, consistent with models of song production mechanics. I propose that the addition of the pitch covariate may complicate the evaluation of vocal deviation, limiting the usefulness of this potential signal for this species. Moreover, producing each trill type at a range of pitches may itself serve some communication function, which could override the potential signal value of trill consistency. Although vocal deviation and trill consistency are male quality indicators in some species, these results suggest that species-specific differences in what constitutes a challenging song may prevent these measures from being universally applicable.

Breeding Biology of the Southern House Wren on Chiloé Island, Southern Chile

We studied the breeding biology of a Southern House Wren (Troglodytes aedon chilensis) population using nest boxes on Chiloé Island, southern Chile (41° S) to make latitudinal comparisons at the intraspecific level. There were no significant differences in body size between adult males and females, although wings were significantly longer in males. Clutch size averaged 4.3 eggs per nest, and brood size was 3.9 nestlings. Egg size averaged 17.3 mm in length and 13.2 mm in width. Incubation and nestling periods averaged 16 days each. The Southern House Wren on Chiloé Island has a larger clutch size than in the tropics, but a smaller clutch size than populations at the same latitude in the Northern Hemisphere. The Southern House Wren has larger eggs and a longer incubation period but a similar nestling period as House Wrens in the Northern Hemisphere.