Variation in the wing-clapping display of Clapper Larks

The pied plumage of the adult Black Sparrowhawk is rather exceptional in the genus Accipiter and it could be explained by functionality or by phylogenetic relationships. The moult pattern of museum specimens is presented, supplementing information from captive birds. The post-juvenile moulting sequence is similar to that of the Northern Goshawk. The moult of primaries starts at, or just after, the beginning of body moult; moult of the secondaries also starts early and progresses from three consecutive foci, and tail moult starts early but is less predictable. A few body feathers and tail feathers may remain in place until the second moult. The pied flank feathers appear at an early stage. Some adult specimens are in arrested annual moult. Two with definite serially-descendant moult were discovered; this is related to the fact that the species is known to be double-brooded. Serially descendant moult was not known in this species and is rarely mentioned in the genus. Possible functions of the pied plumage are discussed: crypsis, mimicry, hunting strategy, and sexual attraction. Its taxanomic status is obscure. Although the streaked juvenile plumage of the Black Sparrowhawk is similar to those of the Northern Goshawk A. gentilis, Meyer's Goshawk A. meyerianus and Henst's Goshawk A. hentsi, adult and juvenile plumages are variable within the genus, and thus are not a reliable indicator of taxanomic relationships.     

Why renew fresh feathers? Advantages and conditions for the evolution of complete post‐juvenile moult

Juveniles of several passerine species renew all of their fresh juvenile feathers immediately after fledging (complete post‐juvenile moult), in contrast to the majority, which perform a partial post‐juvenile moult. To understand the adaptive roles of this phenomenon we compared the quality of juvenile plumage in species that perform a complete post‐juvenile moult with that of species which perform a partial post‐juvenile moult; we similarly compared juveniles and adults in each of these groups. The quality of feathers was measured by mass of primaries, colour, and length. In species which perform a complete post‐juvenile moult the plumage quality of second‐year individuals, in their first breeding season, is similar to the plumage quality of adults, unlike those species that perform a partial post‐juvenile moult. In species which perform complete post‐juvenile moult, the quality of the feathers grown in the nest is lower than the quality of adult post‐breeding feathers. In contrast, in species which perform partial post‐juvenile moult the quality of the feathers grown in the nest is similar to that of adult post‐breeding feathers. We found that a complete post‐juvenile moult strategy is much more common 1) in residents and short‐distance migrants than in long‐distance migrants, 2) in southern latitudes, 3) in species with medium body mass and 4) in omnivores and granivores. Our results indicate two adaptive roles of the complete post‐juvenile moult strategy: 1) achieving high quality plumage in the first year which may increase individual survival probability and fitness and 2) allocating fewer resources to nestling plumage and more to nestling development, which enables the nestlings to leave the nest earlier, thus reducing the probability of encountering nest predators. We suggest that the complete post‐juvenile moult, immediately after fledging, is an optimal strategy in favourable habitats and under low time constraints, as in some tropical ecosystems.     

PTERYLOGRAPHY, PLUMAGE DEVELOPMENT AND MOULT OF JAPANESE QUAIL COTURNIX C. JAPONICA IN CAPTIVITY

Japanese Quail were kept in small cages under controlled conditions of temperature and light, and their pterylography and moult are described. There are 10 primaries, 14 secondaries and corresponding numbers of greater upper and lower wing coverts. The alula has four feathers and the tail from five to six pairs of feathers. There is an apterium in the dorso-pelvic tract similar to that in other quail genera. The arrangement of feathers in the ventral and cervical tracts appears to differ from that described for some North American quail.
The chicks hatch with a covering of natal down. Pre-juvenile moult can be seen when the chicks are three days old. Juvenile body plumage is complete in about 30 days; the sides of the face, around the eyes, are the last places to acquire feathers. The tenth and last juvenile primary to grow is mature when the chicks are 41 days old.
The moult in which the juvenile plumage is replaced overlaps the post-natal moult and in part of the ventral tract natal down is replaced by the first adult feathers. This makes it possible to sex the quail at 14 days old. The first adult moult is complete, in the body tracts, by the time the birds are five to six weeks old. The dropping of juvenile primaries commences at about three weeks old and ceases when about eight weeks old. Only from three to six primaries are replaced; most birds studied replaced five. The significance of this difference from other Galliformes is discussed; it is thought to be associated with the species' migratory behaviour. Quail which remained in the controlled laboratory environment did not undergo any further moult. All birds moulted when both temperature and light period were reduced and most birds moulted when the light period alone was reduced. Adult birds housed in small cages in an unheated, unlit shed underwent a complete moult between August and December in which all primaries were replaced. This moult took 8–14 weeks to complete.     

Plumage quality mediates a life-history trade-off in a migratory bird

Background

Moult is one of the most costly activities in the annual cycle of birds and most avian species separate moult from other energy-demanding activities, such as migration. To this end, young birds tend to undergo the first post-juvenile moult before the onset of migration, but in some species the time window for the pre-migratory feather replacement is too narrow. We hypothesized that in such species an increased investment in the structural quality of juvenile feathers may allow to retain juvenile plumage throughout the entire migratory period and delay moult until arriving at wintering grounds, thus avoiding a moult-migration overlap.

Methods

The effect of juvenile plumage quality on the occurrence of moult-migration overlap was studied in a migratory shorebird, the common snipe Gallinago gallinago. Ca. 400 of first-year common snipe were captured during their final stage of autumn migration through Central Europe. The quality of juvenile feathers was assessed as the mass-length residuals of retained juvenile rectrices. Condition of migrating birds was assessed with the mass of accumulated fat reserves and whole-blood hemoglobin concentration. Path analysis was used to disentangle complex interrelationships between plumage quality, moult and body condition.

Results

Snipe which grew higher-quality feathers in the pre-fledging period were less likely to initiate moult during migration. Individuals moulting during migration had lower fat loads and hemoglobin concentrations compared to non-moulting birds, suggesting a trade-off in resource allocation, where energetic costs of moult reduced both energy reserves available for migration and resources available for maintenance of high oxygen capacity of blood.

Conclusions

The results of this study indicate that a major life-history trade-off in a migratory bird may be mediated by the quality of juvenile plumage. This is consistent with a silver spoon effect, where early-life investment in feather quality affects future performance of birds during migration period. Our results strongly suggest that the juvenile plumage, although retained for a relatively short period of time, may have profound consequences for individuals’ fitness.

     

Plumage development and visual communication in the Greater Kestrel Falco rupicoloides near Pretoria,South Africa

Kemp, A. C. 1999. Plumage development and visual communication in the Greater Kestrel Falco rupicoloides near Pretoria, South Africa. Ostrich 70 (3&4): 220–224.

I trapped, marked, sexed and examined moult and softparts on 101 free-living Greater Kestrels Falco rupicoloides near Pretoria, South Africa, during 1975–1988.1 collected and plucked one kestrel to determine the number and mass of its feather tracts, as an index of materials invested in moult. I also examined moult on 72 museum specimens from southern Africa and observed plumage and softpart changes in four captive birds. During 1975–1979,1 made focal observations on free-living adult kestrels (males 181 h, females 262 h) and recorded monthly samples of their visual communication behaviours to the nearest minute.

Greater Kestrels can be aged for three successive plumage and softpart stages (juvenile, post-juvenile, adult). Plumage changes with potential signal effects involved only small investments at the post-juvenile and first adult moults (3.7% and 11% of total plumage mass respectively). Changes in colouration and communication behaviour correlated with relevant stages of the annual cycle, possibly to miminze conflict with territorial adults and age of first breeding. Remex and rectrix moult starts on average much later in relation to egglaying for Greater and some tropical kestrels than for some temperate species. This and other individual variation in timing may result for variations in nutritional status.     

Condition-dependent variation in the blue-ultraviolet coloration of a structurally based plumage ornament

After years of investigation into the function of sexually dimorphic ornamental traits, researchers are beginning to understand how bright plumage colour in birds acts as an intraspecific signal. This work has focused primarily on pigment-based ornaments because they are highly variable in patch size, hue and brightness for some species. In contrast, structurally based ornaments have been little studied, in part because they do not appear to be as variable as pigment-based ornaments. We investigated a structurally based plumage ornament in a wild population of blue grosbeaks (Guiraca caerulea), a sexually dimorphic passerine. We report plumage variation that extends into the ultraviolet region of the spectrum. The pattern of covariation between four out of five elements of plumage variation suggests that structurally based ornamentation is pushed towards extreme expression of the trait as predicted by the sexual selection theory. The ''bluest'' birds have the highest percentage of blue feathers on the body. These ornamental feathers reflect light maximally at the shortest wavelengths (ultraviolet), with the greatest intensity and the greatest contrast. Age may have some effect on expression of blueness. In addition, plumage variables are correlated with growth bars in tail feathers (a record of nutritional condition during moult in a non-ornamental trait). This suggests that the ornament is partially condition dependent. Thus, blue plumage in male grosbeaks may serve as an honest indicator of age and quality.     

Changes in carotenoid‐based plumage colour in relation to age in European Serins Serinus serinus

Yearling birds generally display duller colours than adults. This may be due to selection favouring birds with more intensely coloured plumage or to an increase in colour after the first complete moult. Most research to date on the topic has been carried out on species with structural plumage coloration or with carotenoid‐based coloration that is produced by the unmodified deposition of pigments. However, no study has been carried out on species whose carotenoids are metabolically modified before deposition. In this study, we assess age‐related changes in the carotenoid‐based coloration of European Serins, a species that metabolically processes carotenoids before they can be deposited into feathers. Birds were captured over consecutive years and we carried out both cross‐sectional and longitudinal analysis. Adults had significantly greater values of lightness and chroma than yearling birds. However, there were no changes in plumage colour when analysing the same individuals captured in subsequent seasons. Plumage lightness and chroma of adult males after moult were related to body mass, suggesting a role of body condition on plumage coloration. Our results suggest that changes in plumage coloration with age in European Serins are due to a selection process that favours more intensely coloured individuals.     

Seasonal Changes in Colour: A Comparison of Structural,Melanin- and Carotenoid-Based Plumage Colours

Background

Plumage coloration is important for bird communication, most notably in sexual signalling. Colour is often considered a good quality indicator, and the expression of exaggerated colours may depend on individual condition during moult. After moult, plumage coloration has been deemed fixed due to the fact that feathers are dead structures. Still, many plumage colours change after moult, although whether this affects signalling has not been sufficiently assessed.

Methodology/Principal Findings

We studied changes in coloration after moult in four passerine birds (robin, Erithacus rubecula; blackbird, Turdus merula; blue tit, Cyanistes caeruleus; and great tit, Parus major) displaying various coloration types (melanin-, carotenoid-based and structural). Birds were caught regularly during three years to measure plumage reflectance. We used models of avian colour vision to derive two variables, one describing chromatic and the other achromatic variation over the year that can be compared in magnitude among different colour types. All studied plumage patches but one (yellow breast of the blue tit) showed significant chromatic changes over the year, although these were smaller than for a typical dynamic trait (bill colour). Overall, structural colours showed a reduction in relative reflectance at shorter wavelengths, carotenoid-based colours the opposite pattern, while no general pattern was found for melanin-based colours. Achromatic changes were also common, but there were no consistent patterns of change for the different types of colours.

Conclusions/Significance

Changes of plumage coloration independent of moult are probably widespread; they should be perceivable by birds and have the potential to affect colour signalling.     

Prebreeding moult, plumage and evidence for a presupplemental moult in the Great Knot Calidris tenuirostris

We studied the prebreeding moult and resulting plumage in a long-distance migrant sandpiper (Scolopacidae), the Great Knot Calidris tenuirostris , on the non-breeding grounds (northwest Australia), on arrival at the staging grounds after the first migratory flight (eastern China) and on or near the Russian breeding grounds (Russian data from museum specimens). We show that breeding plumage scores and breast blackness were affected not only by the increase in moulted feathers but also in the wearing down of overlaying pale tips of fresh feathers. Birds migrating from Australia and arriving in China had completed or suspended moult, but more moult must occur in Asia as Russian specimens had moulted more of their mantle and scapular feathers. Russian birds had significantly more red feathering on their upperparts than had birds in Australia or those arriving in China. The increase in reddish feathers cannot by accounted for simply by continuation of the prealternate moult. Instead, a third, presupplemental moult must occur, in which red-marked feathers replace some scapular and especially mantle feathers that were acquired in a prealternate moult only 1–3 months earlier. Great Knot sexes show little size and plumage dimorphism, whereas two other sandpipers that have supplemental plumages (Ruff Philomachus pugnax and Bar-tailed Godwit Limosa lapponica ) are thought to be highly sexually selected. Bidirectional sexual selection may therefore be involved in the evolution of a supplemental plumage in Great Knots.     

Feather isotope analysis discriminates age-classes of Western, Least, and Semipalmated sandpipers when plumage methods are unreliable

ABSTRACT Avian age‐class discrimination is typically based on the completeness of the first prebasic molt. In several calidrid sandpiper species, juvenal flight feathers grown on Arctic breeding grounds are retained through the first three migrations. Thereafter, flight feathers are grown annually at temperate migratory stopover sites during the fall or on the subtropical wintering grounds. Standard methods for distinguishing age classes of sandpipers rely on a combination of traits, including body plumage, coloration of protected inner median covert edges, and extent of flight feather wear. We tested the ability of stable hydrogen isotope ratios in flight feathers (δD_f) to distinguish young birds in their first winter through second fall from older adults in three calidrid sandpiper species, Western (Calidris mauri), Least (C. minutilla), and Semipalmated (C. pusilla) sandpipers. We compared the apparent reliability of the isotope approach to that of plumage‐based aging. The large expected differences in δD_f values of flight feathers grown at Arctic versus non‐Arctic latitudes enabled use of this technique to discriminate between age‐classes. We determined δD_f values of known Arctic‐grown feathers from juveniles that grew their flight feathers on the breeding grounds. Flight feather δD_f values of southward‐migrating adults showed bimodal distributions for all three species. Negative values overlapped with species‐specific juvenile values, identifying putative second fall birds with high‐latitude grown juvenal feathers retained from the previous year. The more positive values identified older adults who grew their feathers at mid‐ and low latitudes. Importantly, δD_f analysis successfully identified first‐winter and second‐fall birds not detected by plumage‐based aging. Flight feather wear alone was a poor basis for age classification because scores overlapped extensively between putative second fall birds and older adults. Flight feather hydrogen isotope analysis enables more definitive assignment of age classes when standard plumage methods are unreliable.     

MOULT IN FIVE SPECIES OF CORVIDAE IN BRITAIN

This paper presents objective methods for measuring moult and uses them to describe the pattern and rate of the complete moult as a component of the annual cycle in Corvus corone, C. frugilegus, C. monedula, Pica pica and Garrulus glandarius in Britain. The basis of the methods used to measure the rate of moult was the dry weight of the whole plumage and its component tracts and feathers. Within whole tracts of flight feathers showing diversity of size, the longer feathers grew in length a little faster than the others by accumulating feather material very much faster. Thus, for the flight feathers at least length by itself was a poor indicator of size, but, if first related to weight, could be used to predict weight. Hence, to enable realistic comparisons to be made between different flight feathers and tracts of flight feathers on a given individual bird or on individuals of different species, a ‘units’ system was created which would take account of such variations in size. This information provided a standard against which the growth of new flight feathers in a specimen collected in the field could be measured. The progress of moult in each tract was indicated by the sum of the units. In addition, for both the flight feathers and all other tracts, the duration of moult was measured from the start and finish in each tract as indicated by the proportion of birds having either growing or entirely fully-grown feathers in each tract. In the annual cycle body weight and abdominal fat weight were at a maximum in mid-winter and at a minimum in mid-summer in Corvus; variations in these items were apparently absent in G. glandarius. In Corvus probably only post-second-year birds breed, but in P. pica some second-year individuals do so as well; also, increase in testes size in second-year males was greatest in P. pica. The patterns of the relative seasonal timing of the start and finish of moult in each tract were most similar in the three Corvus species, in which moult in the whole plumage began in the primary tract and finished in tracts on the body; P. pica differed principally in the extended growth of the secondary tract; G. glandarius differed in that moult began in the dorsal tract. By summing the data from individual tracts, a measure of the rate of growth in the whole plumage was obtained: all five species moulted at essentially the same time of year. In the primary, secondary, tertiary and rectricial tracts the seasonal accumulation of dry weight of feather material in each tract followed a sigmoid pattern; in the alula tract dry weight increased most rapidly at the beginning. These patterns were correlated with the numbers of feathers growing at different stages in each tract. The primary tract accumulated dry matter at the highest relative rate, while the rectricial, secondary, tertiary and alula tracts did so at successively lower rates. The maximum relative rate of increase in dry weight in any given tract of flight feathers was fairly similar in all five species, but was possibly related inversely to body weight. Maximum absolute rates of increase in dry tract weight were also calculated. During the springtime period when non-moulting and moulting birds were present simultaneously in the population, no difference could be detected between these groups in any species in body and fat weights; in individuals obtained together with evidence of reproductive activity, few had begun primary moult, but in post-second-year C. frugilegus with branchers, males began before females; in C. corone and C. frugilegus testes weight was lower in moulting than in non-moulting birds. In conclusion, some aspects of moult for further research are suggested.     

Testosterone treatment of female Superb Fairy-wrens Malurus cyaneus induces a male-like prenuptial moult, but no coloured plumage

When selection strongly favours a testosterone-dependent trait in males, and this trait is not beneficial to females, a correlated response to selection in females, which also circulate some testosterone, could slow the rate of evolution in males. Here I investigate whether experimental testosterone treatment in female Superb Fairy-wrens Malurus cyaneus can induce the testosterone-dependent sexually selected moult into nuptial plumage, as it does in males. Silastic testosterone implants in females rapidly induced a moult akin to the male prenuptial moult, involving all body areas that are colourful in nuptial males (head, upper back, ear tufts, breast). Moreover, the newly moulted feathers had a similar glistening appearance and morphology as male nuptial feathers. However, the treatment failed to induce production of the blue and black structural colours, and the breast and ear tufts were lighter than the normal grey-brown feathers of females and males in eclipse plumage. Microscopic and ultrastructural analyses of these unusual feathers could further our understanding of structural colour production.     

MOULT OF BUDGERIGARS MELOPSZTTACUS UNDULATUS

In captive Budgerigars Melopsitticus undulatus moult of primaries started in the middle of the tract and moved progressively inwards and outwards, the inner feathers being replaced faster than the outer ones. Full replacement of primaries took six to eight months and a new cycle of moult usually started before completion of the old cycle. Moult of secondaries followed no clear pattern and occurred less frequently than moult of primaries. Moult of rectrices started with the middle pair and moved progressively outwards on both sides. Complete moult of rectrices took about six months and a new cycle often started before completion of the old. Moult of the head and body occurred intermittently throughout the year. Birds fledged in juvenal plumage, they passed into first basic plumage with a partial moult (head and body feathers) and into definitive basic plumage with a moult of all contour feathers.
In the field in inland mid-eastern Australia, there were some birds replacing feathers and some with complete plumage in most months of the year. Birds with complete plumage may have been between moults or within a moult and between replacement of feathers. The proportion of birds in moult did not increase in intensity after breeding, or cease during breeding or before movements. Some birds of both sexes with gonads in a reproductive condition were replacing feathers. Rirds that were replacing feathers had similar lipid deposits to birds that had a complete plumage.     

Entwicklung und Mauser der Spinalflur bei der Bartmeise(Panurus biarmicus)

Zusammenfassung Die Spinalflur nestjunger Bartmeisen(Panurus biarmicus) wird etwa rhombenförmig angelegt. Ihre lateralen Federn werden jedoch schwach ausgebildet und erinnern an Plumae; sie werden sehr bald abgeworfen, so daß flügge Vögel eine schmale, bandförmige Rückenflur haben, die seitlich von nackter Haut (auf der manchmal letzte Federchen sitzen) begrenzt wird. Dieser laterale Teil der Spinalflur kann dann makroskopisch von einem Rain nicht unterschieden werden.Vor Beginn der Jugendvollmauser werden in diesem lateralen Rückenflurbereich durch die Haut Federanlagen sichtbar; die Mauser der Rückenflur (und sehr oft die Mauser überhaupt) wird bei 60% der untersuchten Vögel durch gleichzeitig einsetzendes Wachstum dieser Federn eingeleitet. Die Rückenflur der vermauserten Vögel ist wieder rhombisch wie beim Nestling und bleibt dies fortan.Altvögel werfen lange vor Beginn der Mauser die meisten Plumae ab; die Unterdrückung der lateralen Rückenflur bei Jungvögeln ist wohl eine Analogie dazu.Die Mauser der Rückenflur setzt großflächig ein und unterscheidet sich dadurch von der der Schulter- und Unterflur, wo sie reihenweise, von der Flurmitte ausgehend, erfolgt.Die gesamte Mauser der Bartmeise dauert etwa 50–60 Tage.

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Summary In Bearded Tits(Panurus biarmicus) which are a few days old, the dorsal feather tract is of rhombic shape. The feathers in the lateral part of this tract are feebly developed and are shed soon after the birds leave the nest. Thus the dorsal tract of these birds is in the form of a narrow stripe, flanked by naked skin on both sides. Before the onset of the complete post-juvenile moult, papillae of feathers begin to be visible again under the skin in this area. In 60% of the investigated birds, the growth of dorsal feathers began here, and in many cases this represented the start of the growth of adult plumage as well. The dorsal tract in adult birds is of rhombic shape again and remains so for the rest of their life.Adult Bearded Tits shed their down long before moult. It can, therefore, be concluded that this and the suppression of dorsolateral feathers in juvenile plumage are analogous phenomena.In the dorsal tract of moulting Bearded Tits, feather growth begins in one to three centers simultaneously, whereas moult in the ventral and shoulder tracts starts with the inner rows and proceeds towards the outer ones.Whole moult lasts about 50–60 days in Bearded Tits.

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Herrn Prof. Dr. Rainer Schubert-Soldern zum 70. Geburtstag herzlichst gewidmet.     

Increase of feather quality during moult: a possible implication of feather deformities in the evolution of partial moult in the great tit Parus major

Here we investigate the change in feather quality during partial post‐juvenile and complete post‐breeding moult in great tit Parus major by measuring the change in the number of fault bars and feather holes on wing and tail feathers. Feathers grown during ontogeny usually are of lower quality than feathers grown following subsequent moults at independence. This is reflected by higher number of fault bars and feather holes on juveniles compared to adults. Fault bars are significantly more common on tail and proximal wing feathers than on the distal remiges, indicating a mechanism of adaptive allocation of stress induced abnormalities during ontogeny into the aerodynamically less important flight feathers. On the contrary, feather holes produced probably by chewing lice have a more uniform distribution on wing and tail feathers, which may reflect the inability of birds to control their distribution, or the weak natural selection imposed by them. The adaptive value of the differential allocation of fault bar between groups of feathers seems to be supported by the significantly higher recapture probability of those juvenile great tits which have fewer fault bars at fledging on the aerodynamically most important primaries, but not on other groups of flight feathers. The selection imposed by feather holes seems to be smaller, since except for the positive association between hatching date, brood size and the number of feather holes at fledging, great tits' survival was not affected by the number of feather holes. During post‐juvenile moult, the intensity of fault bars drops significantly through the replacement of tail feathers and tertials, resulting in disproportional reduction of the total number of fault bars on flight feathers related to the number of feathers replaced. The reduction in the number of fault bars during post‐juvenile moult associated with their adaptive allocation to proximal wing feathers and rectrices may explain the evolution of partial post‐juvenile moult in the great tit, since the quality of flight feathers can be increased significantly at a relatively small cost. Our results may explain the widespread phenomenon of partial post‐juvenile moult of flight feathers among Palearctic passerines. During the next complete post‐breeding moult, the total number of fault bars on flight feathers has remained unchanged, indicating the effectiveness of partial post‐juvenile moult in reducing the number of adaptively allocated fault bars. The number of feather holes has also decreased on groups of feathers replaced during partial post‐juvenile moult, but the reduction is proportional with the number of feathers moulted. In line with this observation, the number of feather holes is further reduced during post‐breeding moult on primaries and secondaries, resulting in an increase in feather quality of adult great tits.     

The moult of the Little Stint Calidris minuta in the Kenyan rift valley

Moult data were collected during 1967–80 from some 6900 Little Stints in the southern Kenyan rift valley.
Adults typically moulted from summer to winter body and head plumage during September and early October, soon after arrival. The complete pre-winter wing and tail moult began in most adults between mid-September and early October. Some birds finished by December, but others continued until February and March. Individual duration was usually between 100 and 150 days. Adults which completed this moult early often remoulted outer primaries between January and early April.
Young birds acquired first-winter body plumage during October and early November. Some 90% had a complete pre-winter wing and tail moult. This usually began between December and early February, and finished during March or early April, taking about 70–100 days. In about 10% of young birds, flight feather moult was restricted to the outer primaries and inner secondaries. Birds adopting this strategy typically began moult late, during January or February. Short periods of suspension were common during pre-winter wing moult, particularly in adults. The difference in moult speed between adult arid first-winter birds was attributable in the primary, secondary and tail tracts to differences in numbers of growing feathers.
Practically all birds completed a pre-summer moult involving the entire body and head plumage, most of the tertials, some or all of the tail feathers and many wing coverts. Most birds began this moult between early February and late March, and finished between mid-April and early May. It was typically later and more rapid in first-year birds than adults. In late birds, the onset of pre-summer moult was linked to the final stages of pre-winter moult.
The wing moult of the Little Stint in different wintering areas is discussed. First-winter moult strategy is compared with that in other small Calidris species.     

Experimental evidence that a large raptor can detect and replace heavily damaged flight feathers long before their scheduled moult dates

Because many species of large birds must remain capable of flight during moult and breeding, complete replacement of all flight feathers often takes two or more years, with the result that their plumage normally includes many faded, worn and sometimes even broken feathers. It seems adaptive for such birds to have the ability to quickly replace severely damaged feathers. In search of such a feather replacement mechanism, we cut rectrices on a captive Golden Eagle Aquila chrysaetos and found that feathers cut in their first year of use were replaced, on average, after 11.4 months, whereas uncut feathers before and during the experiment were moulted, on average, after 24 months of use. Feather cutting advanced moult, on average, in excess of a year and thereby demonstrates the existence of a previously undescribed neurophysiological mechanism for preferentially replacing damaged feathers.     

Early exposure to a bacterial endotoxin advances the onset of moult in the European starling

In animals, events occurring early in life can have profound effects on subsequent life‐history events. Early developmental stresses often produce negative long‐lasting impacts, although positive effects of mild stressors have also been documented. Most studies of birds have investigated the effects of events occurring at early developmental stages on the timing of migration or reproduction, but little is known on the long‐term effects of these early events on moulting and plumage quality. We exposed European starling Sturnus vulgaris nestlings to an immune challenge to assess the effects of a developmental stress on the timing of the first (post‐juvenile) and second (post‐breeding) complete annual moult, the length of the flight feathers, and the length and colouration of ornamental throat feathers. The nestlings were transferred to indoor aviaries before fledgling and kept in captivity until the end of post‐breeding moult. Individuals treated with Escherichia coli lypopolysaccharide (LPS) started both moult cycles earlier compared to control siblings. Moult duration was unaffected by the immune challenge, but an advanced moult onset resulted in a longer moult duration. Moreover, female (but not male) throat feather colouration of LPS‐injected individuals showed a reduced UV chroma. We argue that an early activation of the immune system caused by LPS may allow nestlings to better cope with post‐fledging stresses and lead to an earlier moult onset. The effect of early LPS exposure was remarkably persistent, as it was still visible more than one year after the treatment, and highlighted the importance of early developmental stresses in shaping subsequent major life‐history traits, including the timing of moult in birds.