Flight Feather Moult Research Articles

Red-capped Parrot Purpureicephalus spurius: Moult, Age And Sex Determination

SummaryDescriptions of the plumage and soft parts, the timing and duration of moult and some morphometries of wild-caught and captive Red-capped Parrots Purpureicephalus spurius were recorded so that age and sex could be determined. Pluinage characteristics of adults and immatures were very different while those of males and females within age classes were very similar. Presence or absence of a wing-stripe allowed some, but not all, birds within age classes to be sexed. The sequence of flight feather moult was clearly defined and the period of body moult continued throughout the year in all age classes.

The Timing of Thyroid-Dependent Programming in Seasonally Breeding Male American Tree Sparrows (Spizella arborea)

There is convincing evidence that euthyroid male American tree sparrows are already programmed for seasonal reproduction and postnuptial molt by Week 4 of photostimulation. To explore more precisely when, during early photostimulation, thyroid-dependent programming of seasonal events occurs, photosensitive male tree sparrows were radiothyroidectomized or sham thyroidectomized on the first day of photostimulation (Week 0) or at Weeks 1 or 3 thereafter. Birds were monitored for testicular growth and regression over 8 or 12 weeks and then tested for photosensitivity or photorefractoriness by exposing them to constant light and exogenousL-thyroxine for 4 weeks. Molt of the primary flight feathers was scored periodically, and at the end of the experiment, hypothalami were saved for cGnRH-I (chicken gonadotropin-releasing hormone I) assay. Because (1) the thyroid is already dysfunctional by Day 4 after radiothyroidectomy, (2) thyroid-dependent photoinduced gonadal growth is programmed growth, and as demonstrated here, (3) testis length at Week 6 on long days (i.e., maximum or near-maximum testis size) is independent of the time of thyroidectomy at or after the onset of photostimulation, we conclude that male American tree sparrows were programmed for photoperiodic testicular growth during the first week of photostimulation. Based on measurements of testis length and hypothalamic cGnRH-I content, only 2 of 11 birds thyroidectomized at Week 1 were already programmed for photorefractoriness by Week 1, whereas all birds thyroidectomized at Week 3 were so programmed by Week 3. Marked differences in molt scores between photorefractory (thyroidectomized and euthyroid) and photosensitive (thyroidectomized) birds argue that postnuptial molt also was programmed roughly between Weeks 1 and 3. To explain these results, we ascribe organizational-like actions directly or indirectly to endogenous thyroid hormones and argue that the onset of photostimulation opens a window, during which time euthyroid male American tree sparrows are programmed for seasonality. A clear dissociation of photorefractoriness from photoperiodic testicular growth in birds thyroidectomized at Week 1 suggests that separate control circuits mediate these two annually periodic events.

Plumage Condition Affects Flight Performance in Common Starlings: Implications for Developmental Homeostasis, Abrasion and Moult

Variation in length and asymmetry of wing primary feathers can arise from a breakdown of developmental homeostasis, feather abrasion and incomplete growth during moult. Indirect predictions have been made concerning the impact of primary length and asymmetry on the flight ability of birds, but they have not been explicitly tested. Here we provide evidence from both natural variation in primary feather condition and experimental manipulations of primary feather length and asymmetry to indicate that these factors influence aspects of flight performance in the Common Starling Sturnus vulgaris. Damaged and incompletely grown primary feathers reduce escape flight performance. Experimentally reduced primary lengths reduce take-off speed; increased primary asymmetry decreases aerial manoeuvrability. A comparison of the experimental and natural plumage data indicates that birds may be able to adapt to a change in wing morphology, perhaps reducing the effects of feather loss or damage on flight. The results from this study indicate that primary feathers are under strong stabilising selection to maximise developmental homeostasis and reduce feather asymmetry. These findings are also of ecological importance to the damageavoidance and moult strategies of these birds. This is the first experimental evidence to indicate a quantitative reduction in flight performance with feather lengths and asymmetries typical of those observed during flight feather moult and feather damage in any species.

Ageing Immature Black-browed and Grey-headed Albatrosses Using Moult, Bill and Plumage Characteristics

SummaryWe describe how to age immature Black-browed Diomedea melanophris and Grey-headed Albatrosses D. chrysostoma up to age 6 years (when they have usually acquired adult characteristics), from a combination of the age and pattern of moult of flight feathers, bill colouration and certain plumage characteristics. This is based on known-age birds retrapped at colonies during the breeding season. Ageing of immatures at other times may be complicated by them being in active moult; we provide further guidance for these circumstances.

Molt of Bristle-Thighed Curlews in the Northwestern Hawailan Islands

-I studied molt of Bristle-thighed Curlews (Numenius tahitiensis) on Laysan Island in the Northwestern Hawaiian Islands from 1988-1991. Adult curlews underwent a complete prebasic molt between August and December. Duration of primary molt was about 92 days, which is rapid compared with other shorebirds that molt in tropical and southern latitudes. Adults replaced large numbers of primaries and secondaries simultaneously, and about 50% of the birds became flightless during molt. The prealternate molt began in winter and ended in early spring; it involved the body feathers and variable numbers of rectrices but no remiges. Juveniles molted body feathers and some rectrices during their first autumn and winter but did not replace their juvenal primaries until the spring and summer of their second calendar year. Second-year curlews began replacing their new first basic primaries in late summer, in some cases before the outer juvenal primaries had been dropped. The delayed first prebasic primary molt is probably an adaptation allowing inexperienced birds to devote energy expenditure in their first winter to obtaining food rather than to molting remiges. Because second-year birds remain on the wintering grounds throughout the year and do not prepare for migration, there is no selection against replacing new primaries. Unlike most shorebirds, adult Bristle-thighed Curlews gained mass steadily throughout the autumn and winter. Their rapid prebasic molt in autumn may be an adaptation to allow the birds ample time to build up fat reserves during winter. I suggest that the absence of rich intertidal feeding areas and the frequency of winter storms make it difficult for curlews to take on large fat stores in short time periods as do species that winter on continental coasts. The lack of predators and the small size of remote oceanic islands obviate the need for curlews to maintain peak flight efficiency, allowing birds to become flightless during molt in autumn and to carry increasingly large fat stores throughout the winter. Received 8 October 1992, accepted 15 December 1992. SEVERAL GENERAL PATTERNS in the timing and duration of the prebasic molt of shorebirds have been identified. For example, most shorebirds do not overlap molt of flight feathers with either breeding or migration, although molt of body feathers may begin on the breeding grounds (Ferns 1978, Johnson and Johnson 1983). Notable exceptions include some populations of Purple Sandpipers (Calidris maritima; Sutton and Parmelee 1955, Bengston 1975) and Dunlins (C. alpina; Holmes 1966) that replace their primaries while breeding, and Common Redshanks (Tringa totanus; Pienkowski et al. 1976) that molt while migrating. Also, shorebirds wintering in tropical and southern latitudes tend to initiate molt later, and to molt more slowly, than do species that winter farther north (Prater 1981). Despite substantial infor' Present address: Cooperative Wildlife Research Unit, University of Montana, Missoula, Montana 59812, USA. mation on the molt of shorebirds (e.g. Boere 1976, Morrison 1976, Pienkowski et al. 1976, Prater 1981), the ecological factors responsible for these general patterns have been difficult to elucidate. Consequently, there remains a need to document molt in additional species. Bristle-thighed Curlews (Numenius tahitiensis) are one of the rarest and least-studied shorebirds in the world. They breed in remote areas of western Alaska and winter on small islands in the tropical and subtropical Pacific Ocean. The only published information on their molt comes from a small sample of subadults collected in the Marshall Islands during summer (Johnson 1977). Bristle-thighed Curlews exhibit several unusual traits that make a study of their molt particularly interesting: (1) they are the only migratory shorebird whose winter range is restricted to oceanic islands, which they reach after nonstop flights of at least 4,000 km (Marks et al. 1990); (2) they have high annual survivorship and extreme longevity (Marks 1992); (3) most subadults remain on the wintering

Observations at a colony of House MartinsDelichon urbicain SW Spain, with particular reference to moult

An examination of 212 House Martins in SW Spain indicates that the majority are in active flight feather moult when departing on autumn migration. They appear to lack the ectoparasites that are associated with British House Martins.

Is the Painted Bunting Actually Two Species? Problems Determining Species Limits between Allopatric Populations

Painted Buntings, Passerina ciris, breed in two allopatric eastern and western breeding ranges that differ greatly from the breeding ranges of the two currently recognized subspecies (AOU 1957). These two populations differ dramatically in their timing and pattern of molt and migration. All age and sex classes in the western population typically begin fall migration at least two months earlier than their respective age and sex classes in the eastern population. These birds subsequently interrupt their fall migration in exclusively migratory areas in southern Arizona and northwestern Mexico to begin and complete their annual flight feather molt before continuing their fall migration. In contrast, birds in the eastern population usually complete flight feather molt on the breeding grounds before beginning fall migration. Last, the eastern and western populations winter in allopatric ranges; the eastern population winters in southern Florida, the Bahamas, Cuba, Jamaica, and Haiti, and the western population winters in southern Texas, Mexico and Central America. These data strongly indicate that no significant gene flow occurs between these populations, and suggests that they represent valid phylogenetic species. Two subspecies of Painted Buntings, pallidior and ciris, are currently recognized based on previous studies (Mearns 1911, Storer 1951) that documented variation between the eastern and western populations in winglength of adult (in definitive plumage) males and plumage color of adult males and females on the breeding ground. However, this study indicates that the patterns of variation in these characters in males and females within and between populations are inconsistent with the current subspecific geographic limits in this species, and that separating Painted Buntings into subspecies based on these criteria is not warranted.

Molt patterns in the tree swallow (Tachycineta bicolor)

The pattern and timing of molt was examined in 386 museum specimens of tree swallows (Tachycineta bicolor). The primaries were the first flight feathers to begin molt, with the secondaries and rectrices beginning soon after. Body molt began with the back, breast, and belly; the crown, chin, and rump regions were the last to molt. Flight feather molt began in mid-July and was completed by November. Birds from western populations began molt of the primaries later than birds from eastern populations. Birds in juvenal plumage had a complete molt of the primaries, secondaries, and rectrices, and in the eastern population tended to begin molting later than adults. Body molt took place primarily from mid-July through late October; however, from February to April, 34% (21/64) of birds sampled were actively molting chin feathers, and 5% (3/64) were molting crown feathers. The main period of molt (mid-July to mid-November) coincides with fall migration, and there was no evidence for interrupted molt during this time. A comparison of North American swallows suggests that species with northern winter ranges may be constrained to complete molt before winter, whereas species with more southern winter ranges have a protracted molt that is completed on the wintering grounds.

The Seasonally Divided Flight Feather Moult in the Barred Warbler Sylvia nisoria: A New Moult Pattern for European Passerines

Wing and tail feather moult in Barred Warblers was studied during three summers in SE Sweden. Birds arriving at their breeding grounds had on average 3.2-4.9 fresh secondaries and 3.9-9.4 fresh tail feathers, most certainly moulted in winter quarters. A few primaries and tertials had also been renewed. After breeding, normally all primaries and tertials were moulted. Primary moult duration was approximately 40 d for the individual and 60 d for the population. On average, only 0.7-1.4 secondaries were shed. No individuals renewed any winter-grown secondaries the following summer. Normally, 3-4 (mainly central) tail feathers were moulted. Thus, Barred Warblers moult primaries, tertials and central tail feathers in summer, and secondaries and a varying number of tertials and tail feathers in winter. The juvenile winter moult of secondaries shows that the seasonally divided flight feather moult is actively initiated already in the first winter; this is interpreted as a preparation for an early departure from breeding grounds the following summer. This moult pattern has not previously been documented in European passerines.

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.

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.

Re-Appraisal of Moult of Red-Necked Stints in Southern Australia

The Red-necked Stint Calidris ruficollis breeds in the northern hemisphere and migrates to southern latitudes for its non-breeding period where adults undergo a complete moult of the flight feathers. Juveniles follow the adults to the wintering grounds but remain for the breeding season, the southern winter, and do not moult all their flight feathers until the following year. Returning adults and second-year birds begin to moult their primaries between late August and early December and finish between late December and late March. The mean duration of moult of their primaries is calculated as 130 days, fifteen days longer than that previously reported. Previous authors may not have distinguished non-moulting first-year birds and the inaccuracies in their method of calculation probably account for the difference. Distributions of the moult scores of the primaries of the adults are unimodal and we dispel Evans's (1975) suggestion of subgroups. Pooling of data from separate samples, asymmetry between the wings during early stages of moult, decrease in the rate d moult in middle to late stages and possible bias in sampling all may have contributed to the artificial formation of subgroups.

Molt of Flight and Tail Feathers of the Least Sandpiper in Surinam, South America

Molt of Flight and Tail Feathers of the Least Sandpiper in Surinam, South America

Moult of the Red-Necked Stint

Timing and duration of moult of the Red-necked Stint are analysed from specimens collected at the southern limit of the winter range. The mean duration of primary moult is 110–115 days, starting between late August and early December and finishing between mid-December and late March. Secondary moult finishes before primary moult is completed, but moult of rectrices may not finish until shortly after. Thus, moult of the flight feathers coincides with the time spent on the wintering grounds. Pre-basic moult starts before birds arrive on the wintering grounds, and pre-alternate body-moult finishes after they leave. Moult of flight feathers does not start until the pre-basic moult is well advanced and does not finish until after the pre-alternate moult has started. Body-moult may be suspended during migration.

Fluctuation of Numbers of Waders in South-Eastern Tasmania

SUMMARYThomas, D. G. 1970. Fluctuation of numbers of waders in south-eastern Tasmania. Emu 70: 79–85.South-eastern Tasmania, at the limit of the winter range of migrant Palaearctic waders, is ideally situated for the study of variation in numbers. Two-monthly totals are given for migratory species from January 1965 to December 1966 and monthly totals for all species from January 1967 to December 1968. Most” migrants arrive from August to October and leave between mid-March and early May. Only Tringa nebularia increases throughout the wintering period. In most species migration and moult of flight feathers are probably mutually exclusive. Varying proportions of some species remain throughout the breeding season. Probably these are immature birds, and varying numbers result from independent migrations of adults and immatures. The MacArthur-Wilson model for determining the equilibrium number of species on archipelagos appears to be applicable to waders in south-eastern Tasmania. It is suggested that equilibrium has been reached and that the additions to the Tasmanian list since 1958 are because of increased observation. Reasons why some species fail to become established are discussed.