Bill Color Research Articles

Seasonal change in basal bill colour and possibile sex discrimination based on exposed measurements of Eurasian Tree Sparrows in Hokkaido

Seasonal change in basal bill colour and possibile sex discrimination based on exposed measurements of Eurasian Tree Sparrows in Hokkaido

A case report of bill color aberration in a free-living Eurasian Tree Sparrow (Passer montanus): Morphological and physiological description

Color aberration in birds is a common biological phenomenon relative to other vertebrates. To date, a large number of avian species with abnormally colored individuals have been documented. Although evidence has shown that color aberration may co-vary with morphological and physiological traits, little information is available on the variations of morphological and physiological traits of free-living aberrantly colored birds. Here we report a case of a free-living female Eurasian Tree Sparrow (Passer montanus) with bleached bill but normally pigmented plumage. We further compare the differences in 5 morphological indices including body mass, body condition index (BCI), length of the bill, tarsus, and wing, and 14 physiological indices including core temperature, hematocrit (Hct), baseline plasma glucose (GLU), total protein (TP), uric acid (UA), total cholesterol (TC), triglycerides (TG), free fatty acid (FFA), beta-hydroxybutyrate (β-HB), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and creatinine (CREA) between the aberrant individual and other normal birds. Our results show that the aberrant sparrow has significantly shorter tarsi, longer wings, and higher core temperature, lower levels of plasma TP, UA, LDL-C, ALP, and CREA than normal sparrows, while no significant differences were noted in other morphological and physiological indices between the 2 phenotypes. Our results indicate that bill-color aberration in the Eurasian Tree Sparrow may be associated with a few morphological and physiological alterations, especially in terms of thermoregulation and protein metabolism. However, these alterations do not result in dramatic changes in body condition, other plasma metabolites, or enzyme activities.

Phenotypic and morphometric characterization of desi duck of Odisha

The present study was conducted in five districts of Odisha to study the different duck rearing practices by using a questionnaire and to differentiate the characters of ducks. Ducks were raised under semi-intensive management system and mostly depend on scavenging for their nutritional needs. The ducks are raised both for meat and eggs. The annual average egg production per duck was very poor. The flock size is usually small and varies from 9 to 30. In both drake and duck body carriage was slightly upright and bill shape was horizontal. Prominent head colour in drake was greenish black (55.6%) and in duck was fawn-white mix (75.68%). In both drake and duck dominant neck and breast colour was white. Wing colour was brown/grey and white in drake and duck, respectively. Prominent bill colour was yellow and bean colour was black in both drake and duck. Dominant shank and eye colour in drake and duck was orange and grey respectively. Mean values for all the morphometrical measurement, i.e. body length, bill length, bill width, shank length, wing length, head length, neck length and head width was significantly higher in drake. The average body weight of drake and duck were 1.80±0.02 and 1.41±0.02 kg, respectively.

Polymorphisme Gene GH and Morphological Characteristic of Anas platyrhynchos and Cairina moschata

The aims of this research was to identify the qualitative and quantitative difference of the phenotypes of native mallard and Muscovy, and Muscovy the genetic diversity between Muscovy and mallard using RFLP method with growth hormone primer (GH) gene. The materials were 30-week old male and female ducks from 5 strains—Magelang, Mojosari and Tegal ducks, white-feathered, and black and white-feathered Muscovy. Muscovy Completely Randomized Design was used to analyze parameters 5 strains of ducks based on gender and with 5 replications. The parameters measured were local and Muscovy duck phenotypes and genetic diversity (number of alleles) based on GH gene, heterozygosity and genetic distance. Qualitative properties were analyzed descriptively and quantitative properties were analyzed using Anova followed by HSD in case of significant differences, whereas RFLP analysis was used to determine the allele frequencies, genotype frequencies, genetic diversity, and genetic distance of local ducks. Result showed phenotypic differences between Anas platyrhynchos and Cairina moschata. The dominant feather colorof Muscovy was black and white while mallard was brown. The bill color Muscovy Muscovy was pink with dark brown but black in mallard. The dominant shank’s color in both Muscovy and mallard was black. Body size of mallard was larger than that of Muscovy Muscovy, and Magelang ducks weigherd more than Tegal and Mojosari Duck. The PCR-RFLP results showed lower heterozygosity of mallard compared to Muscovy based on GH gene, and genetic distance of the Tegal duck was closer to Mojosari and Magelang ducks, whereas Magelang and Mojosari ducks had a considerable genetic distance based on the GH gene.

Sex chromosome inversions enforce reproductive isolation across an avian hybrid zone.

Across hybrid zones, the sex chromosomes are often more strongly differentiated than the autosomes. This is regularly attributed to the greater frequency of reproductive incompatibilities accumulating on sex chromosomes and their exposure in the heterogametic sex. Working within an avian hybrid zone, we explore the possibility that chromosome inversions differentially accumulate on the Z chromosome compared to the autosomes and thereby contribute to Z chromosome differentiation. We analyse the northern Australian hybrid zone between two subspecies of the long-tailed finch (Poephila acuticauda), first described based on differences in bill colour, using reduced-representation genomic sequencing for 293 individuals over a 1,530-km transect. Autosomal differentiation between subspecies is minimal. In contrast, 75% of the Z chromosome is highly differentiated and shows a steep genomic cline, which is displaced 350km to the west of the cline in bill colour. Differentiation is associated with two or more putative chromosomal inversions, each predominating in one subspecies. If inversions reduce recombination between hybrid incompatibilities, they are selectively favoured and should therefore accumulate in hybrid zones. We argue that this predisposes inversions to differentially accumulate on the Z chromosome. One genomic region affecting bill colour is on the Z, but the main candidates are on chromosome 8. This and the displacement of the bill colour and Z chromosome cline centres suggest that bill colour has not strongly contributed to inversion accumulation. Based on cline width, however, the Z chromosome and bill colour both contribute to reproductive isolation established between this pair of subspecies.

Temperature modulates photoperiodic seasonal responses in the subtropical tree sparrow, Passer montanus.

We studied the effects of temperature on the photoperiodic regulation of seasonal reproduction and related events in the subtropical tree sparrow at Shillong, India. In the first experiment, one group of birds was maintained in an outdoor open aviary receiving natural photoperiod and temperature conditions, while the other group was exposed to natural photoperiod and constant temperature of 17 ± 2°C in an outdoor closed aviary for 12months. Although both sexes achieved peak gonadal growth at the same time (May) under the two conditions, gonadal regression and feathers molt were delayed under the temperature controlled condition. In the second experiment, the groups of birds were exposed to three different temperatures (17, 25 and 30°C) under both long (LD-14L:10D) and short (SD-9L:15D) day lengths for 7months. Birds showed relatively small but significant gonadal growth, darkening of bill color and feathers molt only at 30°C under SD. However, they behaved as though they were under natural conditions and exhibited the above responses significantly at all temperatures under LD. There was delayed gonadal regression at the lower temperature (17°C), while feathers molt delayed with increasing temperature (25, 30°C) under LD. These results clearly indicate that temperature modulates photoperiodic seasonal responses in the tree sparrow.

Sexual signals not so strict

Social Signals![Figure][1] Bill color in waxbills changes with external temperature. PHOTO: MARTIN MECNAROWSKI/SHUTTERSTOCK Sexual signals in animals, such as bright plumage, are thought to be predetermined or to be badges of quality that can reflect an animal's current condition. Direct

Release from ecological constraint erases sex difference in social ornamentation

Sex differences in animal ornamentation are thought largely genetically fixed due to stronger sexual selection on males of species with conventional sex roles. But, other types of sex differences are not genetically fixed. For example, several differences in human social behavior result instead from sociocultural or economic constraints on women. Since gregarious animals use ornamentation for various social functions, perhaps some of their sex differences are, similarly to human behavior, due to social coercion or ecological constraint (their closest equivalents to human social and economic constraints, respectively). We found sex differences in ornamentation that disappear plastically in a social species with conventional sex roles. The red bill of common waxbills (Estrilda astrild) is on average more saturated in males, but in our experiment female bill color correlated with night temperature, an important energetic stressor, suggesting that sexual dichromatism disappears when ecological conditions are favorable to females. Female ornamentation may be more adversely affected by ecology because of their life history that requires balancing investment in ornamentation with maintaining reproductive condition. Manipulation of stress-related physiology (ACTH challenge) suggests that this effect was not mediated by stress mechanisms. Social coercion appears to not explain sexual dichromatism: males were not more aggressive than females, aggressiveness was not related to bill color, and manipulation of reproductive axis’ physiology (GnRH challenge, which in many species mediates aggressiveness) did not increase bill color. Our results show parallels to the plastic sex differences of humans in social animals and suggest that studying their ecological vs. social causes provides a biological backdrop for understanding the human case as well. Many sex differences in human social behavior result from economic or sociocultural constraints on women, while sex differences in the ornamentation of animals with conventional sex roles are thought largely genetically fixed. We show that a sex difference in ornamentation—the redder bills of male than female common waxbills—disappears plastically in an animal with conventional sex roles due to, in part, changes in female ornamentation. Social coercion did not explain reduced female ornamentation: aggressiveness did not predict bill color, and males were not dominant over females. Instead, female bill color was reduced during colder weather, perhaps because females under energetic stress need to balance investment in social ornamentation vs. maintaining reproductive condition. Similarly to humans, some sex differences of gregarious animals may be due to females requiring appropriate conditions to express their full social potential.

Attractiveness of male Zebra Finches is not affected by exposure to an environmental stressor, dietary mercury

ABSTRACT Choosing a high-quality mate contributes to increased reproductive success in birds. Females assess quality in males, in part, via condition-dependent signals such as songs and plumage. The production of these signals of quality can be disrupted by environmental stressors, including toxic pollutants such as mercury. Mercury affects song, plumage, bill color, and courtship behaviors in male birds, but the effect of these changes on female mate choice is unknown. By affecting the condition-dependent signals that females use to assess quality, mercury could alter males' attractiveness to females. We used mate choice of female Zebra Finches (Taeniopygia guttata) to determine if male attractiveness to females is affected by lifetime exposure to mercury. Males were either exposed to dietary mercury or left unexposed and then assessed by unexposed females in 3 types of mate preference tests: song-playback phonotaxis (preference for audio recordings of mercury-exposed or unexposed males' songs); 2-choice...

Mitochondria-targeted molecules determine the redness of the zebra finch bill.

The evolution and production mechanisms of red carotenoid-based ornaments in animals are poorly understood. Recently, it has been suggested that enzymes transforming yellow carotenoids to red pigments (ketolases) in animal cells may be positioned in the inner mitochondrial membrane (IMM) intimately linked to the electron transport chain. These enzymes may mostly synthesize coenzyme Q10 (coQ10), a key redox-cycler antioxidant molecularly similar to yellow carotenoids. It has been hypothesized that this shared pathway favours the evolution of red traits as sexually selected individual quality indices by revealing a well-adjusted oxidative metabolism. We administered mitochondria-targeted molecules to male zebra finches (Taeniopygia guttata) measuring their bill redness, a trait produced by transforming yellow carotenoids. One molecule included coQ10 (mitoquinone mesylate, MitoQ) and the other one (decyl-triphenylphosphonium; dTPP) has the same structure without the coQ10 aromatic ring. At the highest dose, the bill colour of MitoQ and dTPP birds strongly differed: MitoQ birds' bills were redder and dTPP birds showed paler bills even compared to birds injected with saline only. These results suggest that ketolases are indeed placed at the IMM and that coQ10 antioxidant properties may improve their efficiency. The implications for evolutionary theories of sexual signalling are discussed.

Bill colour pattern in Bewick’s swan: information on sex and body size displayed on face?

Ornamental traits in birds (plumage/bare part colours) have been shown to provide information on diverse aspects of individual quality and behaviour. In bird species with achromatic plumages (uniformly white, grey or black), signals encoded in bare parts are the major mode of visual communication. In this study we analysed the influence of sex, age, body condition and selected biometric traits on the bill colour pattern in Bewick’s swans Cygnus columbianus bewickii. The results indicate that sex and body size (weight and tarsus length) are associated with the bill colour pattern in Bewick’s swans. Individuals with a larger black area on the bill were heavier and had a longer tarsus. Moreover, females had more black on their bills than males did. Age, head length and body condition index were not significantly related to bill colour pattern. The present work indicates that Bewick’s swans may display information on their sex and size by means of their bill colour pattern. These findings also suggest the possibility that swans can remotely quantify one another’s traits from the appearance of their bill colouration. Proper assessment of an opponent or of mate quality during face-to-face signalling may help birds to avoid unnecessary interaction or to maintain bonds between mates and family groups.

Interacting effects of early dietary conditions and reproductive effort on the oxidative costs of reproduction.

The hypothesis that oxidative damage accumulation can mediate the trade-off between reproduction and lifespan has recently been questioned. However, in captive conditions, studies reporting no evidence in support of this hypothesis have usually provided easy access to food which may have mitigated the cost of reproduction. Here, I test the hypothesis that greater investment in reproduction should lead to oxidative damage accumulation and telomere loss in domestic zebra finches Taeniopygia guttata. Moreover, since the change or fluctuation in diet composition between early and late postnatal period can impair the ability to produce antioxidant defences in zebra finches, I also tested if early nutritional conditions (constant vs fluctuating early diet) influenced the magnitude of any subsequent costs of reproduction (e.g., oxidative damage and/or telomere shortening). In comparison to pairs with reduced broods, the birds that had to feed enlarged broods showed a higher level of oxidative DNA damage (8-OHdG), but brood size had no effect on telomeres. Fluctuating early diet composition reduced the capacity to maintain the activity of endogenous antioxidants (GPx), particularly when reproductive costs were increased (enlarged brood). The decline in GPx in birds feeding enlarged broods was accompanied by a change in bill colouration. This suggests that birds with lower endogenous antioxidant defences might have strategically increased the mobilization of antioxidants previously stored in other tissues (i.e., bill and liver) and thus, preventing an excessive accumulation of damage during reproduction.

PHENOTYPIC CHARACTERISTICS AND BIOMETRICAL STUDY ON DIFFERENT BREEDS OF PIGEON IN NORTHERN BANGLADESH

The experiment was conducted to characterize different breeds of pigeon phenotypically and to study their body biometry, which are available in the northernBangladesh. During this study 30 farms were selected which have >20 pair of pigeons in the three study area namely Rajshahi, Natore and Pabna districts ofBangladesh. There about 15 breeds have been selected for the observation of phenotypic characteristics such as color of bill, eye, eyelid, skin, shank, toe, egg, head feather, neck feather, body feather, down feather, wing feather, tail feather and shape of bill, body and egg. The biometrical data were collected from the measurement of length of bill, head, body, shank, middle toe, wingspan and mature body weight. In this study the highest mean bill length was found 2.83±0.05cm in Strasser and lowest mean head length 5.00±0.00cm in Kormona, Nun and Jacobin. The highest mean body length was found 41.60±0.38cm in Strasser and lowest mean body length 30.00±0.43cm in Owl. The highest mean wingspan was found 81.00±0.51cm in Jacobin and lowest mean wingspan 60.45±0.76cm in kormona. The heighest mean shank length was found 3.40±0.13cm in Homer and lowest mean shank length 2.50±0.00cm in Giribug, Kormona, Nun, Satinette and Suachandan. The heighest mean middle toe length was found 4.40±0.05cm in pouter and lowest mean middle toe length 3.00±0.00cm in kormona. The heighest mean mature body weight was found 748.20±8.96gm in Strasser and lowest mean mature body weight 265.10±7.03gm in Giribug. Phenotypic correlation among bill length, head length, body length, wing span, shank length, middle toe length and mature body weight of these breeds of pigeon ranged from 0.233 to 0.789. The experiment’s result may contribute to breed up gradation, helps to formulate the conservation and improvement strategies for the breed as genetic resource.

Geographical variation in bill colour in the Long-tailed Finch: evidence for a narrow zone of admixture between sub-species

ABSTRACTThe Long-tailed Finch (Poephila acuticauda) is endemic to Australia’s northern tropics and comprises two sub-species differentiated by bill colour: yellow in the western sub-species acuticauda and red in the eastern sub-species hecki. We present an extensive survey of bill colour variation across the range of the Long-tailed Finch (more than 700 individuals collected across nearly 1500 km of range). Geographic clinal analysis using bill reflectance spectrophotometry data suggests that the greatest extent of bill colour admixture is only ~150 km wide and is centred approximately 50 km west of Katherine, Northern Territory (14.5° S, 132.3° E). Variation in bill colour is generally low outside of this zone, and across widely distributed allopatric populations of both sub-species. However, the best-fit clinal model supports a pattern of asymmetrical introgression of bill colour from the east into the west. The narrow geographic width of bill colour admixture between Long-tailed Finch sub-species and the estimated timing of secondary contact (14–21 kya) suggests a role for selection acting against hybrids and/or parentals in maintaining sub-species as independently evolving populations.

Carotenoids buffer the acute phase response on fever, sickness behavior and rapid bill color change in zebra finches.

Carotenoids are finite resources that animals can allocate to self-maintenance, attractiveness or reproduction. Here we test how carotenoids affect the acute phase response (APR), an intense rapid systemic response characterized by fever, sickness behavior and production of acute phase proteins, which serves to reduce pathogen persistence. We conducted a 2×2 factorial design experiment in captive adult male and female zebra finches (Taeniopygia guttata) to determine the effects of carotenoid supplementation on the intensity of the APR. We measured changes in feeding rate, activity level and body temperature of the birds. We found that, relative to unsupplemented controls, carotenoid-supplemented birds exhibited less severe reductions in feeding and activity, smaller increases in body temperature and lower circulating levels of haptoglobin (an acute phase protein) 24 h after inducing an APR. Among supplemented individuals, those with higher blood carotenoid levels exhibited a lower reduction in activity rate after 24 h. Forty-eight hours after APR induction, birds exhibited a significant decrease in plasma carotenoid levels and a decrease in bill hue, with less reduction in hue in carotenoid-supplemented individuals. These results demonstrate that carotenoids can alleviate several important behavioral and physiological effects of an APR and that bill color can change rapidly following induction of the costly APR immune defense. In particular, immune activation may have caused birds to preferentially draw down carotenoids from the bloodstream, ostensibly for use in health. Rapid bill color changes over a 48-h period support growing evidence that bills may serve as short-term signals of health and condition.

An examination of species limits in the Aulacorhynchus "prasinus" toucanet complex (Aves: Ramphastidae).

The number of species recognized in Aulacorhynchus toucanets has varied tremendously over the past century. Revisors seem to disagree on whether head and bill coloration are useful indicators of species limits, especially in the A. “prasinus” complex. Using morphometrics, I tested the hypothesis that the major color-based subspecific groups of A. “prasinus” sensu lato are simply “cookie-cutter” (i.e., morphologically nearly identical) toucanets with different head and bill colorations. Univariate and multivariate analyses show that they are not simply morphological replicates of different colors: a complex array of morphometric similarities and dissimilarities occur between the major subspecific groups, and these variations differ between the sexes. Latitude and longitude had a small but significant association with female (but not male) PC1 and PC2. Hybridization and intergradation were also considered using plumage and bill characters as a surrogate to infer gene flow. Hybridization as indicated by phenotype appears to be substantial between A. “p.” cyanolaemus and A. “p.” atrogularis and nonexistent between other major groups, although from genetic evidence it is likely rare between A. “p.” albivitta and A. “p.” cyanolaemus. The congruence and complexities of the morphological and color changes occurring among these groups suggest that ecological adaptation (through natural selection) and social selection have co-occurred among these groups and that species limits are involved. Further, hybridization is not evident at key places, despite in many cases (hypothetical) opportunity for gene flow. Consequently, I recommend that this complex be recognized as comprising five biological species: A. wagleri, prasinus, caeruleogularis, albivitta, and atrogularis. Four of these also have valid subspecies within them, and additional work may eventually support elevation of some of these subspecies to full species. Species limits in South America especially need more study.

Body mass and immune function, but not bill coloration, predict dominance in female mallards

Competition over indivisible resources is common and often costly. Therefore, selection should favor strategies, including efficient communication, that minimize unnecessary costs associated with such competition. For example, signaling enables competitors to avoid engaging in costly asymmetrical contests. Recently, bill coloration has been identified as an information-rich signal used by some birds to mediate aggressive interactions and we evaluated this possibility in female mallards Anas platyrhynchos. Specifically, we conducted two rounds of competitive interactions among groups of unfamiliar adult female ducks. By recording all aggressive behaviors exhibited by each individual, as well as the identity of attack recipients, we were able to assign dominance scores and evaluate links between numerous physiological, morphological, and experimental variables that we predicted would influence contest outcome and dominance. Contrary to our predictions, dominance was not linked to any aspect of bill coloration, access to dietary carotenoids during development, two of three measures of immune function, or ovarian follicle maturation. Instead, heavier birds were more dominant, as were those with reduced immune system responses to an experimentally administered external immunostimulant, phytohemagglutinin. These results suggest that visual signals are less useful during the establishment of dominance hierarchies within multi-individual scramble competitions, and that immune function is correlated with contest strategies in competitions for access to limited resources.

Parental care and external sexual characters in the Warbling Doradito (Pseudocolopteryx flaviventris)

Fil: Cardoni, Daniel Augusto. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina

Dynamic Status Signal Reflects Outcome of Social Interactions, but Not Energetic Stress

Social defeat induces stress-responses in a wide array of vertebrates and can generate winner-loser effects. Dynamic condition-dependent signaling systems that reflect preparation for subsequent agonistic interactions, and thereby mediate winner-loser effects, should be more sensitive to competitive history than to non-social sources of stress. Bill color of female American goldfinches (Spinus tristus) is a dynamic condition-dependent ornament that functions as a signal of competitive status and mediates intrasexual agonistic social interactions. We tested the “social experience signaling hypothesis” in female goldfinches by (1) manipulating a non-social energetic stressor by experimentally elevating flight costs via wing-clipping in free-ranging birds, and (2) manipulating social experience by staging competitive interactions among captive birds. Bill color change did not differ between wing clipped and non-clipped females, even though stress-response, as measured by the heterophil to lymphocyte (H:L) ratio, increased significantly in clipped females relative to unclipped females. In contrast, winners and losers in the social experience experiment differed significantly in the degree and direction of bill color change following social contests, with bill color increasing in winners and decreasing in losers. These results suggest that dynamic bill color of female American goldfinches signals recent social history, but is less sensitive to some stressors stemming from non-social sources, and thereby suggest that signals can evolve sensitivity to specific types of processes relevant to the context in which they are used.

Stabilizing survival selection on presenescent expression of a sexual ornament followed by a terminal decline

Senescence is a decrease in functional capacity, increasing mortality rate with age. Sexual signals indicate functional capacity, because costs of ornamentation ensure signal honesty, and are therefore expected to senesce, tracking physiological deterioration and mortality. For sexual traits, mixed associations with age and positive associations with life expectancy have been reported. However, whether these associations are caused by selective disappearance and/or within‐individual senescence of sexual signals, respectively, is not known. We previously reported that zebra finches with redder bills had greater life expectancy, based on a single bill colour measurement per individual. We here extend this analysis using longitudinal data and show that this finding is attributable to terminal declines in bill redness in the year before death, with no detectable change in presenescent redness. Additionally, there was a quadratic relationship between presenescent bill colouration and survival: individuals with intermediate bill redness have maximum survival prospects. This may reflect that redder individuals overinvest in colouration and/or associated physiological changes, while below‐average bill redness probably reflects poorer phenotypic quality. Together, this pattern suggests that bill colouration is defended against physiological deterioration, because of mate attraction benefits, or that physiological deterioration is not a gradual process, but accelerates sharply prior to death. We discuss these possibilities in the context of the reliability theory of ageing and sexual selection.