Coloration In Birds Research Articles

Examining the link between relaxed predation and bird coloration on islands.

Insular ecosystems share analogous ecological conditions, leading to patterns of convergent evolution that are collectively termed as the 'island syndrome'. In birds, part of this syndrome is a tendency for a duller plumage, possibly as a result of relaxed sexual selection. Despite this global pattern, some insular species display a more colourful plumage than their mainland relatives, but why this occurs has remained unexplained. Here, we examine the hypothesis that these cases of increased plumage coloration on islands could arise through a relaxation of predation pressure. We used comparative analyses to investigate whether average insular richness of raptors of suitable mass influences the plumage colourfulness and brightness across 110 pairs of insular endemic species and their closest mainland relatives. As predicted, we find a likely negative relationship between insular coloration and insular predation while controlling for mainland predation and coloration, suggesting that species were more likely to become more colourful as the number of insular predators decreased. By contrast, plumage brightness was not influenced by predation pressure. Relaxation from predation, together with drift, might thus be a key mechanism of species phenotypic responses to insularity.

Genetic Basis of De Novo Appearance of Carotenoid Ornamentation in Bare Parts of Canaries

Unlike wild and domestic canaries (Serinus canaria), or any of the three dozen species of finches in genus Serinus, the domestic urucum breed of canaries exhibits bright red bills and legs. This novel trait offers a unique opportunity to understand the mechanisms of bare-part coloration in birds. To identify the mutation producing the colorful phenotype, we resequenced the genome of urucum canaries and performed a range of analyses to search for genotype-to-phenotype associations across the genome. We identified a nonsynonymous mutation in the gene BCO2 (beta-carotene oxygenase 2, also known as BCDO2), an enzyme involved in the cleavage and breakdown of full-length carotenoids into short apocarotenoids. Protein structural models and in vitro functional assays indicate that the urucum mutation abrogates the carotenoid-cleavage activity of BCO2. Consistent with the predicted loss of carotenoid-cleavage activity, urucum canaries tended to have increased levels of full-length carotenoid pigments in bill tissue and reduced levels of carotenoid-cleavage products (apocarotenoids) in retinal tissue compared with other breeds of canaries. We hypothesize that carotenoid-based bare-part coloration might be readily gained, modified, or lost through simple switches in the enzymatic activity or regulation of BCO2 and this gene may be an important mediator in the evolution of bare-part coloration among bird species.

Cannibals, Colorful Birds, and Exuberant Nature: The Representation of Brazilian Nationalism and Its Tropical Modernity in the 2016 Rio Olympics

Hosting the Olympics is a singular opportunity to build an updated narrative of the nation. Such a narrative is traditionally intended to emphasize the hosting country contributions toward the modern project through the displaying of key nationalistic accounts linking the country’s history to the development of western society. In the case of the 2016 Rio de Janeiro Olympics, its organizing committee has sought into Brazil’s history different elements that were central to both the formation of Brazilian identity and the discussion over current global issues. Therefore, the country’s enduring relation with nature as well as national narratives such as modernist Anthropophagy, the discourse of ethnic miscegenation, and the myth of Brazil as a racial democracy became historical credentials to use environmentalism and tolerance as the paramount features of Rio-2016’s aesthetics as well as a means to denounce xenophobia and the effects of the Anthropocene on the planet. We argue that the exposition of these two issues in the event’s ceremonies was a way to symbolically insert the country within modernity’s forefront. In this article, we examine the sociopolitical aspects that led to the creation and popularization of Brazilian nationalistic narratives that were later used during the Rio 2016 opening ceremony and the ways such aspects were internationally conveyed during the aforementioned theatrical presentation.

Multiple components of feather microstructure contribute to structural plumage colour diversity in fairy-wrens

AbstractClosely related species often differ in coloration. Understanding the mechanistic bases of such differences can reveal whether evolutionary changes in colour are driven by single key mechanisms or changes in multiple pathways. Non-iridescent structural plumage colours in birds are a good model in which to test these questions. These colours result from light absorption by pigments, light scattering by the medullary spongy layer (a nanostructure found within barbs) and contributions from other structural elements. Fairy-wrens (Malurus spp.) are a small clade of closely related birds that display a large diversity of ornamental structural colours. Using spectrometry, electron microscopy and Fourier analysis, we show that 30 structural colours, varying from ultraviolet to blue and purple, share a similar barb morphology. Despite this similarity, we find that at the microscopic scale, variation across multiple structural elements, including the size and density of the keratin cortex, spongy layer and melanin, explains colour diversity. These independent axes of morphological variation together account for sizeable amounts of structural colour variability (R2 = 0.21–0.65). The coexistence of many independent, evolutionarily labile mechanisms that generate colour variation suggests that the diversity of structural colours in this clade could be mediated by many independent genetic and environmental factors.

Juvenile pheomelanin‐based plumage coloration has evolved more frequently in carnivorous species

Distinctive pheomelanin‐based plumage coloration in juvenile birds has been proposed as a signal of immaturity to avoid aggression by older conspecifics, but recent findings suggest a detoxifying strategy. Pheomelanin synthesis implies the consumption of cysteine, a semi‐essential amino acid that is necessary for the synthesis of the antioxidant glutathione (GSH) but that may be toxic if in excess in the diet. As the nestling stage probably represents a low‐stress period with limited requirement for GSH protection, the synthesis of pheomelanin in developing birds may help to maintain cysteine homeostasis, particularly in species with a high content of protein in the diet (i.e. carnivores). Here we confirm this hypothesis showing that, among 53 species of Western Palaearctic birds, juvenile pheomelanin‐based coloration has evolved more frequently in strictly carnivorous species than in species with other diets.

Selection on multiple sexual signals in two Central and Eastern European populations of the barn swallow.

Variation in intensity and targets of sexual selection on multiple traits has been suggested to play a major role in promoting phenotypic differentiation between populations, although the divergence in selection may depend on year, local conditions or age. In this study, we quantified sexual selection for two putative sexual signals across two Central and East European barn swallow (Hirundo rustica rustica) populations from Czech Republic and Romania over multiple years. We then related these differences in selection to variation in sexual characters among barn swallow populations. Our results show that tail length and ventral coloration vary between populations, sexes, and age classes (first‐time breeders vs. experienced birds). We found that selection on tail length was stronger in first‐time breeders than in experienced birds and in males than in females in the Romanian population, while these differences between age groups and sexes were weak in Czech birds. We suggest that the populational difference in selection on tail length might be related to the differences in breeding conditions. Our results show that ventral coloration is darker (i.e., has lower brightness) in the Romanian than in the Czech population, and in experienced birds and males compared with first‐time breeders and females, respectively. The sexual difference in ventral coloration may suggest sexual selection on this trait, which is supported by the significant directional selection of ventral coloration in first‐time breeding males on laying date. However, after controlling for the confounding effect of wing length and tarsus length, the partial directional selection gradient on this trait turned nonsignificant, suggesting that the advantage of dark ventral coloration in early breeding birds is determined by the correlated traits of body size. These findings show that ventral coloration may be advantageous over the breeding season, but the underlying mechanism of this relationship is not clarified.

Inbreeding Fact of Exotic Wild Psittacids in Bangladesh

Captive breeding of short-tailed parrots (4) and long-tailed parakeets (16) out of 20 species were remarkable. These colourful birds were very nice in common appearance. Casual cages were used for their breeding especially for smaller birds. Parrots and parakeets are mainly reared as hobby and due to remarkable production and public acceptance only budgies are commercially abundant in Bangladesh. Parrot, Parakeet, mutated form of Ring-necked Parakeet, Lorikeet, Lovebird, Budgie, Conure, Rosella, Amazon Parrot, Cockatiel, and Cockatoo are common in all pet shop. In aviary, Budgie rearing is common then Lovebird, Cockatiel, and Macaw. Psittacids breeding accessories and its care are more complicated and vary from species to species. In breeding season most of the birds are shown aggressiveness to their pair and human too. Colourful feather, huge variety, nice voice, activeness and for talking ability these birds are excellent pet. Mortality rate of parrots and parakeets were found high. This study was performed in the year 2019

Manipulation of Color Patterns in Jumping Spiders for Use in Behavioral Experiments.

In the field of behavioral ecology, many experiments are designed to investigate the evolutionary purposes of colorful traits in the context of sexual selection and predation. Methods are various but mostly consist of modifying the color patterns of individuals with diverse colorants. Such techniques have been used across many vertebrate taxa, particularly in birds, but have remained underdeveloped for invertebrates because of the difficulty of effectively manipulating color in small organisms. Instead, to manipulate the appearance of invertebrates, scientists have usually modified the lighting environment to filter out certain wavelengths. However, such a method affects not only the phenotypic trait of interest but the entire appearance of the individual and its surrounding. Here, scaling down the techniques previously used on colorful birds, we present ways of manipulating the colors of small arthropods, using equally emblematic but understudied species: the colorful jumping spiders.

Molecular-genetic bases of plumage coloring in chicken

The color of plumage in birds is an important feature, often determining descent to a particular species or breed. It serves as a key factor in the interaction of birds with each other due to their well-developed visual perception of the surrounding world. In poultry including chickens, the color of the plumage can be treated as a genetic marker, useful for identifying breeds, populations and breeding groups with their specific traits. The origin of diverse color plumage is the result of two interrelated physical processes, chemical and optical, due to which pigment and structural colors in the color are formed. The pigment melanin, which is presented in two forms, eumelanin and pheomelanin, is widely spread in birds. The basis for the formation of melanin is the aromatic amino acid tyrosine. The process of melano-genesis involves many loci, part of the complex expression of plumage color genes. In birds, the solid black color locus encodes the melanocortin 1 receptor (MC1R), mutations in which lead to a change in receptor activation and form different variants of the E locus. Using the GWAS analysis, possible genes affecting the formation of color in chickens were detected. The biosynthesis and types of melanin are affected by the activity of the enzyme tyrosine, and mutations in the tyrosinase gene (TYR) cause albinism in different species. The formation mechanism of brown, silver, gold, lavender and a number of other shades is determined by the influence on the work of the MC1R genes and TYR specific modifier genes. Thus, locus I currently associated with the PMEL17 gene inhibits the expression of eumelanin, and the MLPH gene affects tyrosinase function. Research on the mechanisms of formation of the secondary coloring of plumage in chickens is being actively conducted nowadays. The formation of a marble feather pattern is associated with the mutation of the endothelin B2 receptor (EDNRB2), in the coding part of the gene of which a polymorphism is found associated with the mo locus. The molecular base that causes the feather banding (locus B and autosomal recessive banding) is identified. Today, only some genes that determine the color of the plumage of chickens are studied and described. Different genes can produce similar plumage patterns, and different phenotypes can be determined by the polymorphism of a single gene. Using molecular methods, you can more accurately identify these differences. This overview shows the nature of melanin coloration in birds using the example of chickens of various breeds and also attempts to systematize knowledge about the molecular-genetic mechanisms of the appearance of various types of coloration.

A Negative Association between Melanin-Based Plumage Color Heterogeneity and Intensity in Birds.

Even though plumage diversity is one of the most diverse phenotypic traits in nature, the reasons why some species exhibit more distinctive colors than others are poorly known. In the case of melanins, the most abundant pigments in birds, different chemical forms lead to different plumage colors and different amounts of those forms lead to different color intensities. However, the synthesis of some melanin forms is more physiologically limited than others. We hypothesize that an evolutionary solution to this scenario may consist in a negative association between melanin-based color heterogeneity and intensity. Here we confirm this prediction after analyzing the diversity and expression level of melanin-based plumage colors in 96 species of birds breeding in the Iberian Peninsula. After controlling for phylogenetic effects, the intensity of the plumage colors of birds decreased with the number of different colors, suggesting that the physiological mechanism of melanin synthesis does not favor the production of both a heterogeneity of melanin forms and large amounts of these forms. These findings contribute to a better understanding of bird phenotypic diversity.

Spatial variation in carotenoid plumage coloration and relationships between female coloration and quality in Prothonotary Warblers (Protonotaria citrea)

AbstractMany birds use conspicuous plumage coloration to signal quality for sexual or social selection. However, it is still often unclear how intraspecific coloration and associated signaling vary spatially. Plumage coloration that is dependent on carotenoids may be ideal for studying spatial color variation because birds cannot naturally synthesize this pigment; therefore, bird coloration from carotenoids is at least partially contingent upon diet. As food availability often varies spatially, so might color and its signaling strength. While male coloration has received more research focus, less is known about female coloration and its relationships with social rank or sexual quality. To further improve our understanding of spatial variation in plumage coloration and correlations with individual quality, we compared Prothonotary Warblers breeding at 2 ecologically disparate sites separated by 1,300 km: in bottomland forests of Arkansas, USA, and the forests near the tidal freshwater James River in Virginia, USA. We assessed crown and breast plumage coloration for both sexes and compared several color metrics between sites. We then assessed surrogates of female quality (number of young fledged, number of eggs laid, provisioning rate, apparent annual survival, and nest depredation) and compared coloration-quality relationships between sites. We found that coloration of birds breeding in Arkansas was generally more elaborate than those breeding in Virginia. However, this was somewhat dependent on sex: females showed greater differences than males between sites. Additionally, color metrics of females breeding in Virginia showed stronger relationships with quality (all 5 quality metrics) than for birds breeding in Arkansas (only provisioning rate and nest depredation). Proximately, spatial variation in plumage coloration and the associated signaling may be explained by differences in diet between sites. Ultimately, spatial variation in intra- and intersexual selection pressures may explain how spatial variation in plumage signal strength evolved.

You are MORE than what you eat! The dietary basis to painted turtle spot and stripe color.

Carotenoid pigments are important condition-dependent indicator traits that generate sexually selected color in birds, fish, and reptiles. One reason carotenoids are indicator traits is because the identity and amount of carotenoid pigments ingested in an animal’s food are often different from amounts and identities of carotenoids deposited in the animal’s skin. Painted turtle spots and stripes are pigmented by yellow xanthophylls and orange-red keto-carotenoids. The objective of this study was twofold: to feed male and female painted turtles nutritious diets with-, or without-, moderate amounts of orange beta-carotene, and investigate 1) how beta-carotene access changed turtle color in male and female turtles, and 2) whether the identities and concentrations of carotenoids in the blood of turtles given access to—or deprived of—beta-carotene differed from those ingested and those deposited in the skin. Results showed that orange beta-carotene access reduced overall brightness of yellow chin stripes and post orbital spots, reduced ultra-violet chroma in the yellow post-orbital spots, and increased yellow chroma in the orange-red fore-limb stripes. There was no sex effect to these color changes. Moreover, beta-carotene access significantly increased circulating levels of beta-carotene only, and did not increase circulating levels of lutein, zeaxanthin, beta cryptoxanthin or neoxanthin. There was no sex effect to the circulating carotenoid levels. Nevertheless, because the identity of carotenoids in the skin differs from the carotenoids circulating in the blood, the yellow, orange and red colors of painted turtle stripes and spots are in part the result of physiological conversion of available carotenoids.

Fifty shades of brown: Macroevolution of plumage brightness in the Furnariida, a large clade of drab Neotropical passerines.

Both natural and sexual selection are thought to affect the evolution of bird color. Most studies of the topic have focused on sexually dichromatic taxa and showy plumages, which are expected to be more influenced by social selection and usually result in increased conspicuousness. However, many bird clades display dull brown or gray plumages that vary greatly in brightness (lightness), but little in hue (shade). Here, we examine the macroevolution of brightness in one such clade, the Furnariida. We make comparisons across light environments, body parts, monochromatic lineages, and each sex of dichromatic lineages. We found that support for models including light environments is greater for the dorsum than for the venter, and that brightness evolution is more constrained in the former than in the latter. Plumages in this clade have evolved to be darker in darker habitats, consistent with natural selection for increased crypsis. Finally, the features of brightness macroevolution are broadly similar across the sexes of the dichromatic clade, challenging the view that sexual dichromatism is driven by different evolutionary processes acting in each sex. We conclude that, in the Furnariida, light environments and dorsal-ventral variation are more important than sex as axes of color evolution.

How the observed color of the Swallow Tanager (Tersina viridis) changes with viewing geometry

Non-iridescent coloration in birds’ plumage is associated with the quasi-ordered nanostructures of short-range order present within the feather barbs. Even though this type of color does not change with the observation direction, a few bird species which exhibit the so called non-iridescent structurally colored feathers, present significant hue variations as the relative angle between incidence and detection directions is varied. Among these, the Swallow Tanager constitutes an excellent system to investigate this phenomenon as its hue changes remarkably from greens to blues as the angle between the illumination and observation directions increases, and independently of feather orientation. In this paper we elucidate the origin of the striking color change of the Swallow Tanager plumage by computing the reflectance spectra of the feathers’ microstructure. We show that the color observed under different illumination-detection conditions can be predicted quite accurately by applying averaging techniques and by considering the air-spheres microstructure of their feathers’ barbs as the main responsible for the observed color change. This work opens up new possibilities for the design of devices with special color characteristics.

Testing the resource trade-off hypothesis for carotenoid-based signal honesty using genetic variants of the domestic canary.

Carotenoid-based coloration in birds is widely considered an honest signal of individual condition, but the mechanisms responsible for condition dependency in such ornaments remain debated. Currently, the most common explanation for how carotenoid coloration serves as a reliable signal of condition is the resource trade-off hypothesis, which proposes that use of carotenoids for ornaments reduces their availability for use by the immune system or for protection from oxidative damage. However, two main assumptions of the hypothesis remain in question: whether carotenoids boost the performance of internal processes such as immune and antioxidant defenses, and whether allocating carotenoids to ornaments imposes a trade-off with such benefits. In this study, we tested these two fundamental assumptions using types of domestic canary (Serinus canaria domestica) that enable experiments in which carotenoid availability and allocation can be tightly controlled. Specifically, we assessed metrics of immune and antioxidant performance in three genetic variants of the color-bred canary that differ only in carotenoid phenotype: ornamented, carotenoid-rich yellow canaries; unornamented, carotenoid-rich 'white dominant' canaries; and unornamented, carotenoid-deficient 'white recessive' canaries. The resource trade-off hypothesis predicts that carotenoid-rich individuals should outperform carotenoid-deficient individuals and that birds that allocate carotenoids to feathers should pay a cost in the form of reduced immune function or greater oxidative stress compared with unornamented birds. We found no evidence to support either prediction; all three canary types performed equally across measures. We suggest that testing alternative mechanisms for the honesty of carotenoid-based coloration should be a key focus of future studies of carotenoid-based signaling in birds.

Detection of Snps in the Melanocortin 1-Receptor (MC1R) and Its Association with Shank Color Trait in Hs Chicken

ABSTRACT The melanocortin 1 receptor (MC1R) gene plays a key role in controlling the deposition of melanin. In mammals, the MC1Rgene is regarded as a major candidate gene in the control of melanin formation. In domestic animals, the MC1R gene mainly controls the expression of coat, skin, and plumage color in mammals and birds. In order to breed chickens with dark-green shank faster, we screened the molecular markers for shank color in a HS chicken population by exploring the relationship between polymorphism of the MC1R gene and three different shank colors (light green, dark green and yellow). Two primer pairs for code region of the MC1R gene were designed in the basic of chicken genomic sequence. DNA sequencing was performed to detect the polymorphisms and PCR was used to amplify DNA fragment. Sequences analysis indicated that 7 SNPs were predominant the three HS chicken populations with different shank color, including g.18,287,945C>T, g.18,288,088T>C, g.18,288,150G>A, g.18,288,303A>G, g.18,288,512G>A, g.18,288,513T>C, and g.18,288,520A>C. Association analysis revealed that the dark-green shank population showed moderate polymorphism, whereas the light-green shank population showed low polymorphism among overall 7 SNPs and that SNP6 (g.18,288,513T>C) may be significantly associated with three different shank colors in HS chickens. The haplotype CTGGACA had the largest haplotype frequencies, accounting for 56.22%, and the haplotype combination H1H1 is mainly distributed in the dark-green shank population, and may be used as molecular maker for marker-assisted selection of shank color in HS chickens.

Plumage polymorphism and variation in the melanocortin-1 receptor gene in the Fuscous Flycatcher, Cnemotriccus fuscatus (Wied, 1831)

We investigated the possible mechanisms behind the variation plumage color of the Fuscous Flycatcher, Cnemotriccus fuscatus, by sequencing the melanocortin-1 receptor (MC1R) gene, which has been associated with the variation in plumage coloration in birds. C. fuscatus is widely distributed in South America and includes seven subspecies, which differ in their plumage coloration. Here we tested the hypothesis that the variation in the MC1R gene explains the plumage polymorphism found in C. fuscatus. We sequenced the MC1R gene in six subspecies, representing two groups: group 1 (yellow morph), with three subspecies, C. f. duidae, C. f. fumosus, and C. f. fuscatus, and group 2 (white morph), with the remaining subspecies, C. f. bimaculatus, C. f. beniensis, and C. f. fuscatior. The only variation we found among the C. fuscatus sequences were six non-synonymous substitutions from 22 variable sites, none of which were associated systematically with either plumage morph. The result of the neutrality test indicated that the polymorphism of the MC1R gene is not suggestive of significant selection pressure. We conclude that variation in plumage coloration in C. fuscatus does not appear to be determined by the MC1R gene, and that it may be related to other loci or under the influence of environmental factors.

Melanosome diversity and convergence in the evolution of iridescent avian feathers-Implications for paleocolor reconstruction.

Some of the most varied colors in the natural world are created by iridescent nanostructures in bird feathers, formed by layers of melanin‐containing melanosomes. The morphology of melanosomes in iridescent feathers is known to vary, but the extent of this diversity, and when it evolved, is unknown. We use scanning electron microscopy to quantify the diversity of melanosome morphology in iridescent feathers from 97 extant bird species, covering 11 orders. In addition, we assess melanosome morphology in two Eocene birds, which are the stem lineages of groups that respectively exhibit hollow and flat melanosomes today. We find that iridescent feathers contain the most varied melanosome morphologies of all types of bird coloration sampled to date. Using our extended dataset, we predict iridescence in an early Eocene trogon (cf. Primotrogon) but not in the early Eocene swift Scaniacypselus, and neither exhibit the derived melanosome morphologies seen in their modern relatives. Our findings confirm that iridescence is a labile trait that has evolved convergently in several lineages extending down to paravian theropods. The dataset provides a framework to detect iridescence with more confidence in fossil taxa based on melanosome morphology.

The periodic coloration in birds forms through a prepattern of somite origin

The periodic stripes and spots that often adorn animals' coats have been largely viewed as self-organizing patterns, forming through dynamics such as Turing's reaction-diffusion within the developing skin. Whether preexisting positional information also contributes to the periodicity and orientation of these patterns has, however, remained unclear. We used natural variation in colored stripes of juvenile galliform birds to show that stripes form in a two-step process. Autonomous signaling from the somite sets stripe position by forming a composite prepattern marked by the expression profile of agouti Subsequently, agouti regulates stripe width through dose-dependent control of local pigment production. These results reveal that early developmental landmarks can shape periodic patterns upstream of late local dynamics, and thus constrain their evolution.

De novo Transcriptome Assembly of the Clown Anemonefish (Amphiprion percula): A New Resource to Study the Evolution of Fish Color

A fundamental question of evolutionary biology is, why are some animals conspicuously colored? This question may be addressed from both a proximate (genetic and ontogenetic) and ultimate (adaptive value and evolutionary origins) perspective, and integrating these perspectives can provide further insights. Over the last few decades we have made great advances in understanding the causes of conspicuous coloration in terrestrial systems, e.g., birds and butterflies, but we still know relatively little about the causes of conspicuous, ‘poster’ coloration in coral reef fishes. Of all coral reef fishes, the clownfish Amphiprion percula, is perhaps the most conspicuously colored, possessing a bright orange body with three iridescent white bars bordered with pitch black. Here, we review what is known about the proximate and ultimate causes of the conspicuous coloration of clownfishes Amphiprion sp.: coloration has a heritable genetic basis; coloration is influenced by development and environment; coloration has multiple plausible signaling functions; there is a phylogenetic component to coloration. Subsequently, to provide new insights into the genetic mechanisms and potential functions of A. percula coloration we i) generate the first de novo transcriptome for this species, ii) conduct differential gene expression analyses across different colored epidermal tissues, and iii) conduct gene ontology (GO) enrichment analyses to characterize function of these differentially expressed genes. BUSCO indicated that transcriptome assembly was successful and many genes were found to be differentially expressed between epidermal tissues of different colors. In orange tissue, relative to white and black, many GO terms associated with muscle were over-represented. In white tissue, relative to orange and black tissue, there were very few over- or under-represented GO terms. In black tissue, relative to orange and white, many GO terms related to immune function were over-represented, supporting the hypothesis that black (melanin) coloration may serve a protective function. Overall, this study presents the assembly of the A. percula transcriptome, and represents a first step in an integrative investigation of the proximate and ultimate causes of conspicuous coloration of this iconic coral reef fish.