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.     

PRIMARY MOULT,WEIGHT AND BREEDING CYCLES OF THE ROCK PIGEON ON DASSEN ISLAND

Cooper, J. 1975. Primary moult, weight and breeding cycles of the Rock Pigeon on Dassen Island. Ostrich 46:154-156.

The primary moult season of the adult Rock Pigeon Columba guinea on Dassen Island is spread over at least nine months. Individual duration is estimated at eight months. Adult birds were heaviest in the winter months outside the breeding season. Overlap between the breeding and moulting seasons occurred and evidence was obtained of incubating birds with active primary moult. Juveniles were lighter than adults. Adults fed on the mainland and probably made daily flights there.     

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.     

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.     

POPULATION,DIET AND THE ANNUAL CYCLE OF THE LAUGHING DOVE AT BARBERSPAN,PART 3: THE ANNUAL CYCLE

Dean, W. R. J. 1979. Population, diet and the annual cycle of the Laughing Dove at Barbers-pan, Part 3: The annual cycle. Ostrich 50:234-239.

Laughing Doves Streptopelia senegalensis were collected each month from July 1976 to June 1977. In each sample some males and females were breeding. Breeding and primary moult overlapped, and some birds began to moult after starting to breed, and began to breed after starting moult. Adult Laughing Doves require about 120 days to complete primary moult, and juveniles require about 90 days. Weights of moulting birds were not significantly different from those of non-moulting birds, and there were no seasonal trends in the weights of either group. The mean weight of 79 males was 101,6 g and of 39 females was 100,2 g.     

Photoperiodic control of testicular regression and moult in male House Sparrows Passer domesticus

Testis size, bill colour and moult were monitored in male House Sparrows Passer domesticus kept under a natural daylength regime between February and November. On three occasions (at the summer solstice, 25 days later and 39 days later), groups of birds were transferred to a daylength of 18 h of light and 6 h of darkness per day (18L: 6D), the natural daylength at the solstice. In birds under natural daylengths, the testes had regressed significantly by 2 5 days after the solstice. In those transferred to 18L:6D at the solstice, the onset of regression was delayed by about 4 weeks. Transfer to 18L: 6D after the solstice did not cause recrudescence; the testes continued to regress. In birds transferred to 18L: 6D at the solstice, moult was delayed by 4 weeks and progressed more slowly. These results suggest that photoperiodically induced gonadal regression in this species contains elements characteristic of both absolute and relative photorefractoriness.     

Vererbung einer populationsspezifischen Mauser bei Kreuzung von M?nchsgrasmücken (Sylvia atricapilla) verschiedener Populationen

A comparative study of migratory blackcaps from Central Europe (S. Germany) and resident conspecifics from the Cape Verde Islands revealed marked differences in annual periodicity. European blackcaps, with one breeding season per year, have a single-peaked annual gonadal cycle whereas the African birds with two breeding seasons per annum have a two-peaked gonadal cycle. The European birds go through a post-juvenile moult (partial moult in first-year birds) or postnuptial moult (complete moult in adults) and, in addition, through a partial winter moult (all age classes) before the next gonadal cycle and breeding season. Their African conspecifics, on the other hand, have only one moult between two gonadal cycles, the summer moult also being the complete one. Here, we demonstrate that the additional winter moult of European blackcaps is heritable and can be transmitted into interpopulational hybrids. When blackcaps from S. Germany and the Cape Verdes were cross-bred, 16 out of 21 hybrids displayed the partial winter moult of their German parents. The fact that not all but only 76% of the F1 hybrids passed through this moult favours the idea that its incidence is controlled by a polygenic rather than a single locus system. Most likely winter moult in European blackcaps represents a threshold character as several migratory features do.     

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.     

Moult in captive partially migratory and sedentary Australian silvereyes ( Zosterops lateralis ) (Zosteropidae)

In this study, we describe and compare the duration and timing of post-breeding moult of primary and secondary wing feathers, tail feathers, wing coverts and body feathers in captive partially migratory and non-migratory Australian silvereyes (Zosterops lateralis). This study allowed us to follow individual birds through the course of their moult and record the progression of moult in two populations. Both groups of birds underwent a conventional (or basic) post-breeding moult. While all birds followed a similar pattern of feather replacement, differences were found in the timing and duration of moult between migratory and non-migratory birds. The migratory birds generally started their moult earlier in the year and completed it before the non-migratory birds. The migratory birds revealed an overall uniformity in the timing and duration of their moult, while the non-migratory birds showed a greater degree of variability between individuals.     

Transition between moult and migration in a long-distance migratory passerine: organ flexibility in the African wintering area

Phenotypic flexibility of organs in migratory birds has been documented for a variety of species of different genera during the migratory period. However, very little is known about phenotypic mass changes of organs with respect to other events within the annual cycle. This seems particularly interesting when birds face different physiological challenges in quick succession. We investigated mass changes of 13 organs from garden warblers (Sylvia borin) during the transition from moult to migration. These long-distance migratory birds perform a complete moult within their wintering area just shortly before the onset of spring migration. Birds were sampled in three successive stages according to their moult status: group I consisted of birds with growing primary or secondary wing feathers, group II consisted of birds with completed wing moult but with still moulting body feathers, and group III consisted of birds that had completed wing moult and body moult. Size-corrected flight muscle, kidney mass, and pancreas mass differed significantly among the three groups. Flight muscle was heaviest in birds that were about to leave their wintering area (group III) compared with birds still in body moult (group II). Kidney and pancreas showed a pattern similar to each other, with the heaviest mass occurring in birds with moulting wing feathers (group I) and significantly reduced mass in birds that had completed wing moult (group II) or both wing and body moult (group III). Mass reductions of kidney and pancreas during the transition from moult to migration are considered to be related to the demands of moult, while increased flight muscle may be due to moult, migration, or both. Phenotypic mass changes of organs in birds occur during their migration, but they also occur during the transition between other phases of the annual cycle such as moult and migration and are not restricted to the flight muscle.     

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.     

Seasonality in a temperate zone bird can be entrained by near equatorial photoperiods

Birds use photoperiod to control the time of breeding and moult. However, it is unclear whether responses are dependent on absolute photoperiod, the direction and rate of change in photoperiod, or if photoperiod entrains a circannual clock. If starlings (Sturnus vulgaris) are kept on a constant photoperiod of 12h light:12h darkness per day (12L:12D), then they can show repeated cycles of gonadal maturation, regression and moult, which is evidence for a circannual clock. In this study, starlings kept on constant 11.5L:12.5D for 4 years or 12.5L:11.5D for 3 years showed no circannual cycles in gonadal maturation or moult. So, if there is a circannual clock, it is overridden by a modest deviation in photoperiod from 12L:12D. The responses to 11.5L:12.5D and 12.5L:11.5D were very different, the former perceived as a short photoperiod (birds were photosensitive for most of the time) and the latter as a long photoperiod (birds remained permanently photorefractory). Starlings were then kept on a schedule which ranged from 11.5L:12.5D in mid-winter to 12.5L:11.5D in mid-summer (simulating the annual cycle at 9 degrees N) for 3 years. These birds entrained precisely to calendar time and changes in testicular size and moult were similar to those of birds under a simulated cycle at 52 degrees N. These data show that birds are very sensitive to changes in photoperiod but that they do not simply respond to absolute photoperiod nor can they rely on a circannual clock. Instead, birds appear to respond to the shape of the annual change in photoperiod. This proximate control could operate from near equatorial latitudes and would account for similar seasonal timing in individuals of a species over a wide range of latitudes.     

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.     

A comparison of breeding and moult cycles and life histories in two tropical starling species: the Blue-eared Glossy Starling Lamprotornis chalybaeus and Rüppell's Long-tailed Glossy Starling L. purpuropterus

The Blue-eared Glossy Starling Lamprotornis chalybaeus and Rüppell's Long-tailed Glossy Starling Lamprotornis purpuropterus were investigated in the field and in aviaries at Lake Nakuru National Park, Kenya for seasonality in reproductive activity and moult. The former species was found to be a seasonal breeder which nests after the onset of the heavy rains in April. Although some birds had large gonads prior to the rains in the dry season no nesting occurred. The rains were contemporary with increases in gonadal size and the plasma titres of LH, testosterone (T) in males and estradiol (E2) in females. These hormones are associated with the initiation of breeding activity. As breeding ceased in July and the moult began, the plasma titres again decreased. There was a bimodal breeding pattern which paralleled a change in biotope preference for nesting. Early nests, in the heavy rains, were on the open savanna and later nests were in the acacia forest. Late nesting birds also had delayed peaks in gonadal size, plasma titres of LH, T and E2 and a delayed moult onset. Data on individual captive birds demonstrate that these annual cycles have a distinctly individual character superimposed on the seasonal trends. In Rüppell's Long-tailed Glossy Starlings no seasonality in breeding was found although the flight feather moult commenced and was completed in all individuals at about the same time. The moult extended over about ten months, so a great deal of breeding-moult overlap was present. The absence of seasonality in field birds was reflected in the aviary birds, which had no pronounced cycles in the reproductive parameters measured (gonadal size, LH, T and E2 plasma titres). Breeding in field birds was regulated on a pair basis and correlated with increases in duetting. The striking differences in the seasonal organization between this species and Blue-eared Glossy Starlings were presumably due to the different biotope preferences and social behaviour of the two species.     

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.     

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.     

Moult-related reduction of aerobic scope in passerine birds

It is well established that the nutrient and energy requirements of birds increase substantially during moult, but it is not known if these increased demands affect their aerobic capacity. We quantified the absolute aerobic scope of house and Spanish sparrows, Passer domesticus and P. hispaniolensis, respectively, before and during sequential stages of their moult period. The absolute aerobic scope (AAS) is the difference between maximum metabolic rate (MMR) during peak locomotor activities and minimum resting metabolic rate (RMR_min), thus representing the amount of aerobic power above that committed to maintenance needs available for other activities. As expected, RMR_min increased over the moult period by up to 40 and 63% in house and Spanish sparrows, respectively. Surprisingly, the maximum metabolic rates also decreased during moult in both species, declining as much as 25 and 38% compared with pre-moult values of house and Spanish sparrows, respectively. The concurrent changes in RMR_min and MMR during moult resulted in significant decreases in AAS, being up to 32 and 47% lower than pre-moult levels of house and Spanish sparrows, respectively, during moult stages having substantial feather replacement. We argue that the combination of reduced flight efficiency due to loss of wing feathers and reduced aerobic capacity places moulting birds at greater risk of predation. Such performance constraints likely contribute to most birds temporally separating moult from annual events requiring peak physiological capacity such as breeding and migration.

     

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.     

THE MIGRATION SYSTEM OF THE CURLEW SANDPIPER CALIDRIS FERRUGINEA IN AFRICA

Elliot, C: C. H., Waltner, M., Underhill. L. G., Pringle, J. S. & Dick, W. J. A. 1976. The migration system of the Curlew Sandpiper Calidris ferruginea in Africa. Ostrich 47:191-213. Data on ringing and recoveries of Curlew Sandpiper, mainly from the Cape, South Africa are presented. Possible migration routes to the breeding grounds are considered in the light of these and other recoveries from the rest of Africa. Retraps show that the species exhibits ortstreue and some evidence is presented which suggests that some birds may travel together and stay in the south in the same flock during one and subsequent migrations. Sex ratio statistics show an excess of females. Adults complete a full primary moult in the Cape between September and February, taking about 140 days but there is a lot of individual variation. Data from Mauritania show primary moult starting faster, a month earlier than in the Cape, and arrested moult in a few adults. The difference may be because Mauritanian birds move on further south while the Cape is the end point of the migration. Kenyan moult records from the Rift Valley follow the Cape pattern except that some birds arrest moult and finish later. Juvenile moult is shown to be different from that of adults, involving only a moult of the outer primaries and taking place during the overwintering period, April to August. All juveniles in the Cape are thought to overwinter and the modified moult to be an adaptation to this behaviour. The weight of adults but not juveniles increases markedly in the six weeks before migration. Fat and protein analyses suggest that the increase is entirely due to deposition of migratory fat. Kenyan birds have lower mean weights and deposit fat about two weeks later than those at the Cape. The nearer the non-breeding quarters are to the breeding grounds, the earlier moult starts and the later fat deposition takes place.