Malurus Melanocephalus Research Articles

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。

The relative importance of male tail length and nuptial plumage on social dominance and mate choice in the red‐backed fairy‐wren Malurus melanocephalus: evidence for the multiple receiver hypothesis

Understanding why males of many species exhibit two or more sexual ornaments depends upon identifying both the information conveyed and the intended receiver(s) for each signal. Here we focus on identifying the intended receivers for two sexual signals exhibited by male red‐backed fairy‐wrens Malurus melanocephalus, extent of nuptial plumage and tail length. In doing so we test the multiple receiver hypothesis, which predicts that each trait is directed toward a different type of receiver (e.g., males vs females). Male red‐backed fairy‐wrens in nuptial plumage exhibit reversed sexual dimorphism for tail length in the breeding season, when their tails are significantly shorter than those of females or males in eclipse plumage. Using both aviary‐based experiments and indices of mate choice and social dominance from a natural population, we found that extent of nuptial plumage and age primarily affected female mate choice and that shorter tails were primarily associated with male:male dominance signaling. The field and aviary studies combined are consistent with the multiple receiver hypothesis, in that each trait appears to be directed primarily to a different set of receivers (plumage for females and tail length for males), though each trait may also signal information to the other set of receivers as well. We propose that sexual selection may favor shorter tail lengths in male red‐backed fairy‐wrens through social competition mechanisms.

Plumage colour acquisition and behaviour are associated with androgens in a phenotypically plastic tropical bird

Androgens regulate male reproductive behaviour and may be a mechanistic link between sexual signals and physiological condition. However, the role of these hormones in regulating prenuptial moult and male plumage signals of passerine birds is unclear. In the red-backed fairy-wren, Malurus melanocephalus, plumage colour is a sexually selected trait and males express three reproductive phenotypes: males can breed in bright red and black plumage or in dull brown plumage, or assume dull plumage and act as nonbreeding auxiliaries; each phenotype differs in parental and reproductive behaviour. We found that plasma androgen concentrations differed significantly between male phenotypes, with red/black breeding males having the highest levels and auxiliaries having the lowest levels across all nesting stages. These hormonal differences were also present during the prebreeding moult when nuptial plumage is acquired. Males also differed significantly in body condition during moult based on the phenotype acquired in the subsequent breeding season, with red/black breeding males being in the best condition and auxiliaries being in the poorest condition. Moreover, androgen concentrations were positively correlated with body condition during prenuptial moult. Thus, in this species, androgens may determine plumage coloration and provide a link between the expression of sexual signals and body condition.

CAROTENOIDS IN THE SEMINAL FLUID OF WILD BIRDS: INTERSPECIFIC VARIATION IN FAIRY-WRENS

Male secondary sexual characters can provide females with information regarding the fertilizing capacity of a male's sperm. In some fishes and birds, intense nuptial coloration is correlated with male fertilizing capacity, but no mechanistic link between coloration and sperm quality has been established. One plausible mechanism is that carotenoid pigments, which color skin and feathers in many animals, are present in seminal fluid and serve as antioxidant protectors of sperm. We used high-performance liquid chromatography (HPLC) to analyze sperm samples from four species of Australian fairy-wren (Malurus) and detected low concentrations (<1 μg ml−1) of carotenoids in some samples. Xanthophyll carotenoids (including lutein and zeaxanthin), which are typically dietary in origin, were present in the seminal fluid of Superb (M. cyaneus) and Splendid (M. splendens) Fairy-Wrens. In contrast, red ketocarotenoids (including astaxanthin and canthaxanthin), which are likely metabolically derived from dietary precursors, were present in the seminal fluid of Red-backed Fairy-Wrens (M. melanocephalus). This work is the first to report carotenoids in avian seminal fluid and suggests that, although carotenoids are at low levels and thus may have limited antioxidant activity, there may be biological variability in avian semen carotenoids on which selection could act.

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.

Plumage color and reproduction in the red-backed fairy-wren: Why be a dull breeder?

Males of many species can breed in distinct alternative phenotypes; for example, in many birds some males breed in dull plumage while others breed in bright plumage. Because females often appear to prefer brighter males, it is unclear why some males breed in dull plumage. Males in dull plumage might enjoy enhanced within-pair reproductive success if they can gain access to better breeding territories, or they might have relatively high extrapair reproductive success if they are better able to intrude on the territories of other males. To test these possibilities, we examined the reproductive consequences of plumage color in the red-backed fairy-wren (Malurus melanocephalus), a species in which males can breed in either bright plumage or dull plumage or serve as nonbreeding auxiliaries. Male plumage color was distributed bimodally and was loosely associated with age, such that some males molted into bright plumage a year or more earlier than others. Both male phenotypes were cuckolded at similar rates, but bright males sired significantly more extrapair young than did dull males, and this effect was independent of age. Thus, 1-year-old males who bred in dull plumage had low seasonal reproductive success compared with same-aged males who bred in bright plumage. These results suggest that males may not reap any fitness benefits by breeding in dull coloration, compared with breeding in bright plumage, but rather may be constrained to breed in suboptimal plumage by the timing of plumage acquisition.

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

In many animals, an individual's social environment and status can change quickly and unpredictably, suggesting an advantage for signals capable of responding to these changes. However, many signaling traits are fixed for relatively long periods. In birds, for example, most plumage‐based signals are constrained by molt and unable to respond to sudden changes in social environment. Soft parts, conversely, are vascularized and may provide an alternative signaling system that can be updated relatively quickly. In this study, the effects of changes in breeding status are documented for a putative plumage‐based signal, plumage brightness, and a putative soft part signal, bill darkness, in the red‐backed fairy‐wren Malurus melanocephalus. Males that switched from unpaired helper to paired breeder within a breeding season developed significantly darker bills within three weeks of the switch relative to males that did not change status. There was no clear corresponding change in plumage brightness, though the data suggests that changes in plumage brightness are at least possible. These results suggest that bill color is a socially mediated trait capable of responding rapidly to changes in breeding status, and it is proposed that the importance of soft parts as labile signals in birds may be currently under‐appreciated.

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

Burning season influences the response of bird assemblages to fire in tropical savannas

Fire plays a pivotal role in structuring ecosystems and often occurs as a human-mediated disturbance for land management purposes. An important component of fire regime is the season of burn. In tropical savannas, most fire management occurs during the dry season; however, wet season burning is often used for pastoral management and may be useful for controlling introduced plant species. We used replicated, experimental fire treatments (unburnt, dry season burnt and wet season burnt), spanning two habitats (riparian and adjacent open woodland), to examine the short- (within 12 months of fire) and longer-term (within four years of fire) changes of bird assemblages in response to wet and dry season burning in tropical savannas of northern Australia. Within 12 months of fire, we observed higher abundances of birds in the burnt treatments, although some species (e.g., red-backed fairy-wren, Malurus melanocephalus) were rarely observed in burnt sites. Dry season burnt sites contained higher abundances of insectivores and granivores, while wet season burnt sites had more carnivores. Four years following burning, dry season burnt sites were characterized by lower abundances, especially of nectarivores and granivores. Dry season burnt sites also contained a different assemblage than wet season burnt sites, but few differences were observed between wet season burnt and unburnt sites. Our results confirm that differences in fire regimes can substantially alter bird assemblages, especially in riparian zones, and emphasize the importance of incorporating burning season in fire management strategies.

Monitoring change in the vertebrate fauna of central Queensland, Australia, over a period of broad-scale vegetation clearance, 1973—2002

This study reports change in the bird, mammal and amphibian fauna of the Emerald district, central Queensland, as detected from comparison of an inventory study undertaken in 1973–76, with a resurvey undertaken in 2001–02. Over this period, the region was subjected to unusually high rates of vegetation clearance, with the extent of native vegetation declining from 87% to 41%. In Australia, and elsewhere, there are remarkably few such long-term longitudinal studies, and particularly so for those that sample the same sites using identical procedures, and for those undertaken in a region of such dramatic environmental change. The ability to detect change from this dataset is constrained by the relatively small number of survey sites (24–45 survey sites, depending upon the taxonomic group considered). The interpretation of change is also affected by very different climatic conditions between the baseline and resurvey. Higher rainfall in the baseline survey period contributed to the most evident change, a major reduction in the number of waterbirds. However, even with waterbirds excluded, there was a significant change in the bird assemblage across the set of survey sites between the two periods. There were significant increases for a number of typically grassland birds (e.g. red-backed fairy-wren (Malurus melanocephalus), brown quail (Coturnix ypsilophora)) and significant decreases for a range of typically forest or woodland birds (e.g. grey shrike-thrush (Colluricincla harmonica), spiny-cheeked honeyeater (Acanthagenys rufogularis), striped honeyeater (Plectorhyncha lanceolata), grey fantail (Rhipidura fuliginosa)). These changes were largely maintained even when the dataset was restricted to only those sites that remained uncleared: that is, changes were evident not only across the changing landscape as a whole but there were also significant (consequential) changes at uncleared sites. Most of the native mammal species that were recorded sufficiently often to test for change showed a pattern of decline. Again, for some species (pale field-rat (Rattus tunneyi), greater glider (Petauroides volans) and eastern grey kangaroo (Macropus giganteus)), this decline occurred even within uncleared woodland sites. The most notable change in the frog fauna was the major increase in the exotic cane toad (Bufo marinus), but there were also significant declines for two native frog species. These results suggest a general trajectory of decline in distinctive woodland species, and their broad-scale replacement by more commensal species (weedy generalists favoured by human modification of the landscape).

Testing the function of petal-carrying in the Red-backed Fairy-wren (Malurus melanocephalus)

In most species of fairy-wren (Malurus spp.), males are known to carry brightly coloured petals and display them to conspecifics. Although petal-carrying by males is often considered an inter-sexual courtship display, anecdotal observations suggest that it may also serve an intra-sexual aggressive function. In this study, we tested hypotheses for the function of petal-carrying displays in the Red-backed Fairy-wren (Malurus melanocephalus) through behavioural observations and aviary-based experiments. All petal displays observed were perpetrated by males, with 90% directed toward females and 10% toward other males. Most petal displays were performed by males in nuptial plumage during intrusions into neighbouring territories, and most displays coincided with the potential fertile period of the female to whom the display was directed. Display items consisted primarily of seeds from Gahnia sp. and flowers from Banksia sp. and Lantana sp., all of which were red or pink and similar to the red backs of nuptial males. Aviary trials found no significant difference in the responses by adult females or adult males to stimulus males with or without petals, substantiating neither a courtship role nor an aggressive role for the display. On the basis of the context of displays in the field, we conclude that the petal-carrying display in the Red-backed Fairy-wren primarily serves an inter-sexual, courtship function, though we could not rule out an intra-sexual, aggressive function.

Costs and benefits of variable breeding plumage in the red-backed fairy-wren.

The red-backed fairy-wren is a socially monogamous passerine bird which exhibits two distinct types of breeding male, bright males that breed in bright red and black plumage and dull males that breed in dull brown plumage. Most males spend their first potential breeding season in dull plumage and subsequent breeding seasons in bright plumage, but a relatively small proportion of males develop bright plumage in their first breeding season. This study quantifies morphology, behavior, and reproductive success of dull and bright males to assess the adaptive costs and benefits of bright plumage while controlling for age. Older bright males (two years of age or older) attempted to increase their reproductive success via copulations with extrapair females, whereas younger (one-year old) bright males and dull males did not. Thus, older bright males spent less time on their own territories, intruded on neighboring groups with fertile females more frequently, gave more courtship displays, and had larger sperm storage organs than did younger bright males and dull males. Microsatellite analyses of paternity indicate that the red-backed fairy-wren has extremely high levels of sexual promiscuity, and that older bright males had higher within-brood paternity than dull males or younger bright males. Regardless of age, bright males were more attractive to females in controlled mate choice trials than were dull males, and both age classes of bright males obtained higher quality mates earlier in the breeding season than did dull males, when nesting success was higher. In conclusion, although it appears that bright plumage increases access to higher quality mates, age also plays a central role in determining a male's overall reproductive success because of the high levels of sexual promiscuity exhibited by the red-backed fairy-wren.

Clearing savannas for use as rangelands in Queensland: altered landscapes and water-erosion processes

This paper presents a framework and some examples of how tree clearing alters landscapes (vegetation structure and faunal habitat) and processes (run-off and soil erosion) for eucalypt savannas in Queensland. Unaltered savannas have a tree-layer and a well-covered ground-layer of perennial grasses, and they provide habitats favoured by a variety of open woodland birds, reptiles and small mammals. Because unaltered savannas have a high ground-cover, they have low rates of run-off and erosion. When savannas are chained, but otherwise unaltered, trees rapidly regrow and increase in canopy cover. The exotic buffel grass often establishes in chained regrowth (especially if grazed), although the cover of native grasses such as black speargrass remains high (unless heavily grazed). We found that open woodland birds declined on these chained regrowth sites, except for the Weebill, which increased in abundance. When savannas are cleared of trees and woody debris and developed as improved pasture systems, both exotic and native perennial grass increased in cover. However, open woodland fauna abundance declined whereas grassland fauna such as the Red-backed Fairy-wren and the House Mouse increased in abundance. If these pasture sites are heavily utilised by livestock so that ground-cover is reduced, rates of run-off and soil loss are likely to rapidly increase, especially as cover declines below 40%. These run-off and erosion findings suggest that the manner in which savanna landscapes are cleared and subsequently used will have flow-on effects at catchment scales.

A condition dependent link between testosterone and disease resistance in the house finch.

Testosterone has recently been proposed as a link between male quality and health and the expression of sexual traits. We investigated the relationship between testosterone and measures of the individual condition and health of males in a natural population of house finches (Carpodacus mexicanus). We also conducted a captive experiment in order to test for the effects of testosterone on resistance to coccidia, which is a common parasite of house finches. Free-living males in better condition had higher testosterone levels and lower corticosterone levels than free-living males in poor condition. In our captive experiment, increased testosterone accelerated the rate of coccidial infection as compared with sham-implanted or gonadectomized males. Although the differences were not significant, free-living males infected with coccidia had lower levels of testosterone and higher levels of corticosterone than males that were not infected. Thus, experimentally elevating testosterone levels in captive males resulted in a higher percentage of infected males, while free-living males with coccidial infection had low testosterone levels. This apparent discrepancy between captive and free-living males in the association of testosterone and disease may be explained by the condition dependence of testosterone. These results suggest that the testosterone-dependent sexual traits reliably indicate male overall condition and health and, thus, females could benefit from assessing potential mates based on these traits.

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.

Male display rate reveals ejaculate characteristics in the Trinidadian guppy,Poecilia reticulata.

Previous work (Reynolds and Gross 1992) has demonstrated that mate choice enables female guppies, Poecilia reticulata , to obtain heritable benefits (‘good genes’) for their offspring. It is not yet known whether males also signal their functional fertility, that is, their viability as fathers, to female guppies. Our study tested the hypothesis that a male9s behaviour reveals characteristics of his ejaculate. We uncovered a strong correlation between display rate and sperm number in male guppies derived from two wild Trinidadian populations. This result indicates that information on the functional fertility of potential mates is available to females. However, our investigation also found a significant relationship between the frequency of sneaky mating and sperm number. Female guppies in wild populations, particularly those experiencing a high predation regime, are constantly subjected to sneaky mating attempts. As the males responsible for these sneaky matings have highest reserves of sperm they may have the capacity to undermine female choice. The implications of these findings for sperm competition are discussed.

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.

Use of roadside remnants of softwood scrub vegetation by birds in south-eastern Queensland

Birds in roadside and remnant patches of vegetation in the Marburg district of south-eastern Queensland were studied from November 1989 to February 1990. Effects of the length, width and height of the tree, shrub and herb layers, and their major components, on the bird community were determined. In all, 43 species of birds were observed in roadside vegetation; 16 of these were abundant and widely distributed. Silvereyes were most frequently observed (240 observations), followed by superb fairy-wrens (59), yellow thornbills (53), double-barred finches (26), red-backed fairy-wrens (25) and Lewin's honeyeaters (20). Apart from silvereyes (20-654 of observations), and superb fairy-wrens on two roads (12 and 13%) and yellow thornbills on one (15%), no other species constituted more than 10% of observations on any road. In all, 48 species of birds were observed in remnant patches of vegetation, 14 in all of them. Rates of detection in remnant patches ranged from 2.7 to 5.3 birds per 5 min compared with a mean maximum rate for roadside vegetation of 1.3. The richness of the roadside avifauna increased significantly (P=0.001) as the volume (length x width x height) of the tree component, especially the softwood species, increased. The diversity of tree species in softwood remnants and the greater canopy density appear to be important factors that enhance the bird community. The number of birds was also correlated (P=0.05) with the volume of brigalow, Acacia harpophylla. The correlation of the volume of woody weeddshrubs with the number of birds was low (P=0.05), and with the number of species not significant, even though woody weeds were a major component of roadside vegetation. Although supporting fewer birds than remnant patches of vegetation, roadside vegetation contributes importantly to conservation of the avifauna in the Marburg district. Some simple management practices, such as maintaining a minimum width of undisturbed vegetation and retaining vegetation diversity, would ensure or enhance the long-term conservation benefits. Opportunities to regenerate softwood remnants could also be taken, particularly to enhance the value, and possibly prolong the life, of the associated remnants of brigalow.

Penetration of Central Australia by Malurus melanocephalus

Penetration of Central Australia by <i>Malurus melanocephalus</i>