Winter Pelage Research Articles

Färgvariation hos vattenpiplärka Anthus spinoletta i vinterdräkt

This study of colour variation on Water Pipit Anthus spinoletta in winter plumage, is based on photos of 93 individuals from southern Sweden. Using moulting criteria, the birds were aged from the photographs, and the presence or absence of five specific plumage characteristics were recorded. Twelve individuals in this study confirm the hypothesis that adult Water Pipits show a distinct combination of plumage traits during winter. However, the presence of these plumage traits varied in younger birds in their first winter plumage. Among the 81 individuals classified as first winter plumage, 23 (28%) displayed all “adult characteristics”, 32 (40%) one to four of the characteristics, while 26 (32%) lacked all “adult characteristics”. The latter group thus lacked a gray nape/crown, whitish supercilium, and lighter brown colouration of the mantle/scapulars. Ever since the first Swedish records in the mid-1990s, there have been ongoing discussions regarding species-specific characters in Water Pipits. The present quantification of colour variation in different age groups complements previous criteria for a reliable species identification of Water Pipits in winter plumage.

Seasonal changes in plumage density, plumage mass, and feather morphology in the world’s northernmost land bird, the Svalbard Rock Ptarmigan (Lagopus muta hyperborea)

The Svalbard Rock Ptarmigan, Lagopus muta hyperborea, is the only year-round resident terrestrial bird in the high Arctic. Many of the physiological and morphological adaptations permitting its winter endurance in this harsh environment are well understood. However, it remains unknown how the conspicuous moult from a greyish brown summer to a white winter plumage, and any underlying changes in plumage structure and feather morphology, contribute to seasonal acclimatisation. We used standard morphometric techniques to describe the seasonal change in plumage and feather characteristics in six body regions. Then, we investigated whether winter plumage traits differed between first-winter and adult (second winter, or older) birds, because a difference in coat insulation has been suggested as an explanation for why first-winter Svalbard Ptarmigan loose more heat than adults. Plumage feather density (i.e., feathers × cm−2) and mass density (i.e., mg feathers × cm−2) were higher in winter, particularly on the head and feet where individual feathers were also heavier, longer, and downier. Seasonal changes in other regions (back, tarsi) indicated acclimatisation primarily to resist physical wear and wind. First-winter and adult birds had similar feather densities. However, mass density in first-winter birds was significantly lower than in adults in all but one body region (back) because individual feathers weighed less. This can explain previous observations of higher heat loss rates in first-winter birds. Our study suggests that plumage acclimatisation contributes to optimising the winter phenotype of Svalbard Rock Ptarmigan, both through higher insulative capacity and by improved resistance to harsh weather. The extent of these adaptations may be determined by the time or energy available for feather growth, exemplified here by inferior insulation in first-winter birds.

The evolution of white-tailed jackrabbit camouflage in response to past and future seasonal climates

The genetic basis of adaptive traits has rarely been used to predict future vulnerability of populations to climate change. We show that light versus dark seasonal pelage in white-tailed jackrabbits (Lepus townsendii) tracks snow cover and is primarily determined by genetic variation at endothelin receptor type B (EDNRB), corin serine peptidase (CORIN), and agouti signaling protein (ASIP). Winter color variation was associated with deeply divergent alleles at these genes, reflecting selection on both ancestral and introgressed variation. Forecasted reductions in snow cover are likely to induce widespread camouflage mismatch. However, simulated populations with variation for darker winter pelage are predicted to adapt rapidly, providing a trait-based genetic framework to facilitate evolutionary rescue. These discoveries demonstrate how the genetic basis of climate change adaptation can inform conservation.

Mountain- and brown hare genetic polymorphisms to survey local adaptations and conservation status of the heath hare (Lepus timidus sylvaticus, Nilsson 1831)

We provide the first whole genome sequences from three specimens of the mountain hare subspecies the heath hare (Lepus timidus sylvaticus), along with samples from two mountain hares (Lepus timidus timidus) and two brown hares (Lepus europaeus) from Sweden. The heath hare has a unique grey winter pelage as compared to other mountain hares (white) and brown hares (mostly brown), and face regional extinction, likely due to competitive exclusion from the non-native brown hare. Whole genome resequencing from the seven hare specimens were mapped to the Lepus timidus pseudoreference genome and used for detection of 11,363,883 polymorphic nucleotide positions. The data presented here could be useful for addressing local adaptations and conservation status of mountain hares and brown hares in Sweden, including unique subspecies.

Decline of the boreal willow grouse (Lagopus\xa0lagopus) has been accelerated by more frequent snow-free springs

Climate change has influenced a range of species across the globe. Yet, to state a noted decline in the abundance of a given species as a consequence of a specific environmental change, for instance, spatially explicit long-term data are a prerequisite. This study assessed the extent to which prolonged snow-free periods in autumn and spring have contributed to the decline of the willow grouse, the only forest grouse changing into a white winter plumage. Time-series data of willow grouse numbers from summer surveys across the study area were integrated with local data on weather (snow cover), mammalian predator abundance and hunting intensity. Modelling was conducted with a hierarchical Bayesian Poisson model, acknowledging year-, area- and location-specific variability. The results show that while willow grouse numbers had decreased continuously across the study landscapes, the decrease was accelerated at the sites where, and during the years when the preceding April was the most snow-free. This indicates a mismatch between the change into a white winter plumage and the presence of snow, turning the bird into an ill-camouflaged prey. The results thus also confirm past hypotheses where local declines of the species have been attributed to prolonged snow-free periods. Across our study area, autumns and springs have become more snow-free, and the trend has been predicted to continue. Thus, in addition to conservation actions, the future of a species such as the willow grouse is also dependent on its ability to adapt to the changed environmental conditions.

Hair cortisol as a reliable indicator of stress physiology in the snowshoe hare: Influence of body region, sex, season, and predator–prey population dynamics

Hair cortisol concentration is increasingly used as a convenient, non-invasive, and integrative measure of physiology and health in natural populations of mammals. However, the use of this index is potentially confounded by individual variation in body region-specific differences in cortisol deposition rates. Here we examine correlations in cortisol concentrations in hair collected from the ear, shoulder, and thigh of wild snowshoe hares, Lepus americanus, as well as the influence of sex on cortisol measurements. We further evaluated this technique’s ability to capture seasonal and cyclical patterns of snowshoe hare glucocorticoid secretion from 2013 to 2015 in the southwestern Yukon (Canada). We found positive correlations (R2 = 0.20–0.32) in all pairwise comparisons among body regions, and differences among individuals accounted for the greatest proportion of variance (47.3%) in measurements. From 2013 to 2015 the hares’ primary predator – Canada lynx – approximately doubled in population abundance. We found a significant increase in hare hair cortisol concentrations across this time period. Cortisol indices were higher in summer than winter pelage, reflecting predicted physiological responses to seasonal variation in food availability and individual risk. Variation in hair cortisol concentrations was more similar to long-term (weeks-months) integrative indices of adrenal capacity than point samples of fecal glucocorticoid metabolite concentrations. Overall, we find that hair cortisol analysis is a simple and useful tool for estimations of population-level stress physiology in wild mammals, and sampling of core body regions with consistent moulting patterns produced the most robust results in this species.

Seasonal pelage color change of two sympatric arboreal squirrel species in the subarctic region

Some mammal species exhibit pelage color change with seasonal molt. Seasonal molt and pelage color change are beneficial to thermoregulation and concealment, associated with seasonal environmental change. The Eurasian red squirrel Sciurus vulgaris Linnaeus, 1758 and the Siberian flying squirrel Pteromys volans (Linnaeus, 1758) are arboreal and sympatrically distributed in the subarctic northern Eurasian Continent and Sakhalin and Hokkaido islands. We expect that diurnal S. vulgaris may demonstrate more conspicuous difference between summer and winter pelages than nocturnal P. volans, because of its protective coloration in each season. To test this conjecture, we investigated their seasonal pelage color change. To diminish the effect of geographic variation in pelage color, we chose S. vulgaris orientis Thomas, 1906 and P. volans orii (Kuroda, 1921), which are endemic subspecies of Hokkaido Island, Japan. We used skin and stuffed specimens and frozen materials and categorized them into two pelage groups (summer and winter pelages) based on collection date. Pelage color characteristics were measured with a spectrophotometer for lightness, redness and yellowness. Countershading was examined by comparing dorsal and ventral lightness. Both subspecies showed lighter winter pelage than summer pelage, suggesting their greyish-white winter pelage was beneficial to concealment from predators during winter. As we expected, seasonal changes of redness and yellowness were more clearly recognized in S. vulgaris than in P. volans. As S. vulgaris is diurnal and vulnerable to attack by diurnal avian predators, reddish and yellowish pelage patterns may be important for concealment. Because it is nocturnal, P. volans may not need this reddish and yellowish pelage. Sciurus vulgaris also had a remarkably counter-shaded body, indicating that its body may reduce predation risk from daytime visual predators. Differences in seasonal pelage color change of these two arboreal squirrels may be caused by their different circadian rhythms.

Climate change is affecting mortality of weasels due to camouflage mismatch

Direct phenological mismatch caused by climate change can occur in mammals that moult seasonally. Two colour morphs of the weasel Mustela nivalis (M. n.) occur sympatrically in Białowieża Forest (NE Poland) and differ in their winter pelage colour: white in M. n. nivalis and brown in M. n. vulgaris. Due to their small body size, weasels are vulnerable to attacks by a range of different predators; thus cryptic coat colour may increase their winter survival. By analysing trapping data, we found that the share of white subspecies in the weasel population inhabiting Białowieża Forest decreases with decreasing numbers of days with snow cover. This led us to hypothesise that selective predation pressure should favour one of the two phenotypes, according to the prevailing weather conditions in winter. A simple field experiment with weasel models (white and brown), exposed against different background colours, revealed that contrasting models faced significantly higher detection by predators. Our observations also confirmed earlier findings that the plasticity of moult in M. n. nivalis is very limited. This means that climate change will strongly influence the mortality of the nivalis-type due to prolonged camouflage mismatch, which will directly affect the abundance and geographical distribution of this subspecies.

Color and shape of remiges of first winter plumage of Ruddy-breasted Crake <i>Porzana fusca</i> observed in Wakayama Prefecture, western Japan.

Color and shape of remiges of first winter plumage of Ruddy-breasted Crake <i>Porzana fusca</i> observed in Wakayama Prefecture, western Japan.

Development of Sexual Dimorphism and Sexing of Baltic Herring Gull (Larus argentatus argentatus) in Successive Age Classes

Abstract. Discriminant functions based on external body size measurements are widely used to sex different gull species with great accuracy. However, all of them have been derived for adult birds, which puts into question their usefulness for sexing immatures due to possible changes in size as birds mature. To address this issue, discriminant functions that allow sexing of Herring Gulls in immature age classes with an accuracy of 88–100% were developed. In total, 247 males and 111 females of wintering Herring Gulls, including birds in the first, second and third winter plumages and individuals in adult plumage, were measured and sexed in the region of the Gulf of Gdansk (southeastern Baltic coast). In all age classes, total head length and bill depth were the best traits for sexing Herring Gulls. However, bill depth, but not total head length, increased with age. Hence, in the first and second winter plumages, total head length made a much higher contribution to the discriminant function than bill depth. ...

Geographic variation in winter adaptations of snowshoe hares (Lepus americanus)

Understanding adaptations of nonhibernating northern endotherms to cope with extreme cold is important because climate-induced changes in winter temperatures and snow cover are predicted to impact these species the most. We compared winter pelage characteristics and heat production of snowshoe hares (Lepus americanus Erxleben, 1777) on the southern edge of their range, in Pennsylvania (USA), to a northern population, in the Yukon (Canada), to investigate how hares might respond to changing environmental conditions. We also investigated how hares in Pennsylvania altered movement rates and resting spot selection to cope with variable winter temperatures. Hares from Pennsylvania had shorter, less dense, and less white winter coats than their northern counterparts, suggesting lower coat insulation. Hares in the southern population had lower pelage temperatures, indicating that they produced less heat than those in the northern population. In addition, hares in Pennsylvania did not select for resting spots that offered thermal advantages, but selected locations offering visual obstruction from predators. Movement rates were associated with ambient temperature, with the smallest movements occurring at the lower and upper range of observed ambient temperatures. Our results indicate that snowshoe hares may be able to adapt to future climate conditions via changes in pelage characteristics, metabolism, and behavior.

Discovery of a little Bustard (Tetrax tetrax) in the province of Venice (Italy) and review of Venetian reports

<p>[We report the recovery of a wing and the body of a Little Bustard between March 31st and April 7th 2012 in Isiata, San Donà di Piave (VE), it was a female in first winter plumage. Death was almost certainly caused by a collision with electric cables. At the end of 19th century Little Bustard was regular in Veneto, but sightings of this species became progressively scarcer during 20th century, so it was classified as “B40” (species not recorded since 1949) at the suggestion of AERC (Association of European Rarities Committees). The recovery of the corpse in this note is the 4th sighting in Veneto in last 50 years, and we know of 2 additional observations. Between 1950 and the present day there have been 10 regional sightings, so we suggest changing the status of this species in the Veneto to “A30”, according to AERC.]</p><p> </p>

Shaggy Lame Fox Syndrome in Pribilof Island Arctic Foxes ( Alopex lagopus pribilofensis), Alaska.

A previously unrecognized condition is described in wild free-ranging Pribilof arctic foxes ( Alopex lagopus pribilofensis) from the Pribilof Islands, Alaska, USA. This condition is called shaggy lame fox syndrome (SLFS) denoting the primary clinical signs first observed. Criteria used to suspect SLFS on gross examination included emaciation, failure to shed winter pelage and moderate to severe polyarthritis. Criteria used to confirm SLFS histologically included polyarthritis (characterized by lymphoplasmacytic synovitis, tenosynovitis, bursitis, periosteal bony proliferation, and periarticular lymphoplasmacytic vasculitis) and systemic leukocytoclastic vasculitis. Other histological lesions often found included renal cortical infarcts, myocarditis with myocardial infarcts, lymphoplasmacytic meningitis, lymphoplasmacytic cuffing of meningeal and a few cerebral vessels, and cavitating infarcts of the brainstem and thalamus. The cause of SLFS is not known at this time; however, the gross and histological lesions suggest that the cause of SLFS may be a bacterial polyarthritis with a secondary immune-mediated vasculitis. These lesions are consistent with changes described with Erysipelothrix rhusiopathiae in domestic dogs; E. rhusiopathiae was identified from the synovial membrane of a swollen stifle joint and the kidney from one fox using real-time polymerase chain reaction and with culture from a fox that had gross and histological lesions of SLFS. Therefore, E. rhusiopathiae is a possible etiological agent for SLFS.

Plumage colouration variability of male Bluethroats (Luscinia svecica cyanecula) wintering in SE Iberia

Male colouration has a key role in signalling individual quality during the breeding season. Although winter plumage probably correlates with summer plumage, few studies have focused on the determinants of male colouration during the non-breeding period. If plumage colouration is related to an individual’s age or is strongly correlated with body condition during the non-breeding period, this trait could be used by conspecifics to assess quality, origin or status of a given individual.Here,we analysed plumage colouration and body size of male Bluethroats (Luscinia svecica cyanecula) wintering in SE Iberia. We found that young individuals had narrower black bands and wider white bands than adult individuals in their throat patch.Also, thewidth of the chestnut band increased with later capture date. Finally, blue throat colouration was positively correlated with tail length and negatively correlatedwith tarsus length.We could not find any significant relationship between throat patch colouration and bodymass.We concluded that individual’s age and capture date were significantly related to black and chestnut throat colouration, respectively. Therefore, these coloured bands could provide reliable cues on individual’s age and their geographical origins. The variability of plumage colouration of wintering Bluethroats provides an excellent study system in which to test further hypotheses on the role of the throat patch colouration outside the breeding season.

Factors influencing the evolution of moult in the non-breeding season: insights from the family Motacillidae

The number of moults per annual cycle and their final spatial pattern (i.e. topography) show high interspecific variation in the order Passeriformes. Factors behind this variability remain obscure, especially for variability in spatial pattern among species. Here, we explored the relative influence of ten ecological, ontogenetic, social and sexual factors on the evolution of autumn moult (feather replacement largely undertaken by migratory species, which is not necessarily an independent episode within their moult cycle) and prealternate moult among Northern Hemisphere species of the family Motacillidae using phylogenetically controlled analyses, ancestral state reconstruction and analyses of correlated evolution. The results strongly support the presence of prealternate moult and absence of autumn moult as ancestral states in this family. A high rate of change between related species indicates phylogenetic independence among prealternate moult patterns and examined factors. Migration distance and gregariousness are the most important factors influencing prealternate moult evolution, and point toward natural selection and sociality as the most important evolutionary drivers of prealternate moult in Motacillidae. Breeding latitude, seasonal plumage change, winter plumage conspicuousness, sexual dichromatism, plumage maturation and extent of preformative moult show a minor influence, and suggest that ontogeny and sexual selection may have played a limited role in shaping prealternate moult in Motacillidae.

Superb winter fur insulation in the small Siberian musk deer (Moschus moschiferus)

We compared the morphology and thermal characteristics of winter pelage from two Siberian musk deer Moschus moschiferus (aged 5 and 41 mo.; 5.7 and 9.5 kg) and two Eurasian reindeer Rangifer tarandus tarandus (aged >48 mo.; 73 and 79 kg). The depth of the fur over the back of musk deer was less (approximately 30 mm) than in reindeer (approximately 40 mm). Guard hairs of musk deer were longer (mean = 50.0 mm) and had greater diameter at half-length (mean = 314.4 μm) than those of reindeer (mean = 38.6mm and = 243.9 μm, respectively). The thermal characteristics (thermal conductivity and resistance) of the winter pelage of the two species were nevertheless similar (0.057 W·m-1·K-1 and 0.79 K·m2·W-1; and 0.037 W·m-1 ·K-1 and 1.00 K·m2·W-1, respectively) despite a tenfold difference in their body mass.

Light-level geolocators reveal covariation between winter plumage molt and phenology in a trans-Saharan migratory bird

Contingent individual performance can depend on the environment experienced at previous life-stages. Migratory birds are especially susceptible to such carry-over effects as they periodically travel between breeding ranges and 'wintering' areas where they may experience broadly different ecological conditions. However, the study of carry-over effects is hampered by the difficulty of tracking vagile organisms throughout their annual life-cycle. Using information from light-level geolocators on the barn swallow (Hirundo rustica), we tested if feather growth bar width (GBW), a proxy of feather growth rate which depends on individual condition, and wing isometric size and shape predict the phenology of subsequent migration. GBW did not predict duration of wintering but negatively predicted the duration of spring migration and arrival date to the breeding sites, suggesting that migration phenology is not constrained by molt, and individuals in prime condition achieve both faster molt and earlier arrival. Wing morphology did not predict migration duration, as expected if wing shape were optimized for foraging, rather than migration performance, in this aerially foraging, insectivorous bird. Thus, we showed for the first time that migration phenology in a long-distance migratory bird covaries with body condition during wintering, as reflected by the growth rate of feathers.

通河林区黄鼬(Mustela sibirica)冬季被毛形态结构的功能适应性研究

被毛在哺乳动物适应性进化过程中执行保温和保护两个重要功能,其形态结构上存在的功能适应性特征因所处的部位不同而表现出适应性分化现象,由动物体躯干至四肢末端呈显著的梯度变化。以黑龙江省通河林区黄鼬东北亚种（Mustela sibirica manchurica）冬季雌雄成体各10只完整毛皮对象,研究了背中部、腹中部和后肢下部3个部位的直针毛、披针毛、绒针毛、绒毛,以及后趾部硬毛的被毛性状因子,统计分析表明：通河林区黄鼬相同身体部位4种类型毛的长度和细度指标均为直针毛〉披针毛〉绒针毛〉绒毛,相同部位4种类型毛长度的相关性极显著,直针毛细度与披针毛细度相关性极显著（P〈0.01）,绒针毛细度与绒毛细度相关性极显著（P〈0.01）,这种特征使得被毛在整体结构上为实施保温和保护功能奠定基础;同时,黄鼬被毛各性状的保温功能从背部向后趾部呈递减趋势,而保护功能则呈现递增趋势,被毛形态结构性状上的分化与动物机体异温性充分结合,对于黄鼬适应寒冷的森林生态环境具有重要意义。

First Costa Rican record of Pacific Golden-Plover (Pluvialis fulva, Gmelin, 1789) (Aves: Charadriidae)

Here we report on the first observation of Pacific Golden Plover in Central America, from Costa Rica. An individual in winter plumage was observed on salts ponds along with several other roosting waders

Aging Atlantic Puffins Fratercula arctica in summer and winter

Atlantic Puffins Fratercula arctica in summer and winter plumage can be aged as first-year, second-year, third-year, young adult and old adult using the number of grooves on the outer part of the beak. The technique is useful to bird ringers and those dealing with birds found dead in wrecks and pollution incidents where knowledge of the ages of individuals involved can help assess the likely effect on breeding populations.