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The Splendid Fairywren Malurus splendens has four distinct phenotypic forms currently recognised as subspecies, although three species have been recognised within the group in the past. Here, we use multilocus nuclear DNA to test the recent hypothesis that the Splendid Fairywren represents three allopatric taxa with little to no modern-day contact, despite phenotypic evidence of periods of past contact and gene flow. Our nuclear dataset is concordant with earlier mtDNA-based data in supporting three distinct genetic groups within M. splendens. These genetic groups align with the three phenotypically distinct forms recently hypothesised to be allopatric and previously described at species-level – western M. splendens, central M. callainus and eastern M. melanotus. Nuclear gene flow does not appear to be rampant between the three forms; however, several individuals show signals of admixed nuclear ancestry, which we cannot distinguish as having resulted from incomplete lineage sorting, poor phylogenetic signal, or gene flow. Given changing modern taxonomic interpretations of the significance of gene flow in speciation, we argue that recognising three distinct species within the M. splendens complex might better represent their evolutionary distinctiveness, rather than continuing to treat these genetically and morphologically distinct forms as subspecies of a widespread polytypic species. Our study highlights the interesting complexity of determining species status when taxa are in the 'grey zone' near the subspecies/species continuum, and the value gained from adding perspectives from nuclear DNA. [ABSTRACT FROM AUTHOR]

Abstract Historically, bird song complexity was thought to evolve primarily through sexual selection on males; yet, in many species, both sexes sing and selection pressure on both sexes may be broader. Previous research suggests competition for mates and resources during short, synchronous breeding seasons leads to more elaborate male songs at high, temperate latitudes. Furthermore, we expect male–female song structure and elaboration to be more similar at lower, tropical latitudes, where longer breeding seasons and year‐round territoriality yield similar social selection pressures in both sexes. However, studies seldom take both types of selective pressures and sexes into account. We examined song in both sexes in 15 populations of nine‐fairy‐wren species (Maluridae), a Southern Hemisphere clade with female song. We compared song elaboration (in both sexes) and sexual song dimorphism to latitude and life‐history variables tied to sexual and social selection pressures and sex roles. Our results suggest that song elaboration evolved in part due to sexual competition in males: male songs were longer than female songs in populations with low male survival and less male provisioning. Also, female songs evolved independently of male songs: female songs were slower paced than male songs, although only in less synchronously breeding populations. We also found male and female songs were more similar when parental care was more equal and when male survival was high, which provides strong evidence that sex role similarity correlates with male–female song similarity. Contrary to Northern Hemisphere latitudinal patterns, male and female songs were more similar at higher, temperate latitudes. These results suggest that selection on song can be sex specific, with male song elaboration favored in contexts with stronger sexual selection. At the same time, selection pressures associated with sex role similarity appear to favor sex role similarity in song structure.

Personality syndromes in animals may have adaptive benefits for survival. For example, while engaging in predator deterrence, reactive individuals tend to prioritise their own survival, while proactive individuals engage in riskier behaviours. Studies linking animal personality measured in captivity with individual fitness or behaviours in the wild are sparse, which is a gap in knowledge this study aims to address. We used playback experiments in superb fairy-wrens (Malurus cyaneus), a common Australian songbird with a cooperative breeding system, to assess whether three personality traits measured during short-term captivity correlated with behavioural responses in the wild to a perceived nest and adult predator, the grey currawong (Strepera versicolor). We used three standard measures of personality in birds: struggle responses to human handling (boldness), exploration during a novel environment test, and aggressiveness during a mirror presentation. Superb fairy-wrens showed a significantly stronger response to the predator playback than to the control (willie wagtail, Rhipidura leucophrys) playback, suggesting that they recognised the predator playback as a threat without any accompanying visual stimulus. Birds that attacked their mirror image during the mirror presentation and those that spent a moderate amount of time close to the mirror responded more strongly to predator playback (by approaching the speaker faster and closer, spending more time near the speaker, and being more likely to alarm call) compared to those with low aggressiveness or those that spent very short or long durations close to the mirror. Neither boldness nor exploration in the novel environment test predicted playback response. Our results align with a growing number of studies across species showing the importance of animal personalities as factors for fitness and survival. [ABSTRACT FROM AUTHOR]

Personality syndromes in animals may have adaptive benefits for survival. For example, while engaging in predator deterrence, reactive individuals tend to prioritise their own survival, while proactive individuals engage in riskier behaviours. Studies linking animal personality measured in captivity with individual fitness or behaviours in the wild are sparse, which is a gap in knowledge this study aims to address. We used playback experiments in superb fairy-wrens (Malurus cyaneus), a common Australian songbird with a cooperative breeding system, to assess whether three personality traits measured during short-term captivity correlated with behavioural responses in the wild to a perceived nest and adult predator, the grey currawong (Strepera versicolor). We used three standard measures of personality in birds: struggle responses to human handling (boldness), exploration during a novel environment test, and aggressiveness during a mirror presentation. Superb fairy-wrens showed a significantly stronger response to the predator playback than to the control (willie wagtail, Rhipidura leucophrys) playback, suggesting that they recognised the predator playback as a threat without any accompanying visual stimulus. Birds that attacked their mirror image during the mirror presentation and those that spent a moderate amount of time close to the mirror responded more strongly to predator playback (by approaching the speaker faster and closer, spending more time near the speaker, and being more likely to alarm call) compared to those with low aggressiveness or those that spent very short or long durations close to the mirror. Neither boldness nor exploration in the novel environment test predicted playback response. Our results align with a growing number of studies across species showing the importance of animal personalities as factors for fitness and survival.

Historically, bird song complexity was thought to evolve primarily through sexual selection on males; yet, in many species, both sexes sing and selection pressure on both sexes may be broader. Previous research suggests competition for mates and resources during short, synchronous breeding seasons leads to more elaborate male songs at high, temperate latitudes. Furthermore, we expect male–female song structure and elaboration to be more similar at lower, tropical latitudes, where longer breeding seasons and year‐round territoriality yield similar social selection pressures in both sexes. However, studies seldom take both types of selective pressures and sexes into account. We examined song in both sexes in 15 populations of nine‐fairy‐wren species (Maluridae), a Southern Hemisphere clade with female song. We compared song elaboration (in both sexes) and sexual song dimorphism to latitude and life‐history variables tied to sexual and social selection pressures and sex roles. Our results suggest that song elaboration evolved in part due to sexual competition in males: male songs were longer than female songs in populations with low male survival and less male provisioning. Also, female songs evolved independently of male songs: female songs were slower paced than male songs, although only in less synchronously breeding populations. We also found male and female songs were more similar when parental care was more equal and when male survival was high, which provides strong evidence that sex role similarity correlates with male–female song similarity. Contrary to Northern Hemisphere latitudinal patterns, male and female songs were more similar at higher, temperate latitudes. These results suggest that selection on song can be sex specific, with male song elaboration favored in contexts with stronger sexual selection. At the same time, selection pressures associated with sex role similarity appear to favor sex role similarity in song structure. [ABSTRACT FROM AUTHOR]

The details of a breeding season have been investigated and described for many bird species and groups of species, but rarely for an entire breeding community. The collection of such data is the only way of quantifying the number of birds a habitat can support, how many fledglings it can produce, and the avian diversity that can exist in the habitat. Without these quantitative and qualitative measures, the significance of particular habitats for avian conservation is difficult to assess. We have accumulated comprehensive data on a breeding bird community on a 10 ha site for eight seasons, which has enabled us to condense the many aspects of breeding into an 'average' breeding season. The breeding community consisted of 44 species, which used all of the site for nesting. Some species bred each season, while others bred as infrequently as once in the eight seasons. Nesting occurred between the beginning of August and the end of January, different species showed markedly different starting and finishing times, and there were different temporal patterns of breeding within the breeding periods of the different species. The number of pairs that bred on the site varied each season, a pattern that we have previously shown to be related to the value of the Southern Oscillation Index before the start of the season. Nest success rates varied considerably between species, but the overall success rate on the site was approximately 50%. We estimate that the spotted gum forest habitat on the south-east coast of Australia (1200 km2) produces approximately 1.5 million fledglings each season. [ABSTRACT FROM AUTHOR]

Why do senescence rates of fitness-related traits often vary dramatically? By considering the full aging trajectories of multiple traits, we can better understand how a species' life history shapes the evolution of senescence within a population. Here, we examined age-related changes in sex-specific survival, reproduction, and several components of reproduction using a long-term study of a cooperatively breeding songbird, the superb fairy-wren (Malurus cyaneus). We compared aging patterns between traits by estimating standardized rates of maturation, age of onset of senescence, and rates of senescence while controlling for confounding factors reflecting individual variability in life history. We found striking differences in aging and senescence patterns between survival and reproduction as well as between reproductive traits. In both sexes, survival started to decline from maturity onward. In contrast, all reproductive traits showed improvements into early adulthood, and many showed little or no evidence of senescence. In females, despite senescence in clutch size, number of offspring surviving to independence did not decline in late life, possibly due to improvements in maternal care with age. Superb fairy-wrens have exceptionally high levels of extragroup paternity, and while male within-group reproductive success did not change with age, extragroup reproductive success showed a dramatic increase in early ages, followed by a senescent decline, suggesting that male reproductive aging is driven by sexual selection. We discuss how the superb fairy-wrens' complex life history may contribute to the disparate aging patterns across different traits. [ABSTRACT FROM AUTHOR]

Age‐related changes in parental phenotypes or genotypes can impact offspring fitness, but separating germline from nongermline transgenerational effects of ageing is difficult for wild populations. Further, in cooperatively breeding species, in addition to parental ages, the age of 'helpers' attending offspring may also affect juvenile performance. Using a 30‐year study of a cooperative breeder with very high rates of extra‐pair paternity, the superb fairy‐wren (Malurus cyaneus), we investigated the effects of maternal, paternal and helper ages on three measures of offspring performance: nestling weight, juvenile survival to independence and recruitment to the breeding population. Mothers with a longer lifespan had offspring with higher juvenile survival, indicating selective disappearance, but the effect of maternal age on juvenile survival was of similar magnitude but negative. For extra‐pair offspring, there was no evidence of any effect of the ages of either the genetic sire or the cuckolded 'social' father. However, for within‐pair offspring, there was a positive effect of paternal age on juvenile survival, which we suggest may be driven by sexual selection. There were positive associations between the average age of helpers attending a nest and two of the three aspects of offspring performance; these effects were stronger than any of the effects of parental age. In general, the multiple associations between offspring fitness and the ages of adults around them appeared to be driven more by age‐related changes in environmental effects than by age‐related changes in the germline. [ABSTRACT FROM AUTHOR]

By the Robertson–Price identity, the change in a quantitative trait owing to selection, is equal to the trait's covariance with relative fitness. In this study, we applied the identity to long-term data on superb fairy-wrens Malurus cyaneus, to estimate phenotypic and genetic change owing to juvenile viability selection. Mortality in the four-week period between fledging and independence was 40%, and heavier nestlings were more likely to survive, but why? There was additive genetic variance for both nestling mass and survival, and a positive phenotypic covariance between the traits, but no evidence of additive genetic covariance. Comparing standardized gradients, the phenotypic selection gradient was positive, βP = 0.108 (0.036, 0.187 95% CI), whereas the genetic gradient was not different from zero, βA = −0.025 (−0.19, 0.107 95% CI). This suggests that factors other than nestling mass were the cause of variation in survival. In particular, there were temporal correlations between mass and survival both within and between years. We suggest that use of the Price equation to describe cross-generational change in the wild may be challenging, but a more modest aim of estimating its first term, the Robertson–Price identity, to assess within-generation change can provide valuable insights into the processes shaping phenotypic diversity in natural populations. This article is part of the theme issue 'Fifty years of the Price equation'. [ABSTRACT FROM AUTHOR]

Group living can be beneficial when individuals reproduce or survive better in the presence of others, but, simultaneously, there might be costs due to competition for resources. Positive and negative effects on various fitness components might thus counteract each other, so integration is essential to determine their overall effect. Here, we investigated how an integrated fitness measure (reproductive values [RVs]) based on six fitness components varied with group size among group members in cooperatively breeding red-winged and superb fairy wrens (Malurus elegans and Malurus cyaneus , respectively). Despite life-history differences between the species, patterns of RVs were similar, suggesting that the same behavioral mechanisms are important. Group living reduced RVs for dominant males, but for other group members, this was true only in large groups. Decomposition analyses showed that our integrated fitness proxy was most strongly affected by group size effects on survival and was amplified through carryover effects between years. Our study shows that integrative consideration of fitness components and subsequent decomposition analysis provide much needed insights into the key behavioral mechanisms shaping the costs and benefits of group living. Such attribution is crucial if we are to synthesize the relative importance of the myriad group size costs and benefits currently reported in the literature. [ABSTRACT FROM AUTHOR]

Sperm competition is thought to impose strong selection on males to produce competitive ejaculates to outcompete rival males under competitive mating conditions. Our understanding of how different sperm traits influence fertilization success, however, remains limited, especially in wild populations. Recent literature highlights the importance of incorporating multiple ejaculate traits and pre-copulatory sexually selected traits in analyses aimed at understanding how selection acts on sperm traits. However, variation in a male’s ability to gain fertilization success may also depend upon a range of social and ecological factors that determine the opportunity for mating events both within and outside of the social pair-bond. Here, we test for an effect of sperm quantity and sperm size on male reproductive success in the red-back fairy-wren (Malurus melanocephalus) while simultaneously accounting for pre-copulatory sexual selection and potential socio-ecological correlates of male mating success. We found that sperm number (i.e., cloacal protuberance volume), but not sperm morphology, was associated with reproductive success in male red-backed fairy-wrens. Most notably, males with large numbers of sperm available for copulation achieved greater within-pair paternity success. Our results suggest that males use large sperm numbers as a defensive strategy to guard within-pair paternity success in a system where there is a high risk of sperm competition and female control of copulation. Finally, our work highlights the importance of accounting for socio-ecological factors that may influence male mating opportunities when examining the role of sperm traits in determining male reproductive success.

Closely related species often differ in coloration. Understanding the mechanistic bases of such differences can reveal whether evolutionary changes in colour are driven by single key mechanisms or changes in multiple pathways. Non-iridescent structural plumage colours in birds are a good model in which to test these questions. These colours result from light absorption by pigments, light scattering by the medullary spongy layer (a nanostructure found within barbs) and contributions from other structural elements. Fairy-wrens (Malurus spp.) are a small clade of closely related birds that display a large diversity of ornamental structural colours. Using spectrometry, electron microscopy and Fourier analysis, we show that 30 structural colours, varying from ultraviolet to blue and purple, share a similar barb morphology. Despite this similarity, we find that at the microscopic scale, variation across multiple structural elements, including the size and density of the keratin cortex, spongy layer and melanin, explains colour diversity. These independent axes of morphological variation together account for sizeable amounts of structural colour variability (R 2 = 0.21–0.65). The coexistence of many independent, evolutionarily labile mechanisms that generate colour variation suggests that the diversity of structural colours in this clade could be mediated by many independent genetic and environmental factors. [ABSTRACT FROM AUTHOR]

Animal signals of competitive ability allow contests for limited resources to be settled without costly physical fights. Traits indicating competitive ability are diverse and span visual, acoustic or chemical modalities. Although animal signalling has been intensively studied, research has focused mainly on male traits. Little is known about the extent and functionality of competitive signals in females and whether there are sex differences in signal function. We studied whether plumage colour signals competitive ability in female and male lovely fairy-wrens, Malurus amabilis. In this species, both sexes sport elaborate but sexually dichromatic ornamental plumage. Using a mirror image stimulation test, we first assessed the relationship between male and female colour and agonistic behaviour, controlling for other physical, social and ecological variables. We then tested whether colourful plumage influenced aggressive response in both sexes by experimentally manipulating plumage colour and measuring individual responses to their mirror image. Females and males were more aggressive towards naturally less colourful reflections of the cheek patch in the mirror. However, when we manipulated plumage colour, both females and males responded more aggressively to experimentally increased cheek colour reflection in the mirror. Our findings suggest that plumage colour signals competitive ability in an aggressive context in both sexes and raises the possibility that signal reliability may be maintained by social interactions where individuals police and punish dishonest signals. Highlights • Our understanding of female signals and sex differences is still limited. • We used a mirror image test to study whether plumage colour signals aggression. • Both sexes were more aggressive to natural, less colourful mirror reflections. • Manipulated birds were more aggressive to increased colour reflections. • Plumage colour of females and males appears to be used as a competitive signal. [ABSTRACT FROM AUTHOR]

The forces shaping female plumage color have long been debated but remain unresolved. Females may benefit from conspicuous colors but are also expected to suffer costs. Predation is one potential cost, but few studies have explicitly investigated the relationship between predation risk and coloration. The fairy-wrens show pronounced variation in female coloration and reside in a wide variety of habitats across Australasia. Species with more conspicuous females are found in denser habitats, suggesting that conspicuousness in open habitat increases vulnerability to predators. To test this, we measured attack rates on 3-D-printed models mimicking conspicuously colored males and females and dull females in eight different fairy-wren habitats across Australia. Attack rates were higher in open habitats and at higher latitudes. Contrary to our predictions, dull female models were attacked at similar rates to the conspicuous models. Further, the probability of attack in open habitats increased more for both types of female models than for the conspicuous male model. Across models, the degree of contrast (chromatic and achromatic) to environmental backgrounds was unrelated to predation rate. These findings do not support the long-standing hypothesis that conspicuous plumage, in isolation, is costly due to increased attraction of predators. Our results indicate that conspicuousness interacts with other factors in driving the evolution of plumage coloration. [ABSTRACT FROM AUTHOR]

Extra‐pair paternity (EPP) has been suggested to improve the genetic quality of offspring, but evidence has been equivocal. Benefits of EPP may be only available to specific individuals or under certain conditions. Red‐winged fairy‐wrens have extremely high levels of EPP, suggesting fitness benefits might be large and available to most individuals. Furthermore, extreme philopatry commonly leads to incestuous social pairings, so inbreeding avoidance may be an important selection pressure. Here, we quantified the fitness benefits of EPP under varying conditions and across life‐stages. Extra‐pair offspring (EPO) did not appear to have higher fitness than within‐pair offspring (WPO), neither in poor years nor in the absence of helpers‐at‐the‐nest. However, EPP was beneficial for closely related social pairs, because inbred WPO suffered an overall 75% reduction in fitness. Inbreeding depression was nonlinear and reduced nestling body condition, first year survival and reproductive success. Our comprehensive study indicates that EPP should be favored for the 17% of females paired incestuously, but cannot explain the widespread infidelity in this species. Furthermore, our finding that fitness benefits of EPP only become apparent for a small part of the population could potentially explain the apparent absence of fitness differences in population wide comparisons of EPO and WPO. [ABSTRACT FROM AUTHOR]

The Lovely Fairy-Wren (Malurus amabilis) is endemic to the wet tropics of Australia and is one of 11 species in the genus Malurus. Despite the large number of studies on fairy-wrens, little is known about the Lovely Fairy-Wren. This study provides the first detailed description of its ecology, behaviour, and breeding biology. Lovely Fairy-Wrens displayed breeding behaviour characteristic of tropical birds, with groups maintaining territories and breeding year-round, small clutch size (two to three eggs), long juvenile dependence (2 months) and high adult breeder survival (86%). They breed cooperatively, and groups formed when male (but not female) offspring delayed dispersal and remained in their natal group as subordinates. Groups were typically small (2.5 ± 0.8 individuals), possibly because productivity was low: 29% of the monitored groups produced at least one fledgling per year. Males provided high levels of parental care and this, together with low extra-pair courtship and petal displays, suggests that this species may not be as promiscuous as other fairy-wrens. Unlike other Australian fairy-wrens, males maintained their brightly coloured adult plumage year-round after initial acquisition. This lack of seasonal moult into dull plumage, coupled with the unusually colourful plumage of females in this species, suggests that the impact of natural selection on the plumage colour of both sexes may be lower in this species than in their congeners. We discuss similarities and differences in life-history and morphological traits between the Lovely Fairy-Wren and other Malurus species. [ABSTRACT FROM AUTHOR]

Individuals should adjust investment in parental care in order to maximize current and future reproductive success. In cooperative breeders, where helpers assist with raising offspring, larger groups may allow for a reduction in investment (load lightening) of each individual. Additionally, the type of individual, and thus the social context, can play an important role in individual investment. Less attention has been paid to how provisioning rules vary across ecological contexts, although theory suggests that individuals can only afford to reduce their investment when nestling starvation is unlikely, thus under mild conditions. Here, we tested whether previously reported provisioning rules based on social context vary with ecological conditions, by experimental manipulation of signals of chick need, in the cooperatively breeding red-winged fairy-wren, Malurus elegans. Previous work in this species has shown that all group members load-lighten with additional male helpers, but not in response to the number of female helpers in the group (additive care). We show that experimental begging playback resulted in all individuals increasing their provisioning rates, indicating that our treatment was perceived as increased chick need. However, in contrast to our prediction that load lightening should only occur when individuals can afford to do so, signals of increased chick need did not stop individuals from reducing their investment with an increasing number of male helpers in the group. These results suggest that despite some flexibility in parental effort, individuals use strict rules with respect to group composition, suggesting that individual provisioning effort is based on multiple integrated cues, and responses to changes in the environment are highly context dependent. Highlights • Provisioning rules were consistent across contexts in red-winged fairy wrens. • All group members increased feeding rates in response to begging playback. • Load lightening occurred in both the begging and control playback treatments. [ABSTRACT FROM AUTHOR]

Cooperative breeding, in which auxiliary group members help rear related, but nondescendent young, is often explained by kin selection. Reproductive monogamy is predicted in cooperatively breeding systems, as monogamy increases intragroup relatedness and maximizes auxiliary inclusive fitness. While monogamy is observed across many systems, including eusocial insects and cooperatively breeding mammals, some cooperatively breeding birds exhibit high rates of extrapair paternity. Here we quantify paternity and examine the role of auxiliaries on extrapair paternity in the highly cooperative variegated fairy-wren, Malurus lamberti , a species with both male and female auxiliaries. Extrapair paternity occurred in 55.4% of nests, and 39.8% of offspring were the result of extrapair matings. The presence of both male and female auxiliaries had a positive relationship with the percentage of within-pair young sired by dominant males, however, the presence of male auxiliaries had a stronger impact than the presence of females. The number of extrapair young sired by dominant males decreased as the number of male auxiliaries increased. The total number of young sired by dominant males, however, was not predicted by group size or relatedness to their social partner, nor did group composition or relatedness to the breeding pair predict the reproductive success of subordinate males. We hypothesize that breeders use alternative reproductive strategies in the presence or absence of auxiliaries. Males and females may seek extrapair reproductive opportunities when no help is available in their group and nest survival is expected to be low. When help is available, breeders may reduce extrapair paternity, either to increase intragroup relatedness or because confidence in nest survival is high. Our data suggest that group composition is important in understanding extrapair paternity rates in cooperatively breeding birds and that variation in extrapair paternity rates may be the result of flexible breeding strategies when auxiliary presence and identity varies. [ABSTRACT FROM AUTHOR]

Extra-pair paternity ( EPP), where offspring are sired by a male other than the social male, varies enormously both within and among species. Trying to explain this variation has proved difficult because the majority of the interspecific variation is phylogenetically based. Ideally, variation in EPP should be investigated in closely related species, but clades with sufficient variation are rare. We present a comprehensive multifactorial test to explain variation in EPP among individuals in 20 populations of nine species over 89 years from a single bird family (Maluridae). Females had higher EPP in the presence of more helpers, more neighbours or if paired incestuously. Furthermore, higher EPP occurred in years with many incestuous pairs, populations with many helpers and species with high male density or in which males provide less care. Altogether, these variables accounted for 48% of the total and 89% of the interspecific and interpopulation variation in EPP. These findings indicate why consistent patterns in EPP have been so challenging to detect and suggest that a single predictor is unlikely to account for the enormous variation in EPP across levels of analysis. Nevertheless, it also shows that existing hypotheses can explain the variation in EPP well and that the density of males in particular is a good predictor to explain variation in EPP among species when a large part of the confounding effect of phylogeny is excluded. [ABSTRACT FROM AUTHOR]

As a textbook example of a sexually selected trait, song in male birds has been extensively examined in the context of female mate choice and male–male competition for access to mates. Female song is also phylogenetically widespread, and probably ancestral. However, we know relatively little about when and why females sing. Female song may be important for female–male communication, e.g. fertility advertisement, mate attraction or coordinating the care of young. Alternatively, female song may function in the context of female–female competition for reproductive resources, e.g. nest sites, year-round territories or parental assistance. We quantified spontaneous song, and song in response to playback of an unfamiliar female song, in female and male superb fairy-wrens, Malurus cyaneus , across breeding stages. We found that females and males sang with roughly equal frequency spontaneously; however, females sang much more frequently than males in response to playback of unfamiliar female song. We found no difference in song rates across breeding stage, and no effect of age or the presence of subordinates. In both sexes, song rates increased slightly across the breeding season. Female song rates were also repeatable across the season. Overall, the results suggest that although female song is likely to be a multipurpose trait, as in males, the primary function in superb fairy-wrens appears to be female–female competition. [ABSTRACT FROM AUTHOR]

Habitat geometry does not affect levels of extrapair paternity in fairy-wrens, as shown by comparing birds living in fragmented and highly connected habitat. Thereby this study provides no evidence for behavioral plasticity to the nearby availability of mates and to any associated variation in the cost and benefits of mating behavior. Nor can our study explain the recent surprising discovery of a virtually monogamous species among the world’s most unfaithful avian genus.Density of potential mates has often been proposed to explain the enormous variation in extrapair paternity. However, density is often confounded by other ecological factors that might affect extrapair paternity in their own way. Furthermore, extrapair mating shows strong phylogenetic inertia, making both meaningful intra- and interspecific comparisons difficult. An extreme way to change density is through habitat fragmentation that reduces connectivity between territories. Recently, habitat connectivity was hypothesized to explain the surprising discovery of a virtually monogamous species among the world’s most unfaithful bird genus. The monogamous Malurus coronatus lives in narrow riparian strips that limit contact with neighbors to both extreme ends of territories, whereas Malurus species with high levels of extragroup paternity typically live in high-connected habitat in which they are surrounded by neighbors. Here, we test the habitat geometry hypothesis by comparing levels of extragroup paternity of Malurus elegans living in fragmented low-connected habitat and in high-connected habitat. We found that M. elegans does not have lower levels of extragroup paternity in low-connected habitat (68%) than in high-connected habitat (56% of offspring), indicating that connectivity does not limit opportunities for extragroup paternity. Furthermore, there was no evidence that females in low-connected habitat gained extragroup paternity further away or from less sires or that they were more likely to be closely related to their social mate. We conclude that behavioral plasticity in response to density-dependent cost and benefits of mating behavior does not explain intrageneric variation in extragroup paternity in Malurus. Furthermore, habitat fragmentation may not strongly affect inbreeding risk in this species. [ABSTRACT FROM PUBLISHER]

The conservation status of many birds in Australia has been deteriorating in response to human activities. Changes to land-management practices are required to halt declines but, in many cases, the causal mechanisms of declines are poorly known and so it is difficult to provide appropriate management directives. Of the 23 Australian species of Maluridae, 12 have infrataxa that meet the criteria for inclusion within an IUCN Red List category. The family possesses characteristics that make it ideal for research relevant to improving conservation outcomes for the Maluridae and other threatened taxa: the family is widely distributed, has been exposed to the varying pressures that operate in diverse habitats across Australia, and infrataxa have broadly similar ecologies and yet disparate conservation listings. Here we describe the conservation status of the taxa within the Maluridae and outline how the family can be used as models to test mechanisms associated with declines and for developing concepts to enhance conservation management. We argue that disparate responses of sympatric malurids to the same land- management regimes can be used to identify characteristics that make species vulnerable to environmental pressures. Quantitative insights into how malurids respond to threatening processes may provide directives for management of a range of threatened species. [ABSTRACT FROM AUTHOR]

Sexual signals can be important mechanisms of reproductive isolation among incipient species, but the relative effectiveness and geographic distribution of different signals may vary, particularly when those signals have different modes of inheritance (e.g., cultural vs. genetic). Indeed, novel phenotypes may develop when traits with different modes of inheritance or different selection pressures become spatially decoupled from one another in zones of secondary contact, and such novel phenotypes may facilitate or hinder reproductive isolation. We assessed divergence of a culturally transmitted signal (song) and conspecific responses to that signal across a zone of reduced gene flow where plumage characters show asymmetrical introgression among subspecies of the red-backed fairy-wren (Malurus melanocephalus). We found that, in contrast to plumage, geographic variation in many song characteristics correlated well with geographic genetic structure. Additionally, playback experiments revealed that birds responded most strongly to songs from within the same genetic region irrespective of plumage type. These results indicate that song has been resistant to introgression, yet song traits and preferences have not hindered introgression of plumage traits. We suggest that this is because different modes of inheritance (here, cultural vs. genetic) facilitate decoupling of song and plumage, resulting in a large region where males exhibit a novel combination of sexual traits. [ABSTRACT FROM PUBLISHER]

Background: Many species exhibit geographic variation in sexual signals, and divergence in these traits may lead to speciation. Sexual signals may diverge due to differences in ecology if the environment constrains signal production or transmission. Alternatively, sexual signals may diverge stochastically through sexual selection or genetic drift, with little environmental influence. To distinguish between these alternatives we quantified variation in two putative sexual signals - tail length and plumage color - and a suite of non-sexual morphometric traits across the geographic range of the red-backed fairy-wren (Malurus melanocephalus). We then tested for associations between these traits and a number of environmental variables using generalized dissimilarity models. Results: Variation in morphometric traits was explained well by environmental variation, irrespective of geographic distance between sites. Among putative signals, variation in plumage color was best explained by geographic distance, whereas tail length was best explained by environmental variation. Divergence in male plumage color was not coincident with the boundary between genetic lineages, but was greatest across a contact zone located 300 km east of the genetic boundary. Conclusions: Morphometric traits describing size and shape have likely been subject to ecological selection and thus appear to track local environmental variation regardless of subspecies identity. Ecological selection appears to have also influenced the evolution of tail length as a signal, but has played a limited role in shaping geographic variation in plumage color, consistent with stochastic divergence in concert with Fisherian selection on this trait. The lack of coincidence between the genetic boundary and the contact zone between plumage types suggests that the sexual plumage signal of one subspecies has introgressed into the genetic background of the other. Thus, this study provides insight into the various ways in which signal evolution may occur within a species, and the geographic patterns of signal variation that can arise, especially following secondary contact. [ABSTRACT FROM AUTHOR]

In passerine birds, storage and maturation of sperm takes place in the cloacal protuberance (CP), an external swelling of the reproductive organ. The considerable variation in CP size among species is presumed to be a consequence of varying levels of sperm-competition, but whether individual variation in CP size within a species also reflects sperm competition is not well established. Here, we study temporal variation in male CP size in relation to within-pair and extra-pair mating opportunities and cuckoldry risk in purple-crowned fairy-wrens Malurus coronatus. This is a socially monogamous cooperatively breeding passerine that can breed year-round and has low levels of extra-pair paternity (in 6 % of broods). We show that male CP size sharply increased a few weeks before, and rapidly regressed after his partner laid eggs, consistent with a cost of its maintenance and/or sperm production. Surprisingly, despite low levels of extra-pair paternity, CP size of non-breeding and pre-breeding males was positively correlated with the number of breeding females in the population, suggesting that CP size is sensitive to extra-pair mating opportunities. However, CP sizes do not seem to reflect cuckoldry risk: CP size of dominant males was unaffected by the presence of a subordinate that was unrelated to the dominant female, although those subordinates occasionally sire offspring, and had a larger CP than subordinates living with their mother. Our results suggest that, even in a species with low levels of extra-pair paternity, individual investment in sperm storage reflects both within-pair and, albeit to lesser extent, extra-pair mating opportunities. [ABSTRACT FROM AUTHOR]

Colour vision in diurnal birds falls into two discrete classes, signified by the spectral sensitivity of the violet- (VS) or ultraviolet-sensitive (UVS) short wavelength-sensitive type 1 (SWS1) single cone. Shifts between sensitivity classes are rare; three or four are believed to have happened in the course of avian evolution, one forming UVS higher passerines. Such shifts probably affect the expression of shortwave-dominated plumage signals. We have used genomic DNA sequencing to determine VS or UVS affinity in fairy-wrens and allies, Maluridae, a large passerine family basal to the known UVS taxa. We have also spectrophotometrically analysed male plumage coloration as perceived by the VS and UVS vision systems. Contrary to any other investigated avian genus, Malurus (fairy-wrens) contains species with amino acid residues typical of either VS or UVS cone opsins. Three bowerbird species (Ptilonorhynchidae) sequenced for outgroup comparison carry VS opsin genes. Phylogenetic reconstructions render one UVS gain followed by one or more losses as the most plausible evolutionary scenario. The evolution of avian ultraviolet sensitivity is hence more complex, as a single shift no longer explains its distribution in Passeriformes. Character correlation analysis proposes that UVS vision is associated with shortwave-reflecting plumage, which is widespread in Maluridae. [ABSTRACT FROM AUTHOR]