Plumage Research Articles

English

The Two-banded Plover ( Charadrius falklandicus ) ranges from the southern tip of South America, where it reproduces, to southern Brazil, where it winters. Censuses were conducted between 2007 and 2012 on the beaches and in the Lagoa do Peixe, and historical data were consulted in order to determine the distribution and abundance of Two-banded Plovers in southern Brazil and document the reproductive status of this species during the austral summer. During the winter period, from March to September, it occurs in greatest abundance in the Lagoa do Peixe National Park, Brazil, and can be found in densities of up to 4.4 individuals per hectare in the lagoon in March. Analysis showed lower bird abundances in high human impacted wintering sites. In the same way, the bird numbers were negatively correlated with the higher human impacted areas, but not significantly. In October 2011, we documented the first nest for this species near the lagoon, which in addition to sightings of young and adults with breeding plumage indicates that this region serves as a nesting area for part of the population during the summer breeding season

Seasonal male plumage as a multi-component sexual signal: insights and opportunities

Seasonal breeding plumage of male fairy-wrens (Malurus spp.) shows significant inter-and intra-specific variation in several potential signalling components that we systematically review here. There is extensive colour variation in the genus, possibly related to variation in visual sensitivity. In many species, males can delay development of their first complete breeding plumage for one or more years, although males in more complete breeding plumage appear to be reproductively more successful. An additional sexual signal, and an evolutionary innovation, is the timing of the pre-breeding moult. A mechanism regulating this moult is testosterone, which can stimulate initiation of moult and development of male breeding colouration and is presumably required for maintenance of the breeding plumage. Males undertake pre-breeding moult earlier as they age, and early pre-breeding moult appears selected by female choice for extra-pair mates. Few studies have addressed variation in colour quality or the role of plumage in aggressive interactions. Condition-dependence of moult or breeding plumage has not been experimentally investigated. We argue that the genus is particularly suited to comparative analyses, as it provides informative contrasts in colour, plumage development, patterns of moult, colour vision and mating system, offering many exciting opportunities for testing evolutionary theories on function and maintenance of sexual signals.

Rural poultry marketing systems and associated marketing constraints in two agro-ecological zones of central Tigray, Northern Ethiopia

A study on rural poultry marketing was conducted in lowland and midland agro-ecological zones of central Tigray, in northern Ethiopia with the objective of characterization of rural poultry marketing system under rural household management. A total of 160 rural households, 80 from each district, were randomly selected and 50% of them were female headed households. Data were collected using semi structured questionnaire and group discussion with key informants and traders. Twenty seven chicken and egg traders and 60 consumers were also randomly selected and interviewed to collect market information. All age group of chickens except chicks (< 2 months) were sold at market but cocks and cockerels take the largest proportion. The total number of live birds and eggs sold per households per year was significantly greater (P<0.0001) in midland than in lowland. Chicken and egg selling was also significantly greater (P<0.01) in female headed households than in male headed households. Chickens with red plumage color were dominant in the market covers 56.2% of the total chickens. Average numbers of birds and eggs sold per household per year were 4.3 and 48.75 in lowland and 6.2 and 81.25 in midland, respectively. Mean price of matured and grower chickens was 49.96 birr and 35.3 birr in lowland and 51.3 birr and 39.7 birr in midland, respectively, and average price of eggs was 1.3 birr in lowland and 1.4 birr in midland agro-ecology. Average price of chickens and eggs in lowland areas was significantly (P<0.0001) lower than average price in midland agro-ecological zone of the study area. There was also a significant difference (P<0.0001) in price of chicken products between ordinary market days and festival market days. Price of double comb cocks was significantly greater (P<0.0001) than price of single comb cocks. Chicken and egg traders collect chickens and eggs from producers at farm gets, road sides and different local or urban markets. In turn 87.8% of the collected chickens and 74.9% of the collected eggs were sold to direct consumers. Lack of extension service for indigenous ecotypes, lack of appropriate market place and seasonality of market prices in both agro-ecologies were the main constraints of rural poultry marketing in the study area. Therefore, separate market place and appropriate poultry extension and credit packages should be designed to improve rural poultry marketing in both agro-ecologies.

Specific immunity and polymorphism of breeding plumage in pied flycatcher (Ficedula hypoleuca) males (Aves: Passeriformes)

The relationship between the type of melanin-based plumage colouration and the strength of experimentally induced immune response was studied using as an example a pied flycatcher population from the Moscow region. The breeding plumage of pied flycatcher males exhibits the full spectrum of transitions from contrasting black-and-white to cryptic brownish, the latter being very similar to the colouration of females. In spite of numerous studies, the nature of this polymorphism still remains vague. Unlike many other avian species with monocyclic breeding, a considerable fraction of pied flycatchers overlaps two energy-consuming productive processes, breeding and moult, over the whole species range. During the main experimental treatment we activated the humoral immunity of free-living males in chick-rearing period by injection of nonpathogenic multifactorial antigen (sheep red blood cells, SRBC) and estimated the strength of the immune responses after repeated captures in 6–8 days. In addition, after each capture we evaluated the numbers of leucocytes (WBC), heterophil to lymphocyte ratios (H/L) and measured night time basal metabolic rates (BMR). Non-moulting males of different colour types showed the same immune responses. Among moulting birds, the strength of the immune response was significantly higher in pale males (morphs 4–7 by Drost’s scale) than in bright males with rich melanin-based colouration (morphs 2–3). This difference resulted from two opposite processes. During moulting, pale males heightened the antibody titer after immunization, while bright males tended to reduce the strength of immune response. Possibly such an asymmetry in immunocompetence at the first stage of moult reflects the different life strategies of pied flycatcher males—conspicuous birds less commonly overlap breeding with moult than cryptic ones.

Putative Segregation of Two Yellow Wagtail Taxa by Breeding Habitat in Western Siberia: Possible Implications forMotacilla flavaTaxonomy

The Yellow Wagtail Motacilla flava consists of about 18 taxa whose taxonomic relationships are unclear. Some authors elevate 11 taxa to species based on often characteristic nuptial plumages of males, whereas others recognize two species based on molecular data. Hybridization is a regular event but with intriguingly varying intensity between different taxa. In spite of breeding generally in damp fields, their breeding habitat is actually rather diverse, which offers an opportunity for ecological segregation by breeding habitat. Indeed, some authors describe habitat differences between taxa but others do not. Two sympatrically occurring taxa are thunbergi and beema in European Russia and Western Siberia. In this study we describe their breeding habitat and determine whether this differs between taxa. We aimed to determine whether breeding habitat could be an ecological factor for sub-specific segregation in this part of their breeding range. We found strong indications for segregated breeding, despite the rather limited dataset: thunbergi occurred in bogs as a breeding bird and beema was dominantly found breeding in floodplain meadows. On one location bog and floodplain were separated by only 1.5-2 km of forest, yet here too only thunbergi occurred on the bog and beema on floodplain meadows. Following recent molecular taxonomic findings our thunbergi might very well concern plexa, belonging to the eastern species. As beema is assigned to the western species, the observed spatial segregation between plexa and beema may be representative of habitat separation of the western and eastern species in areas where they occur sympatrically. Large scale segregated breeding due to different habitat preferences could have consequences for taxonomic interpretations within the M. flava complex.

A window on the past: male ornamental plumage reveals the quality of their early-life environment

It is well established that the expression of many ornamental traits is dependent on the current condition of the bearer. However, conditions experienced in early life are also known to be important for an individual's subsequent fitness and therefore, directly or indirectly, for the fitness of their mate. Specifically, a recent hypothesis suggests that sexually selected traits might be sensitive to conditions experienced during early-life development and thereby function as honest indicators of developmental history. Whether this applies to colourful male plumage, however, is largely unknown. We tested this idea with a field experiment by manipulating neonatal nutrition in a sexually dichromatic passerine, the hihi (Notymystis cincta). We found that carotenoid supplementation increased nestling plasma carotenoid concentration, which was in turn correlated with increased yellow saturation in male breeding plumage after moulting. We also found that the post-moult luminance (lightness) of the white ear-tufts tended to be reduced in males that had received an all-round nutritional supplement as nestlings. Black breeding plumage was not affected by neonatal nutritional treatment. Although the mechanisms that generate colourful plumage are evidently diverse, our results show that at least some parts of this display are accurate indicators of environmental conditions during development.

Female tawny-bellied seedeaters do not prefer more colorful males in choice experiments

Fil: Facchinetti, Carolina. 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

With Genomes, Pecking Away at Pigeons' Plumage

With Genomes, Pecking Away at Pigeons' Plumage

Increased conspicuousness can explain the match between visual sensitivities and blue plumage colours in fairy-wrens

Colour signals are expected to match visual sensitivities of intended receivers. In birds, evolutionary shifts from violet-sensitive (V-type) to ultraviolet-sensitive (U-type) vision have been linked to increased prevalence of colours rich in shortwave reflectance (ultraviolet/blue), presumably due to better perception of such colours by U-type vision. Here we provide the first test of this widespread idea using fairy-wrens and allies (Family Maluridae) as a model, a family where shifts in visual sensitivities from V- to U-type eyes are associated with male nuptial plumage rich in ultraviolet/blue colours. Using psychophysical visual models, we compared the performance of both types of visual systems at two tasks: (i) detecting contrast between male plumage colours and natural backgrounds, and (ii) perceiving intraspecific chromatic variation in male plumage. While U-type outperforms V-type vision at both tasks, the crucial test here is whether U-type vision performs better at detecting and discriminating ultraviolet/blue colours when compared with other colours. This was true for detecting contrast between plumage colours and natural backgrounds (i), but not for discriminating intraspecific variability (ii). Our data indicate that selection to maximize conspicuousness to conspecifics may have led to the correlation between ultraviolet/blue colours and U-type vision in this clade of birds.

Biological activity of nanoscale colloidal selenium

Several studies have shown that elements (metals and nonmetals) in the nanoscale form are much less toxic and do not accumulate in the body, as they are assimilated as trace elements in the process of metab� olism. Thus, the active ingredients of drugs and feed additives in the form of nanoscale elements are com� plexes of nanoparticles, which are characterized by a high surface activity and ability to penetrate into the cell and can actively influence the intracellular metab� olism by stimulating various processes. Selenium, one of the key trace elements essential for normal functioning of animals and humans, is of great theoretical and practical interest. Selenium is a compo� nent of the enzyme glutathione peroxidase, which is required to scavenge peroxides during metabolism. Selenium is also involved in the regulation of the per� meability of cell membranes, prevention of stomach and heart myopathy, and pancreas fibrous degenera� tion. However, the inclusion of selenium in the diet should be strict standardized. Selenium deficiency results in a reduced weight gain, deterioration of plum� age, muscular dystrophy, and development of exudative diathesis. An excess of selenium in the feed leads to the development of chronic toxicosis and disruption of cal� cium and sulfur metabolism. Disturbances in the syn� thesis of keratin in feathers and bones lead to the devel� opment of enteritis and degeneration of kidneys. Acute selenium poisoning causes hemorrhagic intestine inflammation, blocks oxidation and, as a result, leads to pulmonary edema and bleeding of the liver [1]. At present, a wide range of selenium and selenium� containing feed additives are used. Inorganic (such as selenite and sodium selenate) organic (such as sele�

The proteomics of feather development in pied flycatchers (Ficedula hypoleuca) with different plumage coloration

The genetic theory of morphological evolution postulates that form evolves largely by changing the expression proteins that are functionally conserved. It follows that understanding the function of proteins during different phases of development as well as the mechanisms by which the functions are modified is a prerequisite for understanding evolutionary change. Male pied flycatchers exhibit marked phenotypic variation in their breeding plumage. This variation has repeatedly been shown to have adaptive significance, but the molecular basis of this variation is not known. Here, we characterize the proteome of developing pied flycatcher feathers from differently pigmented males and also introduce a new method for examining the effect sizes of expression differences in protein interaction networks. Approximately 300 proteins were identified in the developing feathers of males. Gene products associated with cellular transport, cell metabolism and protein synthesis formed a large part of the developing feather proteome. Sixty-five proteins associated with the development of the epidermis and/or pigmentation were detected in the data. The examination of expression level differences of protein-protein interaction networks revealed an immunological signalling-related network to exhibit significantly higher expression in black compared to brown males. Additionally, indications of differences in energy balance and oxidative stress related characteristics were detected. Together, these results provide new insight into the molecular mechanisms and evolutionary significance of plumage colour variation.

Social environment affects acquisition and color of structural nuptial plumage in a sexually dimorphic tropical passerine.

Structural colors result from the physical interaction of light with organic materials of differing refractive indexes organized at nanoscale dimensions to produce significant interference effects. Because color properties emerge from these finely organized nanostructures, the production of structural coloration could respond to environmental factors and be developmentally more plastic than expected, functioning as an indicator of individual quality. However, there are many unknown factors concerning the function and mechanisms regulating structural coloration, especially relative to social environment. We hypothesized that social environment, in the form of competitive settings, can influence the developmental pathways involving production of feather structural coloration. We experimentally assessed the impact of social environment upon body condition, molt and spectral properties of two types of structural color that compose the nuptial plumage in blue-black grassquits: black iridescent plumage and white underwing patches. We manipulated male social environment during nine months by keeping individuals in three treatments: (1) pairs; (2) all-male groups; and (3) male-female mixed groups. All morphological characters and spectral plumage measures varied significantly through time, but only acquisition of nuptial plumage coverage and nuptial plumage color were influenced by social environment. Compared with males in the paired treatment, those in treatments with multiple males molted into nuptial plumage faster and earlier, and their plumage was more UV-purple-shifted. Our results provide experimental evidence that social context strongly influences development and expression of structural plumage. These results emphasize the importance of long-term experimental studies to identify the phenotypic consequences of social dynamics relative to ornament expression.

Not Always Black and White: Colour Aberrations in the Dovekie

We describe four records of colour aberrations in the dovekie (Alle alle). During six years of studies of breeding ecology in two large dovekie colonies in West Spitsbergen, we recorded one albino chick (white feathers, red eyes, pinkish legs and feet), one adult or subadult with a “brown” aberration (all black parts turned dark brown), one adult in a typical summer plumage with depigmented (pinkish) legs and feet, and one chick in a typical plumage, but with whitish feathers on back and wing coverts. Albinism and “brown” mutations are heritable traits. The two remaining colour aberrations probably have been acquired and might have been caused by disease, malnutrition, or other unknown factors.

New records and a review of the distribution of the Arctic Tern Sterna paradisaea Pontoppidan, 1763 (Aves: Sternidae) in Brazil

We report new records of the Arctic Tern Sterna paradisaea Pontoppidan, 1763 for the coast of Rio Grande do Sul, southernmost Brazil. Birds were in first alternate plumage, apparently overwintering in the region. A literature and museum review revealed the existence of 21 localities with records of this species in Brazil. Ten specimens were obtained in the country, attributable to eight localities. Records from five other localities were documented with band recoveries or photographs. We were able to clarify information from one of the undocumented records, while the remaining requires further investigation and/or documentation. Our review and new information on migration routes confirm that the Arctic Tern in Brazil is a regular, seasonal visitor from the northern hemisphere. We also suggest that waters off south Brazil may be used by overwintering individuals, especially during the austral winter.

Sex and age differences in the development of breeding plumage in the Wood Sandpiper Tringa glareola during spring migration in north-eastern Poland

We investigated the effects of sex and age on the progression of breeding plumage moult in the Wood Sandpiper, a migrant wader that shows weak sexual size dimorphism and no dichromatism. We sexed the birds by DNA and examined the plumage of 416 Wood Sandpipers caught at a spring stopover site in north-eastern Poland. We scored the proportion of new breeding-type feathers on the head, back and scapulars in 20%-wide stages, and summed these scores as a body moult index, and on the lesser and median wing coverts summed as a wing covert moult index. Only 10% of all these birds fully developed breeding plumage on the upper body and 8% had only 21-40% of new feathers there. About 90% of the birds had moulted less than half of their wing coverts. No Wood Sandpiper showed a complete breeding plumage. We investigated whether moult indices were related to the date of the bird's capture and its body mass adjusted for size, age and sex, using generalised linear models. The best model indicated that the body-moult index was significantly affected by age, sex and year. Immatures had a more advanced body moult than adults, and females were more advanced than males. None of the predictors had a significant effect on the wing-covert moult index.

Conspicuous sexual signals in a socially monogamous passerine: the case of neotropical Blue-black Grassquits

Sexual selection has shaped many traits involving communication, behavior, morphology, and reproductive strategies. Sexual communication in the Blue-black Grassquit Volatinia jacarina involves an iridescent, nuptial plumage and the exhibition of a complex motor and acoustic mating display. Blue-black Grassquits breed in small, aggregated territories, are socially monogamous, but have high rates of extrapair fertilization and intensive paternal care. Here, we discuss the evolution of sexually selected ornaments in this species and review some studies that have evaluated their costs and benefits. Our data suggest that females have an active role in obtaining extrapair fertilizations, but appear to be indiscriminate in their choice of extrapair males. However, it remains necessary to evaluate female choice in natural circumstances, and the effects of such on male reproductive success. This is particularly important because, in the field, we found that the male motor display may provide a useful cue for nest predators, and therefore evolution of female choice may be constrained by the probability of higher nest predation associated with choosing males exhibiting high display rates. Our studies also indicate that small males have an advantage in aggressive interactions with larger males. We hypothesize that small male size may be driven by female choice for male motor performance, including aspects of display agility and acrobatic capacity, leading to better performance by small males in intrasexual interactions involving flight within confined spaces. Alternatively, the food resource may be more valuable to smaller males, resulting in higher aggression to access the food.

Developmental immune history affects adult immune function but not carotenoid‐based ornamentation in mallard ducks

Summary1. Sexually selected traits often honestly advertise aspects of individual quality, such as immune function. Such traits have traditionally been thought to reveal real‐time information (e.g. current health state), but they may also reflect immunological conditions experienced during ontogeny, which can fundamentally shape survival prospects, adult immune function, and reproductive performance.2. We tested the effects of immune challenges (injections of sheep red blood cells) during neonatal development on adult immune function and ornamental coloration in male mallard ducks (Anas platyrhynchos). Mallards have a carotenoid‐pigmented beak that plays a role in mate choice, and because carotenoids are also associated with immune responsiveness, carotenoid accumulation in body tissues may change as a function of immunological state during development and into adulthood.3. We found that mallards that received immune challenges at the completion of growth (8–10 weeks old) had a reduced proinflammatory response (as measured by the local swelling response to phytohemagglutinin; PHA) as adults, compared to control birds and those receiving immune challenges at other developmental time points. Mallards that received immune challenges during the acquisition of nuptial plumage (13–15 weeks old) had an increased humoral immune response as adults, as assessed by antibody production to keyhole limpet hemocyanin (KLH). Body mass, adult beak colour, and carotenoid circulation were not affected by immune challenges issued at any point during development.4. Circulating carotenoid levels prior to adult immune challenge and change in carotenoid titre over the course of the adult immune assessment period were correlated with degree of response to PHA and KLH at adulthood, as well as with nitric oxide production, which is associated with innate immunity. However, the direction of these correlations varied by type of immune assessment. Surprisingly, unlike in several previous studies, we found no link between beak coloration and adult immune function.5. These findings demonstrate the importance of developmental immune challenges in shaping adult immune response, although the precise mechanisms remain unidentified. Moreover, we found support for the hypothesis that carotenoids are linked to immune function, because of the relationship between multiple immune responses and both initial and change in circulating carotenoid levels.6. However, our study does not support the hypothesis that sexual signal expression reveals developmental immune history. Taken together, our findings suggest that the relationships between carotenoid physiology, carotenoid‐based ornamentation, and immune function are complex.

Contour-feather moult of Bar-tailed Godwits (Limosa lapponica baueri) in New Zealand and the northern hemisphere reveals multiple strategies by sex and breeding region

The extreme long-distance migration of Alaskan breeding Bar-tailed Godwits (Limosa lapponica baueri) may present severe constraints on annual moult, and high individual variation in plumage and migration timing suggests that multiple strategies by sex and breeding region may exist. We used digital photography of free-living Bar-tailed Godwits to describe the timing and extent of pre-basic and pre-breeding contour-feather moults in New Zealand, and used plumage of breeding birds in Alaska to infer the proportion of moults occurring in Alaska and Asia. These data demonstrated that: (1) Godwits conducted overlapping pre-alternate and pre-supplemental moults; (2) pre-basic and pre-breeding moults were scheduled differently in relation to southbound and northbound migration respectively; (3) northern and southern Alaskan breeding Godwits of each sex were distinguishable by plumage differences throughout the non-breeding season; and (4) males and northern breeders achieved more extensive breeding plumage by spending longer in pre-breeding moult in New Zealand, rather than through faster moult rates or greater investment in moult during migratory stopover in Asia. The existence of a ventral pre-supplemental moult implies that contemporary selection for red breeding plumage overrides older selection for barred alternate plumage. Our use of individual-based data revealed a continuum of annual moult strategies within the population, which may reflect individual differences in any combination of sex, size, migration distance or breeding location. Even within the highly constrained annual cycle of extreme long-distance migrants, differential selection influences how individuals manage trade-offs among non-breeding activities such as moult, fuelling and migration.

Fluctuations in population composition dampen the impact of phenotypic plasticity on trait dynamics in superb fairy‐wrens

1. In structured populations, phenotypic change can result from changes throughout an individual's lifetime (phenotypic plasticity, age-related changes), selection and changes in population composition (environment- or density-driven fluctuations in age-structure). 2. The contribution of population dynamics to phenotypic change has often been ignored. However, for understanding trait dynamics, it is important to identify both the individual- and population-level mechanisms responsible for trait change, because they potentially reinforce or counteract each other. 3. We use 22 years of field data to investigate the dynamics of a sexually selected phenological trait, the timing of nuptial moult in superb fairy-wrens Malurus cyaneus. 4. We show that trait expression is both climate- and age-dependent, but that phenotypic plasticity in response to climate variability also varies with age. Old males can acquire nuptial plumage very early after high rainfall, but 1- to 2-year-olds cannot. However, males of all ages that defer moult to later in the year acquire nuptial plumage earlier when conditions are warmer. 5. The underlying mechanism appears to be that old males may risk moulting in the most challenging period of the year: in autumn, when drought restricts food abundance and during the cold winter. By contrast, young males always moult during the spring transition to benign - warmer and generally wetter - conditions. Temperature changes dominate this transition that heralds the breeding season, thereby causing both young and late-moulting older birds to be temperature sensitive. 6. Climate and age also affect trait dynamics via a population dynamical pathway. The same high rainfall that triggers early moulting in old males concurrently increases offspring recruitment and thereby reduces the average age of males in the population. Consequently, effects of rainfall on trait dynamics through phenotypic plasticity of old males are dampened by synchronous rejuvenation of the age-structure. 7. A long-term trend towards drier environments prompted phenotypic change because of plasticity, but this was masked by climate-driven demographic change (causing apparent stasis). This suggests a novel explanation for why trait change may fail to reflect the observed pattern of directional selection or phenotypic plasticity.

Sexually Selected Male Plumage Color Is Testosterone Dependent in a Tropical Passerine Bird, the Red-Backed Fairy-Wren (Malurus melanocephalus)

BackgroundSexual signals, such as bright plumage coloration in passerine birds, reflect individual quality, and testosterone (T) may play a critical role in maintaining signal honesty. Manipulations of T during molt have yielded mixed effects on passerine plumage color, in most cases delaying molt or leading to production of drab plumage. However, the majority of these studies have been conducted on species that undergo a post-nuptial molt when T is low; the role of T in species that acquire breeding plumage during a pre-nuptial molt remains largely unexplored.Methodology/Principal FindingsWe experimentally tested the effects of increased T on plumage color in second-year male red-backed fairy-wrens (Malurus melanocephalus), a species in which after-second-year males undergo a pre-nuptial molt into red/black (carotenoid and melanin-based) plumage and second-year males either assume red/black or brown breeding plumage. T treatment stimulated a rapid and early onset pre-nuptial molt and resulted in red/black plumage acquisition, bill darkening, and growth of the sperm storage organ, but had no effect on body condition or corticosterone concentrations. Control males molted later and assumed brown plumage. T treated males produced feathers with similar but not identical reflectance parameters to those of unmanipulated after-second-year red/black males; while reflectance spectra of red back and black crown feathers were similar, black breast feathers differed in UV chroma, hue and brightness, indicating a potentially age and plumage patch-dependent response to T for melanin- vs. carotenoid-pigmentation.Conclusions/SignificanceWe show that testosterone is the primary mechanism functioning during the pre-nuptial molt to regulate intrasexually variable plumage color and breeding phenotype in male red-backed fairy-wrens. Our results suggest that the effects of T on plumage coloration may vary with timing of molt (pre- vs. post-nuptial), and that the role of T in mediating plumage signal production may differ across age classes, plumage patches, and between pigment-types.