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.     

Moult of three Palaearctic migrants in their West African winter quarters

Some theories about moult strategies of Palaearctic passerine migrants assume that birds adapt timing of moult to environmental conditions such as rainfall on their African wintering grounds. Species wintering in the northern tropics should limit moult to the period shortly after their arrival at the end of the rainy season. Passerine migrants wintering in West Africa should also moult more rapidly compared to related species or conspecific populations that moult elsewhere. We investigated the moult of melodious warblers Hippolais polyglotta, willow warblers Phylloscopus trochilus and pied flycatchers Ficedula hypoleuca wintering in Comoé National Park, Ivory Coast, between October 1994 and April 1998. In contrast to previous studies we did not restrict our analyses to moult of flight feathers but also included moult of body feathers. The results differed partially from the general assumptions of previous authors. Melodious warblers moulted twice: a complete moult shortly after their arrival, and a moult of body feathers and in some cases some tertials and secondaries in spring. Willow warblers moulting flight feathers were found between December and March with the majority moulting in January and February. Primary moult was not faster compared to populations moulting in central Africa and South Africa. Body feather moult varied strongly among individuals with birds in heavy moult between December and April. Pied flycatchers moulted body feathers and tertials between January and April. Birds with growing feathers were found throughout the whole period including the entire dry season. Moult strategies are thus not readily related to a few environmental factors in general and our results show that factors other than mere resource availability during certain times on the wintering grounds are likely to govern the timing of moult.Communicated by F.Bairlein     

The ‘chaotic’ flight feather moult of the Steppe Buzzard Buteo buteo vulpinus

Steppe Buzzards breed in Eurasia and spend the non-breeding season in Africa. Adults moult some flight feathers during the breeding season and some during the non-breeding season. Moult is arrested during migration. The extent of moult of flight feathers in adults is highly variable between individuals in southern Africa, with the renewal of two primaries, three secondaries and five rectrices as the most frequently encountered pattern. Time spent on the non-breeding grounds in South Africa is too short to allow for a sequential moult. Moult of flight feathers is restricted to the almost synchronous dropping of a number of feathers upon arrival, with few being replaced subsequently. Any of the flight feathers can be replaced in southern Africa, and the pattern of renewal in primaries and secondaries cannot be distinguished from random. Tail feathers are replaced in an alternating (transilient) pattern. Moult in the non-breeding areas may primarily be complementary to moult on the breeding grounds, but these two partial moults per year are insufficient to renew all flight feathers annually. Middle secondaries and central tail feathers are regularly carried over to a third moult, but this is rare for primaries.     

Continent-wide variation in feather colour of a migratory songbird in relation to body condition and moulting locality

Understanding the causes of variation in feather colour in free-living migratory birds has been challenging owing to our inability to track individuals during the moulting period when colours are acquired. Using stable-hydrogen isotopes to estimate moulting locality, we show that the carotenoid-based yellow-orange colour of American redstart (Setophaga ruticilla) tail feathers sampled on the wintering grounds in Central America and the Caribbean is related to the location where feathers were grown the previous season across North America. Males that moulted at southerly latitudes were more likely to grow yellowish feathers compared with males that moulted more orange-red feathers further north. Independent samples obtained on both the breeding and the wintering grounds showed that red chroma-an index of carotenoid content-was not related to the mean daily feather growth rate, suggesting that condition during moult did not influence feather colour. Thus, our results support the hypothesis that feather colour is influenced by ecological conditions at the locations where the birds moulted. We suggest that these colour signals may be influenced by geographical variation in diet related to the availability of carotenoids.     

European Swallows Hirundo rustica in Botswana during three non-breeding seasons: the effects of rainfall on moult

van den Brink, B., Bijlsma, R.G. & van der Have, T.M. 2000. European swallows Hirundo rustica in Botswana during three non-breeding seasons: the effects of rainfall on moult. Ostrich: 71 (1): 198–204.

The rate of moult of European Swallows spending the non-breeding season in Botswana was studied during December-January of 1992/93,1993/94 and 1994/95 to investigate the effects of variability in rainfall and roosting habitat availability. In January 1994, 2–3 million European Swallows were counted at a traditional roost along the Boteti River. The rate of moult was relatively slow, about one feather (primary, secondary or tail feather) was replaced every two weeks in both adults and juveniles. The speed of moult in juveniles was generally lower than in adults, in particular of secondaries and tail feathers. Moulting rate of both primaries and tail feathers was lowest in 1994/95 during a period of drought and coincided with the almost complete destruction of roosting habitat. In 1992/93, moulting rate was highest when rainfall was moderate and roosting habitat abundant. Moulting rate was intermediate in 1993/94 when rainfall was frequent but roosting habitat reduced because of the low water level in the Boteti River. The combined effect of reduced food availability during droughts and higher densities and longer foraging flights when roosting habitat is scarce might explain the annual variation in moulting rate. From the second week of January onwards many adults started moulting the outermost tail feather before the penultimate feathers. This phenomenon could indicate the importance of long tail streamers in aerial manoeuvring when foraging during the return migration to the breeding grounds.     

The moult of Barred Warblers Sylvia nisoria in Kenya—evidence for a split wing-moult pattern initiated during the birds' first winter*

The moult of Barred Warblers Sylvia nisoria was studied during three winter seasons in southeastern Kenya at a southward passage site (Ngulia) and a wintering site (Mtito Andei). Most Barred Warblers migrating through Ngulia in November had yet to commence winter moult. These birds probably moulted subsequently in winter in northern Tanzania. In December, birds were found in heavy moult at Mtito Andei, and some of these birds were known to stay throughout the winter. By contrast, most birds reaching southeastern Kenya from late December onwards had already completed part or all of their winter moult, presumably at stopover sites in northern and eastern Kenya or in Ethiopia. Thus, winter moult in Barred Warblers takes place mainly in late November and December, either just before or soon after the final leg of autumn migration. In general, first-year birds renewed all tertials and tail feathers, about three to five secondaries per wing and commonly also the outer one to four large primaries per wing. Adults renewed all tertials and tail feathers, almost all secondaries and only occasionally an outer primary. The replacement of relatively fresh juvenile secondaries during the birds' first winter implies that the split moult pattern of this species (secondaries, tertials and tail moulted in winter; primaries and tertials in summer) is endogenously controlled.     

Brown tawny owls moult more flight feathers than grey ones

The mechanisms by which melanin‐based colour polymorphism can evolve and be maintained in wild populations are poorly known. Theory predicts that colour morphs have differential sensitivity to environmental conditions. Recently it has been proposed that colour polymorphism covaries genetically with intrinsic and behavioural properties. Plumage moult is a costly and crucial somatic maintenance function in birds. We used a long‐term data set consisting of 761 observations on 307 individuals captured between 1985 and 2010 to examine differences in partial flight feather moult between grey (pale) and brown (pheomelanic dark) colour morphs of the tawny owl. We find that the brown morph consistently moult more primary flight feathers than the grey morph whereas there is no clear difference between colour morphs in the moulting of secondary feathers. Contrary to expectations, the difference in the number of moulted flight feathers between the morphs was independent of environmental conditions, as quantified by the abundance of prey. We discuss the potential physiological and behavioural causes for and costs of the observed difference in maintenance functions between colour morphs.     

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.     

Non‐moulted primary coverts correlate with rapid primary moulting

Time constraint is a main factor which affects the moult strategies in passerines, mainly during the first year of life. The variability of moult strategies between species is associated with the extent of the moult. In the first year of life, the extent of the moult is highly variable between species and individuals. In most passerine species, juveniles only renew some of their feathers, but the factors that govern which feathers are renewed and which are retained have been largely overlooked. Here we examine the common pattern of non‐moulted primary coverts (PC) in passerines during the first‐year moult cycle (post‐juvenile and first‐year pre‐breeding moults). On the interspecific level we found that among 63 species of passerines, PCs are the least commonly moulted feather tract. For five species (Hirundo rustica, Pycnonotus xanthopygos, Prinia gracilis, Acrocephalus stentoreus and Passer moabiticus) which perform a complete post‐juvenile moult, we found that the PC moult occurs over a longer period than greater coverts (GCs) and is sequential (non‐simultaneous). At the intraspecific level, we found that the main difference between a partial and complete moult in Prinia gracilis is the moulting or non‐moulting of the PCs. We also demonstrate that for Prinia gracilis 1) juveniles which do not moult their PCs, moult their primaries at a higher speed than those which moult their PCs and 2) area/mass ratio of PCs is lower than of GCs. These two findings may explain why many passerines skip PC renewal during the first year of life. Because the PC moult lasts a long time, forgoing this moult enables long term resource savings that allow for dealing with time constraints. Our results highlight the adaptive advantages of non‐moulted PCs in cases of time constraints.     

Plasticity in moult speed and timing in an arctic‐nesting goose species

Environmental constraints are strong in migratory species that breed in the Arctic. In addition to breeding, Anatidae have to renew all their flight feathers during the short arctic summer. We examine how temporal constraints and climate affect the phenology of flight feather moult in the greater snow goose Chen caerulescens atlantica, a High Arctic nesting species. We used a database of 1412 moulting adult females measured over 15 yr on Bylot Island, Nunavut. Ninth (9th) primary length was used to determine the moult stage and speed of feather growth. We found a positive relationship between median annual hatching and moult initiation dates and the slope did not differ from 1. The interval between hatching and moult initiation was thus rather fixed and geese did not initiate moult earlier when reproductive phenology was delayed. Nonetheless, there was no relationship between median hatching date and the date at which birds regained flight capacity, suggesting that date of end of moult is independent of the reproductive phenology. There was a trend for an increase in the speed of flight feather growth in years with delayed hatching date. This is the most likely mechanism that could explain moult phenology adjustment in this species. Finally, we found a positive relationship between 9th primary length (corrected for inter‐annual variations) and body condition, suggesting a delay in moulting for individuals in poor condition. These results suggest that moult plasticity is primarily governed by variations in feather growth speed. This phenotypic plasticity could be necessary to complete flight feather renewal before the end of the arctic summer, independently of reproductive phenology and spring environmental conditions. Our novel results suggest possible phenological adjustments through moult speed, which was considered constant in geese until now.     

Biannual complete moult in the Black-chested Prinia Prinia flavicans

The Black-chested Prinia Prinia flavicans shows two distinctive periods each year during which adult birds undergo a complete moult: there is a fast moult (about 67 days) in spring (September-November) involving all birds simultaneously and a slower moult (about 108 days) in autumn (February-June), when about 95% of adults are moulting during April. A biannual complete moult pattern was also shown to occur in individual birds. The pattern of secondary replacement was variable and unusual for a passerine; the majority replaced S8 to S5/S4 descendantly, or had feathers being renewed ascendantly amongst S4-S7 before the ascendant series starting from the outermost secondary reached the middle secondaries. The descendant series tended to be longer during the autumn moult with S4 most frequently being the last to be replaced in autumn, but S5 last in spring. Breeding was erratic during summer in response to rains and sometimes overlapped extensively with moulting, the onset of which was less variably timed. When breeding occurred during the autumn moult, the new plumage was not the usual winter plumage (without the chest-band), but a new summer plumage.     

Annual routines of non-migratory birds: optimal moult strategies

In a periodically changing environment it is important for animals to properly time the major events of their life in order to maximise their lifetime fitness. For a non-migratory bird the timing of breeding and moult are thought to be the most crucial. We develop a state-dependent optimal annual routine model that incorporates explicit density dependence in the food supply. In the model the birds' decisions depend on the time of year, their energy reserves, breeding status, experience, and the quality of two types of feathers (outer and inner primaries). Our model predicts that, under a seasonal environment, feathers with large effects on flight ability, higher abrasion rate and lower energetic cost of moult should be moulted closer to the winter (i.e. later) than those with the opposite attributes. Therefore, we argue that the sequence of moult may be an adaptive response to the problem of optimal timing of moult of differing feathers within the same feather tract. The model also predicts that environmental seasonality greatly affects optimal annual routines. Under high seasonality birds breed first then immediately moult, whereas under low seasonality an alternation occurs between breeding and moulting some of the feathers in one year and having a complete moult but no breeding in the other year. Increasing food abundance has a similar effect.     

Resistance of flight feathers to mechanical fatigue covaries with moult strategy in two warbler species

Flight feather moult in small passerines is realized in several ways. Some species moult once after breeding or once on their wintering grounds; others even moult twice. The adaptive significance of this diversity is still largely unknown. We compared the resistance to mechanical fatigue of flight feathers from the chiffchaff Phylloscopus collybita, a migratory species moulting once on its breeding grounds, with feathers from the willow warbler Phylloscopus trochilus, a migratory species moulting in both its breeding and wintering grounds. We found that flight feathers of willow warblers, which have a shaft with a comparatively large diameter, become fatigued much faster than feathers of chiffchaffs under an artificial cyclic bending regime. We propose that willow warblers may strengthen their flight feathers by increasing the diameter of the shaft, which may lead to a more rapid accumulation of damage in willow warblers than in chiffchaffs.     

Adaptive fault bar distribution in a long‐distance migratory,aerial forager passerine?

Fault bars are translucent bands produced by stressful events during feather formation. They weaken feathers and increase their probability of breakage, and thus could compromise bird fitness by lowering flight performance. It has been recently suggested ('fault bar allocation hypothesis') that birds could have evolved adaptive mechanisms for reducing fault bar load on the feathers with the highest function during flight. We tested this hypothesis by studying first-year individuals of the long-distance migratory, aerial forager barn swallow Hirundo rustica . We predicted that fault bars should be less abundant on the outermost wing and tail feathers, but more frequent on the tail than on the outermost wing feathers. Accordingly, we found that fault bars occurred more often in tertials than in primaries or secondaries. Tail feathers had fewer fault bars than tertials, but more than primaries. Within the tail, the distribution pattern of fault bars was W-shaped, with the highest fault bar load occurring on the streamers and on the two central feathers. Because streamers are the most important tail feathers for flight performance, this finding seems to contradict the 'fault bar allocation hypothesis'. However, flight performance is much less sensitive to changes in the shape of the tail than of the wings, which could explain why evolutionary forces have not counteracted the increase of fault bars associated with feather elongation during the recent evolution of streamers in the tail of hirundines.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 455–461.     

Moult in Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma

We recorded the age of individual wing and tail feathers of Black-browed and Grey-headed Albatrosses Diomedea melanophris and D. chrysostoma of known age and breeding status at Bird Island, South Georgia. Breeders and non-breeders of both species moult their rectrices annually. Non-breeders moult primaries biennially. In the first year of a cycle, the outer three and some inner primaries are moulted descendantly; in the next year the inner primaries are moulted ascendantly, starting from primary seven. There is a general progression to moulting equal numbers of primaries in each half of the cycle by the time breeding starts at about 10 years of age. Grey-headed Albatrosses usually moult fewer primaries than Black-browed Albatrosses, particularly as 3-year-olds, when they undertake substantial plumage change in body moult. Most secondaries in Black-browed Albatrosses have been replaced once by age 4 years. Breeding Black-browed Albatrosses continue the moult pattern established as immatures whether they fail or not, as do failed Grey-headed Albatrosses. Successful Grey-headed Albatrosses, which breed again 16 months later, moult their three innermost primaries after breeding in the remainder of the current year and, after a period when moult is interrupted, renew the remaining primaries the following year. Comparisons between species and between failed and successful birds within species indicate that moult rate is not closely linked to the length of the interval between breeding attempts. Interspecies differences are better explained by breeding latitude, with tropical albatrosses moulting twice as fast as sub-Antarctic species, possibly reflecting food availability outside the breeding season.     

THE MOULT OF REMIGES AND RECTRICES IN GREAT BLACK-BACKED GULLS LARUS MARZNUS AND GLAUCOUS GULLS L. HYPERBOREUS IN ICELAND

The moult of primaries, secondaries, and rectrices in two closely-related gulls, the Great Black-backed Gull Larus mavinus and the Glaucous Gull L. hyperboreus, was studied in Iceland. Both gulls moult their primaries in an extremely regular sequence, starting with the 1st (innermost) and ending with the 10th (oiltermost) feather. Usually two, less often one or three, primaries are growing per wing during the primary moult, which lasts for about six or seven months. Growlng primaries were estimated to lengthen on the average by 8.7 mm per day in marinus and 7.8 mm per day in hyperboreus. The secondaries, usually 24 in number, are shed in two moult waves, one starting with the innermost feather soon after the start of the primary moult and then progressing slowly outwards, the other beginning with the outermost secondary after the primary moult is about half completed and then progressing rapidly inwards. The moult is completed just before the end of the primary moult as the two moult waves meet at about the 16th secondary. There are no marked differences between the two gulls in the moult of secondaries. The moult of rectrices shows large variations in both species, some feathers being much more irregular than others in their time of shedding. In both species, indications of an obscured centrifugal pattern of replacement are seen, although the 5th (next to the outermost) rectrix is usually the last one to be shed. Significant differences were observed between the two species in the degree of regularity of shedding of some feathers and in the average position in the moulting sequence of others. The moult of rectrices starts soon after the moult of primaries is half completed. The feathers are then shed in rapid succession, and the moult is completed some time before the end of the primary moult. The need for good powers of flight at all times is undoubtedly the reason for the protracted primary moult. This in turn causes the moult to start early, in adults sotnetimes before the eggs are laid; immatures moult even earlier than this. The rectrix moult and the main part of the secondary moult do not begin in adults until the young have fledged, but then progress very rapidly. Presumably, the loss of some of these feathers would impair the flying ability to an extent sufficient to make it difficult for the gulls to care for their young, while the rapid moult is necessary in order for the replacement of these feathers to be completed by the time the primary moult is over.     

黄腹山鹪莺成鸟的秋季换羽

黄腹山鹪莺(Prinia flaviventris)具有冬羽尾羽长于繁殖羽尾羽的特点,可能意味着一种新的生存和繁殖策略。为此,从2006年9月～2007年2月,在广东省肇庆市江溪村对黄腹山鹪莺的秋季换羽进行研究。结果显示:(1)黄腹山鹪莺成鸟繁殖羽体长和尾羽长皆极显著短于冬羽(P<0.01),繁殖羽翼长显著短于冬羽(P<0.05),其余身体量度的差异均不显著(P>0.05)。(2)9月17日获得第一个黄腹山鹪莺换羽个体,初级飞羽已更换到P5,次级飞羽已更换到S6,11月20日后所获样本均已完成羽毛的更换。(3)初级飞羽的换羽模式为递降换羽,次级飞羽为递升换羽,尾羽为离心型换羽。(4)换羽期间,10月的个体平均体重最大,显著(P<0.01)重于11月的体重,其他各月无显著性差异(P>0.05)。据此,推测黄腹山鹪莺秋季种群换羽的持续时间约100d;相对其他羽毛而言,尾羽更换对黄腹山鹪莺生长发育的影响更为明显。     

Zum Ablauf der postnuptialen Vollmauser der Rohrammer (Emberiza schoeniclus)

Zusammenfassung 1. Die Mauser der Großen Oberen Handdecken ist mit der Mauser der Handschwingen streng linear korreliert. Eine Schutzfunktion während der Mauser konnte nicht festgestellt werden.2. Die Großen Oberen Armdecken werden nicht synchron vermausert. In der Regel findet sich in der Mitte der Deckfederreihe ein Mauserzentrum, von dem aus je eine Mauserwelle nach beiden Seiten divergiert.3. Die Carpale Deckfeder fügt sich gut in diese Mauserwelle ein. Für die Theorie, daß diese Feder die Decke einer im Laufe der Evolution verschwundenen Schwungfeder ist, finder sich damit ein neuer Hinweis. Die 10. Armdecke am proximalen Ende der Armdeckfederreihe fügt sich nicht in den Mauserrhythmus der Armdecken ein. Somit erscheint es sinnvoller, ihr eine andere phylogenetische Bedeutung beizumessen.4. Bei der Körpermauser zeigen sich sowohl in der zeitlichen Lage als auch in der Schnelligkeit des Wechsels deutliche Unterschiede zwischen Kopfgefieder, Körperoberseite und Körperunterseite.5. Die Kleingefiedermauser dauert bedeutend länger als der Wechsel des Großgefieders.6. Der Ablauf der Armschwingen-, Schirmfeder- und der Schwanzmauser wurde quantitativ erfaßt. Die langsame Mauser der Schirmfedern wird als Anpassung an die Schutzfunktion gedeutet, die dadurch auch während der Mauser kaum beeinträchtigt wird. Diejenigen Armschwingen, die flugtechnisch von untergeordneter Bedeutung sind, werden in rascherer Folge erneuert als die für die Flugfähigkeit wichtigeren distalen Armschwingen. Individuen, die spät mit dem Wechsel der Armschwingen einsetzen, mausern die Armschwingen schneller als früh beginnende Individuen. Dadurch wird ein mehr oder weniger gleichzeitiger Abschluß der Mauser der verschiedenen Mauserwellen des Großgefieders erreicht.7. Da zwischen den Anfängen der einzelnen Mauserwellen des Großgefieders zwar eine Korrelation besteht, sich die Mauserwellen jedoch nicht gegenseitig anstoßen, wird vermutet, daß ein gemeinsamer Auslöser vorhanden ist, auf den die Federreihen mit unterschiedlicher Sensibilität reagieren.

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The sequence of the complete postnuptial moult in the reed buntingEmberiza schoeniclus

Summary 1. A significant correlation exists between the moult of the primaries and the moult of primary coverts. During moult the primary coverts do not protect either the papilla nor the pin of a new feather.2. The greater coverts are not moulted synchronously. There is a moult centre in the middle of the row of these feathers from where moult procedes to both directions.3. Regarding the moult sequence of the greater coverts the carpal covert seems to be a part of them. This might be another hint that this feather is the covert of a secondary which was reduced and lost during evolution. The small covert at the proximal end of the greater coverts (tenth greater covert) is moulted later than the greater coverts. This suggests another phylogenetic significance.4. There are obvious differences in time and rapidity of moult of the plumage sets of head, upperparts and underparts.5. The moult of body plumage starts at the same time as the moult of the wing feathers but lasts much longer.6. Secondary, tertiary and retricial moult is described quantitatively. The slow rapidity of moult of the tertials is assessed as an adaptation to their function as a protection for the other flight feathers. The inner secondaries which are not as important for flight as the outer ones are moulted more rapidly than the distal secondaries. Specimens that start the moult of secondaries later moult these feathers more rapidly than specimens that begin early. In consequence the end of primary and secondary moult (and also of tertial and tail moult) is approximately at the same time.7. As there is a correlation in the timing of the start of moult between the different moulting sets of remiges and retrices although they do not release each other a common releaser is supposed to which each set seems to react with its own sensibility.

     

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.     

Phenotypic flexibility of a southern African duck Alopochen aegyptiaca during moult: do northern hemisphere paradigms apply?

Phenotypic flexibility during moult has never been explored in austral nomadic ducks. We investigated whether the body condition, organ (pectoral muscle, gizzard, liver and heart) mass and flight‐feather growth Egyptian geese Alopochen aegyptiaca in southern Africa show phenotypic flexibility over their 53‐day period of flightless moult. Changes in body mass and condition were examined in Egyptian geese caught at Barberspan and Strandfontein in South Africa. Mean daily change in primary feather length was calculated for moulting geese and birds were dissected for pectoral muscle and internal organ assessment. Mean body mass and condition varied significantly during moult. Body mass and condition started to decrease soon after flight feathers were dropped and continued to do so until the new feathers were at least two‐thirds grown, after which birds started to regain body mass and condition. Non‐moulting geese had large pectoral muscles, accounting for at least 26% of total body mass. Once moult started, pectoral muscle mass decreased and continued to do so until the flight feathers were at least one‐third grown, after which pectoral muscle mass started to increase. The regeneration of pectoral muscles during moult started before birds started to gain overall body mass. Gizzard mass started to increase soon after the onset of moult, reaching a maximum when the flight feathers were two‐thirds grown, after which gizzard mass again decreased. Liver mass increased significantly as moult progressed, but heart mass remained constant throughout moult. Flight feather growth was initially rapid, but slowed towards the completion of moult. Our results show that Egyptian geese exhibit a significant level of phenotypic flexibility when they moult. We interpret the phenotypic changes that we observed as an adaptive strategy to minimize the duration of the flightless period. Moulting Egyptian geese in South Africa undergo more substantial phenotypic changes than those reported for ducks in the northern hemisphere.