Body Moult Research Articles

Colony attendance and moult pattern of Cory's Shearwaters (Calonectris borealis) differing in breeding status and age

Migratory birds must fit three costly life‐history events within the annual cycle, reproduction, moult and migration, to minimize their overlap and maximize survival and breeding success. However, some seabirds, such as Cory's Shearwater Calonectris borealis, overlap body moult and breeding, with flight feather renewal occurring in late chick‐rearing. In contrast, the moult patterns of non‐breeding adult (sabbatical) and immature Cory's Shearwaters, which also attend the colony during the breeding season, remain poorly understood. Furthermore, the potential implications of life‐stage and breeding status trade‐offs on moult status and colony attendance in non‐breeders has rarely been investigated. Surveying different areas within one colony between June and September 2013 and 2014, we studied the age and breeding status composition of birds attending the breeding colony and scored moult of their body (breast and upper‐neck), wing and tail feathers. We found that in addition to breeders (n = 165), 57.6% of the birds (n = 389) attending the colony were 4‐ to 10‐year‐old immatures (n = 132) and adult sabbatical shearwaters (n = 92). Sabbaticals and 8‐ to 10‐year‐old immatures (n = 28) were present at the colony during incubation, whereas only three sabbatical birds and no 8‐ to 10‐year‐old immatures were captured in late chick‐rearing. Conversely, 4‐ to 7‐year‐old immatures arrived later in the season but were still present in late chick‐rearing. Sabbatical and 8‐ to 10‐year‐old immatures were moulting body feathers at the same time as adult breeders, whereas, among 4‐ to 7‐year‐old immatures, older birds moulted earlier than younger birds. A larger proportion of sabbatical birds were replacing tail feathers compared with adult breeders. However, there was no evidence that sabbaticals or 8‐ to 10‐year‐old immatures differed in wing moult from adult breeders until August. Overall, our study shows that colony attendance by non‐breeding adults and immatures is widespread in this population. The synchronous moult schedule of flight and body feathers across age groups at different life‐history stages may suggest that this aspect of moult is controlled by environmental conditions.

Diet-Related Plumage Erythrism in the Western Tanager and Other Western North American Birds

Consumption of the berries of two exotic bush honeysuckles (genus Lonicera) containing the red carotenoid pigment rhodoxanthin has resulted in abnormal erythristic plumages in several species of birds in eastern North America. Here we report 12 examples of plumage erythrism in the Western Tanager (Piranga ludoviciana), in both live birds (5) and museum specimens (7), that we suspect have the same etiology. The erythristic tanagers feature overtly orange to red feathers variously scattered on the head, rump, wing coverts, and/or underparts, areas of the plumage normally colored by carotenoid pigments. All were in their year of hatching, so the reddened feathers, including replaced median coverts with orange tips, represent formative plumage grown on or near the breeding grounds where berries containing rhodoxanthin are available. By contrast, adult Western Tanagers undergo body molt primarily in the Mexican monsoon region in fall and on their winter grounds in early spring where bush honeysuckles are nonexistent. We also report examples of Red-breasted Sapsuckers (Sphyrapicus ruber) with anomalous red pigmentation on their backs and of Cedar Waxwings (Bombycilla cedrorum) with orange tail bands, as previously documented in the East. In these species, the reddened areas are typically yellow or green, colors based on carotenoid pigments that can be altered through the consumption of fruits containing rhodoxanthin. We conclude that these reddened feathers are the result of the consumption of honeysuckle berries or possibly the red arils of the Pacific Yew (Taxus brevifolia), representing a first report of diet-related erythrism in western North America.

Drought disrupts year-round breeding readiness in a tropical songbird

Climate change is expected to increase the prevalence and severity of extreme weather events like drought. For many opportunistically breeding tropical bird species, precipitation serves as a primary cue for onset of breeding, and sustained drought can have major impacts on reproductive fitness. The physiological effects of drought are poorly understood, but understanding physiological responses can help resolve the mechanisms underlying effects of drought on population demography. We used physiological data collected on a year-round breeding New Guinea endemic passerine, the White-shouldered Fairywren (<em>Malurus alboscapulatus</em>), during years with persistent rainfall and during the 2015–2016 El Niño drought event to assess patterns of breeding readiness, body condition, and molt. Many males lost their cloacal protuberances, a sperm storage organ they typically maintain year-round, during the drought period. Body molt, which also occurs year-round in this species, was higher in males during the drought period. Using a sliding-window statistical model approach, we identified a critical precipitation window of 0–40 days prior to capture for cloacal protuberance volume and a window of 8–53 days for molt, with lower precipitation associated with smaller cloacal protuberances and greater molt. Plasma androgens were predictive of variation in male cloacal protuberance volume and molt, thus potentially mediating transitions between life-history stages in response to environmental conditions. Female molt, androgens, and male mass varied with photoperiod, with longer but decreasing day lengths characteristic of the austral summer associated with increasing molt and decreasing androgens. Collectively, our results indicate the potential for photoperiod to cue some life-history stages, whereas reduced rainfall impacts male but apparently not female reproductive physiology and readiness to breed. Improving our understanding of environmental regulation of life-history transitions in tropical taxa is essential for identifying which taxa are most at risk under a changing climate.

Physiological parameters of a plover during nonbreeding and breeding seasons in Patagonia, Argentina

Migratory shorebirds are the most threatened avian species due to the effects of human activities and climate change. Physiological parameters are useful to evaluate the health status of free-living animals. Here we investigated lymphocytes, heterophils, heterophils/lymphocytes, and glucose for female and male Two-banded Plovers (Charadrius falklandicus Latham, 1790) during nonbreeding (body moult) and breeding (incubation) seasons in coastal areas of northern Patagonia, Argentina. We also measured corticosterone for the first time for this species during the breeding season. Nonbreeding Two-banded Plovers were more likely to have higher physiological measurements that were not dependent on body moult nor body condition, being similar between sexes. Differences found in glucose are likely related to recent feeding in nonbreeding birds compared with fasting during incubation. The gregarious nonbreeding behaviour in comparison with the isolated breeding pairs would increase the risk of acquiring parasites and (or) pathogens inducing a response of the immune system reflected in higher values of lymphocytes. Baseline corticosterone during breeding was similar between sexes and were lower compared with other values reported for breeding plovers. Two-banded Plovers undergo energetically demanding physiological changes during the nonbreeding stage, strengthening the idea that conservation of the environmental resources at these locations may be more important than previously thought.

Effect of the Social Environment on Spring Migration Timing of a Songbird

The influence of the social environment on the timing of the annual cycle is poorly understood. Seasonally migratory birds are under pressure to accurately time their spring migration, and throughout the annual cycle, they may experience variability of the local sex-ratio. A population-level male-biased sex ratio is predicted to advance spring migration timing in males and is attributed to the increased intra-specific competition for access to females and/or breeding territories. The present study had two goals. First, to develop a method that utilizes digitally coded radio-transmitters to quantify the activity of flocked individuals in captivity. Second, to use this method to test the hypothesis that the social environment influences the spring migration traits of male yellow-rumped warblers (Setophaga coronata coronata). To accomplish this, birds were captured in the fall in Long Point, Ontario, and transferred to the Advanced Facility for Avian Research, London, Ontario. In the winter, they were assigned to a slightly male- or female-biased treatment and housed in flocks in large free-flight rooms. Throughout the experimental period, we took body mass measurements and standardized photos to monitor body condition and molt progression. To measure locomotor activity, the birds were outfitted with digitally coded radio-transmitters in April and photo-triggered to enter a migratory phenotype. The tagged birds were released at their capture site in May and the Motus Wildlife Tracking System was used to determine stopover departure timing and migratory movements. Sex ratio did not influence body mass or molt progression. However, males from the male-biased treatment had significantly less locomotor movement than those from the female-biased treatment. Additionally, a lower proportion of males from the male-biased treatment initiated migratory restlessness, an indicator of the urge to migrate. Overall, these findings suggest that the social environment can influence behavior of songbirds, but do not support the hypothesis that a male-biased sex ratio accelerates migration.

Urban links to molt schedule, body condition and carotenoid‐based coloration in the house finch Haemorhous mexicanus

Animals in urban environments are exposed to novel conditions, such as habitat and dietary alterations, and night‐time light pollution, that can shift the timing and expression of life‐history traits. Birds are popular urban‐ecological study subjects, and in these feathered animals regular plumage molt is a critical process for maintenance of feather quality and their associated functions (e.g. thermoregulation, aerodynamics and communicative coloration). We hypothesized that environmental changes associated with urbanization might affect the timing and progression of molt. As molt is energetically and nutritionally costly, we also tested whether putative urban–rural molt differences might be explained by indirect effects of urban environments on aspects of health (i.e. body condition, sexually selected plumage color). We tracked body molt intensity during molt onset, peak and completion in both sexes of urban and rural house finches Haemorhous mexicanus, and related this to body condition and sexually selected carotenoid‐based plumage coloration. We found that urban birds began molting earlier, peaked at a lower molt intensity and ended molt later than rural conspecifics. We also find that both body condition and plumage hue in males explain variation in body molt intensity differently for urban and rural populations at various points during the molting period. Overall, we demonstrate that songbird molt patterns and the development of carotenoid‐based sexual ornaments can be altered in urban environments, and that rapid urbanization may have broader implications for molt dynamics, annual life‐history traits and sexual selection.

Sex‐specific patterns of fuelling and pre‐breeding body moult of Little Stints Calidris minuta in South Africa

The timing and duration of each stage of the life of a long‐distance migrant bird are constrained by time and resources. If the parental roles of males and females differ, the timing of other life stages, such as moult or pre‐migratory fuelling, may also differ between the sexes. Little is known about sexual differences for species with weak sexual dimorphism, but DNA‐sexing enables fresh insights. The Little Stint Calidris minuta is a monomorphic long‐distance migrant wader breeding in the Arctic tundra. Males compete for territories and perform elaborate aerial displays. Females produce two clutches a season. Each sex may be a bigamist and incubate one nest a season, each with a different partner. We expect that these differences in breeding behaviour entail different preparations for breeding by males and females, so we aimed to determine whether Little Stints showed any sex differences in their strategies for pre‐breeding moult and pre‐migratory fuelling at their non‐breeding grounds in South Africa. We used body moult records, wing length and body mass of 241 DNA‐sexed Little Stints that we caught and ringed between 27 January and 29 April in 2008–2018 at two neighbouring wetlands in North West Province, South Africa. For each individual we assessed the percentage of breeding plumage on its upperparts and took blood samples for DNA‐sexing. We calculated an adjusted Body Moult Index and an adjusted Wing Coverts Moult Index, then used the Underhill–Zucchini moult model to estimate the start dates and the rate of body moult in males and females. We estimated the changes in the sex ratio of the local population during their stay in South Africa, and also estimated the timing and rate of pre‐migratory fuelling and the potential flight ranges for males and females. The males started body moult on average on 7 February and the females on 12 February, but the sexes did not differ in their timing of wing covert moult, which started on average on 10 February. In January to mid‐February, males constituted c. 57% of the population, but their proportion declined afterwards, indicating an earlier departure than females. We estimated that both sexes began pre‐migratory fuelling on average on 15 March. The sexes did not differ in fuelling rate, but most females stayed at the non‐breeding site longer than the males, and thus accumulated more fuel and had longer potential flight ranges. These patterns of moult and fuelling suggest sex differences in preparations for breeding. We suggest that the males depart from South Africa earlier but with smaller fuel loads than the females to establish breeding territories before the females arrive. We conclude that for each sex the observed trade‐offs between fuelling and moult at the non‐breeding grounds are precursors to different migration strategies, which in turn are adaptations for their different roles in reproductive behaviour.

Occurrence of Life Cycle Dependent Monophasic and Biphasic Molting in a Parasitic Isopod, Mothocya renardi

This paper reports the occurrence of life cycle dependent monophasic and biphasic molting in Mothocya renardi (Bleeker, 1857), a protandrous hermaphroditic cymothoid parasitizing the banded needle fish, Strongylura leiura. Although the molting in manca I is monophasic, the infective manca II, juvenile and adult stages including male, transitional, and female opt biphasic molting in which the posterior half of the body molts first, followed by the anterior half. The molt cycle (monophasic and biphasic) in M. renardi is broadly divided in to four sequential stages, premolt, molt, postmolt and intermolt. Five distinct premolt stages (D0-D4) were also identified through the microscopic observation of characteristic changes reflected in different appendages of manca stages and adult infective stages. Pleotelson, uropod rami and dactylus of the first pereopod and antennae were used for the identification of stages of monophasic molt cycle. By undergoing monophasic molting, the manca I was transformed into the manca II which then undergoes biphasic molt. The characteristic changes related to biphasic molting were well reflected in the maxillule. When the maxillule showed characters of the premolt stage D2, the posterior half of the body had already exuviated. Molting of the anterior half ensued within 2–3 days after posterior half ecdysis. Occurrence of a series of biphasic molts resulted in the transformation of manca II into the successive stages in the order juvenile, male, transitional and female.

ATLANTIC BIRD TRAITS: a data set of bird morphological traits from the Atlantic forests of South America

Scientists have long been trying to understand why the Neotropical region holds the highest diversity of birds on Earth. Recently, there has been increased interest in morphological variation between and within species, and in how climate, topography, and anthropogenic pressures may explain and affect phenotypic variation. Because morphological data are not always available for many species at the local or regional scale, we are limited in our understanding of intra- and interspecies spatial morphological variation. Here, we present the ATLANTIC BIRD TRAITS, a data set that includes measurements of up to 44 morphological traits in 67,197 bird records from 2,790 populations distributed throughout the Atlantic forests of South America. This data set comprises information, compiled over two centuries (1820-2018), for 711 bird species, which represent 80% of all known bird diversity in the Atlantic Forest. Among the most commonly reported traits are sex (n=65,717), age (n=63,852), body mass (n=58,768), flight molt presence (n=44,941), molt presence (n=44,847), body molt presence (n=44,606), tail length (n=43,005), reproductive stage (n=42,588), bill length (n=37,409), body length (n=28,394), right wing length (n=21,950), tarsus length (n=20,342), and wing length (n=18,071). The most frequently recorded species are Chiroxiphia caudata (n=1,837), Turdus albicollis (n=1,658), Trichothraupis melanops (n=1,468), Turdus leucomelas (n=1,436), and Basileuterus culicivorus (n=1,384). The species recorded in the greatest number of sampling localities are Basileuterus culicivorus (n=243), Trichothraupis melanops (n=242), Chiroxiphia caudata (n=210), Platyrinchus mystaceus (n=208), and Turdus rufiventris (n=191). ATLANTIC BIRD TRAITS (ABT) is the most comprehensive data set on measurements of bird morphological traits found in a biodiversity hotspot; it provides data for basic and applied research at multiple scales, from individual to community, and from the local to the macroecological perspectives. No copyright or proprietary restrictions are associated with the use of this data set. Please cite this data paper when the data are used in publications or teaching and educational activities.

Evidence for exposure to selenium by breeding interior snowy plovers (Charadrius nivosus) in saline systems of the Southern Great Plains.

Interior snowy plover (Charadrius nivosus) population declines and deteriorating conditions throughout the Southern Great Plains (SGP) of Texas, New Mexico, and Oklahoma may be linked to environmental contaminants. Concentrations of V, As, Cd, Pb, and Se were quantified in breeding snowy plover blood, feathers (5th primary; P5), and potential prey (tiger beetles [Cicindela circumpicta and C. togata]). Se was (a) most commonly detected relative to other quantified elements and (b) frequently quantified at levels exceeding background or toxicity thresholds. Of samples greater than instrumentation detection limits, 98% of snowy plover blood and 22% of feather samples were greater than Se toxicity thresholds of 1 ppm ww for blood and 5 ppm dw for feathers (blood quantifiable range: 0.83-15.12 ppm; feathers quantifiable range: 1.90-27.47 ppm). Almost all tiger beetle Se concentrations were below reported invertebrate thresholds of 30 ppm dw (quantifiable range: 0.54-45.84 ppm). Snowy plover blood Se concentrations were related to sex, individual body condition, and local tiger beetle Se concentrations, while plover P5 Se concentrations were related to state, sex, and presence of body molt. Tiger beetle Se concentrations were related to individual study sites in Texas. These results provide some of the first evidence of Se exposure risk for interior snowy plovers nesting in saline lake and alkali flat environments of the SGP. Future efforts should focus upon specific Se uptake pathways during breeding and nonbreeding seasons, as snowy plovers breeding in the SGP appear to be exposed to Se throughout their annual cycle.

Molting while breeding? Lessons from New World Tyrannus Flycatchers

Songbirds must annually undergo two energetically demanding but important activities: breeding and feather molt. Due to the high energetic investment that each demands, these two events are generally not carried out simultaneously. However, substantial variation in the level of annual reproductive investment among populations may result in variation in molt-breeding overlap between them. With the goal of understanding whether different songbird populations overlap molt and breeding, and, if so, to determine directions for research on the potential tradeoffs involved, we describe the relationship between clutch size, molt, and energetic condition within a genus of New World Flycatchers (Tyrannus). Of 219 Flycatchers sampled, only one individual molted flight feathers while breeding, suggesting that molting flight feathers and breeding simultaneously is too energetically expensive at any clutch size. However, some Flycatchers molted body feathers during the breeding season. When we tested for an effect of clutch size, sex and energetic condition on body molt intensity during the breeding season, only clutch size and sex had significant effects, with a negative effect of clutch size on body molt intensity in males but not in females. Based on these results, we develop a set of hypotheses to guide future studies on the potential tradeoffs between investment in reproduction and molt.

Seasonal expression of migratory behavior in a facultative migrant, the pine siskin

The vast majority of what is known about migration comes from studies of obligate migration—regular and predictable “to-and-fro” seasonal movements. Much less is known about facultative migration, which occurs less predictably in space and time. Here, we use pine siskins (Spinus pinus), nomadic and irruptive finches, as a captive model to advance our understanding of facultative migration. Building on approaches used to study obligate migration, we investigate whether pine siskins exhibit migratory restlessness in captivity, similar to obligate migrants, and whether pine siskins express a seasonal pattern of migratory behavior. Pine siskins exhibited nocturnal migratory restlessness that was remarkably similar to that in obligate migrants; it was characterized by jumping and wing whirring behavior that was preceded by a period of quiescence. This behavior was expressed seasonally, peaking in the spring, when free-living pine siskins frequently migrate. As in many obligate migrants, migratory restlessness in pine siskins coincided with elevated body condition and showed minimal overlap with body molt. Although pine siskins are both nocturnal and diurnal migrants, patterns of diurnal activity did not mirror patterns of nocturnal activity and were more difficult to interpret. Free-living pine siskins frequently migrate in the fall, but in captivity showed no clear pattern of fall migratory restlessness. We suggest that this could reflect a relatively predictable and programmed spring migration and a more facultative fall migration. Migrations are undertaken by a diverse array of animals and are important to the functioning of many ecosystems. The goal of this study was to shed light on an important, but understudied form of migration: facultative migration. Facultative migrations occur less predictably than the better-studied “to-and-fro” seasonal migrations of obligate migrants. Using a songbird, the pine siskin, as a model, we sought to determine if pine siskins express a migratory state in captivity and whether pine siskins exhibit a seasonal pattern of migratory behavior. We found that pine siskins showed behavioral and physiological changes associated with a migratory state, which were remarkably similar to those in obligate migrants. Pine siskins showed seasonal changes in migratory behavior in the study that suggest that this species has a predictable and programmed spring migratory period and a much more flexible fall migration.

Migration distance and breeding latitude correlate with the scheduling of pre-alternate body moult: a comparison among migratory waders

Moult is an important maintenance activity that should be carefully timed within the annual cycle. Many birds perform a pre-alternate moult of body feathers some time prior to the breeding season. In migrants, the timing of the pre-alternate moult coincides with the migration from wintering to breeding areas. In this study, we used visual plumage scores collected on the Continental Black-tailed Godwit Limosa limosa limosa in Portugal and The Netherlands to establish that the pre-alternate body moult of these birds during the northward migration between West Africa and The Netherlands takes place only in staging areas in the Iberian peninsula from late January to late February. A comparison of the moult strategy of these godwits with that of 20 other migratory wader populations (13 species) revealed that the former had a rather uncommon moult schedule which was more characteristic of populations with rather short migrations that breed at lower latitudes. We argue that this unusual moult schedule can be explained by a combination of ecological opportunity and proximate and ultimate trade-offs (hormonal incompatibly and maximization of plumage quality vs. time spent on migration, respectively).

Effect of food on seasonal response in Indian weaver bird (Ploceus philippinus)

We investigated the effect of normal (adlib) and supplementary food on body mass, testes growth, moult and plumage color in Indian weaver birds. Birds intially were kept under natural day length (NDL) and then exposed to short day lengths (8 h light: 16 h darkness) for at least 2 weeks before being subjected to an experimental regime. They were divided into five groups (n=4 each), groups 1 and 2 were held under SDL (Short day length -8L: 16D), groups 3 and 4 were exposed to LDL (Long daylength-16L: 8D) and simultaneously group 5 held under natural day length, served as control. One group of SDL (Group 2) and LDL (group 3) as well as group 5 (NDL) were fed on grain with supplement proteinaceous food and groups 2 and 4 were fed on adlib food (grain) only. Observations on body mass, testis growth, bodymolt and plumage color were recorded bi weekly. A significant change in the body mass under both photoperiodic groups (SDL; group 2 and LDL; group 4), but the testicular growth was noticed on long day lengths (LDL: 16L: 8D) and control (NDL) group. However the supplement food modulated the testes growth, body molt, beak pigmentation and body plumage regeneration. Early feather regeneration was found in supplementary food group under long day length. It is suggested that the supplementary food, affects the timing of the development of secondary sexual characteristics.

Moult of three Tristan da Cunha seabird species sampled at sea

AbstractPrimary, tail and body moult of three seabirds from Tristan da Cunha archipelago were studied by castnetting offshore south Brazil from February 2006 to August 2007. Timing, duration and synchronization of primary and tail moult are described relative to the annual calendar. Body moult overlapped breeding in Atlantic yellow-nosed albatrosses (Thalassarche chlororhynchos), but tail and primary moult did not. Spectacled petrels (Procellaria conspicillata) had protracted body moult, whereas primary and tail moult were completed by August. We documented onset of primary moult during chick-rearing in spectacled petrels and great shearwaters (Puffinus gravis) of unknown breeding status, and suggest that the south-west Atlantic Ocean holds important numbers of moulting birds of both species during the summer–early autumn. The albatrosses and the spectacled petrels replaced rectrices alternately. Great shearwaters replaced rectrices outward, starting at the central pair. Primary, tail and body moult largely overlap in all three species, suggesting that the metabolic costs of primary moult may not be overly restrictive. Metabolic and nutritional ability to afford simultaneous moult of different feather tracts support the idea that impaired flight caused by wing moult is a strong factor driving no overlap of primary moult and breeding.

Moulting patterns drive within-individual variations of stable isotopes and mercury in seabird body feathers: implications for monitoring of the marine environment

One major limitation in the use of body feathers of seabirds as a monitoring tool of the trophic structure and contamination levels of marine ecosystems is the degree of heterogeneity in feather chemical composition within individuals. Here, we tested the hypothesis that moulting patterns drive body feather heterogeneity, with synchronous moult minimizing within-individual variations, in contrast to asynchronous feather growth. Chicks of white-chinned petrels Procellaria aequinoctialis (representative of bird chicks) and adults of king penguins Aptenodytes patagonicus (representative of adult penguins) that moult their body feathers synchronously showed very low within-individual variations in their feather δ13C and δ15N values and mercury (Hg) concentrations. By contrast, body feathers of adults of Antarctic prions Pachyptila desolata (representative of adult seabirds with asynchronous feather growth during a protracted moult) presented much higher within-individual variances for the three parameters. These findings have three important implications for birds presenting a synchronous body moult. (1) They suggest that all body feathers from the same individual have identical δ13C and δ15N values and Hg content. (2) They predict negligible within-individual variations in the body feather values of other useful stable isotopes, such as δ2H and δ34S, as well as in the concentrations of other compounds that are deposited in the keratin structure. (3) Analysis of one or any number of pooled body feathers is equally representative of the individual. In conclusion, we recommend that long-term routine monitoring investigations focus on birds presenting synchronous rather than asynchronous moult of body feathers both in marine and terrestrial environments. This means targeting chicks rather than adults and, for seabirds, penguins rather than adults of flying species.

Sex and age differences in the development of breeding plumage in the Wood Sandpiper Tringa glareola during spring migration in north-eastern Poland

We investigated the effects of sex and age on the progression of breeding plumage moult in the Wood Sandpiper, a migrant wader that shows weak sexual size dimorphism and no dichromatism. We sexed the birds by DNA and examined the plumage of 416 Wood Sandpipers caught at a spring stopover site in north-eastern Poland. We scored the proportion of new breeding-type feathers on the head, back and scapulars in 20%-wide stages, and summed these scores as a body moult index, and on the lesser and median wing coverts summed as a wing covert moult index. Only 10% of all these birds fully developed breeding plumage on the upper body and 8% had only 21-40% of new feathers there. About 90% of the birds had moulted less than half of their wing coverts. No Wood Sandpiper showed a complete breeding plumage. We investigated whether moult indices were related to the date of the bird's capture and its body mass adjusted for size, age and sex, using generalised linear models. The best model indicated that the body-moult index was significantly affected by age, sex and year. Immatures had a more advanced body moult than adults, and females were more advanced than males. None of the predictors had a significant effect on the wing-covert moult index.

Age structure and age-related differences in molt status and fuel deposition of Dunlins during the nonbreeding season at Chongming Dongtan in east China

Although most shorebirds exhibit deferred migration and deferred breeding during their first summer, Dunlins (Calidris alpina) migrate to breeding areas and breed during their first summer. First-year and adult Dunlins should, therefore, have similar fueling and molt patterns if energetic and physiological constraints are responsible for deferred migration. From 2006 to 2008, we examined the age structure of Dunlins during the nonbreeding season at Chongming Dongtan, an estuarine wetland in the Yangtze River estuary in east China, and examined the effects of date, age, and molt status on fuel deposition during migration and during the winter. The Dunlin population at Chongming Dongtan was composed primarily of first-year birds. Most adults and first-year birds arrived together in late August. Regression analyses indicated that age, date, and molt status affected fuel deposition (as indicated by body mass) of Dunlins. Adults had significantly greater fuel deposits than first-year Dunlins near the end of northward migration (May: adults 70.8 ± 6.4 g, first-year 63.8 ± 8.0 g) and at the start of southward migration (September: adults 50.2 ± 6.1 g, first-year 47.2 ± 4.9 g). Adults also had significantly higher fuel deposition rates than first-year Dunlins during northward migration. Nonetheless, first-year Dunlins migrate and breed in their first summer. Thus, other factors, such as migration distance and body size, may be more important in determining if first-year shorebirds defer migration during their first spring and summer. During boreal spring and autumn, first-year Dunlins in active body molt had greater body mass than those that had not initiated body molt or those in suspended molt, and premigratory fuel deposits for northward migration were greatest after prealternate molt was completed. These results suggest that body molt requires additional fuel deposits and imposes a constraint on fuel deposition for migratory flights. ©2011 The Authors. Journal of Field Ornithology

Migration within the annual cycle: species, sex and age differences

The three main energy-demanding events in the yearly cycles of birds—breeding, moult and migration—tend to occur at different times of year from one another, with minimal overlap. The sequence in which these various events occur varies according to the ecological conditions (including those encountered during migration) in which particular populations live, and in general, moult is more variable in timing than other events. Some migratory birds moult in their breeding areas after nesting is over, others moult at a staging area on migration, while others moult in winter quarters. Yet others show a split moult, replacing part of their plumage in one place and part in another, moult usually being arrested during the intervening migration. Split moults are often associated with split migrations, as the birds pause for several weeks on their journeys to replace their feathers. Different variants in these patterns occur in different geographical populations of the same species. Some types of birds overlap breeding and moult, and some also overlap moult and migration, especially body moult, which can occur without reducing flight efficiency. A few bird species, with short breeding cycles, have been found to nest in two different areas in a single year, separated by migration. In species in which the young are raised by only one parent, the other parent is able to begin post-breeding moult or migration at a much earlier date. In species in which individuals do not breed in their early years of life, moults and migrations are shifted into the more favourable period which in older birds is occupied by breeding. The main message of this review is the huge variation that occurs in the annual cycles of birds, in the timing and duration of different processes, the sequence in which they occur, and the degree of overlap between them. Variations occur not only between species and populations but also between sex and age-groups within the same population. It is suggested that many species remain in a state of suspended readiness for breeding, moult or migration, and can undertake any of these processes over a greater part of the year than that in which they are normally expressed. Two or more of these processes can remain in this state of readiness simultaneously, enabling the bird to suppress, advance or delay a particular process, according to the conditions in which it finds itself.

Population structure, biometrics and moult of migrant Purple Sandpipers Calidris maritima in southwest Iceland in spring

Capsule Iceland is a stop‐over site for a population of Purple Sandpipers that winter in Britain. Here, they accumulate fuel loads for onward migration along with birds that have wintered in Iceland. Aims To establish whether Purple Sandpipers from Britain stop‐over in Iceland during spring migration and, if so, to describe their population structure, changes in mass and moult. Methods Purple Sandpipers were cannon‐netted on the coast of the Reykjanes Peninsula in southwest Iceland during May 2003 and 2005. Birds were aged, sexed (some by DNA) and standard biometric measurements made. Active body moult was scored. Results Bill and wing lengths showed that the Purple Sandpipers we caught were similar to one of the populations that winter in Britain rather than Icelandic breeding birds. There were more males than females throughout the migration period (63% males for first‐year‐birds and 67% for adult birds). Accounting for a bias due to a higher percentage of males in a less usual habitat (muddy/sandy bays), the values for rocky sites were 52% males for first‐year birds and 62% for adults. The percentage of first‐year birds was 19% in 2003 and 32% in 2005, though the latter figure was biased by catches in muddy/sandy bays where there was a higher percentage of young birds. The percentage of first‐year birds was 25% on just the rocky shores in 2005. Many birds were in latter stages of body moult, and males were slightly in advance of females. Increasing mass showed that they were preparing for onward migration. The average increase of 0.58 g per day was similar to the rate measured in Orkney at an earlier point on the migration route. However, a high turnover of birds could be the reason for these low values. By late May, and close to the assumed departure date, the Purple Sandpipers of the different age/sex classes had fuel indices of 24–29% (33–42% of the lean mass). This was lower than that for the high Arctic sandpipers (Knots and Sanderlings) leaving southwest Iceland for Greenland and Canada. Conclusions Our study confirmed that Purple Sandpipers do stop‐over in Iceland, and the possible lower rate of fuel accumulation and smaller amount stored, compared with Knots and Sanderlings, suggests a different migration pattern.