Plumage Pigmentation Research Articles

The effect of dietary carotenoid access on sexual dichromatism and plumage pigment composition in the American goldfinch

We investigated potential dietary and biochemical bases for carotenoid-based sexual dichromatism in American goldfinches ( Carduelis tristis). Captive male and female finches were given access to the same type and amount of carotenoid pigments in the diet during their nuptial molt to assess differences in the degree to which the two sexes incorporated ingested pigments into their plumage. When birds were fed a uniform, plain-seed diet, or one that was supplemented with the red carotenoid canthaxanthin, we found that males grew more colorful plumage than females. HPLC analyses of feather pigments revealed that male finches incorporated a higher concentration of carotenoids into their pigmented feathers than females. Compared to females, males also deposited significantly more canary xanthophyll B into feathers when fed a plain-seed diet and a greater concentration and proportion of canthaxanthin when fed a carotenoid-supplemented diet. These results indicate that sex-specific expression of carotenoid pigmentation in American goldfinches may be affected by the means by which males and females physiologically utilize (e.g. absorb, transport, metabolize, deposit) carotenoid pigments available to them in the diet.

Carotenoid access and intraspecific variation in plumage pigmentation in male American Goldfinches (Carduelis tristis) and Northern Cardinals (Cardinalis cardinalis)

Summary Behavioural ecologists have shown much interest recently in the factors that promote variation in carotenoid‐based colour displays. Because vertebrates cannot synthesize the pigments needed to attain this form of bright coloration, most research has focused on the effect of dietary access to pigments on carotenoid ornamentation. However, few studies have considered experimentally how the availability of carotenoid pigments in the diet influences variability in the expression of carotenoid‐based coloration. Dietary access to carotenoids was manipulated in captive groups of male American Goldfinches (Carduelis tristis L.) and Northern Cardinals (Cardinalis cardinalis L.) to assess the role of pigment acquisition in shaping intraspecific variation in carotenoid‐based plumage pigmentation. Substantial variation was detected in the plumage displays of captive male goldfinches and cardinals within a diet treatment, such that birds with unlimited access to the same diet type displayed carotenoid‐based plumage variation that did not differ significantly from that typical of wild males from each species. Additionally, the natural plumage brightness that male goldfinches displayed at capture predicted the degree to which they grew colourful plumage under controlled conditions in our experiments. These results suggest that carotenoid‐based plumage variation in male goldfinches and cardinals is less sensitive to pigment availability in the diet than colour variation observed in other studied taxa. Differences in ornamental coloration among males from these two passerine species may instead reflect their ability to utilize ingested pigments physiologically.

The influence of carotenoid acquisition and utilization on the maintenance of species-typical plumage pigmentation in male American goldfinches (Carduelis tristis) and northern cardinals (Cardinalis cardinalis).

Birds display a tremendous variety of carotenoid-based colors in their plumage, but the mechanisms underlying interspecific variability in carotenoid pigmentation remain poorly understood. Because vertebrates cannot synthesize carotenoids de novo, access to pigments in the diet is one proximate factor that may shape species differences in carotenoid-based plumage coloration. However, some birds metabolize ingested carotenoids and deposit pigments that differ in color from their dietary precursors, indicating that metabolic capabilities may also contribute to the diversity of plumage colors we see in nature. In this study, we investigated how the acquisition and utilization of carotenoids influence the maintenance of species-typical plumage pigmentation in male American goldfinches (Carduelis tristis) and northern cardinals (Cardinalis cardinalis). We supplemented the diet of captive goldfinches with red carotenoids to determine whether males, which are typically yellow in color, were capable of growing red plumage. We also deprived cardinals of red dietary pigments to determine whether they could manufacture red carotenoids from yellow precursors to grow species-typical red plumage. We found that American goldfinches were able to deposit novel pigments in their plumage and develop a striking orange appearance. Thus, dietary access to pigments plays a role in determining the degree to which goldfinches express carotenoid-based plumage coloration. We also found that northern cardinals grew pale red feathers in the absence of red dietary pigments, indicating that their ability to metabolize yellow carotenoids in the diet contributes to the bright red plumage that they display.

Carotenoids in bird plumage: the complement of red pigments in the plumage of wild and captive bullfinch ( Pyrrhula pyrrhula)

We have studied the carotenoid pigments in the red plumage of male bullfinch ( Pyrrhula pyrrhula) immediately following capture and after the completion of the moult in captivity under dietary control. Astaxanthin, adonirubin, and α-doradexanthin, as well as papilioeritrinone and canthaxanthin (in lower amounts) are in every case the dominant carotenoids in the plumage pigment of wild individuals. α-Doradexanthin is responsible for the reddish-rose colour, which captive individuals adopt after a diet consisting mainly of lutein as disposable carotenoid. The red pigmentation biogenesis of captive bullfinch is compared with those of other red pigmented Carduelinae in which male individuals usually lose the red colour in captivity, namely Carpodacus roseus, Carpodacus rubricilloides, Uragus sibiricus, Carduelis cannabina, Carduelis flammea, Loxia curvirostra and Pinicola enucleator.

Plumage redness predicts breeding onset and reproductive success in the House Finch: a validation of Darwin's theory

Darwin (1871) and later Fisher (1958) suggested that sexual selection can drive the evolution of ornamental traits in monogamous species when female preferences for these traits allow well‐ornamented males to begin breeding earlier in a season and, as a result, gain reproductive advantages over poorly ornamented males. However, few studies have been conducted to test this fundamental concept upon which much of the sexual selection theory for monogamous species has been based. In this study, we examined the relationship between breeding onset, reproductive success, and male ornamentation in the House Finch Carpodacus mexicanus, a species in which males display bright carotenoid‐based plumage pigmentation. In previous work, it has been shown that bright male House Finches are preferred as social mates by females and, as a result, begin nesting earlier in the season than do drab orange and yellow males. Here we show that, by initiating breeding earlier in the season, brightly colored males fledge more offspring in a season than do drab males. Thus, differential timing of breeding generates considerable variance in reproductive success among male House Finches and contributes to sexual selection for male plumage ornamentation in this species.

Common Buzzard (Buteo buteo): A raptor with hyperpolymorphic plumage morphs, but low allozyme heterozygosity

The analysis of 25 allozyme loci in up to 469 Common Buzzards (B. b. buteo) from five locations in Germany revealed allelic polymorphism at twelve loci, but a prevalence of rare alleles resulted in a very low heterozygosity of Ho=0.0057. This rather low level of genetic variation characterizes a most abundant raptor species with highly polymorphic plumage pigmentation. The results of monitoring 571 buzzard breeding pairs from the Hakel forest (Sachsen-Anhalt) over 27 years indicate that neither the among-pair fertility variance, which slightly increased the genetically effective population size against the numerical size, nor the yearwise fluctuation of the breeder numbers, nor other population ecological characters were likely to erode the genetic variation of the numerically large buzzard population. One or repeated phyletic or historical bottle-necks are postulated to have diminished the allozyme variability, and at the same time to have created new genetic variance of the pigment-coding genes from non-additive components of genetic variance. Thus, the plumage colour diversity of the Common Buzzard could be a direct result of diminished single-locus genetic variation.

Effects of Coccidial and Mycoplasmal Infections on Carotenoid-Based Plumage Pigmentation in Male House Finches

Effects of Coccidial and Mycoplasmal Infections on Carotenoid-Based Plumage Pigmentation in Male House Finches

Effects of Coccidial and Mycoplasmal Infections on Carotenoid-Based Plumage Pigmentation in Male House Finches

AbstractCarotenoid pigments produce the ornamental red, orange, and yellow integumentary coloration of many species of animals. Among individuals of a population, the hue and saturation of carotenoid-based ornaments can be extremely variable, and studies of fish and birds have shown that females generally prefer males that display the most saturated and reddest coloration. Consequently, there has been a great deal of interest in determining the proximate factors that affect individual expression of carotenoid-based pigmentation. Parasites might affect production of ornamental coloration, and the Hamilton-Zuk hypothesis proposes that parasitized males will show decreased expression of the secondary sexual traits preferred by females. We found that captive male House Finches (Carpodacus mexicanus) experimentally infected with Isospora spp. (coccidians) and/or Mycoplasma gallisepticum produced carotenoid-based plumage coloration that was significantly less red and less saturated than that of noninfected males. These observations validate a necessary condition of the Hamilton-Zuk hypothesis, but heritable resistance to the pathogens we examined remains to be demonstrated.

Chemical analysis of melanin pigments in feather germs of Japanese quail Bh (black at hatch) mutants.

Bh (black at hatch) is a mutation of Japanese quails which causes darkening or lightening of the plumage in heterozygotes or homozygotes, respectively. We chemically analyzed melanin pigments in feather germs of Bh mutant embryos and in feathers of adult animals. Dark brown dorsal feathers of wild-type adult animals had white barrings, but heterozygous ones lacked clear barrings. The feathers of wild-type and heterozygote animals contained both eumelanins and pheomelanins, the latter being more pheomelanic. On the dorsal skin of 10-day old wild-type embryos, longitudinal stripes from black and yellow rows of feather germs developed; two or three longitudinal rows of black feather germs and then two or three rows of yellow feather germs next to the short central feather germs. Heterozygous embryos appeared black in plumage pigmentation, due to the presence of 'gray' feather germs in rows of dorsal feather germs that corresponded to yellow rows in wild-type embryos. Homozygous dorsal feather germs did not develop the black and yellow longitudinal stripes, but were brown. Chemical analysis showed that embryos of each genotype contained both eumelanins and pheomelanins in the feather germs; however, the eumelanin content in homozygous feather germs was very low. These results suggest that the Bh mutation causes pheomelanic changes in feathers of quails.

Effects of testosterone on growth, plumage pigmentation, and mortality in Black‐headed Gull chicks

In the Black‐headed Gull Larus ridibundus, sibling chicks defend small territories against conspecifics with testosterone‐dependent aggressive behaviour. The energetic requirements for the performance of this behaviour may trade off against the energetic requirements for growth. There are indications that testosterone suppresses growth in birds and, therefore, regulate this trade‐off. In this study, the effect of testosterone on growth and plumage pigmentation of Black‐headed Gull chicks was analysed. Young chicks in small groups were treated for ten days with testosterone or sham treated. Testosterone‐treated birds showed decreased growth rate (daily increase in body mass, head‐bill length and tarsus‐length) and a marked decrease in juvenile pigmentation of the plumage (tail‐bar, back, and secondary coverts). Field measurements revealed a negative correlation between nest density, which correlates positively with aggressive behaviour of adults, and plumage coloration. Furthermore, these measurements showed an increase in mortality of chicks that had low levels of pigmentation early in life. The data suggest that chicks face a testosterone‐regulated trade‐off between growth and territory defence.

Plumage Redness and Pigment Symmetry in the House Finch

The redness of carotenoid pigmentation has been shown to be an indicator of individual condition. I tested whether the asymmetry of carotenoid pigmentation of male House Finches Carpodacus mexicanus, an indicator of developmental stability, decreases with plumage redness. Consistent with predictions, I found a significant relationship between the symmetry of carotenoid-based crown pigmentation and the redness of body plumage redder plumage was more symmetrical. There was no significant relationship between the symmetry of the outer rectrices and either crown symmetry or plumage redness. The energetic cost of having asymmetrical carotenoid pigmentation is no greater for males with elaborate ornamentation (red plumage) than for males with less elaborate ornamentation (orange or yellow plumage). These observations are consistent with the idea that the magnitude of fluctuating asymmetry of an ornamental trait reflects the phenotypic or genotypic condition of the individual.

Bh (black at hatch) gene appears to be expressed in melanocytes of feather germs in the Japanese quail (Coturnix coturnix japonica).

The Bh (black at hatch) gene was examined to determine whether it is expressed in plumage melanocytes by analyzing pigmentation patterns of Bh melanocytes placed in the micro-environment of the feather germs of quail embryos with pink eyes. These host quails genetically lack a large part of plumage melanin. The Bh locus in these almost white quails is wild-type. When Bh neural crest cells were transplanted orthotopically into the host embryos, wild-type and Bh/+ melanocytes, which differentiated from the transplanted neural crest cells, formed plumage pigmentation patterns characteristic of each genotype in the micro-environment of the host feather germs. Brown plumage pigmentation, which was very similar to that of 10-day Bh/Bh embryos, was also observed in the feather germs of host embryos that received Bh neural crest cells, although the genotype of the donors could not be determined. These donors died before pigmentation of their feather germs occurred. The results demonstrate that pigmentation patterns of Bh melanocytes are not altered in the micro-environment of the host germs, suggesting that the Bh gene is autonomous in Bh melanocytes and is expressed in melanocytes of both Bh and the host feather germs, and that it causes the normal pigmentation pattern to be altered.

Effect of Chronic Naloxone and Morphine Treatments on Testicular, Body Weight, and Plumage Pigmentation Cycle of Lal Munia, Estrilda amandava

At Imphal (24° 44′ N) testes of lal munia, Estrilda amandava,began in June/July, peaked in September/October, and thereafter declined to a minimum in December/January. Daily im treatments of 2.5–10 mg/kg/bird/30 days of naloxone during progressive phase suppressed testicular growth, but without effects during quiescent, peak, and regression phases. Daily morphine (5 mg/kg/bird) during progressive and peak phases stimulated testicular growth, but without effects during quiescent and regression phases. Daily morphine (10 mg/kg/bird) during progressive phase stimulated the testes, an effect reversed by daily im treatments of an equivalent dose of naloxone. Seasonal changes in body weight closely correlated with testicular size. Daily im naloxone (5 and 10 mg/kg/bird/30 days) during progressive phase inhibited the increased body weight, but had no effects during quiescent, peak, and regression phases. Morphine (5 mg/kg/bird/day) during progressive and peak phases increased body weight, but had no effects during quiescent and regression phases. Morphine (10 mg/kg/bird/day) during progressive phase increased body weight, an effect which was reversed by equivalent dose of naloxone. Plumage color increased progressively between May and August/September, was maintained during October, and thereafter declined to reach dull-brown henny feathers by December. Daily im naloxone (2.5–10 mg/kg/bird/30 days) regardless of the reproductive states did not affect plumage color cycle. Morphine (5 mg/kg/bird/day) accelerated plumage pigmentation between June and August, but had no effect during progressive or peak phases. Postnuptial decline in plumage color was inhibited by morphine (5 and 10 mg/kg/bird/day) and naloxone failed to reverse this effect. It is concluded that in the lal munia, endogenous opioid peptides are important constituents of the neuroendocrine mechanisms that influence development of the testes and body weight.

Bh(black at hatch) Gene Appears to Cause Hemorrhage in the Homozygous Quail Embryo Lung

Abstract Abnormal development in Bh quail embryos was histologically examined. In addition to the abnormal plumage pigmentation in Bh-heterozygotes and homozygotes, and subcutaneous hemorrhage and liver degeneration in homozygotes as previously reported, the lungs in all 10-day homozygotes examined showed hemorrhage, suggesting that the Bh gene may also be expressed in this organ. Other organs, including the esophagus, the gizzard, the small intestine, the large intestine, the pancreas, the metanephros, the heart, the gonads and the hemopoietic organs in heterozygotes and homozygotes were histologically normal on days 7 and 10, though the development of homozygotes was slightly delayed. Primordial germ cells and hemopoietic cells were normally developed in gonads and hemopoietic organs such as the bursa of Fabricius and the spleen of the homozygote, respectively. These results suggest that Bh is a mutation inducing pleiotropic effects such as plumage pigmentation changes in both heterozygotes and homozygo...

Interspecific Variation in Plasma Hue in Relation to Carotenoid Plumage Pigmentation

Much of the bright yellow, orange, and red coloration of plumage results from carotenoid pigmentation (Brush 1978, Goodwin 1984). Carotenoids are unique among plumage pigments in that they cannot be synthesized by birds de novo; they must be ingested (Goodwin 1984, Brush 1978, 1990). An understanding of carotenoid pigmentation, therefore, requires an understanding of how birds get carotenoids from food into developing feathers. Unfortunately, the processes of carotenoid uptake, transport, and metabolism remain poorly understood (for reviews, see Brush 1978, 1990), with carotenoid transport perhaps the least studied aspect of carotenoid pigmentation (Brush 1990). To get from food in the gut to growing feathers, carotenoids must be transported in the blood. Trams (1969) was among the first to determine the carotenoid content of blood in relation to plumage coloration. He compared the blood of bright-red-plumaged Scarlet Ibises (Eudocimus ruber) with the blood of closely related but white-plumaged White Ibises (E. albus). As predicted, the blood of Scarlet Ibises contained much greater concentrations of red carotenoid pigments, as well as greater concentrations of a high-density lipoprotein that Trams (1969) speculated was the carrier protein for the carotenoids. Trams' study was conducted with birds that were not molting and, thus, at a time when carotenoid pigments in the blood would not be of use to the birds as feather

Geographic variation in the carotenoid plumage pigmentation of male house finches (Carpodacus mexicanus)

Geographic variation in both the colour and pattern of carotenoid plumage pigmentation displayed by males in two subspecies of house finches (Carpodacus mexicanus frontalis and C. m. griscom) was quantified. The extent of ventral carotenoid pigmentation (patch size) differed markedly between these two subspecies; frontalis males from the U.S. (New York, Michigan, California and Hawaii) displayed a medium patch extending from their throats to their lower bellies, while griscomi males sampled in Guerrero, Mexico displayed small patches restricted to their throats. Frontalis males sampled in Michigan and New York and griscomi males were relatively bright in colouration, while frontalis males sampled in Hawaii were relatively drab. Populations of frontalis in California showed substantial local variation in average male colouration: in two areas only 12 km apart males were as colourful and as drab as any population sampled. In aviary experiments in which they were fed either a plain seed diet or a diet supplemented with red carotenoid pigments during moult, males from all populations converged on a similar appearance, except that griscomi males attained a brighter plumage than frontalis males when their diet was supplemented with red pigments. Regardless of diet, the difference in patch size between frontalis and griscomi males persisted after moult in captivity. The author concludes that the difference in patch size between frontalis and griscomi males reflects genetic differences between these populations, but that the differences in the mean plumage colouration of males among populations reflect differences in the access that males have to carotenoid pigments during moult.

Geographic variation in the carotenoid plumage pigmentation of male house finches (Carpodacus mexicanus)

Geographic variation in both the colour and pattern of carotenoid plumage pigmentation displayed by males in two subspecies of house finches (Carpodacus mexicanus frontalis and C. m. griscom) was quantified. The extent of ventral carotenoid pigmentation (patch size) differed markedly between these two subspecies; frontalis males from the U.S. (New York, Michigan, California and Hawaii) displayed a medium patch extending from their throats to their lower bellies, while griscomi males sampled in Guerrero, Mexico displayed small patches restricted to their throats. Frontalis males sampled in Michigan and New York and griscomi males were relatively bright in colouration, while frontalis males sampled in Hawaii were relatively drab. Populations of frontalis in California showed substantial local variation in average male colouration: in two areas only 12 km apart males were as colourful and as drab as any population sampled. In aviary experiments in which they were fed either a plain seed diet or a diet supplemented with red carotenoid pigments during moult, males from all populations converged on a similar appearance, except that griscomi males attained a brighter plumage than frontalis males when their diet was supplemented with red pigments. Regardless of diet, the difference in patch size between frontalis and griscomi males persisted after moult in captivity. The author concludes that the difference in patch size between frontalis and griscomi males reflects genetic differences between these populations, but that the differences in the mean plumage colouration of males among populations reflect differences in the access that males have to carotenoid pigments during moult.

Effect of melatonin on gonads, body weight, and luteinizing hormone (LH) dependent coloration of the Indian finch, Lal munia ( Estrilda amandava)

Four doses of melatonin were administered intramuscularly over 30 days in separate groups of intact adult male Lal munia, Estrilda amandava, during mid-day (1300 hr) and mid-night (0100 hr) in separate sets during the month of August (late progressive phase), and their effects were studied on the body weight, gonadal and thyroidal activities, and luteinizing hormone (LH)-dependent plumage and beak pigmentation. Melatonin, irrespective of its dose and the time of administration, invariably induced complete inhibition of seasonal gonadal growth and activity, and also the LH-dependent plumage pigmentation. Melatonin had no effect on LH-dependent beak coloration. The inhibitory effect of melatonin on the body weight growth was found to be dependent on the time of administration and the dose of the hormone. Melatonin inhibited the thyroid activity in all the groups. These findings seem to suggest that while melatonin influences gonadal activity, body weight growth, and thyroid activity by acting directly at the hypothalamo-hypophyseal complex, it counteracts the effect of LH at the feather papillae level. Further, synthesis and/or release of FSH seems to be more sensitive to melatonin than that of LH. However, the metabolic action of melatonin might be species specific.

Thyroid and annual gonad development, body weight, plumage pigmentation, and bill color cycles of lal munia, Estrilda amandava

Long-term administration of l-thyroxine (T 4) in the wax bill (lal munia) inhibited the current gonad development cycle, and the increase in gonadal volume in the second cycle was suppressed only by higher concentrations. Gonadal inhibition by high but not by low doses of l-T 4 was associated with a failure in the development of LH-dependent pigmented nuptial plumage. This suggests that l-T 4 depresses FSH secretion more readily than LH secretion. The results indicate that the effects of l-T 4 administration on the body weight cycle depends upon the physiological and/or gonadal status of the bird at the start of the experiment and that the juvenile hhpothalamo-hypophysial-gonadal axis is more sensitive to l-T 4 than that of the adult birds. The bill color, like plumage pigmentation, appears to be LH controlled. It is suggested that while thyroid hormone, acting by way of the hypothalamo-hypophysial complex and/or by direct action on the feather papillae, modulates the annual cycles of plumage pigmentation, bill color, gonad development, and body weight of lal munia, the finch has an endogenous mechanism which enables it to adapt to chronic hyperthyroidism in such a way that breeding occurs at the normal time of the year.

Persistence of abnormal melanocytes in immunosuppressed chickens of the autoimmune "DAM" line.

The delayed amelanotic (DAM) line of chickens (Gallus gallus) is characterized by the postnatal elimination of melanocytes from regenerating feathers and from the choroid. The process of elimination is accompanied by a massive infiltration of mononuclear leukocytes (MNL) into the supporting connective tissues. When surgically bursectomized at day of hatching, chickens from this lineage develop significantly less amelanosis of the feathers. We report here a histological analysis of regenerating feathers and choroids from bursectomized birds that maintained their plumage pigmentation. In the feathers we observed the presence of morphologically abnormal melanocytes in the absence of MNL infiltration. Choroids also contained abnormal melanocytes without MNL infiltration; however, we observed a few cases of amelanotic choroids with a few MNL. These findings indicate that melanocytes of pigmented birds are morphologically abnormal even in the absence of a bursa and in the absence of leukocytic infiltrates into regenerating feathers and possibly into the choroids. We conclude from these findings that the amelanosis in unbursectomized DAM birds is due to the response of the immune system to an abnormality in the melanocytes which, by itself, does not lead to depigmentation.