Coloration In Birds Research Articles

Identifying anatomical sites of carotenoid metabolism in birds

Carotenoid metabolism has long interested plant and animalbiochemists (Goodwin 1986; Lu and Li 2008). Identifyingtissue sites and enzymes responsible for carotenoid trans-formations (e.g., β-carotene to vitamin A) has beenchallenging. Colorful birds have recently become a modelfor studying carotenoid nutrition and metabolism, in thecontext of sexual selection and honest signaling (McGraw2006). In a recent paper published in Naturwissenschaften,del Val et al. (2009) described carotenoid profiles in tissuesof male common crossbills (Loxia curvirostra), with theaim of localizing metabolic site(s) for a ketocarotenoidpigment—3-hydroxy-echinenone (3HE)—present in redfeathers. They found 3HE in blood and liver, unlikeprevious studies of colorful songbirds where metabolizedintegumentary carotenoids were found only at peripheraltissues (e.g., beak, legs; McGraw 2004). Thus, the authorsconcluded that the liver was the site of ketocarotenoidsynthesis in crossbills. Here, I outline the limitations ofsuch descriptive pigment analyses, when carotenoid typesare present in various tissues, and discuss fruitful directionsfor future lines of research in this area.Because carotenoids are dietary in origin in animals butcan be modified in body tissues enzymatically, careful foodand physiological studies allow for accurate identificationof pigment origins and transformations. Traditional rigor-ous methods for identifying carotenoid metabolic sites,processes, and products in animals include direct enzymeidentification (Wyss 2004), isotope labeling of precursors(Burri and Clifford 2004), and by inference from ex vivochemical reactions (Khachik et al. 1998) or where caroten-oid types exist in no other tissue type (McGraw 2004).del Val et al. (2009) undertook none of these types ofinvestigation. The first step in such research is to rule out adietary source to the pigment, but the authors did not studyfood carotenoids in crossbills; they sampled only liver,skin, and feathers from accidentally field-killed animals anddrew blood from molting birds. While red carotenoids arenot currently thought to be common in diets of herbivorousland birds (e.g., rubixanthin in rose hips, rhodoxanthin inTaxus berries), this is a key assumption to biochemicallyvalidate for any species, given the paucity of informationon avian food carotenoids.del Val et al. (2009) based their assertion that 3HE wasmetabolized in the liver of crossbills on the observation that3HE was the most proportionally concentrated (and mostvariably occurring) carotenoid in liver. However, data onother types of body carotenoids were not presented in thispaper, the molt status of dead birds was not given, and withsmall sample sizes (n=7) no statistics were performed.Thus, we have no context for understanding which and howcertain carotenoid pigments occurred in different crossbilltissues. Follicles actually contained proportionally more3HE than liver (61% vs. 35% of total carotenoids,respectively), and while the authors argue that this isexpected (given that “maturing follicles would just accu-mulate this red derivative until the pigment would beincorporated finally into growing feathers during moult”;p. xxx), this makes the non-null assumption that folliclespreferentially retain 3HE over other circulating carotenoids.Even if we assume that 3HE is not dietary in origin,alternate tissues with carotenoidmetabolismcapabilitieswerenot studied. The oxygenase enzyme that cleaves β-carotene

The Utility of Plumage Coloration for Taxonomic and Ecological Studies

Plumage coloration in birds serve multiple purposes, including species recognition, sexual selection cues, and camouflage. Differences in plumage coloration can be used to infer evolutionary relationships, identify distinct taxonomic units, and characterize geographic variation. With the advent of electronic devices to quantify plumage coloration quickly and reliably, taxonomic or geographic differences can be exploited for ecological studies. To evaluate the utility of plum- age coloration for taxonomic and ecological studies, I review the basis of plumage coloration and sources of variation. I then review how different studies have used plumage coloration to better understand taxonomic relationships and provide insights into ecological problems.

The colour of domestication and the designer chicken

Colour is an important feature of most living organisms. In the wild, colour has great significance affecting the survival and reproductive success of the species. The environmental constraints which lead to the specific colours of birds and animals are very strong and individuals of novel colours tend not to survive. Under domestication, mankind has transformed all the species involved which have thus been freed from environmental pressures to a large extent. Early colour variants were mostly selected for utility reasons or religious practices. In more recent centuries colour varieties have been created purely for ornament and pleasure, fashion playing a surprisingly large part in their development. A bewildering array of colours and patterns can now be found in all our commensal species, especially the Domestic Fowl ( Gallus gallus domesticus).

A multifactorial test of the effects of carotenoid access, food intake and parasite load on the production of ornamental feathers and bill coloration in American goldfinches

It has been well established that carotenoid and melanin pigmentation are often condition-dependent traits in vertebrates. Expression of carotenoid coloration in birds has been shown to reflect pigment intake, food access and parasite load; however, the relative importance of and the potential interactions among these factors have not been previously considered. Moreover, carotenoid and melanin pigmentation have been proposed to signal fundamentally different aspects of individual condition but few data exist to test this idea. We simultaneously manipulated three environmental conditions under which American goldfinches (Cardeulis tristis) grew colorful feathers and developed carotenoid pigmentation of their bills. Male goldfinches were held with either high or low carotenoid supplementation, pulsed or continuous antimicrobial drug treatment, or restricted or unlimited access to food. Carotenoid supplementation had an overriding effect on yellow feather coloration. Males given more lutein and zeaxanthin grew yellow feathers with hue shifted toward orange and with higher yellow chroma than males supplemented with fewer carotenoids. Parasites and food access did not significantly affect yellow feather coloration, and there were only minor interaction effects for the three treatments. By contrast, bill coloration was significantly affected by all three treatments. Carotenoid supplementation had a significant effect on yellow chroma of bills, drug treatment and food access both had a significant effect on bill hue, and food access had a significant effect on the yellow brightness of bills. Neither the size nor blackness of the black caps of male goldfinches was affected by any treatment. These results indicate that pigment intake, food access and parasite load can have complex and variable effects on color displays, and that feather and bill coloration signal different aspects of male condition.

Feeding visit time of fruit-eating birds in Cerrado plants: revisiting the predation risk model

Fruiting plants that attract frequent visits by fruit-eating birds tend to be predictable patches for a predator. Consequently, the risk of a predator attack increases the longer a bird stays on a fruiting plant. We tested whether large and cryptic species of fruit-eating birds spend more time per feeding visit than smaller and conspicuous ones in fruiting plants of the Brazilian Cerrado. Data were obtained from the literature for eight fruiting plant species and from field observations of birds feeding on fruits of Zanthoxylum rhoifolium (Rutaceae). We searched for a positive linear relationship between the mean visit time and the total length of the species, considering bird color as a covariate. Feeding visits of the large and cryptic bird species lasted longer than feeding visits of small and conspicuous species. Large birds may be safer from predators because large predators are less common. Cryptic birds may be difficult to be detected by predators and, consequently, may be less likely to be attacked by predators than conspicuous birds. Thus, our results provide support to the hypothesis that vulnerable bird species spend less time foraging in fruiting plants.

Methods for correcting plumage color fading in the Barn Swallow

Abstract It is necessary to correct plumage color fading when comparing the plumage coloration of birds captured at different times during the breeding season. We proposed two methods for correcting plumage color fading and compared them using the throat feathers of the Barn Swallow (Hirundo rustica gutturalis). One method uses the color shift of feathers on live birds during the same breeding season (the field method). The other method uses longitudinal color measurements of feathers placed on the open ground (the experimental method). This method has an advantage of not capturing the birds twice. The field and experimental methods estimated similar rates of fading of hue and brightness. Saturation was predicted to fade with time in the experimental method, which is unrealistic because there was no effect of time on saturation in live birds. Using the field method, we derived an equation for correcting plumage color fading in Barn Swallows. When assessing changes in plumage color, the field method should...

EFFECTS OF SPECIMEN AGE ON PLUMAGE COLOR

Abstract Museum specimens are valuable for studies of plumage color in birds, but feather color may fade over time and not accurately reflect the colors of live birds. In particular, it has been suggested that ultraviolet (UV) color may be more susceptible to degradation than human-visible colors. We used a reflectance spectrophotometer to measure feather color in five species of passerines for which museum specimens were collected consistently over the past 100 years. We found that the feather colors of museum specimens collected within the past 50 years were related closely to the feather colors of live birds. In fact, over a wide range of different colors, we found little change in color measurements for recent (<50 years old) specimens. Furthermore, UV color was not affected more severely by fading than human-visible colors when we confined our analyses to recent specimens. These results provide strong support for the continued use of museum specimens to examine coloration in birds, provided that the ...

The colour of fossil feathers

Feathers are complex integumentary appendages of birds and some other theropod dinosaurs. They are frequently coloured and function in camouflage and display. Previous investigations have concluded that fossil feathers are preserved as carbonized traces composed of feather-degrading bacteria. Here, an investigation of a colour-banded feather from the Lower Cretaceous Crato Formation of Brazil revealed that the dark bands are preserved as elongate, oblate carbonaceous bodies 1-2 microm long, whereas the light bands retain only relief traces on the rock matrix. Energy dispersive X-ray analysis showed that the dark bands preserve a substantial amount of carbon, whereas the light bands show no carbon residue. Comparison of these oblate fossil bodies with the structure of black feathers from a living bird indicates that they are the eumelanin-containing melanosomes. We conclude that most fossil feathers are preserved as melanosomes, and that the distribution of these structures in fossil feathers can preserve the colour pattern in the original feather. The discovery of preserved melanosomes opens up the possibility of interpreting the colour of extinct birds and other dinosaurs.

Multiple ways to become red: Pigment identification in red feathers using spectrometry

Red hues are a challenge in studies on the evolution of bird coloration, as multiple pigments such as carotenoids, pheomelanin, psittacofulvins, porphyrins, turacin, haemoglobin and even exogenous iron-oxides, may confer red colors. Determining the pigment type is paramount and here we investigate the differences in spectrum reflectance for six pigments resulting in red colorations in feathers of different species, with a focus on discriminating among melanins and carotenoids. Pigment chemical identification was obtained from the literature or using High Performance Liquid Chromatography (HPLC) in our laboratory. We have also derived discriminant formulas for identification of the major known types of pigments based on parameters of the reflectance curves obtained with a portable spectrometer. Our results indicate that the reflectance patterns of coloration perceived as red patches widely differ. The distinction between carotenoid- and melanin-based reflectance curves is relatively straightforward: sigmoid versus straight slope. The spectral reflectance curves of feathers containing red psittacofulvins are sigmoid, whereas iron oxide and porphyrin-containing feathers recall pheomelanins in rendering a straight slope. In the case of turacin-based coloration, the spectral shape is unique. For the pigments with enough number of species sampled (i.e., carotenoids, melanins and psittacofulvins) the differences in reflectance shape are important enough to allow separation of carotenoid and melanin derived colorations based on reflectance curves alone.

Recessive black Is Allelic to the yellow Plumage Locus in Japanese Quail and Associated With a Frameshift Deletion in the ASIP Gene

The recessive black plumage mutation in the Japanese quail (Coturnix japonica) is controlled by an autosomal recessive gene (rb) and displays a blackish-brown phenotype in the recessive homozygous state (rb/rb). A similar black coat color phenotype in nonagouti mice is caused by an autosomal recessive mutation at the agouti locus. An allelism test showed that wild type and mutations for yellow, fawn-2, and recessive black in Japanese quail were multiple alleles (*N, *Y, *F2, and *RB) at the same locus Y and that the dominance relationship was Y*F2 > Y*Y > Y*N > Y*RB. A deletion of 8 bases was found in the ASIP gene in the Y*RB allele, causing a frameshift that changed the last six amino acids, including a cysteine residue, and removed the normal stop codon. Since the cysteine residues at the C terminus are important for disulphide bond formation and tertiary structure of the agouti signaling protein, the deletion is expected to cause a dysfunction of ASIP as an antagonist of alpha-MSH in the Y*RB allele. This is the first evidence that the ASIP gene, known to be involved in coat color variation in mammals, is functional and has a similar effect on plumage color in birds.

Preen waxes do not protect carotenoid plumage from bleaching by sunlight

The plumage coloration of wild birds often changes during the breeding season. One of the possible reasons for this is that sunlight, and particularly ultraviolet (UV) wavelengths, degrades the pigments responsible for plumage coloration. It has been suggested that birds may apply preen wax to feathers to protect feathers from bleaching. This hypothesis is tested by exposing carotenoid‐based breast feathers of Great Tits to ambient light, light filtered to exclude UV and darkness. Preen waxes were experimentally removed from feather samples and the effect of light on coloration of treatment and control feathers compared. Ambient light had an effect on feather colour but preen wax did not. Feathers exposed to sun gradually became less saturated and hues shifted towards shorter wavelengths. This was not apparent in control feathers kept in darkness. Feathers exposed to full‐spectra sunlight faded more than those that were kept in light with UV wavelengths removed. There was a decrease in brightness of feathers in both experimental and control groups, which was assumed to be an effect of dirt accumulation. This experiment confirmed earlier suspicions regarding the detrimental effects of UV irradiation on carotenoid‐based coloration of avian feathers but failed to show any protective function of preen waxes. The possible consequences of these mechanisms of colour change for birds with regard to mating strategies are discussed.

Phylogeny, biogeography and taxonomy of the African wattle-eyes (Aves: Passeriformes: Platysteiridae)

The African wattle-eyes (genera Platysteira and Dyaphorophyia) comprise 10 species endemic to Africa. We analyzed both mitochondrial and nuclear DNA sequence data to test the monophyly of this group and its two genera, provide a preliminary assessment of species limits, and gain insight into the phylogeographic history of the wattle-eye radiation. Analyses based on mitochondrial ND2 sequences failed to recover wattle-eye monophyly, but the alternatives were not well-supported. In contrast, analyses of two nuclear introns (myoglobin intron-2 and β-fibrinogen intron-5) recovered wattle-eye monophyly, as did combined analyses of mitochondrial and nuclear data. These analyses, however, did not support reciprocal monophyly of the two wattle-eye genera typically recognized, suggesting instead that Platysteira is nested within a paraphyletic Dyaphorophyia. The diversification of most wattle-eye species and many subspecies occurred through the divergence of allopatric populations well before the Pleistocene. Species and subspecies with disjunct distributions are typically characterized by deep genetic divergences, suggesting that many of these populations are evolutionary independent and could be recognized as additional phylogenetic species. In D. castanea and D. chalybea, for example, divergent haplotypes from geographically disjunct populations were paraphyletic with respect to those of D. tonsa and D. jamesoni, respectively. Similarly, Platysteira laticincta is highly divergent from its sister taxon P. peltata (∼9.5% ND2 sequence divergence), consistent with species level recognition of this endangered species. In contrast, more broadly distributed taxa inhabiting a greater diversity of habitats (e.g., P. peltata and P. cyannea) show evidence of gene flow and connectivity among regions, suggesting that previously isolated populations expanded and fused into one another. Our study provides a framework for additional analyses of intraspecific phylogeography and species limits in these colorful birds.

An Indian FOPSE (Innovations Case Discussion: Keggfarms)

India on a case for my Harvard Business School class on international entrepreneurship. A friend of mine had invited me to attend the ceremony for the first Innovations for India Awards in Mumbai. Several Indian businesspeople received the award, but I was particularly struck by a dignified silver-haired gentleman who took the stage to receive the award for social innovation. He then proceeded to eloquently describe the development of a business concept centered on the rural poor of India, which was based on a specially bred “superchicken” that was twice as big and five times as productive as the typical backyard chicken. The incongruity of Vinod Kapur’s elegant appearance and his subject matter struck me as fascinating, but the most intriguing element of the presentation was how he arranged an entire system of distribution to deliver the hatched chicks to these remote villagers and did so in a way that enabled everyone to profit in concrete financial terms, from Keggfarms itself to the rural villagers. Almost a million households are today affected by Keggfarms, and the numbers are constantly rising. The most striking element of Keggfarms is the chicken itself—it is a beautiful, big, colorful bird, and I must say that the meat and eggs are by far the tastiest poultry products I have eaten in my life. But the most significant innovation is not the chicken per se but the business model, in particular the distribution system used to get the newly hatched chicks into the hands of the villagers quickly and safely. It is difficult to imagine a more nightmarish distribution problem: The customers are dispersed geographically in regions of relatively low population density. The transportation infrastructure is undeveloped—most of the customers can be reached only by footpath. The products are perishable, vulnerable to heat and disease. The product is considered to be a commodity with little price elasticity. The customers have extremely limited purchasing power so that high distribution costs cannot be transferred to them. It would be prohibitively expensive for any company to establish its own distribution system to bring tens of millions of live chicks into the rural villages. Furthermore, it would be difficult to organize and even more difficult to control. Such a distribution system would be required to some extent to build on established distribution patterns, in which the various parties would be extrinsically

Testing whether macroevolution follows microevolution: Are colour differences among swans (Cygnus) attributable to variation at the MC1R locus?

BackgroundThe MC1R (melanocortin-1 receptor) locus underlies intraspecific variation in melanin-based dark plumage coloration in several unrelated birds with plumage polymorphisms. There is far less evidence for functional variants of MC1R being involved in interspecific variation, in which spurious genotype-phenotype associations arising through population history are a far greater problem than in intraspecific studies. We investigated the relationship between MC1R variation and plumage coloration in swans (Cygnus), which show extreme variation in melanic plumage phenotypes among species (white to black).ResultsThe two species with melanic plumage, C. atratus and C. melanocoryphus (black and black-necked swans respectively), both have amino acid changes at important functional sites in MC1R that are consistent with increased MC1R activity and melanism. Reconstruction of MC1R evolution over a newly generated independent molecular phylogeny of Cygnus and related genera shows that these putative melanizing mutations were independently derived in the two melanic lineages. However, interpretation is complicated by the fact that one of the outgroup genera, Coscoroba, also has a putative melanizing mutation at MC1R that has arisen independently but has nearly pure white plumage. Epistasis at other loci seems the most likely explanation for this discrepancy. Unexpectedly, the phylogeny shows that the genus Cygnus may not be monophyletic, with C. melanocoryphus placed as a sister group to true geese (Anser), but further data will be needed to confirm this.ConclusionOur study highlights the difficulty of extrapolating from intraspecific studies to understand the genetic basis of interspecific adaptive phenotypic evolution, even with a gene whose structure-function relationships are as well understood as MC1R as confounding variation make clear genotype/phenotype associations difficult at the macroevolutionary scale. However, the identification of substitutions in the black and black-necked swan that are known to be associated with melanic phenotypes, suggests Cygnus may be another example where there appears to be convergent evolution at MC1R. This study therefore provides a novel example where previously described intraspecific genotype/phenotype associations occur at the macroevolutionary level.

Carotenoid plumage hue and chroma signal different aspects of individual and habitat quality in tits

We hypothesized that Blue Tits Cyanistes caeruleus and Great Tits Parus major from low quality habitat (small woods) would have less yellow ventral plumage than those from high quality habitat (large woods) because they moult faster and/or their diet contains fewer carotenoids. They moult faster because they moult later in the season and are subject to more rapidly shortening daylengths. We tested this using a database of the plumage coloration (chroma, hue and lightness) of birds breeding in woods of different sizes, by manipulating the speed of moult in captive Blue Tits, and by counting the abundance and size of caterpillars (the major source of dietary carotenoids) in the diet of nestlings. In accordance with our hypothesis, juveniles of both species (which moult about three weeks later than adults) were about 8% less saturated in colour (lower chroma) than adults, but there was no significant difference in chroma between habitats. However, both species did differ significantly in hue between large and small woods. Blue Tits forced to moult faster in captivity, at a rate similar to that caused by a month's delay in the start of moult, had yellow flank feathers that were 32% less saturated in colour than those allowed to moult more slowly. Blue Tit nestlings in large woods consumed 47% more caterpillar flesh (per gram of faecal material voided) than those in small woods, and Great Tit pulli 81% more. When habitat effects were controlled for in ANOVAs, Blue Tits mated assortatively on the basis of flank hue and Great Tits on the basis of flank lightness. Flank colour therefore has the capacity to provide information about the potential quality of both habitats, and individual birds, to potential colonists and sexual partners.

Carotenoid Coloration in Greenfinches Is Individually Consistent Irrespective of Foraging Ability

Carotenoid-based plumage coloration of birds has been hypothesized to honestly reflect individual quality, either because carotenoids are difficult to acquire via food or because of a trade-off in allocation of carotenoids between maintenance and signaling functions. We tested whether differential foraging ability is a necessary precondition for maintaining individual differences in carotenoid-based plumage coloration in male greenfinches (Carduelis chloris). Wild-caught birds were brought into captivity, where half of them were supplemented with carotenoids while the other half was maintained on a carotenoid-poor diet. Color of the yellow parts of tail feathers, grown under natural conditions, was compared with that of the replacement feathers, grown in captivity. Carotenoid supplementation increased feather chroma (saturation). Color of wild-grown feathers significantly correlated with the color of lab-grown feathers. This result demonstrates the existence of a significant component of variation in carotenoid coloration, which reflects physiological qualities or genetic differences among individuals independent of foraging ability. Among both experimental groups, plasma carotenoid concentration during feather growth strongly correlated with chroma of the feathers grown in captivity. This indicates that carotenoid-based plumage coloration can reveal circulating carotenoid levels over a very wide range of concentrations, suggesting the ample signaling potential of such a mechanism.

Bird Coloration.

Abstract The following critiques express the opinions of the individual evaluators regarding the strengths, weaknesses, and value of the books they review. As such, the appraisals are subjective assessments and do not necessarily reflect the opinions of the editors or any official policy of the American Ornithologists' Union.

Transfer of serial reversal learning in the pigeon

Pigeons were trained on a series of reversals of a simultaneous visual discrimination and were then shifted to a second series of reversals with different visual discriminanda. Pigeons that were given discrimination reversals with one pair of colours (Group Colour) and then shifted to a second pair of colours made fewer errors with the second pair than the first. In contrast, pigeons that were initially given reversals with a pair of orientations (Group Orientation) and then shifted to colours made as many errors during colour reversals as Group Colour had during initial colour training. When birds in Group Colour were subsequently shifted to orientation discrimination reversals, they performed no better than Group Orientation had during initial orientation training. The present results suggest that positive transfer from one series of discrimination reversals to a second, independent series may be constrained by the nature of the stimulus shift.

Bird Coloration. Volume I: Mechanisms And Measurements

Bird Coloration. Volume I: Mechanisms And Measurements

Errata

Functional EcologyVolume 21, Issue 2 p. 386-386 Free Access Errata First published: 15 March 2007 https://doi.org/10.1111/j.1365-2435.2007.1258_1.xAboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Saks, L., McGraw, K. J. & Hõrak, P. (2003) How feather colour reflects its carotenoid content. Functional Ecology 17, 555–561. Equation 2 (p. 557) in Saks et al. (2003) describing the calculation of chroma was erroneously presented. The value of chroma was calculated according to Endler (1990) and the correct presentation of this calculation should be as follows: (eqn 2) where B = (Qb/Qt), G = (Qg/Qt), Y = (Qy/Qt), R = (Qr/Qt). Unfortunately, the erroneous version of this equation has also been reprinted in Montgomerie (2006). References Endler, J.A. (1990) On the measurement and classification of colour in studies of animal colour patterns. Biological Journal of the Linnean Society 41, 315– 352. Montgomerie, R. (2006) Analyzing colors. Bird Coloration. Vol. I. Mechanisms and Measurements (eds G.E. Hill & K.J. McGraw), Table 3.2, p. 108. Harvard University Press, Cambridge, MA. Volume21, Issue2April 2007Pages 386-386 ReferencesRelatedInformation