Marked Animals Research Articles

Fitness and fur colouration: Testing the camouflage and thermoregulation hypotheses in an Arctic mammal.

Selection for crypsis has been recognized as an important ecological driver of animal colouration, whereas the relative importance of thermoregulation is more contentious with mixed empirical support. A potential thermal advantage of darker individuals has been observed in a wide range of animal species. Arctic animals that exhibit colour polymorphisms and undergo seasonal colour moults are interesting study subjects for testing the two alternative hypotheses: demographic performance of different colour morphs might be differentially affected by snow cover with a cryptic advantage for lighter morphs, or conversely by winter temperature with a thermal advantage for darker morphs. In this study, we explored whether camouflage and thermoregulation might explain differences in reproduction and survival between the white and blue colour morphs of the Arctic fox Vulpes lagopus under natural conditions. Juvenile and adult survival, breeding propensity and litter size were measured for 798 captive-bred and released or wild-born Arctic foxes monitored during an 11-year period (2007-2017) in two subpopulations in south-central Norway. We investigated the proportion of the two colour morphs and compared their demographic performance in relation to spatial variation in duration of snow cover, onset of snow season and winter temperatures. After population re-establishment, a higher proportion of blue individuals was observed among wild-born Arctic foxes compared to the proportion of blue foxes released from the captive population. Our field study provides the first evidence for an effect of colour morph on the reproductive performance of Arctic foxes under natural conditions, with a higher breeding propensity of the blue morph compared to the white one. Performance of the two colour morphs was not differentially affected by the climatic variables, except for juvenile survival. Blue morph juveniles showed a tendency for higher survival under colder winter temperatures but lower survival under warmer temperatures compared to white morph juveniles. Overall, our findings do not consistently support predictions of the camouflage or the thermoregulation hypotheses. The higher success of blue foxes suggests an advantage of the dark morph not directly related to disruptive selection by crypsis or thermoregulation. Our results rather point to physiological adaptations and behavioural traits not necessarily connected to thermoregulation, such as stress response, immune function, sexual behaviour and aggressiveness. Our findings highlight the need to explore the potential role of genetic linkage or pleiotropy in influencing the fitness of white and blue Arctic foxes as well as other species with colour polymorphisms.

A bird that changes colour without moulting: how the wîskicâhk (Canada Jay, Perisoreus canadensis) tricked the taxonomists

Avian and mammalian colours are thought to be constant in life and in museum specimens, but several early 20th-century taxonomists singled out the Canada Jay (Perisoreus canadensis (Linnaeus, 1766)) as having unstable feather pigments and warned against using old museum specimens for taxonomic purposes. One such error was Brisson’s (1760) original naming of the species as “the Brown Jay of Canada”. Another was Ridgway’s (1899) naming of the “Gray Jay” as a new subspecies, Perisoreus (canadensis) griseus, through inappropriate comparison of fresh grey specimens with old brown ones. We discovered that browning of initially grey plumage also occurs between annual moults in living individuals of the Canada Jay’s Pacific morphotype. We documented this change using photographs and re-sightings of colour-banded individuals and through spectral analysis of year-old (brown) and incoming (grey) rectrices collected from the same moulting individuals. To assess the distribution of this colour change, we compared September vs. May eBird photographs from across North America. We showed that seasonal colour change is normal in the Pacific morphotype but rare in the two other morphotypes. Collectively, these data have important implications for the taxonomy of the Canada Jay and are a cautionary tale for taxonomists studying animal colouration.

Behavioural thresholds of blue tit colour vision and the effect of background chromatic complexity

Vision is a vital attribute to foraging, navigation, mate selection and social signalling in animals, which often have a very different colour perception in comparison to humans. For understanding how animal colour perception works, vision models provide the smallest colour difference that animals of a given species are assumed to detect. To determine the just-noticeable-difference, or JND, vision models use Weber fractions that set discrimination thresholds of a stimulus compared to its background. However, although vision models are widely used, they rely on assumptions of Weber fractions since the exact fractions are unknown for most species. Here, we test; i) which Weber fractions in long-, middle- and shortwave (i.e. L, M, S) colour channels best describe the blue tit (Cyanistes caeruleus) colour discrimination, ii) how changes in hue of saturated colours and iii) chromatic background noise impair search behaviour in blue tits. We show that the behaviourally verified Weber fractions on achromatic backgrounds were L: 0.05, M: 0.03 and S: 0.03, indicating a high colour sensitivity. In contrast, on saturated chromatic backgrounds, the correct Weber fractions were considerably higher for L: 0.20, M: 0.17 and S: 0.15, indicating a less detailed colour perception. Chromatic complexity of backgrounds affected the longwave channel, while middle- and shortwave channels were mostly unaffected. We caution that using a vision model whereby colour discrimination is determined in achromatic viewing conditions, as they often are, can lead to misleading interpretations of biological interactions in natural – colourful – environments.

United colours of the city: A review about urbanisation impact on animal colours

AbstractHabitat colour gradients characterise urban areas: from green prevailing in the least urbanised areas dominated by lawn, shrubs and trees, to grey characteristic of heavily urbanised areas dominated by impervious surfaces. These changes may promote modifications in community composition and intraspecific colour changes in species occurring in urban areas. This review's objectives were: (1) to analyse reported patterns of animal colour change between urban and non‐urban areas; (2) to identify the main mechanisms underlying those patterns; and (3) to determine research bias and suggest future research directions. A bibliometric on animal colour patterns using Scopus resulted in 62 studies being found and their findings assessed. Most studies were focused on birds (N = 38) and were conducted in the Northern Hemisphere (N = 55), with 90% analysing intraspecific colour changes. Intraspecific studies found three main patterns: (1) urban melanism, with polymorphic species of insects, birds and reptiles showing darker colouration in urban areas than in non‐urban areas; (2) urban dullness, with carotenoid‐based plumage colours being duller in urban than in rural areas; and (3) a reduction in conspicuousness of sexually selected plumages in urban areas. Interspecific studies suggested that urban areas are filters for animal colours, promoting the colonisation of those species that increase camouflage or exhibit warning colours to predators. More studies are needed in the Southern Hemisphere and at the interspecific level to determine the role of animal colours in urban colonisation.

Characteristics of sun bear chest marks and their patterns of individual variation

Animal coloration is widely involved in a variety of social interactions, and mammals can convey information to conspecifics by visual signals, such as colored or contrasting body marks. The sun bear (Helarctos malayanus) has a vibrant and unusual chest mark. Here, we describe the characteristics of sun bear chest marks and their patterns of individual variation by (1) sex, (2) time, and (3) some biochemistry values related to fur pigmentation. Sun bear pictures were taken from 2009 to 2018 at the Bornean Sun Bear Conservation Centre and Free the Bears sanctuary. We hypothesize that chest marks may serve in conspecific communication and, thus, we mainly expect that (a) these marks allow for sexual recognition and, thus, they should show remarkable differences by sex; (b) marks do not change over time because their consistency allows for easier intraspecific recognition; and (c) patterns of variation may be dependent on the age and/or physical condition of an individual. The most common shapes of sun bear chest marks (n = 63 M and 108 F) were U (M = 60.3%, F = 57.4%) and V (M = 31.8%, F = 32.4%) shapes. We did not detect differences in shape patterns by sex and, over the years, chest mark shape never changed for the same bear (n = 49 individuals, 16 M and 33 F). The number of dark dots in chest marks showed large amounts of individual variation (mean ± SD = 37.7 ± 26.8 dots; range = 1–143), and the quantity of dark dots increased with bear age. The complexity of sun bear chest marks might be related to the existence of complex interactions among individuals of the same species, which may allow for recognition and evaluation of their individual characteristics, such as age and health. Experimental approaches are needed to understand the potential functions of sun bear chest marks.

МАНІФЕСТАЦІЇ МУЛЬТИМОДАЛЬНОСТІ В СУЧАСНОМУ АНГЛОМОВНОМУ ХУДОЖНЬОМУ ДИСКУРСІ

This article suggests the analysis of artistic forms as multimodal construals being formed in integration of verbal, visual, and auditory semiotic modes in contemporary Anglophone artistic discourse, namely the Eurovision 2021 Song Contest (Maneskin performance) and the animated movie The Croods: A New Age. Multimodality paradigm serves as a predominant theoretical and methodological framework of the research that itself testifies to the topicality of the study. The paper views multimodality as integration and combination of various modes in contemporary Anglophone artistic discourse. The aim of the article is to reveal ways and means of artistic forms construction, as well as their interaction in the discourse under scrutiny. Methods to analyze visual mode of the constructed forms represented by colors in Maneskin performance on the Eurovision stage include computer-assisted methods, namely a special software Image color summarizer. It suggests descriptive statistics for an image, determining the average color saturation and the most representative colors in the image. Further interpretation of the gained results is conducted by means of using thesauri of symbols and psychology, which foster inference of colors' symbolic senses. Then, the findings of the visual mode analysis are combined with the ones received due to componential, textual, interpretative, and stylistic analysis of the verbal mode applied in both case studies. In Maneskin performance verbal mode is represented by the song lyrics featuring metaphors and other stylistic means combined with three consecutive color stages each with its prevailing color scheme as a manifestation of the visual mode. On the one hand, the color images used in Maneskin performance complement and enhance the senses encoded in the verbal component. On the other hand, they restrict possible interpretations of it. Gradual interchange of dominant colors in combination with audio-visual, kinesthetic, and verbal images expresses the persona's implicit attitude towards the world, society, its rules and nature. The research findings show that multimodal forms constructed in the animated movie The Croods: A New Age are of paradoxical character. It is revealed in visual and verbal modes. For instance, colors of animals are unnatural, they do not coincide with the animals' natural colors in reality. The same can be stated about the characters' names and behavior. Interaction of visual, auditory, and verbal modes produces paradoxical worlds and characters.

Обозначения цвета и близкие понятия в донесениях русского представителя в Речи Посполитой В. М. Тяпкина

From the point of view of history of color names in Russian language the records of the first representative of Russia in the Polish-Lithuanian state (V. M. Tyapkin) not published in full are of significant value. The most abundant in respect to the color were the records relating to the events of 1676, which is explained by the mass activities that occurred at this time — such as a magnificent funeral of the Polish kings and the coronation of the new monarch. Analysis of the source showed that belyy, zolotoy, krasny, and chernyy are represented with greater frequency. Most often, color designations were used to convey the appearance of fabrics, banners made of them, clothing; less often — interiors and decorations, the color of animals and the appearance of persons. The study determines that the terms krasny and zolotoy were specified by similar concepts, which are different variations on the theme of these colors: zlatoy, zolotnyy; as well as rumyanets, skarlatnyy, chervonnyy and chervchatyy. However, as it turned out, the language “palette” of the document is somewhat poorer than the expressive means of the Russian language of the 17th century. Nevertheless, the residency materials help to clarify the existence of certain lexemes and reveal their etymology. The author introduces new information about the use in speech of educated representatives of the Moscow Russia vocabulary units barvyanyy, farba, and specifies the history of using the term tsvetnoy. A unique case has been identified: the writing of zlatopisanyy — zolotopisannyy is inherent in the monument under study, and we do not know any other examples of its use during this period. Another variant of the well-known word, zolototsvetnyy, found in the source under study, was discovered in the works of M. V. Lomonosov.

Retracted] Application of Photoshop Graphics and Image Processing in the Field of Animation

With the rapid development of digital art and machine science and technology, the production form of modern animation tends to be diversified, and with the important role of animation color in the animation film foil and rendering, more and more attention was paid by the animation design industry. Computer graphic technology is a new type of artistic creation method, and its birth and development are closely related to computer technology. The purpose of this paper is to make some analysis and induction from the perspective of science and technology and culture and to explore the application of Photoshop graphics and image processing technology in the field of animation. First, the definition of “animation” and the extension of the animation category are introduced. Then, the main functions of Photoshop image processing technology are described in detail. According to the research content, this paper designs a self‐made experimental short film “future city.” After the simulation of experimental animation film and the setting and positioning of the experimental scene, Photoshop software was used to show the animation scene. The experimental results show that the color changes in the short film “future city.” After the saturation of sunny scenery is reduced by 3 points and the brightness is reduced by 20 points and the filter, mode change, and color adjustment are carried out, a complete rainy scenery can be obtained. The self‐made experimental short film has guiding significance for the creation and practice.

Nautilus belauensis population demographics and trap yields in Palau were similar between surveys in 1982 and 2015

Due to demand for their unique and beautiful shells, chambered nautiluses are at risk of overharvesting throughout their ranges across the tropical Indo-Pacific region. In Palau, collection and harvest of the endemic Nautilus belauensis is minimal. To evaluate the N. belauensis population on Uchelbeluu reef near Koror, we compared population demographics and trap yields observed during surveys in 1982 with new surveys from 2015. Identical trap designs and protocols from 1982 were used on the same reef locations for the 2015 surveys. We captured 96 N. belauensis in 5 trap sets that soaked for 2 d in 2015, for an average catch-per-unit-effort (CPUE) of 9.6 Nautilus trap-1 d-1. N. belauensis CPUE showed no significant differences between 1982 (9.76 Nautilus trap-1 d-1) and 2015. Mature animals in 2015 comprised 86.4% of the total catch, of which 63.2% were males and 36.8% females with 1 animal of indeterminate sex. The overall sex ratio in 2015 was 1.71:1 and did not significantly differ from 1982 (1.87:1). There were no recaptures of marked animals in 2015, and no shells bore inscribed numbers from prior studies. While the lack of studies during the years between 1982 and 2015 preclude our ability to comment on the temporal stability of the N. belauensis population, the resemblance of the population demographics and trap yields over a 33 yr period suggests similar population characteristics during the survey years.

Estimating disease prevalence and temporal dynamics using biased capture serological data in a wildlife reservoir: The example of brucellosis in Alpine ibex (Capra ibex)

The monitoring of the disease prevalence in a population is an essential component of its adaptive management. However, field data often lead to biased estimates. This is the case for brucellosis infection of ibex in the Bargy massif (France). A test-and-cull program is being carried out in this area to manage the infection: captured animals are euthanized when seropositive, and marked and released when seronegative. Because this mountainous species is difficult to capture, field workers tend to focus the capture effort on unmarked animals. Indeed, marked animals are less likely to be infected, as they were controlled and negative during previous years. As the proportion of marked animals in the population becomes large, captured animals can no longer be considered as an unbiased sample of the population. We designed an integrated Bayesian model to correct this bias, by estimating the seroprevalence in the population as the combination of the separate estimates of the seroprevalence among unmarked animals (estimated from the data) and marked animals (estimated with a catalytic infection model, to circumvent the scarcity of the data). As seroprevalence may not be the most responsive parameter to management actions, we also estimated the proportion of animals in the population with an active bacterial infection. The actual infection status of captured animals was thus inferred as a function of their age and their level of antibodies, using a model based on bacterial cultures carried out for a sample of animals. Focusing on the population of adult females in the core area of the massif, i.e. with the highest seroprevalence, this observational study shows that seroprevalence has been divided by two between 2013 (51%) and 2018 (21%). Moreover, the likely estimated proportion of actively infected females in the same population, though very imprecise, has decreased from a likely estimate of 34% to less than 15%, suggesting that the management actions have been effective in reducing infection prevalence.

Transpositional features of the word ala «potty, spotted, piebald» (about the color of animals); «motley, multi-colored; spotted»; «light» in the Turkic languages (based on Bashkir and Karachay-Balkarian languages)

The article is devoted to a comprehensive study of the lexico-semantic, derivational, word-composition, inflectional features of the attributive component of descriptive phrases, the indicator of variegated color designation, the term-forming unit of the word ala «potty, spotted, piebald» (about the color of animals) (Bashkir); «motley, multicolored, spotted; light» (Karachay-Balkarian) in Bashkir and Karachay-Balkarian languages, participating in the categorization of mixed segments of the lingua-color space. It examines the features of free and lexicalized phrases, idioms of a phraseological type, paired-repeated constructions formed as a result of combining the word «ala» with denotative and abstract nouns, with asemantic analogues that repeat the second syllable of the reference word and are its phonetically modified version without lexical meaning. It examines the distinctive and integrating features of the noted syntactic structures from the point of view of functioning in various language levels and lexicographic interpretation. The article analyzes the features of a selective combination of «double names» with inventory units of morphology in the process of further morphologization of two-syllable attributive-nominal bases, which, depending on the contextual environment, express an adverbial feature and belong to the category of «rolling» words.

Natural Photonic Structures from Birefringent Core-Shell Nanoparticles

Photonic structures are responsible for the vivid colors of many animals, and also serve as reflectors and filters in vision. Our recent work has explored the core–shell photonic nanostructures involved in the eyes of several decapod crustaceans, and motivates further research into exploiting spatial variation of birefringence in designing ultrathin reflecting photonic structures.

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.

Feather morphological predictors of angle-dependent color changes in parrot plumage

Among the most ornate animal traits in nature are the angle-dependent (e.g. iridescent) structural colors of many fishes, damselflies, birds, beetles, and butterflies. Though we now have a solid understanding of the mechanisms that create angle-dependent coloration in several groups, we know little about whether pigmentary colors reflect light in an angle-dependent fashion or if similar or different mechanisms govern angle-dependent reflectance from pigmentary versus structural colors. Here for the first time we describe non-iridescent angle-dependent coloration from the tail and wing feathers of several parrot species (Aves: Psittaciformes). We employed a novel approach—by calculating chromatic and achromatic contrasts (in just noticeable differences, JNDs) of straight and angled measurements of the same feather patch—to test for perceptually relevant angle-dependent changes in coloration on dorsal and ventral feather surfaces. We found, among the 15 parrot species studied, significant angle dependence for seven of our eight feather JND parameters. We then measured micro-scale features on each side of feathers, including size and color of barbs and barbules, to attempt to predict interspecific variation in degree of angle-dependent reflectance. We found that barb height, plumage-color type (e.g. melanin, structural), and differences between barb-barbule coloration (measured using Euclidean distances) were the strongest predictors of angle-dependent coloration. Interestingly, there was no significant phylogenetic signal in any of the angle-dependence models tested. These findings deepen our views on the importance of microscopic feather features in the production of directional animal coloration, especially in tissues that are colored predominantly by pigments and appear to be statically colored.

Molecular Plasticity in Animal Pigmentation: Emerging Processes Underlying Color Changes.

Animal coloration has been rigorously studied and has provided morphological implications for fitness with influences over social behavior, predator-prey interactions, and sexual selection. In vertebrates, its study has developed our understanding across diverse fields ranging from behavior to molecular biology. In the search for underlying molecular mechanisms, many have taken advantage of pedigree-based and genome-wide association screens to reveal the genetic architecture responsible for pattern variation that occurs in early development. However, genetic differences do not provide a full picture of the dynamic changes in coloration that are most prevalent across vertebrates at the molecular level. Changes in coloration that occur in adulthood via phenotypic plasticity rely on various social, visual, and dietary cues independent of genetic variation. Here, I will review the contributions of pigment cell biology to animal color changes and recent studies describing their molecular underpinnings and function. In this regard, conserved epigenetic processes such as DNA methylation play a role in lending plasticity to gene regulation as it relates to chromatophore function. Lastly, I will present African cichlids as emerging models for the study of pigmentation and molecular plasticity for animal color changes. I posit that these processes, in a dialog with environmental stimuli, are important regulators of variation and the selective advantages that accompany a change in coloration for vertebrate animals.

High-resolution characterization of male ornamentation and re-evaluation of sex linkage in guppies.

Coloration plays a key role in the ecology of many species, influencing how an organism interacts with its environment, other species and conspecifics. Guppies are sexually dimorphic, with males displaying sexually selected coloration resulting from female preference. Previous work has suggested that much of guppy colour pattern variation is Y-linked. However, it remains unclear how many individual colour patterns are Y-linked in natural populations as much of the previous work has focused on phenotypes either not found in the wild, or aggregate measures such as total colour area. Moreover, ornaments have traditionally been identified and delineated by hand, and computational methods now make it possible to extract pixels and identify ornaments with automated methods, reducing the potential for human bias. Here we developed a pipeline for semi-automated ornament identification and high-resolution image analysis of male guppy colour patterns and applied it to a multigenerational pedigree. Our results show that loci controlling the presence or the absence of individual male ornaments in our population are not predominantly Y-linked. However, we find that ornaments of similar colour are not independent of each other, and modifier loci that affect whole animal coloration appear to be at least partially Y-linked. Considering these results, Y-linkage of individual ornaments may not be important in driving colour changes in natural populations of guppies, or in expansions of the non-recombining Y region, while Y-linked modifier loci that affect aggregate traits may well play an important role.

When animal coloration is a poor match

Biologists usually pursue the adaptationist paradigm in trying to explain the functional significance of animal coloration. Here I collate instances in which coloration may be a poor match in the context of background matching, Batesian mimicry, aposematism, and colour polymorphisms. This can occur because of trade-offs with other functions, relaxed selection from predation, or colour trait neutrality. Also, mechanistic, pleiotropic and chance genetic effects can all result in a poor match to the background environment or to signaling efficiently. While biologists implicitly recognise these constraints placed on adaptive coloration, they rarely explicitly acknowledge the heterodox notion that coloration might be under weak selection or no selection at all. Unfortunately, it is difficult to show this definitively, as illustrated in an investigation into the function of colour polymorphisms in coconut crabs.

Does conspicuousness scale linearly with colour distance? A test using reef fish.

To be effective, animal colour signals must attract attention-and therefore need to be conspicuous. To understand the signal function, it is useful to evaluate their conspicuousness to relevant viewers under various environmental conditions, including when visual scenes are cluttered by objects of varying colour. A widely used metric of colour difference (ΔS) is based on the receptor noise limited (RNL) model, which was originally proposed to determine when two similar colours appear different from one another, termed the discrimination threshold (or just noticeable difference). Estimates of the perceptual distances between colours that exceed this threshold-termed 'suprathreshold' colour differences-often assume that a colour's conspicuousness scales linearly with colour distance, and that this scale is independent of the direction in colour space. Currently, there is little behavioural evidence to support these assumptions. This study evaluated the relationship between ΔS and conspicuousness in suprathreshold colours using an Ishihara-style test with a coral reef fish, Rhinecanthus aculeatus. As our measure of conspicuousness, we tested whether fish, when presented with two colourful targets, preferred to peck at the one with a greater ΔS - from the average distractor colour. We found the relationship between ΔS and conspicuousness followed-- a sigmoidal function, with high ΔS colours perceived as equally conspicuous. We found that the relationship between ΔS and conspicuousness varied across colour space (i.e. for different hues). The sigmoidal detectability curve was little affected by colour variation in the background or when colour distance was calculated using a model that does not incorporate receptor noise. These results suggest that the RNL model may provide accurate estimates for perceptual distance for small suprathreshold distance colours, even in complex viewing environments, but must be used with caution with perceptual distances exceeding- -10 ΔS.

Plumage colouration in gulls responds to their non‐breeding climatic niche

AbstractAimGlobal variation in animal colouration has inspired ecogeographical rules that suggest common patterns of recurrent adaptations to climate. However, little attention has been paid to the relative influence of the different climatic conditions encountered by species during their annual life cycle. We explored this question by testing whether breeding or non‐breeding climatic conditions most influence plumage colouration in gulls, a cosmopolitan group of birds with extensive variation in plumage darkness and seasonal migratory strategies.LocationGlobal.Time periodContemporary.Major taxa studiedAll species and subspecies of gulls (Aves, Laridae).MethodsWe used literature data and digital images to assess two characteristics of plumage colouration in all 80 species and subspecies of gulls: the darkness of the mantle and the proportion of black on wingtips. For each species and subspecies, we collected data on migration distance and environmental variables across its breeding and non‐breeding range for both breeding and non‐breeding seasons. We performed a phylogenetic comparative analysis to quantify the relative influence of climatic conditions experienced during the breeding and non‐breeding season on plumage colouration.ResultsThe climatic conditions encountered during the non‐breeding season explained interspecific variation in colouration better than the climate experienced during the breeding season. In accordance with hypotheses on the role of dark colouration in thermoregulation and feather protection, darker mantle colouration was positively correlated with insolation and negatively with air temperature. The proportion of black on wingtips was greater for long distance migrants wintering under insolated conditions than short distance migrants or residents occupying less insolated regions.Main conclusionsIn gulls, plumage colouration is predominantly shaped by selection experienced outside the breeding period, in accordance with the hypothesized photoprotective and thermoregulatory functions of avian plumage. This highlights the importance of taking into account seasonality and migration to understand global spatial patterns of avian colouration.

Avian Pigment Pattern Formation: Developmental Control of Macro- (Across the Body) and Micro- (Within a Feather) Level of Pigment Patterns.

Animal color patterns are of interest to many fields, such as developmental biology, evolutionary biology, ethology, mathematical biology, bio-mimetics, etc. The skin provides easy access to experimentation and analysis enabling the developmental pigment patterning process to be analyzed at the cellular and molecular level. Studies in animals with distinct pigment patterns (such as zebrafish, horse, feline, etc.) have revealed some genetic information underlying color pattern formation. Yet, how the complex pigment patterns in diverse avian species are established remains an open question. Here we summarize recent progress. Avian plumage shows color patterns occurring at different spatial levels. The two main levels are macro- (across the body) and micro- (within a feather) pigment patterns. At the cellular level, colors are mainly produced by melanocytes generating eumelanin (black) and pheomelanin (yellow, orange). These melanin-based patterns are regulated by melanocyte migration, differentiation, cell death, and/or interaction with neighboring skin cells. In addition, non-melanin chemical pigments and structural colors add more colors to the available palette in different cell types or skin regions. We discuss classic and recent tissue transplantation experiments that explore the avian pigment patterning process and some potential molecular mechanisms. We find color patterns can be controlled autonomously by melanocytes but also non-autonomously by dermal cells. Complex plumage color patterns are generated by the combination of these multi-scale patterning mechanisms. These interactions can be further modulated by environmental factors such as sex hormones, which generate striking sexual dimorphic colors in avian integuments and can also be influenced by seasons and aging.