Red Feathers Research Articles

Weaving feathers of intangible and tangible knowledge: Historical records and human‐bird interactions in the Marquesas Islands

AbstractBirds fulfilled an essential role in ancient Polynesian cultures. They were prized for their bones and colourful feathers, fat, and protein; their cultural importance is further highlighted in Polynesian oral histories. This research investigates the dynamics of human‐bird interactions over time in the Marquesas Archipelago as known from archaeology, oral histories, ethnohistorical records, and museum collections. I analyse the range of avian taxa represented across the various datasets and their cultural uses. The results demonstrate that while some species are represented across one or more datasets, understanding the full extent of species’ cultural roles and use requires more than one thread of analysis, particularly for those taxa with limited or no archaeological signature. Two forms of managed resource use emerge from this study. One is tapu (prohibition of use), and the second is the conservative use of birds as a resource such as restricted feather collecting. Red feathers, represented in museum objects and historical accounts, highlight multiple taxa being used for specific adornment types. The combined analyses provide insights into the loss and persistence of species, as well as aspects of Marquesan cultural management.

Substrate Specificity of Bacillus megaterium UСM B-5710 Keratinase

The specifics of the processing of livestock and poultry products is that in the process of obtaining the main marketable products, about half the feedstock at various stages of the technological process turns into waste that pollutes the environment. These by-products contain large amounts of the hard-to-digest keratin protein. The use of specific enzymes capable of degrading this protein helps not only to reduce the negative anthropogenic impact on nature but also to obtain valuable hydrolysates that can be used as a fertilizer for plants or a feed additive. The aim of this work was to study the ability of Bacillus megaterium UCM B-5710 to split various keratin-containing substrates: black and white chicken feathers, white turkey feathers, parrot feathers of various colors, sheep wool, pig bristles, and baby hair and nails. Methods. The culture was grown under conditions of submerged cultivation at 40 °C, with a nutrient medium stirring rate of 201 rpm for 6 days. For growth, a basic nutrient medium containing 0.5% defatted chicken feathers or other keratin-containing substrates as sole sources of carbon and nitrogen were used. Keratinase activity was assessed by UV absorption at 280 nm of hydrolysis products of keratin-containing raw materials. Protein was determined by the Lowry method, caseinolytic (total proteolytic) activity was determined by the Anson method modified by Petrova, and amino acid content was determined by the ninhydrin method. The degree of hydrolysis of the substrates was evaluated by the ratio of the initial and final weight of the substrate. Results. It was shown that the synthesis of keratinase by the culture of B. megaterium UCM B-5710 begins from the 6th hour of cultivation. The level of protein and proteolytic activity and the content of amino acids increased throughout the entire period of culture growth. The supernatant of the culture liquid of B. megaterium UCM B-5710 was most effective in splitting white chicken’s and turkey’s feathers, a little slower — feathers of black chicken and blue parrots, as well as wool of white sheep. According to the degree of splitting, the substrates used can be arranged in the following order: white turkey feathers > white chicken feathers > black chicken feathers > blue parrot feathers > white sheep wool > baby nails > pig bristle > baby hair. The study of the effect of feather color on the resistance to decomposition showed that black, blue, and red feathers are more resistant, which coincides with the literature data. Conclusions. B. megaterium UCM B-5710 produces keratinase capable of splitting both α- and β-keratins, however, with different efficiencies and rates.

Moult performance varies in relation to colour patterns in crossbills

Carotenoid-based ornamentation can vary greatly among individual birds of the same population. This variability might consider the timing and duration of moult. Crossbills (genus Loxia) show large variation in their colour patterns, ranging from dull yellow to red. Thus, they provide an excellent avian model for testing whether the timing and duration of their moult are associated with their dominant colour patterns. Using a dataset of more than 1900 crossbills captured in the Pyrenees (Spain), we observed that individuals with red feathers started their primary moult early, while those with yellow feathers started moult on an average of 18 days later. We also found that yellow crossbills were more likely to suspend moults (i.e. temporally interrupt moult), postponing a part of the moult until September. These differences in the moulting process may be related to plumage colour, which reflect individual condition.

Diet-Related Plumage Erythrism in the Western Tanager and Other Western North American Birds

Consumption of the berries of two exotic bush honeysuckles (genus Lonicera) containing the red carotenoid pigment rhodoxanthin has resulted in abnormal erythristic plumages in several species of birds in eastern North America. Here we report 12 examples of plumage erythrism in the Western Tanager (Piranga ludoviciana), in both live birds (5) and museum specimens (7), that we suspect have the same etiology. The erythristic tanagers feature overtly orange to red feathers variously scattered on the head, rump, wing coverts, and/or underparts, areas of the plumage normally colored by carotenoid pigments. All were in their year of hatching, so the reddened feathers, including replaced median coverts with orange tips, represent formative plumage grown on or near the breeding grounds where berries containing rhodoxanthin are available. By contrast, adult Western Tanagers undergo body molt primarily in the Mexican monsoon region in fall and on their winter grounds in early spring where bush honeysuckles are nonexistent. We also report examples of Red-breasted Sapsuckers (Sphyrapicus ruber) with anomalous red pigmentation on their backs and of Cedar Waxwings (Bombycilla cedrorum) with orange tail bands, as previously documented in the East. In these species, the reddened areas are typically yellow or green, colors based on carotenoid pigments that can be altered through the consumption of fruits containing rhodoxanthin. We conclude that these reddened feathers are the result of the consumption of honeysuckle berries or possibly the red arils of the Pacific Yew (Taxus brevifolia), representing a first report of diet-related erythrism in western North America.

Feather Gene Expression Elucidates the Developmental Basis of Plumage Iridescence in African Starlings.

Iridescence is widespread in the living world, occurring in organisms as diverse as bacteria, plants, and animals. Yet, compared to pigment-based forms of coloration, we know surprisingly little about the developmental and molecular bases of the structural colors that give rise to iridescence. Birds display a rich diversity of iridescent structural colors that are produced in feathers by the arrangement of melanin-containing organelles called melanosomes into nanoscale configurations, but how these often unusually shaped melanosomes form, or how they are arranged into highly organized nanostructures, remains largely unknown. Here, we use functional genomics to explore the developmental basis of iridescent plumage using superb starlings (Lamprotornis superbus), which produce both iridescent blue and non-iridescent red feathers. Through morphological and chemical analyses, we confirm that hollow, flattened melanosomes in iridescent feathers are eumelanin-based, whereas melanosomes in non-iridescent feathers are solid and amorphous, suggesting that high pheomelanin content underlies red coloration. Intriguingly, the nanoscale arrangement of melanosomes within the barbules was surprisingly similar between feather types. After creating a new genome assembly, we use transcriptomics to show that non-iridescent feather development is associated with genes related to pigmentation, metabolism, and mitochondrial function, suggesting non-iridescent feathers are more energetically expensive to produce than iridescent feathers. However, iridescent feather development is associated with genes related to structural and cellular organization, suggesting that, while nanostructures themselves may passively assemble, barbules and melanosomes may require active organization to give them their shape. Together, our analyses suggest that iridescent feathers form through a combination of passive self-assembly and active processes.

Thermal Response of Three Strains of Hens Housed in a Cage-Free Aviary at the Amazon Rainforest

ABSTRACT This study aimed to evaluate the thermal response of three strains of hens housed in a cage-free system at the Amazon rainforest in order to evaluate how feather coverage influences thermal exchange with the environment. The experimental method was completely randomized and treatments comprised three strains of hens (Rhode Island Red (red feathers with feathers on the neck), alternative strain FCI (red feathers without feathers on the neck), and alternative strain FCIII (white feathers without feathers on the neck)), with 20 hens (replicates) analyzed per strain. Thermal images of each bird were captured in order to record the birds’ surface temperatures on five points in five targets. All data collected in this study were subjected to ANOVA and subsequently to the Tukey test at p≤0.01 and p≤0.05. The aviary’s left wall presented a lower average temperature, indicating lower heat accumulation, while the floor presented higher heat accumulation. FCIII hens (white feathers) presented higher (p<0.05) heat accumulation on the head and legs, and lower (p<0.05) heat accumulation on the neck and back in relation to other analyzed hens, indicating increased heat exchange efficiency and high concentration of this process in specific body areas. FCI and FCIII hens (without feathers on the neck) presented lower (p<0.05) heat accumulation on the neck and higher (p<0.05) heat accumulation on the head and legs, indicating that the feather coverage directly influenced heat exchange mechanisms, and an increased area without feathers provided great heat exchange zones for birds in a tropical climate.

CYP2J19 mediates carotenoid colour introgression across a natural avian hybrid zone.

It has long been of interest to identify the phenotypic traits that mediate reproductive isolation between related species, and more recently, the genes that underpin them. Much work has focused on identifying genes associated with animal colour, with the candidate gene CYP2J19 identified in laboratory studies as the ketolase converting yellow dietary carotenoids to red ketocarotenoids in birds with red pigments. However, evidence that CYP2J19 explains variation between red and yellow feather coloration in wild populations of birds is lacking. Hybrid zones provide the opportunity to identify genes associated with specific traits. Here we investigate genomic regions associated with colour in red-fronted and yellow-fronted tinkerbirds across a hybrid zone in southern Africa. We sampled 85 individuals, measuring spectral reflectance of forecrown feathers and scoring colours from photographs, while testing for carotenoid presence with Raman spectroscopy. We performed a genome-wide association study to identify associations with carotenoid-based coloration, using double-digest RAD sequencing aligned to a short-read whole genome of a Pogoniulus tinkerbird. Admixture mapping using 104,933 single nucleotide polymorphisms (SNPs) identified a region of chromosome 8 that includes CYP2J19 as the only locus with more than two SNPs significantly associated with both crown hue and crown score, while Raman spectra provided evidence of ketocarotenoids in red feathers. Asymmetric backcrossing in the hybrid zone suggests that yellow-fronted females mate more often with red-fronted males than vice versa. Female red-fronted tinkerbirds mating assortatively with red-crowned males is consistent with the hypothesis that converted carotenoids are an honest signal of quality.

Colored feathers in museum collections: A spectroscopic study of 3 bio-pigments and their lightfastness

Abstract Yellow to red feathers in ornithological and ethnographical museum collections are known to be sensitive to light exposure. However, only a few studies on the interaction of light with the color of feathers have been published. This work provides fresh insight into the sensitivity of feathers for better conservation and exhibit of ethnographic collections, with a specific focus on carotenoids, psittacofulvins and porphyrins-based feathers. A first approach was to evaluate the use of Fiber Optics Reflectance Spectroscopy (FORS) in the visible range to characterize the chemical nature of the bio-pigments. It was implemented on 19 ornithological specimens preserved in the Museum national d’histoire naturelle (MNHN) in Paris, and on assigned feathers from more than 40 objects from the collections of the musee du quai Branly - Jacques Chirac (mqB-JC). Then, microfading tests were carried out on molting feathers or picked up on dead birds. Two different setups were used in order to determine a reproducible protocol for these 3D materials. Several variables were considered including the positioning of the feather and the duration of measurements. In addition to the visible range, the near-infrared (NIR) region was also investigated to determine if the color fading is concomitant to any structural modification. Then the developed protocol was applied on some loose lumps of feathers from objects of the mqB-JC collections. The data were compared against each other and to the Blue Wool Standards fading rates.

Madness as Ecological Consciousness in Bole Butake’s Lake God and John Nkengasong’s Black Caps and Red Feathers

This paper seeks to demonstrate that madness is not perceived in its strict sense but it can equally stand for ecological sensitization as indicated by Butake and Nkengasong’s dramaturgy. The plays of these playwrights indicate that environmental advocacy is a strange phenomenon in the universe and is welcomed by a few persons in the community who are regarded as strange beings in the midst of destructive and domineering humans. The paper argues that modernity and technological development have blinded humanity to an extent that anyone who still holds to environmental conservation is seen as a mad person. Madness is a complex word and the root cause of stigmatization, whose existence and concreteness can be seen in its interpretation. Its paradox lies in its existence or complexities when analyzed. According to Sueellen Campbell, madness is an aspect of the society which humans do not want to accept. Wild, on her part, sees madness as the strange behaviour or frenzy state in man. Madness exposes some realities of man’s true self which he does not want to acknowledge in his life/ society. The methodology adopted for this paper is a comparative and an analytical study of the texts. The article is predicated on the hypothesis that madness is not often regarded in its pure state but often incubates a certain reality when analysed.&#x0D; The theoretical framework used for the analysis of this paper is ecocriticism that addresses the question of ecological consciousness. Ecocriticism is a theory of literary criticism that studies the relationship between literature and the physical environment as defined by Glotfelty Cheryll and it is relevant in treating the issues discussed here. This work is based on Sueellen Campbell’s tenet which holds: “From the Middle Ages on, in different ways at different times, we have called mad what we do not want to acknowledge in ourselves, what we do not want to acknowledge in our society […]” Glotfelty &amp; Fromm, 128). It considers madness as a means of societal escapism from environmental truth. Campbell’s view is of interest as he evokes the term madness which is in light with the objective of the paper. Only abnormal people dodge from societal obligations and stigmatise the just as they are called mad. The conclusion arrived at is that environmental protection is still observed by a handful of persons as a reality. Humans have a long way to go and need sensitization talks in order for it to be understood. Those interested in ecological conservation are termed mad and end up with name calling/ stigmatized as mad.

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

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

Plumage redness signals mitochondrial function in the house finch.

Carotenoid coloration is widely recognized as a signal of individual condition in various animals, but despite decades of study, the mechanisms that link carotenoid coloration to condition remain unresolved. Most birds with red feathers convert yellow dietary carotenoids to red carotenoids in an oxidation process requiring the gene encoding the putative cytochrome P450 enzyme CYP2J19. Here, we tested the hypothesis that the process of carotenoid oxidation and feather pigmentation is functionally linked to mitochondrial performance. Consistent with this hypothesis, we observed high levels of red ketolated carotenoids associated with the hepatic mitochondria of moulting wild house finches (Haemorhous mexicanus), and upon fractionation, we found the highest concentration of ketolated carotenoids in the inner mitochondrial membrane. We further found that the redness of growing feathers was positively related to the performance of liver mitochondria. Structural modelling of CYP2J19 supports a direct role of this protein in carotenoid ketolation that may be functionally linked to cellular respiration. These observations suggest that feather coloration serves as a signal of core functionality through inexorable links to cellular respiration in the mitochondria.

SOX10 regulates multiple genes to direct eumelanin versus pheomelanin production in domestic rock pigeon.

The domesticated rock pigeon (Columba livia) has been bred for hundreds of years to display an immense variety of ornamental attributes such as feather color and color patterns. Color is influenced by multiple loci that impact the type and amount of melanin deposited on the feathers. Pigeons homozygous for the “recessive red” mutation, which causes downregulation of Sox10, display brilliant red feathers instead of blue/black feathers. Sox10 encodes a transcription factor important for melanocyte differentiation and function, but the genes that mediate its promotion of black versus red pigment are unknown. Here, we present a transcriptomic comparison of regenerating feathers from wild‐type and recessive red pigeons to identify candidate SOX10 targets. Our results identify both known and novel targets, including many genes not previously implicated in pigmentation. These data highlight the value of using novel, emerging model organisms to gain insight into the genetic basis of pigment variation.

The Effect of Light-Emitting Diode Light on the Physical Traits of Chicks

Environmental conditions including light are considered a critical element of chicks well-being. The aim of the present study was to investigate the effect of LED light on the physical traits of chicks. We took forty-one-day-old chicks and randomly separated it into two groups. The chicks in the first group were reared under the effect of incandescent lamp light and in the second one were under the effect of white LED lighting. Chicks were daily monitored for individual chick body, weight gain, feed intake, feather color and fear responses. The distance between chicks and source of light was 50 cm. Student’s t-test test was used for statistical evaluation at p < 0.05 level. The results of the current study showed that chicks reared under incandescent light bulb had significantly higher body weight compared with chicks reared under LED light. The magnitude of body weight in LED group was lower (1192.75 ± 149.9 g) compared to incandescent light group (1307.75 ± 110.5 g). The obtained results revealed that LED light reared chicks were more active; it showed long mobility duration and high levels of exploration in the farm as compared to those in incandescent light group. The results also indicated that incandescent light chicks were less fearful than LED chicks. Furthermore, the study showed that LED light reared chicks have pale pink combs and white feathers that cover all over the body. On the other hand, incandescent light reared chicks have dark red combs and whitish-yellow feathers that cover certain areas of the body especially chick wings, tail and head.

Frequency dispersion reveals chromophore diversity and colour-tuning mechanism in parrotfeathers.

Variation in animal coloration is often viewed as the result of chemically distinct pigments conferring different hues. The role of molecular environment on hue tends to be overlooked as analyses are mostly performed on free pigments extracted from the integument. Here we analysed psittacofulvin pigments within parrot feathers to explore whether the in situ organization of pigments may have an effect on hue. Resonance Raman spectra from a red region of a yellow-naped amazon Amazona auropalliata tail feather show frequency dispersion, a phenomenon that is related to the presence of a range of molecular conformations (and multiple chromophores) in the pigment, whereas spectra from a yellow region on the same feather do not show the same evidence for multiple chromophores. Our findings are consistent with non-isomeric psittacofulvin pigments behaving as a single chromophore in yellow feather barbs, which implies that psittacofulvins are dispersed into a structurally disordered mixture in yellow feathers compared with red feathers. Frequency dispersion in red barbs may instead indicate that pigments are structurally organized through molecule–molecule interactions. Major differences in the hues of parrot feathers are thus associated with differences in the organization of pigments within feathers.

Colouration Genetics: Pretty Polymorphic Parrots

The bright yellow, green and red feathers of parrots depend on unique pigments termed 'psittacofulvins'. The discovery of a gene underlying psittacofulvin colouration shows that this evolutionary innovation was achieved by co-opting an existing gene into feather development.

Divergence in Pigmentation as a Result of Wet Forests in an Insular Population of Flameback Woodpeckers

Sri Lanka’s wet zone forests are considered as the wettest tropical forests in the South Asian region. Within the island of Sri Lanka, the wet zone forests are darker and wetter than its dry zone counterpart. The woodpecker genus Dinopium flamebacks has a distinctive yellow color plumage across its range except in the Sri Lankan wet zone. Here in the wet zone they show an endemic red coloration. According to the Gloger’s rule, animals become darkly colored in habitats where relative humidity is high and pale colored where humidity is low. Hence we checked, whether these dark environment in wet zone forests contribute to the evolution of woodpecker plumage coloration in Sri Lanka. We measured Plumage reflectance spectra of 18 live flamebacks 58 skin samples (29 D. psarodes–red, 16 D. benghalense-yellow and 13 hybrids - orange) using a miniature spectrometer together with a light source of spectral range 375–700 nm. The pigments from mantle feathers of this same samples were extracted under mild conditions into different polar solvents. Extractions were analyzed by using UV-visible absorption spectroscopy, TLC and HPLC. A subset of mantle feathers were also analysed using ATR-FTIR spectrometry. Yellow and red feathers showed reflectance peaks at ~510 nm and ~575 nm wavelengths respectively. Polar solvents (chloroform, ethyl acetate and methanol) produce the characteristic carotenoid absorbance spectra therefore xanthophyll pigments are responsible for flameback colorations.TLC and HPLC chromatograms and ATR-FTIR spectrograms showed two sets of bands (TLC) or peaks (HPLC and ATR-FTIR) in red feathers, however yellow feathers had a single set of bands or peaks corresponding the yellow color. Our results showed a new endemic pigment molecule in red color woodpeckers. This new pigment molecule is absent in yellow flameback feathers. A reduced concentration of endemic pigment produce the orange coloration in genetic hybrids in a narrow hybrid zone ranges from Puttulum to Mulativu. Since the darker environment in wet zone might favor dark birds and light environment in the dry zone and in the rest of the mainland favor light color birds, here we showed evidence for divergence of acarotenoid pigmentas a response to the dark wet zone forests that caused the absorbance of yellow color and express red color, triggering a speciation event that adds an endemic species to the island of Sri Lanka. Keywords: Carotenoids, Dinopium, Divergence, Pigment ecology, Sri Lanka

Consumers' acceptance of medicinal herbs: An application of the technology acceptance model (TAM)

Ethnopharmacological relevanceThe shift in consumers’ preferences from synthetic to ‘natural’ products has led to a resurgence of interest in medicinal plants, particularly in developing countries. However, research data about consumers’ preferences for particular products is hard to find. Aims and objectivesThe main objective of this study was to contribute to the general understanding of consumers’ intention for selecting medicinal herbs for consumption. Materials and methodsFactors underpinning consumers’ acceptance of medicinal herbs were studied with the technology acceptance model (TAM) in Rasht City of Iran using a structured questionnaire. ResultsMost respondents had low to moderate familiarity with consumption of medicinal herbs. However, about half of the respondents (47.5%) showed a high level of acceptance of medicinal herbs. Herbs like spearmint (Mentha spicata L.), spinach (Spinacia oleracea L.), basil (Ocimum basilicum L.), Damask rose (Rosa × damascena Herrm.), saffron (Crocus sativus L.), cinnamon (Cinnamomum verum J.Presl), flixweed [Descurainia sophia (L.) Webb ex Prantl], red feathers (Echium amoenum Fisch. & C.A.Mey.), and green tea [Camellia sinensis (L.) Kuntze] had the highest consumption rate among the majority (over 75%) of citizens of Rasht. The highest rate of perceived usefulness of medicinal herbs was related to their perceived role in healing diseases. The variable of importance of use of medicinal herbs had the strongest direct effect and the variables of perceived usefulness and attitude towards use had the second and third strongest direct effect on the acceptance of medicinal herbs’ use at p < 0.01. ConclusionsFindings provide a useful evaluation of the acceptance of medicinal herbs and may serve as a benchmark for future research and evaluation concerning the use of medicinal herbs over time. For plant producers, more effective and targeted crop development should be encouraged, whereas for retailers better marketing and delivery strategies should be sought.

Testosterone regulates scarlet plumage in red-backed fairy-wrens

As the days begin to lengthen and winter recedes for yet another year, many birds dust off their most glamorous plumage to attract a mate. Males often opt for ostentatious displays while females tend to the dowdier end of the spectrum. But what factors regulate the dramatic differences in avian regalia between males and females? Willow Lindsay from the University of Gothenburg, Sweden, explains that the hormones that regulate sexual differences were thought to play a key role in defining plumage patterns, but the precise role of individual hormones was less clear. As testosterone starts flowing in spring, male red-backed fairy-wrens (Malurus melanocephalus) shed their dreary brown feathers in favour of a vivid scarlet and glossy black coat, while the females retain their dingy brown and white plumage. So, Lindsay and Douglas Barron headed south to Queensland, Australia, to find out how the plumage of red-backed fairy-wrens altered after they received a testosterone implant.Initially, the males and females both looked drab; however, soon after the birds received the implant, the females moulted and began sprouting shorter male-like feathers. The females also produced a vibrant patch of red feathers on their backs, similar to the bright red streak on the males’ backs. In addition, the feathers on the crown, belly and breast of the females turned a shade of pinky-orange, which Lindsay said was: ‘Never previously documented on a red-backed fairy-wren’. Only one female went on to produce black feathers like those of the males, although the beaks of all of the females became darker. And when Lindsay and Barron injected some females with gonadotropin-releasing hormone, in a bid to naturally raise the birds’ testosterone levels, the females were unable to increase the levels of the hormone in their blood.So, it seems that testosterone is the hormone that regulates the production of the carotenoid pigments that produce the males’ scarlet plumage; however, the hormone was unable to elicit production of the jet-black melanin pigment that produces their distinctive dark feathers. It seems that the female fairy-wrens still maintain the essential hormone mechanism that allows the males to put on their gaudy display, although the females are unable to produce sufficient testosterone to trigger the masculine transformation.

Genetic Basis for Red Coloration in Birds

The yellow and red feather pigmentation of many bird species [1] plays pivotal roles in social signaling and mate choice [2, 3]. To produce red pigments, birds ingest yellow carotenoids and endogenously convert them into red ketocarotenoids via an oxidation reaction catalyzed by a previously unknown ketolase [4-6]. We investigated the genetic basis for red coloration in birds using whole-genome sequencing of red siskins (Spinus cucullata), common canaries (Serinus canaria), and "red factor" canaries, which are the hybrid product of crossing red siskins with common canaries [7]. We identified two genomic regions introgressed from red siskins into red factor canaries that are required for red coloration. One of these regions contains a gene encoding a cytochrome P450 enzyme, CYP2J19. Transcriptome analysis demonstrates that CYP2J19 is significantly upregulated in the skin and liver of red factor canaries, strongly implicating CYP2J19 as the ketolase that mediates red coloration in birds. Interestingly, a second introgressed region required for red feathers resides within the epidermal differentiation complex, a cluster of genes involved in development of the integument. Lastly, we present evidence that CYP2J19 is involved in ketocarotenoid formation in the retina. The discovery of the carotenoid ketolase has important implications for understanding sensory function and signaling mediated by carotenoid pigmentation.

Morphological basis of glossy red plumage colours

Brightly coloured feathers, including the brilliant reds produced by carotenoids, are sometimes shiny in appearance. Gloss is a common property of materials and usually arises through specular reflection from smooth, flat surfaces. However, the production of gloss on red feathers has never been examined. In the present study, we compared the optical and structural properties of glossy and matte carotenoid-based red feathers of multiple species to identify the proximate basis for their glossiness. Although specular reflectance did not differ between glossy and matte feathers, diffuse reflectance was lower in glossy than in matte feathers, leading to a higher contrast gloss. Compared to matte feathers, glossy red feathers had thicker barbs with a flatter and more homogeneous morphology, consistent with expectations, as well as thicker outer keratin cortices. Moreover, glossiness was predicted by a principal component regression using these same morphological traits. We demonstrate that the gloss of carotenoid-based red feathers is produced at least in part by a smooth, flattened barb microstructure and an enhanced nanostructure, illustrating a novel colour-producing interaction that neither pigment, nor microstructure could alone attain. How the ecology and evolution of species with glossy red feather differ from those with typical matte red feathers represent rich areas for future study.