SOME INTERESTING RHODESIAN RECORDS—IV

Austin, G. T. 1979. Pattern and timing of moult in penduline tits (Anthoscopus). Ostrich 49:168-173.

Moult was examined in species of Anthoscopus. Second and subsequent prebasic moults were complete. Primary and rectrix moult was typical of passerines, but secondary moult was some what irregular. Moult was largely non-overlapping with breeding, although some body moult was noted during the breeding season. In southern Africa there was some regional variation in timing of moult. First year birds moulted after adults had largely completed feather replacement. This first prebasic moult was incomplete.     

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.     

8. SHORT NOTES

Stutterheim, C. J. 1980. Moult cycle of the Redbilled Oxpecker in the Kruger National Park. Ostrich 51:107-112.

This paper describes the pattern and rate of the complete moult cycle in the Redbilled Oxpecker Buphagus er ythrorhynchus. The average duration of primary moult in adult birds was 340 days and the mean time to replace a primary feather was calculated as 34 days. The moult of the secondaries is initiated at two points, at the first secondary and at the innermost secondary. Secondary moult takes seven months. The differentiated inner secondaries moult in the normal middle/inner/outer passeriform fashion. The rectrices moulted only once annually. The two body moult cycles correspond with the moult of the differentiated inner secondaries. First-year birds undergo a partial postjuvenile feather replacement at three months of age.     

REVIEWS

Jones, P. J. 1978. Overlap of breeding and moult in the Whitebrowed Sparrowweaver in northwestern Botswana. Ostrich 48:21-24.

Female Whitebrowed Sparrowweavers Plocepasser mahali trapped on the nest while incubating showed advanced active moult of wing and tail feathers, indicating a complete overlap of moulting and breeding schedules. Additional moult data indicated an unusually protracted primary moult of 183 days. It is suggested that the low daily metabolic demands of a slow moult enable it to be compatible with breeding activities, which may be of advantage to some species living in semi-arid environments.     

3. THE GENERA TURDUS,GEOKICHLA, PSOPHOCICHLA,MONTICOLA AND COSSYPHA IN NYASALAND

Summary

Hanmer, D. B. 1981. Mensural and moult data of nine species of sunbird from Moçambique and Mala?i. Ostrich 52: 156–178.

Wing length, culmen length, weight and moult data are given for the Coppery Sunbird Nectarinia cuprea, Purplebanded Sunbird N. bifnsclata, Yellowbellied Sunbird N. venusta, Whitebellied Sunbird N. talatala. Grey Sunbird N. veroxii, Black Sunbird N. amethystina. Scarletchested Sunbird N. senegalensis. Collared Sunbird Anthreptes collaris and Violet-backed Sunbird A. longuemarei from Mopeia (Moçambique) and Nchalo (Mala?i). Moulting seasons, immature age at moult, the duration of primary moult, its relation to the breeding season, weight changes with moult, the breeding season, altitude and latitude, and the sequence and timing of moult in remiges and rectrices are discussed for all species except N. veroxii, N. amethystina and A. longuemarei. Softpart and plumage colour changes with age are discussed and some data are given on habits and migration.     

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 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.     

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.     

CHAIRMAN'S REPOST, 1954–55

Brown, C. R. 1986. Feather growth, mass loss and duration of moult in Macaroni and Rockhopper Penguins. Ostrich 57:180-184.

The development of new feathers, loss of body mass and the duration of moult were investigated in Macaroni Penguins Eudyptes chrysolophus and Rockhopper Penguins E. chrysocome at Marion Island, southern Indian Ocean. New feathers began developing under the skin before the birds returned ashore to moult, and only began protruding through the skin about five days later when they were already over half their final length. Feather synthesis was complete by 21 days after the birds returned ashore. Loss of body mass was similar to previous observations for the species, but previous reports on the duration of moult do not take into account that moult begins while the birds are still at sea.     

MEASUREMENTS AND MOULT OF FIVE SPECIES OF BULBUL FROM MOÇAMBIQUE AND MALAŴI

Summary

Hanmer, D. B., 1978. Measurements and moult of five species of bulbul from Moçambique and Mala?i. Ostrich 49:116-131.

The wing length, weight and moult of five species of bulbul, Blackeyed Pycnonotus barbatus, Sombre Andropadus importunus, Yellowbellied A. flaviventris, Terrestrial Phyllas-trephus terrestris and Yellowspotted Nicator Nicator gularis, are given for two localities in tropical lowland (Mopcia, Moçambique and Nchalo, Mala?i). The characters identifying immatures and the length of time these are retained, are given with reference to skull pneumatization, retrapped birds and the breeding season, for Pycnonotus barbatus, Andropadus intportunus and Phyllastrephus terrestris. Weights are compared with some published for other parts of Africa. The months during which moult occurred are given. Duration and timing of primary moult and its relation to the breeding season, are given for Pycnonotus barbatus, Andropadus importunus and Phyllastrephus terrestris. The age at which immatures moult is given for these three species. Instances of interrupted moult are mentioned.     

SOME NOTES ON THE BIRDS OF THE ISOKA DISTRICT OF THE NORTHERN PROVINCE OF NORTHERN RHODESIA

Dean, W. R. J. 1978. Moult seasons of some Anatidae in the western Transvaal. Ostrich 49:76-84.

Spurwinged Geese Plectropterus gambensis, Egyptian Geese Alopochen aegyptiacus, Yellow-billed Ducks Anas undulata, Redbilled Teal A. erythrorhyncha and Southern Pochard Netta erythrophthalma have a flightless moult mainly during the dry season, from April to August, in the western Transvaal. South African Shelduck Tadorna cana moult during October to February after breeding during July and August. The Cape Shoveller Anas smithii has two main flightless periods, April-May and October-January. Cape Teal A. capensis have been recorded in flightless moult in October, December and January.

The duration of the flightless period correlates with wing length; larger and longer winged Anatidae require proportionally more time for wing moult than do smaller and shorter winged Anatidae.

Geese and shelducks moult on large open lakes with an open shore. Ducks have been recorded flightless on lakes and dams, with or without emergent vegetation.     

NOTICES

Schmitt, M. B., Baur, S. &; Von Malitz, F. 1980. Observations on the Steppe Buzzard in the Transvaal: Ostrich 51:151-159.

During a three year study 247 Steppe Buzzards Buteo buteo vulpinus were captured in the Transvaal, South Africa. Density, mensural data and moult are discussed and compared with findings from the Cape Province. Linear density is 7,3 times lower in the Transvaal as compared with the Cape. Identification criteria for second-year birds are given. Second-year birds moult primaries descendently and symmetrically, secondary moult is mainly ascendent and symmetrical, tail moult irregular but symmetrical. Adult birds moult irregularly. Recorded food items are listed.     

The effects of long‐distance migration on the evolution of moult strategies in Western‐Palearctic passerines

Although feathers are the unifying characteristic of all birds, our understanding of the causes, mechanisms, patterns and consequences of the feather moult process lags behind that of other major avian life‐history phenomena such as reproduction and long‐distance migration. Migration, which evolved in many species of the temperate and arctic zones, requires high energy expenditure to endure long‐distance journeys. About a third of Western‐Palearctic passerines perform long‐distance migrations of thousands of kilometres each year using various morphological, physiological, biomechanical, behavioural and life‐history adaptations. The need to include the largely non‐overlapping breeding, long‐distance migration and feather moult processes within the annual cycle imposes a substantial constraint on the time over which the moult process can take place. Here, we review four feather‐moult‐related adaptations which, likely due to time constraints, evolved among long‐distance Western‐Palearctic migrants: (i) increased moult speed; (ii) increased overlap between moult and breeding or migration; (iii) decreased extent of plumage moult; and (iv) moult of part or all of the plumage during the over‐wintering period in the tropics rather than in the breeding areas. We suggest that long‐distance migration shaped the evolution of moult strategies and increased the diversity of these strategies among migratory passerines. In contrast to this variation, all resident passerines in the Western Palearctic moult immediately after breeding by renewing the entire plumage of adults and in some species also juveniles, while in other species juvenile moult is partial. We identify important gaps in our current understanding of the moult process that should be addressed in the future. Notably, previous studies suggested that the ancestral moult strategy is a post‐breeding summer moult in the Western Palearctic breeding areas and that moult during the winter evolved due to the scheduling of long‐distance migration immediately after breeding. We offer an alternative hypothesis based on the notion of southern ancestry, proposing that the ancestral moult strategy was a complete moult during the ‘northern winter’ in the Afro‐tropical region in these species, for both adults and juveniles. An important aspect of the observed variation in moult strategies relates to their control mechanisms and we suggest that there is insufficient knowledge regarding the physiological mechanisms that are involved, and whether they are genetically fixed or shaped by environmental factors. Finally, research effort is needed on how global climate changes may influence avian annual routines by altering the scheduling of major processes such as long‐distance migration and feather moult.     

THE RELATIONSHIP BETWEEN CLIMATE AND ANNUAL CYCLES IN THE COTINGIDAE

This survey is based primarily or the state of moult of over 4000 specimens of cotingas from all parts of the neotropical region. The seasonality of moult thus revealed is combined with existing knowledge of breeding seasons and seasonal environmental changes in an attempt to work out the broad pattern of annual cycles and their relation to climate. Within any local population the date of onset of moult may vary according to sex and age. In genera in which both sexes participate in nesting, males and females begin to moult at about the same time, or the males slightly in advance of the females. In genera with marked sexual dimorphism, in which only the female attends the nest, males may begin to moult well before females, at about the time that the latter begin egg-laying. The former group includes the genera Pachyramphus and Tityra, comprising species that are largely insectivorous, and the latter group includes the more specialized frugivorous genera. In all areas with well-marked seasonality, the ‘frugivorous group’ moults on average before the ‘Pachyramphus group’. It appears to be a general rule for first-year birds to moult earlier than older birds. A regional survey embracing all parts of the neotropical region shows that the peak of onset of moult occurs towards the end of the dry season (frugivorous group) or early in the wet season (Pachyramphus group). The changing moult seasons, strikingly in conformity with the geographical changes in the period of heaviest rainfall, are traced along a number of transects from Mexico in the north to Paraguay and Bolivia in the south. Such evidence as there is suggests that the main period of onset of moult in the frugivorous and Pachyramphus groups coincides with the period when their food is approaching or at its seasonal peak of abundance. It seems that both breeding and moult, which are almost entirely mutually exclusive, are as far as possible timed to coincide with this most favourable period; but whereas the moult takes a more or less fixed length of time the period when breeding is possible varies greatly in different species. Widely different patterns of annual cycle may result from the interaction of the two processes. Examples are given both from the cotingas and from species of other families with similar ecology. The proximate factors controlling the timing of the moult are briefly considered. It is suggested that increasing food availability is the main environmental controlling factor, and that an endogenous circannual cycle of moult must also be involved.     

Ascendente Handschwingen-Mauser beiMuscicapa striata

Zusammenfassung Ascendente Mauser der Handschwingen beiMuscicapa striata wird beschrieben. Der Ersatz der Handschwingen von der äußeren zur inneren fortschreitend ist einzigartig bei den Passeres. Bisher war von allen untersuchten Passeres nur die descendente, von innen nach außen fortschreitende Mauser der Handschwingen bekannt. Auch die nächstverwandten ArtenMuscicapa gambagae, M. sibirica undM. latirostris mausern descendent. Vermutlich verlaufen auch die Mauser der Armschwingen und der Schwanzfedern beiM. striata nach einem anderen Schema als bei den übrigen Passeres. Die mögliche Bedeutung der Erscheinung wird diskutiert.

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Summary The examination of eight specimens of the palearctic FlycatcherMuscicapa striata collected in the wintering grounds in Tanganyika Territory and Kenya Colony, all in different stages of complete prenuptial moult, yielded the unexpected result of ascending primary moult (beginning with the outermost primary), in contrast to the descending mode so far known to be followed by all Passeriformes.With regard to the moult of secondaries and tail-feathers the material, somewhat scanty in this respect, seems to show that in both these feather-tracts too the ordinary Passerine sequence is reversed, the rectrices being moulted centripetally and the secondaries diverging from a single moult centre represented by the sixth, but this needs corroboration.A superficial search among other members of the genusMuscicapa, includingM. gambagae, and among other genera of Flycatchers disclosed the usual descending primary moult in all these forms (listed in the text).A possible functional meaning of the ascending primary moult inMuscicapa striata is discussed.

     

Non‐breeding Cackling,Ross's and Snow Geese on Baffin Island show no loss of body mass during wing moult

Non‐breeding Cackling Branta hutchinsii, Ross's Anser rossii and Lesser Snow Geese Anser caerulescens caerulescens captured during remigial moult on Baffin Island in 2015 showed no loss of body mass with moult stage, and individual variation in mass was largely explained by sex and measures of body size (tarsus length). Exceptional conditions in 2015 resulted in almost no reproductive effort or success in that year, so captured geese of all three species were likely to have been non‐breeding individuals that initiated moult early, whereas there were almost no failed or successful breeders, which would normally moult later. This suggests that in a non‐breeding year (i.e. in the absence of competition from large numbers of goslings), locally moulting geese can obtain sufficient exogenous energy to meet their needs during the flightless wing moult period without losing body mass. This also is consistent with the hypothesis that in other species of geese, accumulation of fat stores prior to, and depletion of such stores during, wing moult is adaptive and likely to be a feature of individual plasticity to meet particular needs, such as undertaking moult migration to remote sites where precise foraging and predation conditions cannot be anticipated, or where competition from more dominant individuals may restrict their access to a reliable food supply.     

Greater energy stores enable flightless moulting geese to increase resting behaviour

Many species of waterfowl undergo a post‐breeding simultaneous flight feather moult (wing moult) which renders them flightless and vulnerable to predation for up to 4 weeks. Here we present an analysis of the correlations between individual time‐budgets and body mass states in 13 captive Barnacle Geese Branta leucopsis throughout an entire wing moult. The daily percentage of time spent resting was positively correlated with initial body mass at the start of wing moult. Behaviour of individual birds during wing moult is dependent on initial physiological state, which may in turn be dependent on foraging ability; the storage of energy before the start of wing moult will help birds to reduce exposure to the dangers of predation.     

A model for avian primary moult

The regression methods frequently used to estimate the parameters associated with primary moult in birds are unsatisfactory. Results obtained using least squares regression, and various ad hoc adaptations, are so obviously incorrect that many authors have fitted lines ‘by eye’ (Newton 1968, Thomas & Dartnall 1971, Elliott et al. 1976, Morrison 1976, Appleton & Minton 1978). In a comparison of seven regression methods, estimates of the average starting date varied between 29 June and 31 July, completion date between 2 and 24 October, and duration of moult between 72 and 109 days for the Redshank Tringa totanus, in spite of the very large sample of 1482 observations (Summers et al. 1983). In this paper we present a new approach to the analysis of primary moult and develop a mathematical model specifically designed for moult data.     

Seasonally divided moult in the Barred Warbler (Sylvia nisoria) is an endogenously controlled strategy

The seasonal timing of moult in migratory birds is an adaptation to cope with time constraints in the annual cycle. Kiat and Izhaki analysed moult patterns in Palaearctic passerines and rejected the proposition that seasonally divided moult is an endogenously controlled strategy. Instead, they advocated the view that it occurs due to a flexible and opportunistic timing of moult. In contrast, we argue that Kiat and Izhaki’s analysis is flawed and that they overlooked several important facts about moult in the Barred Warbler Sylvia nisoria and other species showing seasonally divided moult. These include the facts that juveniles replace a few secondaries already in their first winter, and that the moult sequences of primaries and secondaries are decoupled compared with the typical passerine complete moult sequence. We argue that seasonally divided moult is an adaptive strategy that is largely under endogenous control.     

Causes and consequences of individual variation in the extent of post‐juvenile moult in the blue tit Cyanistes caeruleus (Passeriformes: Paridae)

Moult, comprising the growth or replacement of feathers in birds, is an energetically demanding process. As a result, in many species, the extent of the post‐juvenile moult can vary substantially. However, the reasons underlying this variation remain poorly understood, and the potential life‐history consequences of variation in moult extent are even less clear. In the present study, we aimed to use individual‐specific data to identify factors affecting the extent of the post‐juvenile moult in a population of over 2500 blue tits Cyanistes caeruleus Linnaeus 1758, and to assess the consequences of individual variation in moult extent on reproduction in the first year of life. There was a substantial sex difference in post‐juvenile moult extent, with males moulting more extensively than females. Putative immigrant birds had moulted on average less than those born locally. However, there was little evidence of carry‐over effects of the natal environment on moult extent because we found no relationship between moult extent and fledging date or nestling mass. Evidence that moult extent, and hence feather brightness, affected subsequent reproductive success was limited. Moult extent had no effect on recruitment in males, although female recruits had moulted significantly less than nonbreeders. Because it was not influenced by features of the natal environment, moult extent may not be an honest signal of individual quality in C. caeruleus. As a result, the potential consequences of variation in moult extent for fitness are likely to be small.