Male Plumage Research Articles

Using point-of-care devices to examine covariation among blood nutritional-physiological parameters and their relationships with poxvirus infection, habitat urbanization, and male plumage coloration in house finches (Haemorhous mexicanus).

The development of inexpensive and portable point-of-care devices for measuring nutritional physiological parameters from blood (e.g., glucose, ketones) has accelerated our understanding and assessment of real-time variation in human health, but these have infrequently been tested or implemented in wild animals, especially in relation to other key biological or fitness-related traits. Here we used point-of-care devices to measure blood levels of glucose, ketones, uric acid, and triglycerides in free-ranging house finches (Haemorhous mexicanus)-a common songbird in North America that has been well-studied in the context of urbanization, nutrition, health, and sexual selection-during winter and examined (1) repeatability of these methods for evaluating blood levels in these wild passerines, (2) intercorrelations among these measurements within individuals, (3) how blood nutritional-physiology metrics related to a bird's body condition, habitat of origin (urban vs. suburban), poxvirus infection, and sex; and (4) if the expression of male sexually selected plumage coloration was linked to any of the nutritional-physiological metrics. All blood-nutritional parameters were repeatable. Also, there was significant positive covariation between concentrations of circulating triglycerides and glucose and triglycerides and uric acid. Urban finches had higher blood glucose concentrations than suburban finches, and pox-infected individuals had lower blood triglyceride concentrations than uninfected ones. Last, redder males had higher blood glucose, but lower uric acid levels. These results demonstrate that point-of-care devices can be useful, inexpensive ways of measuring real-time variation in the nutritional physiology of wild birds.

Losses of sexual dichromatism involve rapid changes in female plumage colors to match males in New World blackbirds.

Differences in coloration between the sexes (sexual dichromatism) can increase or decrease in a species through evolutionary changes in either or both sexes diverging or converging in their colors. Few previous studies, however, have examined the relative rates of such changes, particularly when dichromatism is lost. Using reflectance data from 37 species of the New World blackbird family (Icteridae), we compared evolutionary rates of plumage color change in males and females when dichromatism was either increasing (colors diverging) or decreasing (colors converging). Increases in dichromatism involved divergent changes in both sexes at approximately equal rates. Decreases in dichromatism, in contrast, involved changes in females to match male plumage colors that were significantly more rapid than any changes in males. Such dramatic changes in females show how selection can differ between the sexes. Moreover, these evolutionary patterns support the idea that losses of dimorphism involve genetic mechanisms that are already largely present in both sexes, whereas increases in dimorphism tend to involve the appearance of novel sex-specific traits, which evolve more slowly. Our results have broad implications for how sexual dimorphisms evolve.

The impact of habitat and migration on plumage colour in Cardinalidae

Abstract Plumage coloration arises from a complex concert of selection pressures incorporating regional ecology, the light environment and genomic architecture. Here, we analyse the evolution of coloration in cardinals and grosbeaks (Cardinalidae) from the avian visual perspective and test the relative roles of life-history traits in shaping plumage evolution. We incorporate life-history data from three separate sources to analyse the correlated evolution of plumage coloration and ecological and habitat classifications for males and females. Our results show that males and females evolve under different axes of selection and that correlations with life-history traits differ between the sexes. We find that preferences for semi-open, fragmented habitat are correlated with male, but not female, plumage complexity. We also find that migration, long heralded as a driver of sexual dichromatism, is correlated with reduced plumage complexity in females, but not significantly correlated with male plumage coloration. Finally, our results showcase that user-defined categorical metrics can influence or, potentially, even mislead the interpretation of results, highlighting the need to measure habitat quantitatively rather than with subjective, categorical metrics.

Male’s age and plumage coloration predicts brood sex ratio in the Common Kingfisher (Alcedo atthis)

Plumage ornaments of birds, both pigment-based and structural, are considered age or condition-dependent, honestly signalling male quality, sexually selected traits, influencing the variation in breeding performance as well as adaptive sex allocation. In the present study, we examine the effect of age of males on the plumage structural colour in Common Kingfisher, and evaluate the breeding output (laying date, total number of young per breeding season, mean number of young per nest, total number of broods) and sex ratio in relation to two ornamental traits (forehead and rump structural colour). During the three years 2016–2018 in the Danube river system (south-western Slovakia), we collected data from 49 males, 102 broods and 645 nestlings. Our data demonstrate that structural colour is a condition-related and age-sensitive signal, while males with increased weight expressed less saturated blue forehead feathers, and old males displayed more saturated cyan rump feathers than young ones. Moreover, the brood sex ratio varies with male coloration in an age-dependent manner. The plumage colour of young males did not affect the brood sex ratio, whereas old males with increasing intensity of cyan rump had more sons than duller ones. Neither single ornamental trait nor age predicted breeding output of kingfisher males. Nevertheless, our results indicate that the blue structural plumage of kingfisher males may serve as an indicator of age and a certain kind of quality with a consequence on adaptive sex allocation in this species.

Extra‐pair paternity is not repeatable between years in Pied Flycatchers (Ficedula hypoleuca): a role for social context

Extra‐pair paternity (EPP) is the consequence of the interactions between a social pair and extra‐pair males during the female's fertile phase in a specific social context and ecological environment. Although EPP occurs in many avian species, there is a lack of understanding of how environmental factors may impact its frequency. Accordingly, the relative importance of individual characteristics on the one hand, and of their immediate social environment on the other, may affect EPP repeatability and thereby the capacity of this trait to respond to selection. If EPP is an individual genetically based trait that may respond to selection, we expect it to be repeatable across breeding seasons. To check this possibility, we analysed the within‐individual repeatability in EPP of breeding males and females in two natural populations of Pied Flycatchers Ficedula hypoleuca in central Spain during three field seasons. We then studied the relationship between EPP and individual male and female traits (only some of which were themselves repeatable), as well as key context variables such as breeding synchrony and population density. Our results showed no repeatability for EPP in either sex. We found a positive association with laying date and stronger associations of EPP with male plumage and morphological traits than with female characteristics. We suggest that the variable social environment is an important modulator of EPP patterns, and that differences between field EPP studies in this respect may explain contradictory results in the same species, even in the same populations in different years.

Male plumage colouration predicts female reproductive investment and nestling survival in a colour dimorphic tropical songbird

In sexually colour dimorphic bird species, males can exhibit phenotypic variation, with males breeding in either dull female-like plumage or brightly coloured plumage. Two contradictory hypotheses predict that the male phenotype variation can influence the female investment in a given breeding attempt. Whereas females usually prefer males in bright coloured plumage, the “differential allocation hypothesis” predicts that females should invest more in their reproductive output when mating with them; while the “compensatory investment hypothesis” predicts that females should invest more when mating with non-preferred males. To test those predictions, we analysed reproductive data for two consecutive breeding seasons (2018–2019 and 2019–2020) of Lined Seedeaters Sporophila lineola. S. lineola is a socially monogamous songbird species in which males exhibit two breeding phenotypes, a black-and-white plumage being the most common, and a less common female-like brownish plumage. Our findings show that females mated with brownish males have a higher reproductive investment (i.e., egg volume) than those mated with black-and-white males. Despite the lower investment of females in egg volume, our results showed that black-and-white males have a higher nestling survival, producing more hatchings and fledglings per season than brownish males, which could suggest a higher fitness. Our findings indicate that investment allocation on the eggs and offspring survival rates can be attributed to the plumage colour of males.

Female and male plumage brightness is positively correlated among populations of the dichromatic Variable Seedeater

Abstract Because studies of plumage coloration often focus on highly elaborate and conspicuous males, little is known about the factors driving theevolution of drab plumage in females of dichromatic species. We explored variation in the color properties of drab female plumage across subspecies of the Variable Seedeater (Sporophila corvina) and found a correlation between plumage brightness of male and female plumage patches. This correlation is consistent with the hypothesis that differences in plumage brightness among females result, at least partially, from a genetic correlation or shared developmental pathway with the more conspicuous male plumage traits that are shaped by sexual selection. Furthermore, we modeled the perception of female plumage using the avian visual system and found that most of the variation in color among females is undetectable by birds; therefore, it is unlikely for such variation to have evolved via direct sexual selection as a signal for recognition or assortative mating. Together, these results suggest that variation in S. corvina female color result from non-adaptive processes. However, we found a reduced variation on color of dorsal patches compared with that of ventral patches among females, which could be explained by natural selection on crypsis, reducing the variation on dorsal patches. Finally, we found little differences in plumage color between adult females and juveniles, which suggest selection for juveniles to resemble adult females possibly to reduce aggression from adult males. Additional within-population studies and behavioral experiments are needed to discern the evolutionary factors driving variation on S. corvina female color and its function.

Male plumage signal expression is related to feather corticosterone concentration in the Pied Flycatcher Ficedula hypoleuca

Male signals may express the capacity to sustain environmental challenges. In some migratory birds like the Pied Flycatcher Ficedula hypoleuca, plumage ornaments are molted in the winter quarters shortly before spring migration while most feathers are replaced shortly after the breeding season in the breeding areas. The concentration of corticosterone in feathers (CORTf) may relate to baseline CORT levels at the time of molt which could be expressed through plumage signals. Male Pied Flycatchers present white patches on forehead feathers and tertials which are molted before spring migration and on secondaries and primaries replaced after breeding. They also express a variable degree of melanisation of head and back feathers molted in the wintering areas. All these plumage traits have been previously shown to function in social contests and/or mate attraction. Here we have collected tertials on the two wings and two tail feathers, molted in wintering and breeding areas respectively, of males in a Spanish montane population and analysed CORTf in the laboratory with standard enzyme immunoassays. There is no correlation within individuals between CORTf in the two types of feathers, although levels are similar. The size of the forehead patch is negatively associated with CORTf in tail feathers, mainly in small males, while the blackness of head and back is negatively related to CORTf in tertials, mainly in large males. The size of the wing patch composed of patches on feathers molted both in wintering (tertials) and breeding areas (primaries and secondaries) is not related to CORTf in any type of feather. Different male plumage traits thus may reflect circulating CORT levels during molt processes occurring in the wintering respectively breeding range as expressed by CORTf in different types of feathers.

Sex Determination of Eastern Red-Tailed Hawks (Buteo jamaicensis borealis) Using Morphometrics

Abstract Determining the sex of monomorphic species, such as Red-tailed Hawks (Buteo jamaicensis), can be very difficult in the field as the plumage of males and females is similar and body masses overlap between sexes. Our purpose was to develop age-class specific methods that could be used in field settings to accurately determine the sex of Red-tailed Hawks within an Upper Midwestern USA landscape. Red-tailed Hawk carcasses (n = 648) were grouped by age class, weighed, measured, and necropsied to determine the sex of each individual. We compared morphological measurements between males and females and used discriminant function analysis to identify morphological characteristics that were useful in sexing Red-tailed Hawks in-hand. We developed separate equations for hatch-year, second-year, after-second-year, and after-hatch-year Red-tailed Hawks that were 80–88% accurate in correctly classifying eastern Red-tailed Hawks (B. j. borealis) to sex. The region-specific methods we developed should be useful to raptor researchers and managers.

Extra-pair paternity drives plumage colour elaboration in male passerines.

The elaborate ornamental plumage displayed by birds has largely been attributed to sexual selection, whereby the greater success of ornamented males in attaining mates drives a rapid elaboration of those ornaments. Indeed, plumage elaboration tends to be greatest in species with a high variance in reproductive success such as polygynous mating systems. Even among socially monogamous species, many males are extremely colourful. In their now-classic study, Møller and Birkhead (1994) suggested that increased variance in reproductive success afforded by extra-pair paternity should intensify sexual selection pressure and thus an elaboration of male plumage and sexual dichromatism, but the relatively few measures of extra-pair paternity at the time prevented a rigorous test of this hypothesis. In the nearly three decades since that paper's publication, hundreds of studies have been published on rates of extra-pair paternity and more objective measures of plumage colouration have been developed, allowing for a large-scale comparative test of Møller and Birkhead's (1994) hypothesis. Using an analysis of 186 socially monogamous passerine species with estimates of extra-pair paternity, our phylogenetically controlled analysis confirms Møller and Birkhead's (1994) early work, demonstrating that rates of extra-pair paternity are positively associated with male, but not female, colouration and with the extent of sexual dichromatism. Plumage evolution is complex and multifaceted, driven by phylogenetic, ecological, and social factors, but our analysis confirms a key role of extra-pair mate choice in driving the evolution of ornamental traits.

The evolutionary history and mechanistic basis of female ornamentation in a tropical songbird.

Ornamentation, such as the showy plumage of birds, is widespread among female vertebrates, yet the evolutionary pressures shaping female ornamentation remain uncertain. In part this is due to a poor understanding of the mechanistic route to ornamentation in females. To address this issue, we evaluated the evolutionary history of ornament expression in a tropical passerine bird, the White‐shouldered Fairywren, whose females, but not males, strongly vary between populations in occurrence of ornamented black‐and‐white plumage. We first use phylogenomic analysis to demonstrate that female ornamentation is derived and that female ornamentation evolves independently of changes in male plumage. We then use exogenous testosterone in a field experiment to induce partial ornamentation in naturally unornamented females. By sequencing the transcriptome of experimentally induced ornamented and natural feathers, we identify genes expressed during ornament production and evaluate the degree to which female ornamentation in this system is associated with elevated testosterone, as is common in males. We reveal that some ornamentation in females is linked to testosterone and that sexes differ in ornament‐linked gene expression. Lastly, using genomic outlier analysis we identify a candidate melanogenesis gene that lies in a region of high genomic divergence among populations that is also differentially expressed in feather follicles of different female plumages. Taken together, these findings are consistent with sex‐specific selection favoring the evolution of female ornaments and demonstrate a key role for testosterone in generating population divergence in female ornamentation through gene regulation. More broadly, our work highlights similarities and differences in how ornamentation evolves in the sexes.

Progress on the formation mechanism of sexual dimorphism plumage color in birds.

Sexually dimorphic plumage coloration is widespread in birds in which the male plumage is brighter than the female. This phenomenon is related to the environmental constraints on sexual selection or intraspecific competition between males and females in birds. The physiological factors and genetic regulation mechanism affecting the color of sexual dimorphism plumages in birds have always attracted significant attention in research. Understanding the diversity of sexually dimorphic traits provides insights into the mating strategies of the sexes and their behavior, ecology, and evolution. Interestingly, the ASIP, MC1R, TYRP1, and BCO2 genes have been identified to play a potential role in the coloration of melanin and carotenoids in bird sexual dimorphism plumages, either by controlling the rate and type of melanin or carotene synthesis or degradation by exerting an effect on the pigment biosynthetic pathway. In this review, we systematically summarize the biological significance, the direct causes (chemical and physical color), and the influence of sex hormones in sexually dimorphic plumage coloration. We also investigate the molecular mechanism underlying the roles of some genes on sexual dimorphism coloration, thereby providing a reference for in-depth understanding on the formation mechanism(s) of sexual dimorphic coloration in birds.

Wing-moult and seasonal occurrence of sunbirds (Nectariniidae) captured at four sites in the Eastern Cape, South Africa

Ringing activity in the Eastern Cape province, South Africa, spanned 30 years, with three sites active concurrently over a 14-year period, and three sites over a 6-year period. In total, in the course of 714 ringing days, in all months, we handled 1 207 Amethyst Sunbirds, 708 Southern Double-collared Sunbirds, 707 Greater Double-collared Sunbirds, 381 Grey Sunbirds, 121 Malachite Sunbirds and 140 Collared Sunbirds. Although individuals of all six species were recaptured more than five years after ringing, and despite evidence of the seasonal passage of sunbirds at two sites near the Indian Ocean coast, no birds were recaptured away from the original ringing site. The extent of seasonal movement by these species remains unclear. All species have a complete post-breeding moult, with a period of eclipse plumage in males of the Malachite Sunbird and Southern Double-collared Sunbird. Primary wing-moult in adult Greater and Southern Double-collared Sunbirds extends over three months beginning in December. Inland populations of adult Amethyst Sunbirds and Malachite Sunbirds start primary moult in April. Moult apparently proceeds more rapidly in Malachite Sunbirds (70 days to completion) than in Amethyst Sunbirds (125 days), but the Malachite Sunbird is the only species that frequently displays interrupted/suspended moult in this region. Adult Amethyst Sunbirds in the coastal population evidently start moulting earlier, in late February, with a similar duration to completion as inland birds. Juvenile Amethyst Sunbirds start to moult some two months later than adults in each region and they may complete moult more quickly. Collared Sunbirds appear to have the most protracted moult, extending over five months from November, but estimates of moult parameters for this species and the Grey Sunbird (three months from December) are based on small samples.

Bigger or long-winged male common crossbills exhibit redder carotenoid-based plumage coloration.

Carotenoid-based ornaments are often considered reliable (honest) individual condition signals because their expression implies physiological costs unaffordable for low-quality animals (handicap signals). Recently, it has been suggested that efficient cell respiration is mandatory for producing red ketocarotenoids from dietary yellow carotenoids. This implies that red colorations should be entirely unfalsifiable and independent of expression costs (index signals). In a precedent study, male common crossbills, Loxia curvirostra, showing a red plumage reported higher apparent survival than those showing yellowish-orange colors. The plumage redness in this species is due to ketocarotenoid accumulation in feathers. Here, we correlated the male plumage redness (a 4-level visual score: yellow, patchy, orange, and red) and the body morphology in more than 1,000 adult crossbills captured in 3 Iberian localities to infer the mechanisms responsible for color evolution. A principal component analysis summarized morphometry of 10 variables (beak, wing, tarsus length, etc.). The overall body size (PC1) and the length of flight feathers regarding body size (PC3) showed significant positive relationships with plumage redness. Plumage redness was barely correlated with bill shape measures, suggesting no constraint in acquiring carotenoids from pine cones. However, large body sizes or proportionally long flying feathers could help carotenoid acquisition via social competition or increased foraging ranges. Proportionally longer flight feathers might also be associated with a specific cell respiration profile that would simultaneously favor flying capacities and enzymatic transformations needed for ketocarotenoid synthesis. Such a phenotypic profile would agree with the hypothesis of ketocarotenoid-based colors acting as individual quality index signals.

A global analysis of aerial displays in passerines revealed an effect of habitat, mating system and migratory traits.

Aerial displaying is a flamboyant part of the sexual behaviour of several volant animal groups, including birds. Nevertheless, little attention has been focused on identifying correlates of large-scale diversity in this trait. In this study, we scored the presence and absence of aerial displays in males of 1732 species of passerine birds (Passeriformes) and employed Bayesian phylogenetically informed mixed models to test for associations between aerial displays and a set of life-history and environmental predictors. Our multi-variate models revealed that species with males that perform aerial displays inhabited open rather than closed (forested) habitats. These species also exhibited higher levels of polygyny, had more elongated wings, migrated over longer distances and bred at higher latitudes. When we included species where the sexual function of displays has not been explicitly described but is likely to occur, we found that aerial displaying was also associated with smaller body size and increased male plumage coloration. Our results suggest that both sexual selection and natural selection have been important sources of selection on aerial displays in passerines.

Taxonomic status of grey-headed Yellow Wagtails breeding in western China

BackgroundField studies from 2011 onwards have demonstrated the presence of a breeding population of Yellow Wagtails (Motacilla flava) in the Xinjiang Uygur Autonomous Region, China that is phenotypically distinct from known subspecies occurring in Asia. Here we describe the plumages and vocalisations of this population and discuss its taxonomic status.MethodsThe analysis of plumage is based on field studies and photos available online. Recordings of vocalisations are compared with recordings from other Yellow Wagtail populations, and differences are analysed based on sonograms. Mitochondrial DNA from one individual is compared to other Yellow Wagtail taxa.ResultsUnlike M. flava subspecies breeding in or near Xinjiang, males in the studied population show a blue-grey head without prominent white supercilium, being most similar to the widely disjunct M. f. cinereocapilla. They differ from the similarly widely allopatric M. f. thunbergi, which might occur as a migrant or vagrant in Xinjiang, by on average cleaner yellow breast and more extensive white on the throat, and from the widely disjunct M. f. plexa and M. f. macronyx, which might also occur on migration in that area, by softer contact calls and slower pace of song. Females are similar to female M. f. feldegg in plumage. The mitochondrial ND2 tree shows the single sample from Xinjiang to be nested in the clade of western Yellow Wagtail taxa.ConclusionWe discuss whether the Xinjiang breeding population could represent an intergrade between subspecies breeding nearby, or whether it is better regarded as a separate as yet unrecognized subspecies. We argue that the localization of its apparent range in relation to other subspecies along with fairly consistent male and female plumages suggest that it is more likely to represent an undescribed taxon, but conclude that more research is needed to firmly establish its status.

Dräktförändring hos en intersex gräsand Anas platyrhynchos över en sexårsperiod

Intersex individuals with a mixture of female and male plumage traits are reported regularly, but at low frequency. Here we describe the changes in plumage in a Mallard Anas platyrhynchos intersex individual over six years (2015–2020), from a mixed female–male phenotype to a predominantly male phenotype. Already at the first observation, typical male characteristics were present, such as greyish-white tail with two central curved black rectrices and a greenish tinge to parts of the head. The bird attained a more male-like plumage with the next moult and maintained that plumage for the rest of the study period. However, presence of female-patterned body feathers continued until 2019, but in reduced frequency, except for the cheeks and ear-coverts, which displayed a variation in colour. The bill remained female-patterned throughout and the bird did not enter eclipse plumage.

Why neotypification of emLophorina/em emsuperba/em (Pennant, 1781) (Aves: Paradisaeidae) is justified-and necessary.

We review Irestedt et al.'s (2017) neotypification of the senior species name superba Pennant, 1781 in the bird-of-paradise genus Lophorina in response to Elliott et al. (2020) who challenged the resultant shift in name from the small isolate in New Guinea's Vogelkop to the widespread species in the island's central cordillera. In nine male plumage traits which differentiate the two species, six of which had been identified as novel by Irestedt et al., we show that the only two figures of the perished male holotype of superba match the central cordillera species more closely than the Vogelkop. We find as well that not only was the trading of bird-of-paradise skins from the central cordillera to coastal ports in the Vogelkop feasible before European contact, but application of superba to the central cordillera species also promotes nomenclatural stability: the name has been used overwhelmingly at species rank for that widespread form throughout post-19th century media. Re-assessment of Irestedt et al.'s point-by-point justification of neotypification under Article 75.3 of the ICZN (1999) Code establishes, furthermore, that their case meets the requirements of every condition specified in the article; the neotypification is thus valid. Elliott et al.'s alternative to fix superba to the Vogelkop isolate by type locality restriction is not Code-compliant, nor is their evidence for interpreting J.R. Forster as the author of the name. In conclusion, we lay out the correct nomenclature for the taxa of Lophorina under the Code.

Choosy females drive isolation

Speciation Rapid radiations of recently diverged species represent an excellent opportunity for exploring drivers of speciation. The capuchino seedeaters, a group of South American birds, include a number of species that, in the field, are often discernable only through male plumage and song. Turbek et al. used genomes and behavioral experiments to identify potential isolating factors in two members of this group and found that, though entirely sympatric, females mated only with conspecific males and that only a few genes differed between the species (see the Perspective by Jarvis). Thus, a small reshuffling of genes and reinforcement through mate choice has driven divergence in these overlapping and very similar species. Science , this issue p. [eabc0256][1]; see also p. [1312][2] [1]: /lookup/doi/10.1126/science.abc0256 [2]: /lookup/doi/10.1126/science.abg5454

Rapid speciation via the evolution of pre-mating isolation in the Iberá Seedeater.

Behavioral isolation can catalyze speciation and permit the slow accumulation of additional reproductive barriers between co-occurring organisms. We illustrate how this process occurs by examining the genomic and behavioral bases of pre-mating isolation between two bird species (Sporophila hypoxantha and the recently discovered S. iberaensis) that belong to the southern capuchino seedeaters, a recent, rapid radiation characterized by variation in male plumage coloration and song. Although these two species co-occur without obvious ecological barriers to reproduction, we document behaviors indicating species recognition by song and plumage traits and strong assortative mating associated with genomic regions underlying male plumage patterning. Plumage differentiation likely originated through the reassembly of standing genetic variation, indicating how novel sexual signals may quickly arise and maintain species boundaries.