Red-backed Fairy-wren Malurus Melanocephalus Research Articles

First record of black feathering in a female Red-backed Fairy-wren Malurus melanocephalus under natural conditions

During the breeding season, male Red-backed Fairy-wrens Malurus melanocephalus can exhibit a spectrum of plumages from wholly black-and-red to entirely brown. By contrast, females generally appear completely brown, although observations of birds in the hand have revealed that some females also develop some red feathers. Here, we document, for the first time, observations of a female Red-backed Fairy-wren that has developed both black and red feathers under natural conditions. We explore possible explanations for this including whether changes to the individual’s hormonal milieu could be responsible for the unusual plumage that we observed.

Endocrine correlates of mate choice and promiscuity in females of a socially monogamous avian mating system with alternative male reproductive phenotypes

Abstract While our understanding of male reproductive strategies is informed by extensive investigations into endocrine mechanisms, the proximate mechanisms by which females compete for mates and adjust reproduction to social environment remains enigmatic. We set out to uncover endocrine correlates of mate choice, social environment, and reproductive investment in female red-backed fairy-wrens Malurus melanocephalus. In this socially monogamous, yet highly sexually promiscuous species, females experience discrete variation in the phenotype of their mates, which vary in both plumage signals and level of paternal care, and in the composition of their breeding groups, which consist of either the pair alone or with an additional cooperative auxiliary; female investment varies according to these social parameters. We found that androgen, estrogen, and glucorticoid levels varied with reproductive stage, with highest androgen and estrogen concentrations during nest construction and highest corticosterone concentrations during the pre-breeding stage. These stage-dependent patterns did not vary with male phenotype or auxiliary presence, though androgen levels during pre-breeding mate selection were lower in females obtaining red/black mates than those obtaining brown mates. We found no evidence that androgen, estrogen, or corticosterone levels during the fertile period were related to extra-pair young (EPY) frequency. This study demonstrates clear changes in steroid levels with reproductive stage, though it found little support for variation with social environment. We suggest hormonal responsiveness to social factors may be physiologically constrained in ways that are bypassed through exogenous hormone manipulations.

セアカオーストラリアムシクイの非繁殖期群への野火の影響

オーストラリア熱帯モンスーン地域に生息するセアカオーストラリアムシクイの非繁殖期群の群れ構成に与える野火の影響に関して研究を行った。全体として，平均群れサイズは乾季の中頃で大きく，季節の進行とともに縮小した。大きな群れは野火で焼け出された地域に多く出現し，野火の及ばなかった地域では2個体だけの群れが多く，平均群れサイズは焼けた地域より小さかった。野火は生息場所を破壊し，生息個体の移出を引き起こした。一方，野火の及ばなかった地域は，一時的な避難場所となったが， このような安定した地域は小サイズの群れのなわばりで飽和しており，移入個体は再移出を余儀なくされた。野火の後，焼け出された地域には多くの個体が周辺部から移入し，不安定な大サイズの群れを形成した。これらの群れも，季節の進行とともに，群れメンバーの若い個体の離脱により，繁殖期直前には群れサイズが縮小した。 野火は個体群の再構成となわばりの入れ替わりを引き起こした。

DIVERGENCE ACROSS AUSTRALIA'S CARPENTARIAN BARRIER: STATISTICAL PHYLOGEOGRAPHY OF THE RED-BACKED FAIRY WREN (MALURUS MELANOCEPHALUS)

Multilocus analysis of phylogeography and population history is a powerful tool for understanding the origin, dispersal, and geographic structure of species over time and space. Using 36 genetic markers (29 newly developed anonymous nuclear loci, six introns and one from mitochondrial DNA, amounting to over 15 kb per individual), we studied population structure and demographic history of the red-backed fairy wren Malurus melanocephalus, a small passerine distributed in the northern and eastern part of Australia across the Carpentarian barrier. Analysis of anonymous loci markers revealed large amounts of genetic diversity (pi= 0.016 +/- 0.01; average number of SNPs per locus = 48; total number of SNPs = 1395), and neither nuclear nor mitochondrial gene trees showed evidence of reciprocal monophyly among Cape York (CY), Eastern Forest (EF), and Top End (TE) populations. Despite traditional taxonomy linking TE and CY populations to the exclusion of EF, we found that the CY population is genetically closer to the EF population, consistent with predicted area cladograms in this region. Multilocus coalescent analysis suggests that the CY population was separated from the other two regions approximately 0.27 million years ago, and that significant gene flow between the ER and the CY populations ( approximately 2 migrants per generation) suggests geographic continuity in eastern Australia. By contrast, gene flow between the CY and the TE populations has been dampened by divergence across the Carpentarian barrier.

The effects of delayed plumage maturation on aggression and survival in male red-backed fairy-wrens

The occurrence of multiple phenotypes within a sex of a single species has long puzzled behavioral ecologists. Male red-backed fairy-wrens Malurus melanocephalus exhibit 3 behaviorally distinct types in their first breeding season: breed in bright nuptial plumage, breed in dull plumage, or remain as an unpaired auxiliary (helper) with dull plumage. The retention of dull plumage by auxiliaries and dull breeders is an example of delayed plumage maturation (DPM), a widespread phenomenon in birds whose costs and benefits are not well understood. At a mechanistic level, DPM might allow dull males either to deceptively mimic females (female mimicry hypothesis) or to honestly signal their subordinate status (status-signaling hypothesis). DPM might function via either mechanism to provide ultimate benefits relative to developing nuptial plumage by increasing reproductive success, survival, or both. In this study, we tested the hypothesis that DPM is related to increased male survival in the red-backed fairy-wren via either female mimicry or status signaling. Aviary-based experiments revealed that dull males were perceived as male, which is consistent with the status-signaling hypothesis but contradicts the female mimicry hypothesis. Further aviary and field-based experiments also revealed that dull males were socially subordinate to bright males and received less aggression than bright males, further evidence for status signaling. However, male survival was not related to plumage coloration or breeding status. These findings indicate that male plumage coloration signals social status but that dull plumage does not afford a net survival advantage, perhaps because plumage color is a conditional strategy.

Changes in breeding status are associated with rapid bill darkening in male red-backed fairy-wrens Malurus melanocephalus

Changes in breeding status are associated with rapid bill darkening in male red-backed fairy-wrens Malurus melanocephalus

Clearing and grazing impacts on vegetation patch structures and fauna counts in eucalypt woodland, Central Queensland

There is national and international concern that tree clearing and cattle grazing reduce habitat for native fauna. In this paper we quantify how the degree of clearing and the level of grazing change the patch structure and composition of vegetation in eucalypt woodlands, and how these habitat changes affect counts for 10 species including birds, reptiles and small mammals. These species were selected because they were abundant, hence providing the data needed for ordinations and regressions. We studied 37 sites occurring in two regions of central Queensland: Blackwater/Emerald and Alpha/Jericho. On each site, indices for the degree of tree clearing and the level of livestock grazing were assessed, the cover and size of tree groves, shrub thickets, log hummocks, termite mounds and perennial grass clumps were measured, and abundances of 10 common vertebrate species were estimated. As expected, the cover and size of tree groves declined and the cover of grass clumps increased as the degree of clearing increased. Native grass composition changed to introduced Buffel Grass as the level of grazing increased. Clearing affected fauna counts more than grazing did. The Grey Butcherbird Cracticus torquatus, Yellow-throated Miner Manorina flavigula, Striated Pardalote Pardalotus striatus and Pale-headed Rosella Platycercus eximius had significantly lower counts on cleared sites, but the Red-backed Fairy-wren Malurus melanocephalus had higher counts. The introduced House Mouse Mus musculus also had higher counts on cleared sites, but Carnaby's Skink Cryptoblephrus carnabyi had lower counts. Counts of the Weebill Smicrornis brevirostris, Bynoe's Gecko Heteronotia binoei and the Delicate Mouse Pseudomys delicatulus did not significantly change with clearing. Counts for the Pale-headed Rosella increased as the level of grazing increased, but counts for the other fauna species did not significantly change with our grazing index. Except for Bynoe's Gecko, fauna counts significantly changed with various vegetation patch attributes, particularly those strongly affected by clearing. From these results, we know which of the 10 fauna species are likely to decline or increase with clearing and grazing, and this knowledge can be used by land managers.

Helpers liberate female fairy-wrens from constraints on extra-pair mate choice

In cooperatively breeding superb fairy-wrens (Malurus cyaneus), all males contribute to the feeding and defence of young. Despite the expectation that such paternal care should be directed only to relatives, DNA fingerprinting revealed that most offspring (76%, 138 out of 181) were sired by extra-group males that contributed no care, and that almost all broods (95%, 38 out of 40) contained young sired by extra-group fathers. This is the highest known incidence of cuckoldry. This remarkable mating system is produced by female control of fertilization and consistent preference for certain extra-group male genotypes. This choice leads to the production of sons that also gain extra-group fertilizations. One constraint on the extra-pair mate choice of females is the level of parental assistance received from males. Males living in pairs contribute relatively more parental care and are more likely to gain paternity in one of their broods (85%, 11 out of 13) than dominant males in multi-male cooperative groups (30%, 8 out of 27). In groups helpers compensate for the lower parental assistance of dominant males, so the total feeding rate is similar between pairs and groups. This suggests that females allow males in pairs more paternity to ensure their assistance with parental care. Helpers provide an alternative source of paternal investment, and allow females to express unrestricted mate choice. Mating options for females in other species with female control of fertilization may also reflect a trade-off between acquiring the genes of high-quality males for their offspring and parental care of those offspring.