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.     

Sexual differences in moult–breeding overlap and female reproductive costs in pied flycatchers, Ficedula hypoleuca

1. In this study I show that a sexual difference in timing of the post-nuptial moult frequently occurs in a sub-arctic population of the pied flycatcher.
2. Most pairs started to moult after fledging of their young, but an overlap between moult and nestling feeding was more common among males than females. This sexual difference in moult–breeding overlap increased as the season progressed.
3. Females with moult–breeding overlap laid smaller clutches than non-moulting females. In addition to many other factors explaining the seasonal decline in clutch size that has been found for many bird species, it is possible that females adjust their clutch size according to their own risk of having to start moulting while still feeding the nestlings.
4. Nearly 24% of the females were deserted by their mate before the young fledged. Desertion imposed no fitness costs to males in terms of fledgling number or quality, suggesting that their females managed to adjust their care for the loss of male care.
5. Deserted females started moulting later than aided females, which may be a result of their increased reproductive investment.
6. Deserted females and females aided by moulting males had lower survival rate than females aided by non-moulting males.
7. These findings suggests that delayed moult may be one mechanism causing inter-annual reproductive costs in birds, and the relationship between a sexual difference in timing of moult and its fitness consequences may be widespread among passerine birds.     

Plumage development and visual communication in the Greater Kestrel Falco rupicoloides near Pretoria,South Africa

Kemp, A. C. 1999. Plumage development and visual communication in the Greater Kestrel Falco rupicoloides near Pretoria, South Africa. Ostrich 70 (3&4): 220–224.

I trapped, marked, sexed and examined moult and softparts on 101 free-living Greater Kestrels Falco rupicoloides near Pretoria, South Africa, during 1975–1988.1 collected and plucked one kestrel to determine the number and mass of its feather tracts, as an index of materials invested in moult. I also examined moult on 72 museum specimens from southern Africa and observed plumage and softpart changes in four captive birds. During 1975–1979,1 made focal observations on free-living adult kestrels (males 181 h, females 262 h) and recorded monthly samples of their visual communication behaviours to the nearest minute.

Greater Kestrels can be aged for three successive plumage and softpart stages (juvenile, post-juvenile, adult). Plumage changes with potential signal effects involved only small investments at the post-juvenile and first adult moults (3.7% and 11% of total plumage mass respectively). Changes in colouration and communication behaviour correlated with relevant stages of the annual cycle, possibly to miminze conflict with territorial adults and age of first breeding. Remex and rectrix moult starts on average much later in relation to egglaying for Greater and some tropical kestrels than for some temperate species. This and other individual variation in timing may result for variations in nutritional status.     

THE WINTERING AND MOULT OF RUFFS PHILOMACHUS PUGNAX IN THE KENYAN RIFT VALLEY

Some 5700 Ruffs were ringed in the southern Kenyan rift valley during 1967–79, mainly at Lakes Nakuru and Magadi. These have produced 15 recoveries outside East Africa, 14 in Siberia between 73° and 154°E and one in India. Adult males returned to Kenya mainly during August, and females during late August and early September. Females greatly outnumbered males at all times. Most wintering males departed late in March and early in April, but females not until about a month later. First-year birds appeared from the end of August, but remained in low numbers until late October or November. Most departed during April and May, but a few females oversummered. First-year birds typically accounted for about 25% of the wintering Nakuru females, but about 50% of those at Magadi. At both sites they accounted for a higher proportion of male birds than females. Most of the birds at Nakuru throughout late August to May appeared to be local winterers, and many individuals remained in the area for many months each year. Retrapping indicated that approximately 60% of each season's birds returned the following season. Adult males and most adult females commenced pre-winter wing moult before arrival, but completed most of it in Kenya. Males moulted 3–4 weeks ahead of females, and most had finished before December. Females typically finished during December and early January. Most second year birds timed their pre-winter moult similarly to older adults. Suspension was recorded in over 15% of all moulting birds examined. Adult pre-summer moult involved most or all of the tertials, some or all of the tail feathers, most of the inner wing coverts and the body and head plumage. It occurred mainly during January to March (males) or February to April (females), although tertial renewal commonly began a month earlier. Males showed no sign in Kenya of the supplementary prenuptial moult. First-year birds moulted from juvenile into first winter body plumage during late September to November. They underwent a pre-summer moult similar in extent and timing to that of adults, and again about a month earlier in males than females. Spring feathers acquired were often as brightly coloured as those of adults. About 15% of first-year birds renewed their outer 2–4 pairs of large primaries during January to April. Adult and first-year birds fattened before spring departure, commonly reaching weights 30–60% above winter mean. Weights of adult males peaked early in April, those of adult females early in May, and those of first-winter females later in May. Weights were relatively high also during August and September. This was due to the arrival of wintering birds carrying ‘spare’ reserves, and also apparently to the presence of a late moulting fattening passage contingent. The wing length of newly moulted adults was about 3 mm longer than that of newly arrived first-year birds, but there was no evidence of an increase in the wing kngth of adults with successive moults. Adult wing length decreased by 4–5 mm between the completion of one moult and the middle stages of the next. The migrations and annual timetable of Kenyan wintering Ruffs are discussed, and their moult strategy is compared with that of other Holarctic waders.     

Annual Report of the Edward Grey Institute (May 1958, to April 1959)

First-brood Fan-tailed Warblers may begin nesting activity when only 3–¸4 months old, so that adult males face additional competition for their territory from midsummer. Both of these factors seem to influence the moult strategies shown by the species.     

The biannual primary moult of Willow Warblers Phylloscopus trochilus in Europe and Africa

The Willow Warbler Phylloscopus trochilus is one of the few bird species that undergoes two primary moults a year, a post-nuptial moult in the breeding area and a moult in the wintering area. Primary-moult data for Willow Warblers from Finland, Sweden, Britain, the Netherlands, Belgium. Guinea-Bissau, Uganda, Kenya, Malawi, Zambia, Zimbabwe, Botswana and South Africa are analysed. The parameters of primary moult (mean starting date, standard deviation of starting date, and duration) are estimated using the techniques of Underhill & Zucchini (T.988 Ibis 1 30: 358–372) and Underhill, Zucchini & Summers (1990 Ibis 132: 118-12 3). The scheduling of moult in relation to theother main components of the annual cycle, breeding and migration, is considered. The mean durations of post-nuptial moult for P. t. trochilus and P. t. acredula are 36.5 and 38.3 days, respectively; the start and termination of moult for P. t. trochilus are about 3.5 days later for each degree of latitude northwards, and the start and termination of moult for P. t. acredula, are about 10 days later than that of the most northerly populations of P. t. trochilus studied. Females start their postnuptial moult about 10 days later than males. Southward migration commences as soon as post-nuptial moult is complete. There is an increasing constraint on the timing of breeding and post-nuptial moult events at higher latitudes, leading to overlap between them. The duration of pre-nuptial moult is longer than that of post-nuptial moult, and is completed shortly prior to northward migration.     

The timing of gonadal development and moult in three raptors with different breeding seasons: effects of gender, age and body condition

Differences between species in breeding seasons are thought to be mediated through differences in their reproductive physiology. Little is known about how the timing and duration of gonadal maturation varies between raptor species, how the timing of moult relates to the gonadal cycle, whether the timing and degree of sexual maturation varies between juveniles and adults or whether body condition has a significant effect. To address these questions, data on gonadal size and moult for adults and juveniles of both sexes of three raptor species were extracted from the Predatory Bird Monitoring Scheme (based on birds found dead by members of the public). The three species, Sparrowhawk Accipiter nisus, Kestrel Falco tinnunculus and Barn Owl Tyto alba, have different ecologies – diurnal bird predator, diurnal mammal predator and nocturnal mammal predator, respectively. All are single‐brooded but have different breeding seasons. The duration of gonadal maturation was markedly different between the species. Barn Owls showed the earliest maturation and the latest gonad regression, and Sparrowhawks the latest maturation and earliest gonad regression. Kestrels were intermediate. In males of all species, the testes remained fully mature throughout their respective breeding seasons. In females, the ovaries remained partially mature throughout the breeding season. Moult started slightly earlier in Sparrowhawks than in Kestrels and coincided with gonadal regression in the two species. Although females of the two species started to moult earlier than males, moult duration was similar between the sexes. Barn Owls showed no distinct annual pattern of moult. In juveniles of all three species, the gonads were smaller than in adults throughout spring and started to mature later. Gonad size in birds that had starved tended to be smaller than in birds dying from other causes, but did not influence the difference in gonad mass between adults and juveniles and between seasons. Body condition had no effect on moult. Whilst ecology has led to the evolution of different breeding seasons, differences between species, and between adults and juveniles, are mediated through adaptive differences in their reproductive physiology.     

Sex‐specific patterns of fuelling and pre‐breeding body moult of Little Stints Calidris minuta in South Africa

The timing and duration of each stage of the life of a long‐distance migrant bird are constrained by time and resources. If the parental roles of males and females differ, the timing of other life stages, such as moult or pre‐migratory fuelling, may also differ between the sexes. Little is known about sexual differences for species with weak sexual dimorphism, but DNA‐sexing enables fresh insights. The Little Stint Calidris minuta is a monomorphic long‐distance migrant wader breeding in the Arctic tundra. Males compete for territories and perform elaborate aerial displays. Females produce two clutches a season. Each sex may be a bigamist and incubate one nest a season, each with a different partner. We expect that these differences in breeding behaviour entail different preparations for breeding by males and females, so we aimed to determine whether Little Stints showed any sex differences in their strategies for pre‐breeding moult and pre‐migratory fuelling at their non‐breeding grounds in South Africa. We used body moult records, wing length and body mass of 241 DNA‐sexed Little Stints that we caught and ringed between 27 January and 29 April in 2008–2018 at two neighbouring wetlands in North West Province, South Africa. For each individual we assessed the percentage of breeding plumage on its upperparts and took blood samples for DNA‐sexing. We calculated an adjusted Body Moult Index and an adjusted Wing Coverts Moult Index, then used the Underhill–Zucchini moult model to estimate the start dates and the rate of body moult in males and females. We estimated the changes in the sex ratio of the local population during their stay in South Africa, and also estimated the timing and rate of pre‐migratory fuelling and the potential flight ranges for males and females. The males started body moult on average on 7 February and the females on 12 February, but the sexes did not differ in their timing of wing covert moult, which started on average on 10 February. In January to mid‐February, males constituted c. 57% of the population, but their proportion declined afterwards, indicating an earlier departure than females. We estimated that both sexes began pre‐migratory fuelling on average on 15 March. The sexes did not differ in fuelling rate, but most females stayed at the non‐breeding site longer than the males, and thus accumulated more fuel and had longer potential flight ranges. These patterns of moult and fuelling suggest sex differences in preparations for breeding. We suggest that the males depart from South Africa earlier but with smaller fuel loads than the females to establish breeding territories before the females arrive. We conclude that for each sex the observed trade‐offs between fuelling and moult at the non‐breeding grounds are precursors to different migration strategies, which in turn are adaptations for their different roles in reproductive behaviour.     

Biannual complete moult in the Black-chested Prinia Prinia flavicans

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

The timing, duration and pattern of moult and its relationship to breeding in a population of the European Greenfinch Carduelis chloris

Moult was studied in 1 year among Greenfinches trapped in a garden in east‐central England. Over the period June–December 2003, 333 captures of 179 individual adults provided information on breeding condition, moult, body weight, sex and age (yearling or older adult, equivalent to birds in their second or later calendar years, respectively). About 95% of all birds (sex and age groups combined) started primary feather moult from 2 July to 14 August, and finished from 10 October to 22 November. The mean date of moult onset in the population as a whole was 24 July. On average, males began 8 days before females, and yearlings began 6 days before older birds. The mean duration of moult was 100 days, whether the figure was calculated for the population as a whole or just for the 36 individual birds that were caught more than once during moult. However, moult rate was slightly slower, and moult duration slightly longer, in yearlings than in older adults of both sexes. No evidence was found for any systematic relationship between moult onset date and rate (duration). Breeding and moult overlapped by up to 5 weeks or more in individual birds, and some birds probably started to moult as early as the incubation stage of their last clutch of the season. The cloacal protuberance (taken as indicative of breeding condition) had regressed in all males by the time the fifth primary was shed, and the brood patch had regressed and re‐feathered in all females by the time the fourth primary was shed. The bulk of feather replacement in the secondary, tail and body tracts occurred in the second half of primary moult, and after cloacal protuberances and brood patches were completely regressed. In all birds examined near the end of primary moult the secondaries were still growing, and would have continued growth for up to another 19 days or more, extending the end of the moulting season into December. Body mass during moult was affected significantly by sex and age, as well as by time of day, amount of food in gullet, reproductive condition and date. No firm evidence emerged that body mass was affected by moult stage, after allowing for effects of date and other variables (although there was a non‐significant negative relationship between moult stage and body mass in males). In the population as a whole, the breeding season (from first egg‐laying to independence of last young) was spread over 21 weeks and moult over 24 weeks. With an overlap between the two events at the population level of up to 9 weeks, the two processes together took up to 36 weeks, some 69% of the year.     

SEASONALITY, DENSITY AND DIVERSITY OF BIRDS OF A PAPYRUS SWAMP IN WESTERN KENYA

The commoner birds of a western Kenya papyrus swamp are listed. This avifauna is probably as rich as in any papyrus habitat, dominated by warblers (Sylviinae) in which interspecific competition between species of similar size is reduced by preference for swamp-edge rather than interior habitats, preference for papyrus over standing water, or vertical habitat partitioning. Comparisons with other west Kenyan habitats show that it is a specialized avifauna with low species diversity indices and few species. Density figures for common species are higher than in forest undergrowth or thicket. There is little ecological diversity of habitat in uniform stands of papyrus which form ecological islands, and this high density may be interpreted as a density compensation on a speciespoor ‘island’ compared to a species-rich ‘mainland’. Rainfall is the most seasonally variable climatic factor in west Kenyan papyrus habitats. In this climatic area of Uganda and western Kenya there is a modal egg-laying period from March to June coinciding with the long rains, and a postnuptial primary moult period from June to November, which extends into the short rains of October and November. On average, a complete moult of the remiges takes six or seven months. In general the moult of immatures begins and ends about two months later than adult moult, but birds reared during the short rains had primary moult only half complete at the beginning of the following long rains. There is very little evidence of interrupted moult. The 1969 rainfall pattern was exceptional, with the heaviest rainfall in February, and there is evidence of a correspondingly early onset of postnuptial moult in that year. Females moulted significantly earlier than males in 1969 whereas males moulted marginally earlier in other years, suggesting that female moult schedules are more flexible.     

The food of the Afrotropical nightjars

Jackson, H.D. 2000. The food of the Afrotrapical nightjars. Ostrich 71(3&4): 408-415. A synthesis of 722 published and unpublished records of nightjar stomach contents from Afrotropical specimens was undertaken. Coleoptera were found in 84.6% of the stomachs, often in substantial numbers, beetles providing these birds with their staple diet. Lepidoptera occurred in 34.9% of the stomachs and were often present in large numbers; moths are an extremely important part of the nightjar diet in the Afrotropics, especially during winter. Orthoptera, Hemiptera and Dictyoptera, although present in 24.7, 16.3 and 11.5% of the stomachs, respectively, usually occurred in rather small numbers. Hymenoptera and lsoptera were often present in great numbers, yet were found in only 10.4 and 10.1% of the stomachs, respectively, so a limited number of individual nightjars had found emerging swarms of alate ants or termites in season. Neuroptera, Diptera, Odonata and Dermaptera were found in a few stomachs (2.4, 1.2, 0.6 and 0.3%, respectively) but these insects clearly play a very small part in the diet of nightjars in the Afrotropics. Similarities and differences in diet between some closely related nightjar species are discussed. Grit was found in 16 stomachs only, so deliberate ingestion of stones to aid digestion is regarded as extremely unlikely among nightjars in the Afrotropics. The contents of a full stomach may account for as much as 20-25% of the body mass of a nightjar.     

The effect of a period of food restriction on gonad size and moult of male and female Starlings Sturnus vulgaris under constant photoperiod

The effects of food availability on the reproductive cycle and on the timing and duration of moult were investigated in first-year male and female Starlings Sturnus vulgaris under a constant photoperiod of 12 hours. A 20% lower body mass during the first 9 weeks of restricted feeding had a slight negative effect on testicular growth during the first 3 weeks of the experiment and delayed the onset of moult for 12 days after the return to ad libitum feeding conditions. No effects were found on changes of beak colour and moult duration of males. Females exposed to the shorter feeding time similarly showed a reduced body mass (21%) but compared with controls, did not differ in beak colour, in follicle growth, or in the onset and duration of moult. In contrast to males, body mass of the experimental females after the food restriction period remained lower for more than 6 weeks, compared to control birds. Females had a longer reproductive cycle and started moult later than males. The later an individual started to moult, the faster it moulted. Two females started to moult extremely late and did not moult their first primaries.
These results indicate that in male Starlings food restriction slightly affected the rate of photoinduced gonadal growth and the onset of postnuptial moult. These effects were not observed in females subjected to the same experimental conditions.     

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.     

Prolonged and flexible primary moult overlaps extensively with breeding in beach‐nesting Hooded Plovers Thinornis rubricollis

We present the first report of complete overlap of breeding and moult in a shorebird. In southeastern Australia, Hooded Plovers Thinornis rubricollis spend their entire lives on oceanic beaches, where they exhibit biparental care. Population moult encompassed the 6‐month breeding season. Moult timing was estimated using the Underhill–Zucchini method for Type 2 data with a power transformation to accommodate sexual differences in rates of moult progression in the early and late stages of moult. Average moult durations were long in females (170.3 ± 14.2 days), and even longer in males (210.3 ± 13.5 days). Breeding status was known for most birds in our samples, and many active breeders (especially males) were also growing primaries. Females delayed the onset of primary moult but were able to increase the speed of moult and continue breeding, completing moult at about the same time as males. The mechanism by which this was achieved appeared to be flexibility in moult sequence. All moult formulae fell on one of two linked moult sequences, one faster than the other. The slower sequence had fewer feathers growing concurrently and also had formulae indicating suspended moults. Switching between sequences via common formulae is possible at many points during the moult cycle, and three of 12 recaptures were confirmed to have switched sequences in the same moult season. Hooded Plovers thus have a prolonged primary moult with the flexibility to change their rate of moult; this may facilitate high levels of replacement clutches that are associated with passive nest defence and low reproductive success.     

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.     

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.     

Notes on the moult of red-backed shrikes ( Lanius collurio ) in their non-breeding range

Moult data from 302 museum skins and 11 trapped birds from sub-Saharan Africa show the course of flight feather moult. Most birds seem to start flight-feather moult soon after arrival in their southern African non-breeding ranges. About 75% of the birds had started before mid-December, i.e., during the main arrival time of the species. The mode of moult scores 1 and 2 was reached on 7 December; the last birds with a score of zero occurred in the first days of January. The mode of moult scores 5 and 6 was reached on 27 February. Thus, the time elapsed between the days when 50% of the population had reached the first and last stages of recorded moult was about 82 days; nine days later 75% had reached this last stage before moult was completed. Thus, individual moult may be estimated to cover about 80–90 days. The main moulting period is between mid-November and mid-March, thus covering about four months. No temporal difference was detected between males and females. A tendency for an advancement of adults compared to young birds was not statistically significant. According to the progress of the moult, sexing of young birds in the field is possible for 50% of the birds towards the end of January and for most birds before mid-February.     

Sex‐dependent response of primary moult to simulated time constraints in the rock sparrow Petronia petronia

There is growing evidence that moult speed affects plumage quality. In many bird species, males and females differ in terms of breeding effort, survival expectation and the relationship between fitness and plumage quality. Consequently, differences in moult strategies between the sexes can be expected. The aim of this study was to assess whether, under simulated time constraints and with no parental investment in the previous breeding season, males and females differed in: a) timing and duration of primary moult, b) growth rates of individual primary feathers, and c) number of concurrently growing feathers. We investigated the effect of time constraints generated by a treatment consisting of two decreasing photoperiods (slow changing photoperiod, SCP=2 min day^?1 and fast changing photoperiod, FCP=8 min day^?1) on the primary post‐nuptial moult of captive rock sparrows Petronia petronia. Females started to moult on average 14 and 15 days later than males in both experimental groups. Primary moult duration was 10 (FCP) and 24 (SCP) days longer in males than in females, and, within sex, 34 (females) and 48 (males) days longer in SCP birds than in FCP ones. Females renewed a larger number of primaries simultaneously (5.7% in FCP and 12.8% in SCP) and had a higher total daily feather mass grown (9.9% in FCP and 22.4% in SCP), even though daily growth rates of individual primaries did not differ between sexes. As a result, males and females completed their primary moult at the same time within treatment. The observed differences in timing, duration and energy allocation for primary moult between the sexes probably have a genetic basis, as birds did not engage in reproduction during the preceding breeding season.