Population dynamics of Black-browed and Grey-headed Albatrosses Diomedea melanophrys and D. chrysostoma at Campbell Island, New Zealand, 1942–96

The numbers of Black-browed Albatrosses Diomedea melanophrys and Grey-headed Albatrosses D. chrysostoma at Campbell Island, New Zealand, have declined dramatically since the 1940s. Black-browed Albatross numbers went into a steep decline in the 1970s and, since at least 1984, have been increasing slightly at average rates of 1.1% and 2.1% per annum at two colonies. The long-term downward trend in numbers of the Grey-headed Albatross has continued into the 1990s, averaging annually between 3.0% and 4.8% per annum at different colonies. A demographic study carried out between 1984 and 1996 indicates that Black-browed and Grey-headed Albatrosses have similarly high annual adult survival rates (0.945 and 0.953, respectively). Black-browed Albatrosses breed for the first time at a younger average age than do Grey-headed Albatrosses (10 years and 13.5 years, respectively), have a higher average breeding success (0.663 compared with 0.397 for the latter species) and are annual breeders whereas Greyheaded Albatross show a typical biennial pattern of breeding. Both show low survival from fledging to first breeding; averaging 0.186 and 0.162 for Black-browed and Grey-headed Albatrosses, respectively. Both species are accidentally killed in the Japanese long-line fishery for tuna Thunnus sp. in the Australasian region. The steep decline of Black-browed Albatross numbers in the 1970s was concomitant with the development of this fishery in the foraging region of the Campbell Island birds. Currently, the slight increase in numbers is due to high adult survival rates and breeding success, and is coincident with a great reduction in long-line fishing. With stable and high adult survival rates, it is expected that future population trends will be mainly influenced by the recruitment rates. The continuous decline in Grey-headed Albatross numbers since the 1940s, before long-line fishing developed in this region, indicates that natural environmental processes contributed to the downward trend in breeding numbers. Modelling indicates that Grey-headed Albatross numbers will continue to decrease with the present demographic parameters. A comparison between the species breeding at different sites shows that differing environmental conditions influence demographic characteristics.     

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.     

THE PRIMARY MOULT OF WADERS ON THE ATLANTIC COAST OF MOROCCO

Data from 3659 waders of 23 species live-trapped in the years 1971-73 on the Atlantic coast of Morocco during the period of autumn moult and migration are analysed to estimate duration and timing of primary moult. Common Sandpiper was the only species to moult primaries in its first autumn (unless published ageing criteria are incorrect). Several species showed a low incidence of arrested primary moult and a higher incidence was observed in Ringed, Kentish and Grey Plovers. This is discussed in relation to breeding and migration. Similar rates of primary feather replacement relative to specific moult duration were observed in all species for which information was available. Comparisons between species and with published studies showed that variations in rate of moulting between species and between different geographical populations of the same species were largely due to differences in feather growth rate rather than in the numbers of primaries concurrently in growth. Variations in rate between individuals of the same population were achieved, at least in the first part of moult, by differences in feather dropping rate resulting in differences in the numbers of primaries growing concurrently. The timing and duration of moult in different populations and differences between breeding and non-breeding components were closely related to the requirements of other annual cycle activities, notably breeding and migration. Non-breeding birds summering in Morocco had started moult early. Locally breeding birds had an early start to a fairly slow moult which overlapped with breeding and which in some cases passed through an arrested stage. Birds breeding in cold temperate and arctic regions and wintering in Morocco moulted in a short time soon after arrival. In some cases, notably in Ringed Plovers, birds had commenced moulting on the breeding grounds and arrested moult during migration. Most Redshank and possibly Dunlin migrated in active wing moult. The fastest primary moult was achieved by high arctic breeding birds, Curlew Sandpiper and possibly Little Stint, which stopped to moult in Morocco before moving on to wintering areas further south. This situation is contrasted with that of populations of these two and other species wintering in the southern hemisphere where moult occurs over an extended period during the northern winter.     

THE FOOD AND FEEDING ECOLOGY OF GREY-HEADED ALBATROSS DIOMEDEA CHRYSOSTOMA AND BLACK-BROWED ALBATROSS D. MELANOPHRIS

The food and feeding ecology of Black-browed Albatrosses and Grey-headed Albatrosses was studied from 1975 to 1978 at Bird Island, South Georgia. Two hundred and seventy food samples (averaging 75–85 % by weight of the mean chick feed) were collected from adults of each species in February and March. Chicks of both species received meals of the same size, of which half consisted of liquid. The three major components of the solid diet (krill, squid and fish) were similar for both albatrosses. By weight, fish represented about 35 % of the diet of both species; squid predominated (50 %) in the diet of Grey-headed Albatross, and krill (40 %) in the diet of Black-browed Albatross. Lampreys were confined to the Grey-headed Albatross and, although squid of similar sizes were taken by both species, Black-browed Albatrosses took a much greater diversity of squid. Each major prey type was associated with a characteristic amount of liquid in the complete samples and only in the case of krill and lamprey was this lipid-rich.
As these two albatrosses are of similar size, breed over the same period and feed meals of equivalent weight to their chicks at similar intervals, the difference in the composition of the diet is possibly the most significant mechanism of ecological segregation (in the breeding season).
Evidence of the effect of krill shortage in drastically reducing Black-browed Albatross breeding success is presented to support this. The two species have largely non-overlapping winter oceanic ranges which are probably also correlated with the distribution of preferred prey.     

Lesser Whitethroats under time-constraint moult more rapidly and grow shorter wing feathers

Migrating passerines moulting in the breeding quarters before autumn migration sometimes end up with less time than needed for a normal moult. To deal with this the birds could for example suspend moult or moult faster. In this paper we investigate the effect of an induced time-constraint on the moult of Lesser Whitethroats Sylvia curruca . The time-constraint was induced through a shift in light regime large enough to transfer the birds to a date when, under normal conditions, they already should have started moulting. Time-constrained birds moulted faster and also grew shorter wing feathers, resulting in a shorter wing, compared to control birds. Only one individual responded by interrupting moult and retained a number of inner primaries unmoulted. The observed adjustments of moult, and the higher fuel loads towards the end of moult, are consistent with the ideas that time is an important factor in bird migration, affecting not only migration but also the events preceding it.     

Reproductive endocrinology of the Black-browed albatross Diomedea melanophris and the Grey-headed albatross D. chrysostoma

Gonadal size and the circulating concentrations of two pituitary hormones (luteinizing hormone and prolactin) and three gonadal steroids (testosterone, progesterone and oestradiol-17β) were measured in two closely related Diomedea albatrosses at South Georgia. The Grey-headed albatross D. chrysostoma , if successful in rearing a chick, usually breeds biennially, whilst the Black-browed albatross D. melanophris normally breeds annually. Direct examination (by laparoscopy) of the gonads showed that the testes of both species underwent annual cycles, whilst endocrine data confirmed that those male Grey-headed albatrosses at the colony in the pre-laying period but not breeding in that year (having bred successfully the previous year) were apparently in full reproductive condition with elevated testosterone levels typical of breeding birds. However, the females of the two species differed markedly. Grey-headed albatrosses, in a year following successful breeding, had undeveloped ovaries with low levels of circulating oestradiol but high levels of progesterone, whereas the Black-browed albatrosses showed a pattern consistent with annual ovarian development. The profiles of gonadal steroids through the breeding season were similar for the males of both species but differences existed between the females. In the female Grey-headed albatrosses, transient peaks of progesterone were present throughout chick rearing but these were absent from Black-browed albatrosses. Prolactin had a similar profile in both species, with uniformly high levels throughout incubation and a rapid fall near the end of the brood-guard period. It is suggested that Grey-headed, like Black-browed, albatrosses are intrinsically annual breeders. However, if a female Grey-headed albatross breeds successfully in one year, then nutritional factors operate to ensure that in the following year the female does not show ovarian development, although the ovary is active in terms of progesterone secretion.     

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.     

Conditions at the breeding grounds and migration strategy shape different moult patterns of two populations of Eurasian golden plover Pluvialis apricaria

Events in the life cycle of migrant birds are generally time‐constrained. Moult, together with breeding and migration, is the most energetically demanding annual cycle stages, but it is the only stage that can be scheduled at different times of the year. However, it is still not fully understood what factors determine this scheduling. We compare the timing of primary feather moult in relation to breeding and migration between two populations of Eurasian golden plover Pluvialis apricaria, the continental population breeding in Scandinavia and in N Russia that migrates to the Netherlands and southern Europe, and the Icelandic population that migrates mainly to Ireland and western UK. Moult was studied at the breeding grounds (N Sweden, N Russia, Iceland) and at stopover and wintering sites (S Sweden, the Netherlands). In both populations, primary moult overlapped with incubation and chick rearing, and females started on average 9 d later than males. Icelandic plovers overlapped moult with incubation to a larger extent and stayed in the breeding grounds until primary moult was completed. In contrast, continental birds only moulted the first 5–7 primaries at the breeding grounds and completed moult in stopover and wintering areas, such as S Sweden and the Netherlands. This overlap, although rare in birds, can be understood from an annual cycle perspective. Icelandic plovers presumably need to initiate moult early in the season to be able to complete it at the breeding grounds. The latter is not possible for continental plovers as their breeding season is much shorter due to a harsher climate. Additionally, for this population, moulting all the primaries at the stopover/wintering site is also not possible as too little time would remain to prepare for cold‐spell movements. We conclude that environmental conditions and migration strategy affect the annual scheduling of primary feather moult in the Eurasian golden plover.     

Postnuptial moult in a Belgian population of Nuthatches Sitta europaca

Postnuptial moult was studied in three consecutive years in a small population of Nuthatches. Fourteen to 25 individuals were captured in active moult each year with an average of 2.1 captures per bird per season. The total duration of moult was estimated as 88 days. Secondary moult was completed a few days after the end of primary moult. Primary moult rate was maximal at the beginning of moult, because many feathers were then growing simultaneously. Individual differences in the timing of moult were small, with a maximal spread of 21 days, and there was little variation between years. No differences in moult were found between sexes or age classes. Birds with failed broods moulted before successful breeders and early breeding females before late breeders. Duration and timing of moult are compared with other resident passerine species. A hypothesis based on summer territorial behaviour is put forward to explain the high degree of synchronization within the population and the relation between breeding and moulting.     

Age‐specific variation in relationship between moult and pre‐migratory fuelling in Wood Sandpipers Tringa glareola in southern Africa

Trans‐equatorial avian migrants tend to breed, moult and migrate – the main energy‐requiring events in their lifecycle – at different times. Little is known about the relationship between wing moult and pre‐migratory fuelling in waders on their non‐breeding grounds, where time is less constrained than during their brief high‐latitude breeding season. We determined age‐related strategies of Wood Sandpipers Tringa glareola to balance the energetic demands of primary moult against pre‐migratory fuelling in southern Africa by analysing body mass and primary moult at first capture of 1721 birds mist‐netted in 1972–96 at waterbodies in Zimbabwe. Adults moulted all their primaries in August–December, but immatures underwent a supplemental moult of varying numbers of outer primaries in December–April, close to departure. We used locally weighted linear regression to estimate trends in Wood Sandpiper body mass from 1 July to 1 May. They maintained low mass from arrival in July–September to February–early March. Adults fuelled from 10 February to 1 May at a mean rate of 0.25 g/day (sd = 0.16). Most adults (98%) began fuelling 10–75 days after completing primary moult. Immatures fuelled from 4 March to 13 April at 0.24 g/day (sd = 0.14). They used varying strategies depending on their condition: a brief gap between moult and fuelling; an overlap of these processes near departure, leading to slower fuelling; or skipping fuelling altogether and staying in southern Africa for a ‘gap year’. Immatures moulting three or five outer primaries fuelled more slowly than post‐moult birds. Immatures moulting four outer primaries started fuelling 3 weeks later but at a higher rate than did post‐moult birds of this group. In post‐moult immatures, the later they ended moult, the later and faster they fuelled. The heaviest adults and immatures using all moult patterns accumulated fuel loads of c. 50% of lean body mass, and could potentially cross 2397–4490 km to reach the Great Rift Valley in one non‐stop flight. Immatures were more flexible in the timing and extent of moult and in the timing and rate of fuelling than adults. This flexibility enables inexperienced Wood Sandpipers to cope with inter‐annual differences in feeding conditions at Africa's ephemeral inland waterbodies.     

Annual variation in the timing of breeding and moulting in male and female Pied Flycatchers Ficedula hypoleuca

During five breeding seasons, the timing of breeding and moulting was studied in the Pied Flycatcher Ficedula hypoleuca. In central Sweden, on average 67% of the males and 41% of the females started moulting before the young fledged. The proportion of individuals with an overlap between breeding and moulting varied considerably between years, with the highest proportion of moulting males being recorded in the year when the females started egg-laying on the latest date. Despite a large annual variation in the proportion of individuals showing a moult/breeding overlap, the duration of this overlap varied insignificantly between years. The onset of moult in males seemed to be related to both calendar date and timing of the current breeding attempt. Most females postponed their moult until just before or just after the fledging of their young, independent of calendar date. There was no significant relationship between male and female moult scores and nestling weight at fledging or fledging success of their brood. Thus, in long-distance migrants such as Pied Flycatchers, it may be adaptive to have some overlap between reproduction and moult, but there seems to be a limit to how early in the breeding cycle they are able to start moulting.     

Experimental test of a trade‐off between moult and immune response in house sparrows Passer domesticus

A trade‐off between immune system and moulting is predicted in birds, given that both functions compete for resources. However, it is unclear whether such a trade‐off exists during post‐breeding moult. This study tests such a trade‐off in the house sparrow (Passer domesticus). Males injected with an antigen (lipopolysaccharide) significantly moulted slower than sham‐injected males. Moreover, males whose seventh primaries were plucked to simulate moult showed smaller immune response to phytohaemagglutinin than control males, in which seventh primaries were clipped. A trade‐off between moult speed and body mass was also found. The results show a clear trade‐off between moult and immune response in the house sparrow: immune response negatively affected moult and moult negatively affected immune response. These findings suggest that only individuals in good condition may have an efficient moult and simultaneously respond effectively in terms of immunity to pathogens, which could explain how plumage traits honestly indicate parasite resistance in birds.     

Contrasting strategies for wing‐moult and pre‐migratory fuelling in western and eastern populations of Common Whitethroat Sylvia communis

Trade‐offs between moult and fuelling in migrant birds vary with migration distance and the environmental conditions they encounter. We compared wing moult and fuelling at the northern and southern ends of migration in two populations of adult Common Whitethroats Sylvia communis. The western population moults most remiges at the breeding grounds in Europe (e.g. Poland) and migrates 4000–5000 km to western Africa (e.g. Nigeria). The eastern population moults all remiges at the non‐breeding grounds and migrates 7000–10 000 km from western Asia (e.g. southwestern Siberia) to eastern and southern Africa. We tested the hypotheses that: (1) Whitethroats moult their wing feathers slowly in South Africa, where they face fewer time constraints than in Poland, and (2) fuelling is slower when it coincides with moulting (Poland, South Africa) than when it occurs alone (Siberia, Nigeria). We estimated moult timing of primaries, secondaries and tertials from moult records of Polish and South African Whitethroats ringed in 1987–2017 and determined fuelling patterns from the body mass of Whitethroats ringed in all four regions. The western population moulted wing feathers in Poland over 55 days (2 July–26 August) at a varying rate, up to 13 feathers simultaneously, but fuelled slowly until departure in August–mid‐September. In Nigeria, during the drier period of mid‐February–March they fuelled slowly, but the fuelling rate increased three‐fold in April–May after the rains before mid‐April–May departure. The eastern population did not moult in Siberia but fuelled three times faster before mid‐July–early August departure than did the western birds moulting in Poland. In South Africa, the Whitethroats moulted over 57 days (2 January–28 February) at a constant rate of up to nine feathers simultaneously and fuelled slowly from mid‐December until mid‐April–May departure. These results suggest the two populations use contrasting strategies to capitalize on food supplies before departure from breeding and non‐breeding grounds.     

The moults of captive Scottish ptarmigan (Lagopus mutus)

The moults of captive Scottish ptarmigan were studied at Banchory, north-east Scotland from December 1968 to February 1971. In the autumn moult (June to September) which included the primaries, cock ptarmigan moulted earlier and more completely than hens. In the winter moult (September to February) hens moulted earlier and both sexes moulted more completely than in spring. In the spring moult (February to June) cocks moulted more rapidly to begin with but by mid-April hens had caught up and thereafter moulted at least as rapidly as cocks. When kept indoors at slightly higher temperatures ptarmigan grew more pigmented feathers during the winter moult. In a colder winter the birds became whiter than in a milder one. First-winter ptarmigan completed the winter moult later than older birds. Birds from the Cairnwell hills had more dark feathers in winter than those from the eastern Cairngorms. There was no correlation between the start or finish of egg-laying and moulting.     

MOULT OF BUDGERIGARS MELOPSZTTACUS UNDULATUS

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

Moult of the giant petrels Macronectes halli and M. giganteus at South Georgia

Moult scores were collected from colour-ringed individuals of known reproductive status of the two species of giant petrel, Macronectes halli and M. giganteus , at Bird Island, South Georgia between 1978–81.
Both species showed a substantial overlap between breeding and wing-moult, unlike most other Southern Ocean seabirds. Males started moult before females and both sexes of M. giganteus moulted at an earlier stage of the breeding cycle than M. halli , which breeds six weeks earlier than its congener.
Changes in moult rate during the breeding season are documented for both species, with Id. halli showing a rapid increase as the chick nears fledging. Male M. giganteus show a notably different pattern to the other three species-sex groups, starting moult much earlier (at egg-laying), with greater individual synchrony and usually suspending primary moult throughout the main chick growth period, whereas only two male M. halli and no females of either species suspended moult. Differences in pattern, timing and rate of moult are interpreted in terms of availability of food resources and the competing energy demands of other activities, especially chick-rearing.
Completion of primary moult could not be observed in the field but was estimated using data frcsm non-breeding birds and failed breeders; the latter started a rapid moult almost immediately they failed. In both sexes of both species moult is probably concluded at least by early winter.
The general pattern of moult in giant petrels at Bird Island is contrasted with that of other populations and species of Southern Ocean seabirds. It is suggested that the unusually extensive overlap between breeding and moult in giant petrels is a consequence of the very abundant and easily available summer food supplies (especially carrion) and the much diminished winter resources, favouring a completion of moult by the beginning of the winter.     

Moult of Malayan Barn Owls Tyto alba

Moult in Malayan Barn Owls Tyto alba was studied in two pairs of wild collected captive birds and from feathers taken from nest sites throughout peninsular Malaysia.
Post-juvenile captive birds moulted nearly to completion prior to first breeding, beginning with P6 at a mean age of 301.5 days. This contrasted with the only other study of moult in captive Barn Ow-Is in Germany when moult began at an age of 400 days, and then continued for a protracted period of two years separated by a suspension of moult during the normal breeding season.
The complex sequence of moult in primaries and secondaries both in the Malayan and German birds was similar.
Moult among adult Malayan birds in the wild showed a broad and somebyhat irregular seasonal trend With lower incidence during peak breeding periods.     

Rapid or slow moult? The choice of a primary moult strategy by immature Wood Sandpipers Tringa glareola in southern Africa

Immature migrant waders have more complex patterns of primary moult than adults, but these have been described only fragmentarily. The Wood Sandpiper Tringa glareola breeds in the taiga region of the Palearctic and part of the population migrates to southern Africa. We selected this population for a study of the primary moult strategies of an immature wader. After analysing the moult formulae of 674 immatures, we discuss potential factors that influence the choice of moult strategy. All moulters replaced two to six outer primaries; 91% moulted four or five. We used the Underhill–Zucchini model to estimate the timing and duration of moult in immatures replacing different numbers of primaries. A slow moult of five or six primaries, adopted by 29%, lasted on average 98–111 days, beginning on average 8–16 December. Moult of four primaries (63%) began on 6 January and averaged 73 days. A rapid moult of three primaries (7%) began on 24 January and averaged 55 days. All groups ended their moult between 19 and 28 March. GLM models showed that heavier immatures were more likely to start moulting than leaner birds. This tendency was more pronounced in November–January than in later months. The later the moult started, the fewer feathers were replaced and the faster the process. Departure time set the limit for the end of moult. We suggest the ability to choose different strategies allows immature Wood Sandpipers to adjust their moult to the variable conditions they encounter at wetlands in southern Africa.     

Use of trace elements in feathers of sand martin Riparia riparia for identifying moulting areas

We investigated whether trace elements in tail feathers of an insectivorous and long-distance migratory bird species could be used to identify moulting areas and hence migratory pathways. We analysed tail feathers from birds of different age and sex collected from a range of different breeding sites across Europe. The site of moult had a large effect on elemental composition of feathers of birds, both at the European and African moulting sites. Analysis of feathers of nestlings with known origin suggested that the elemental composition of feathers depended largely upon the micro-geographical location of the colony. The distance between moulting areas could not explain the level of differences in trace elements. Analysis of feathers grown by the same individuals on the African wintering grounds and in the following breeding season in Europe showed a large difference in composition indicating that moulting site affects elemental composition. Tail feathers moulted in winter in Africa by adults breeding in different European regions differed markedly in elemental composition, indicating that they used different moulting areas. Analysis of tail feathers of the same adult individuals in two consecutive years showed that sand martins in their first and second wintering season grew feathers with largely similar elemental composition, although the amounts of several elements in tail feathers of the older birds was lower. There was no difference between the sexes in the elemental composition of their feathers grown in Africa. Investigation of the trace element composition of feathers could be a useful method for studying similarity among groups of individuals in their use of moulting areas.     

Moulting strategies of a long-distance migratory seabird, the Mediterranean Cory's Shearwater Calonectris diomedea diomedea

Seabird moult is poorly understood because most species undergo moult at sea during the non-breeding season. We scored moult of wings, tail and body feathers on 102 Mediterranean Cory's Shearwaters Calonectris diomedea diomedea accidentally caught by longliners throughout the year. Primary renewal was found to be simple and descendant from the most proximal (P1) to the most distal (P10) feather. Secondaries showed a more complex moulting pattern, with three different asynchronous foci: the first starting on the innermost secondaries (S21), the second on the middle secondaries (S5) and the latest on the outermost secondaries (S1). Rectrix moult started at a later stage and was simple and descendant from the most proximal feather (R1) expanding distally. Although a few body feathers can be moulted from prelaying to hatching, moult of ventral and dorsal feathers clearly intensified during chick rearing. Different moulting sequences and uncoupled phenology between primary and secondary renewal suggest that flight efficiency is a strong constraint factor in the evolution of moulting strategies. Moreover, moult of Cory's Shearwaters was synchronous between wings and largely asynchronous between tail halves, with no more than one rectrix moulted at once. This result is probably related to the differential sensitivity of wings and the tail on flight performance, ultimately derived from different aerodynamic functions. Finally, Cory's Shearwater females renewed feathers earlier and faster than males, which may be related to the lower chick attendance of females.