Timing and duration of moult in three populations of Purple Sandpipers Calidris maritima with different moult/migration patterns

Timing and duration of primary moult in three populations of Purple Sandpipers Calidris maritima were described and discussed in relation to the birds’ need to complete moult before the onset of winter, when resources are required for survival. We predicted that moult would be completed earlier by birds wintering at higher latitudes. The south Norwegian breeding population, which moults and winters along the coast of east Britain (54–57°N) had a mean starting date of 21 July for primary moult (16 July for females and 24 July for males), a mean duration of 61 days, and completed on 20 September. Resident Icelandic (64–65°N) birds had a mean starting date of 22 July for primary moult (17 July for females and 25 July for males), a mean duration of 51 days, and completed on 11 September. Birds moulting in north Norway (70°N) arrived in north Norway in suspended primary moult or without having started moult, and completed it there. They had a mean completion date of 2 November for primary moult (31 October for females and 3 November for males). Starting date and duration could not be estimated because some suspended moult for an undetermined period, but it was thought that they started in late August. It is likely that most originated from Russia. The onset of moult appears to be set by the end of breeding and there is little overlap in these two events. The earlier start of moult by females in all three populations may be because they abandon the males when the chicks hatch, leaving the males to attend the chicks. Although the duration of primary moult followed the expected trend, being fastest in north Norway and slowest in Britain, the onset of moult was so late in north Norway that they had an unexpectedly late completion date, despite their rapid moult. The late completion of primary moult in north Norway suggests that wintering in the far north may not pose the energetic constraints on Purple Sandpipers that had previously been supposed.     

Rapid moult among palaearctic passerines in West Africa- an adaptation to the oncoming dry season?

Moult of some palaearctic migrant passerines was studied at a wintering site in northern Ghana, West Africa. We present data on moult pattern and estimated moult duration for a sample of species. Savi's Warbler Locustella luscinioides , Woodchat Shrike Lanius senator and probably Grasshopper Warbler Locustella naevia deviated from the ordinary descendent moult sequence. Different measures of moult speed (moult speed of retrapped individuals, growth of individual feathers, wing raggedness and first date of completion of moult) showed unexpectedly rapid moult among individuals of several species, notably the Great Reed Warbler Acrocephalus arundinaceus and the Sedge Warbler A. schoenobaenus. The rapid moult might be an adaptation to a limited period of abundant food which comes to an end at the beginning of the dry season.     

A comparative study of migratory behaviour and body mass as determinants of moult duration in passerines

Birds moult to maintain plumage function through life, but the factors that determine moult duration are poorly understood. In temperate areas, variation in moult duration could be largely associated with between-species differences in migratory behaviour (migrants have less time for moulting after breeding), and body mass (because the aerodynamic cost of rapid moult increases allometrically with body size). Moreover, if the energetic cost of transport favours a smaller body size in migratory species, then the effects of migratory behaviour and body mass on moult duration could be confounded. We conducted a comparative study of the duration of adult complete moult in 48 European passerine species, in relation to body mass and migratory behaviour (sedentary, short-distance migrants and long-distance migrants). Lighter and more migratory species moulted faster than heavier and more sedentary species, but migration was not associated with body mass. If accelerated moult compromises the success of migration, changes in the physiology or phenology of moult in migratory birds are better interpreted as adaptive responses to compensate for such costs.     

Relationships among timing of moult,moult duration and feather mass in long‐distance migratory passerines

Moult is a costly but necessary process in avian life, which displays two main temporal patterns within the annual cycle of birds (summer and winter moult). Timing of moult can affect its duration and consequently the amount of material invested in feathers, which could have a considerable influence on feather structure and functionality. In this study, we used two complementary approaches to test whether moult duration and feather mass vary in relation to the timing of moult. Firstly, we conducted a comparative study between a sample of long‐distance migratory passerine species which differ in moult pattern. Secondly, we took advantage of the willow warbler's Phylloscopus trochilus biannual moult, for which it is well‐known that winter moult takes longer than summer moult, to assess between‐moult variation in feather mass. Our comparative analysis showed that summer moulting species performed significantly shorter moults than winter moulters. We also detected that feathers produced in winter were comparatively heavier than those produced in summer, both in between‐species comparison and between moults of the willow warbler. These results suggest the existence of a trade‐off between moult speed and feather mass mediated by timing of moult, which could contribute to explain the diversity of moult patterns in passerines.     

Primary moult of continental Black-tailed Godwits Limosa limosa limosa in the Doñana wetlands,Spain

Capsule: Most Continental Black-tailed Godwits Limosa limosa limosa using the Doñana wetlands during post-breeding migration appear to begin moult before they arrive and suspend moult before they migrate onwards to West Africa.

Aims: We aim to describe the primary moult strategies and patterns in the Continental Black-tailed Godwits using the Doñana wetlands, a major passage and wintering area for waterbirds in southern Spain.

Methods: Individual godwits were captured, marked and their primary moult was scored in Doñana during the non-breeding season (June–March) in 2011 and 2012. Data from resightings of colour-marked godwits and birds equipped with satellite transmitters were used to estimate stopover duration during post-breeding migration (June–September) to determine if godwits move to West Africa before completing their primary moult.

Results: Average primary moult duration was estimated to be 84 days?±?9 se, during 29 June–21 September and did not differ between sexes. Only 2% of individuals were observed with suspended moult. We estimated stopover duration in Doñana to be 13 days?±?2 se before migrating to West Africa.

Conclusions: Most godwits stage for about two weeks in the Doñana wetlands during southward migration, moult their primaries and appear to suspend moult before crossing the Sahara. Others may complete their primary moult in Doñana, or elsewhere in Europe and overwinter in Doñana where increasing numbers of godwits have been detected in recent years. A few individuals may finish the moult in Doñana and migrate to West Africa late in the post-breeding season.     

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.     

Plasticity of moult and breeding schedules in migratory European Stonechats Saxicola rubicola

Timing is crucial in seasonal environments. Passerine birds typically use a combination of physiological mechanisms and environmental cues to ensure that breeding, moult and migration occur without major temporal overlap and under the most favourable conditions. However, late in the breeding season some individuals initiate additional clutches , whereas others initiate moult. Such alternative strategies are thought to reflect trade‐offs between reproductive benefits and timely investment in maintenance and survival. The degree of seasonal plasticity differs between species, depending on the mechanisms that govern their annual routine. Migrants are generally under pressure to complete breeding and moult before the autumn departure and often show little plasticity. We studied seasonal plasticity of breeding and moult schedules in the European Stonechat Saxicola rubicola. This species, an obligate short‐distance migrant in Central Europe, sometimes initiates late clutches after typically at least two earlier breeding attempts. Based on life‐history theory and on observations in captivity, which revealed photoperiodic regulation of breeding and moult, we predicted relatively little seasonal plasticity in Stonechats. We further predicted that reproductive gains of late breeders should be offset by reduced survival. These predictions were tested on long‐term field data, using Underhill–Zucchini models to estimate moult. Late breeding occurred in c. 40% of pairs and increased their reproductive success by a third. Both sexes modified moult timing but in different ways. Late breeding females postponed moult approximately until chick independence without compensating for delay by faster moult. Males started moult on time and overlapped it with breeding, associated with markedly slowed plumage change. Sex differences in moult score increased with lay date, but due to their respective modifications, both sexes delayed moult completion. Nonetheless, we could not detect any evidence for survival costs of late breeding. Breeding and moult of European Stonechats appear relatively flexible, despite migratory schedules and photoperiodic programs for seasonal timing. Individuals can modify seasonal behaviour in late summer, presumably depending on their condition, and may profit considerably from extended breeding.     

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 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.     

Moult cycle and its chronology in Mysis mixta and Neomysis integer (Crustacea, Mysidacea): implications for growth assessment

The moult-staging technique was used to determine the main moult stages (MS) and their duration in laboratory-reared juveniles and subadults of Mysis mixta and Neomysis integer. The relative duration of each stage was similar for both species with premoult occupying the major part of the moult cycle (51% and 44% for M. mixta and N. integer, respectively), followed by postmoult (26% and 34%) and intermoult (23% and 22%). Effects of temperature and feeding regimes on the chronology of the moult cycle were investigated. When the duration of the moult cycle (MCD) was extended by manipulating the feeding regime, animals prolonged their late postmoult and early premoult stages. At 12 and 5 °C, no specific moult stage varied in relative duration as long as food supply was high. Field application of moult staging for growth assessment was tested using wild-caught M. mixta. The MCD estimated via moulting experiments was compared to that obtained by analyzing moult stage distribution combined with the experimentally obtained data on stage duration. Close correspondence between two methods of MCD assessment was observed with moult-staging technique being particularly useful in situations when conducting of experiments immediately after collection is not feasible.     

Variation in the wing-clapping display of Clapper Larks

The pied plumage of the adult Black Sparrowhawk is rather exceptional in the genus Accipiter and it could be explained by functionality or by phylogenetic relationships. The moult pattern of museum specimens is presented, supplementing information from captive birds. The post-juvenile moulting sequence is similar to that of the Northern Goshawk. The moult of primaries starts at, or just after, the beginning of body moult; moult of the secondaries also starts early and progresses from three consecutive foci, and tail moult starts early but is less predictable. A few body feathers and tail feathers may remain in place until the second moult. The pied flank feathers appear at an early stage. Some adult specimens are in arrested annual moult. Two with definite serially-descendant moult were discovered; this is related to the fact that the species is known to be double-brooded. Serially descendant moult was not known in this species and is rarely mentioned in the genus. Possible functions of the pied plumage are discussed: crypsis, mimicry, hunting strategy, and sexual attraction. Its taxanomic status is obscure. Although the streaked juvenile plumage of the Black Sparrowhawk is similar to those of the Northern Goshawk A. gentilis, Meyer's Goshawk A. meyerianus and Henst's Goshawk A. hentsi, adult and juvenile plumages are variable within the genus, and thus are not a reliable indicator of taxanomic relationships.     

Do Seaducks Minimise the Flightless Period?: Inter- and Intra-Specific Comparisons of Remigial Moult

Remigial moult is one of the crucial events in the annual life cycle of waterfowl as it is energetically costly, lasts several weeks, and is a period of high vulnerability due to flightlessness. In waterfowl, remigial moult can be considered as an energy-predation trade-off, meaning that heavier individuals would minimise the flightless period by increasing feather growth rate and energy expenditure. Alternatively, they could reduce body mass at the end of this period, thereby reducing wing-loading to increase flight capability. We studied timing of remigial moult, primary growth rates, flightlessness duration, and the pattern of body mass variation in 5 species of captive seaducks (Melanitta fusca, M. perspicillata, Clangula hyemalis, Histrionicus histrionicus, and Somateria mollissima) ranging in size from 0.5 to 2.0 kg. Their feather growth rates weakly increased with body mass (M^0.059) and no correlation was found at the intra-specific level. Consequently, heavier seaduck species and especially heavier individuals had a longer flightless period. Although birds had access to food ad libidum, body mass first increased then decreased, the latter coinciding with maximum feather growth rate. Level of body mass when birds regained flight ability was similar to level observed at the beginning of remigial moult, suggesting they were not using a strategic reduction of body mass to reduce the flightlessness duration. We suggest that the moulting strategy of seaducks may be the result of a compromise between using an intense moult strategy (simultaneous moult) and a low feather growth rate without prejudice to feather quality. Despite the controlled captive status of the studied seaducks, all five species as well as both sexes within each species showed timing of moult reflecting that of wild birds, suggesting there is a genetic component acting to shape moult timing within wild birds.     

CHAIRMAN'S REPOST, 1954–55

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

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

Population structure,biometrics and moult of migrant Purple Sandpipers Calidris maritima in southwest Iceland in spring

Capsule Iceland is a stop‐over site for a population of Purple Sandpipers that winter in Britain. Here, they accumulate fuel loads for onward migration along with birds that have wintered in Iceland.

Aims To establish whether Purple Sandpipers from Britain stop‐over in Iceland during spring migration and, if so, to describe their population structure, changes in mass and moult.

Methods Purple Sandpipers were cannon‐netted on the coast of the Reykjanes Peninsula in southwest Iceland during May 2003 and 2005. Birds were aged, sexed (some by DNA) and standard biometric measurements made. Active body moult was scored.

Results Bill and wing lengths showed that the Purple Sandpipers we caught were similar to one of the populations that winter in Britain rather than Icelandic breeding birds. There were more males than females throughout the migration period (63% males for first‐year‐birds and 67% for adult birds). Accounting for a bias due to a higher percentage of males in a less usual habitat (muddy/sandy bays), the values for rocky sites were 52% males for first‐year birds and 62% for adults. The percentage of first‐year birds was 19% in 2003 and 32% in 2005, though the latter figure was biased by catches in muddy/sandy bays where there was a higher percentage of young birds. The percentage of first‐year birds was 25% on just the rocky shores in 2005. Many birds were in latter stages of body moult, and males were slightly in advance of females. Increasing mass showed that they were preparing for onward migration. The average increase of 0.58 g per day was similar to the rate measured in Orkney at an earlier point on the migration route. However, a high turnover of birds could be the reason for these low values. By late May, and close to the assumed departure date, the Purple Sandpipers of the different age/sex classes had fuel indices of 24–29% (33–42% of the lean mass). This was lower than that for the high Arctic sandpipers (Knots and Sanderlings) leaving southwest Iceland for Greenland and Canada.

Conclusions Our study confirmed that Purple Sandpipers do stop‐over in Iceland, and the possible lower rate of fuel accumulation and smaller amount stored, compared with Knots and Sanderlings, suggests a different migration pattern.     

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.     

Moult Strategies Affect Age Differences in Autumn Migration Timing in East Mediterranean Migratory Passerines

Adult passerines renew their flight feathers at least once every year. This complete moult occurs either in the breeding areas, just after breeding (summer moult), or, in some long-distance migratory species, at the non-breeding areas, after arrival to the southern wintering area at the end of autumn migration (winter moult). The aim of this study was to relate moult strategies with the DMD, the difference in median migration date, through Israel, between juveniles and adults. Our data on autumn migration timing in juveniles and adults was based on ringing data of 49,125 individuals belonging to 23 passerine species that breed in Europe and Western Asia and migrate through Israel. We found that DMD was associated with moult timing. In all species that perform a winter moult, adults preceded juveniles during autumn. Among migrants who perform a summer moult, we found evidence of both migration timing patterns: juveniles preceding adults or adults preceding juveniles. In addition, in summer moulters, we found a significant, positive correlation between mean breeding latitude and DMD. Although previous studies described that moult duration and extent can be affected by migration, we suggest that moult strategies affect both migration timing and migration strategy. These two moult strategies (summer or winter moult) also represent two unique migration strategies. Our findings highlight the evolutionary interplay between moult and migration strategies.     

Wing-feather moult phenotypes differ between the preformative and prealternate episodes and along passerine phylogeny

Passerine wing-feather moult has been studied historically in terms of its intensity, duration, timing and extent. However, little is known about variation of wing-moult phenotypes (i.e. the identity of moulted wing feathers in a given individual) within species, among moult episodes and in relation to passerine phylogeny. Here we studied 5373 wing-moult cards from 285 Holarctic and 155 Neotropical passerine species. Variation of moult phenotypes, although high, was far below that expected by chance, and the same phenotypes were repeated among individuals within and among species, suggesting the existence of shared mechanisms of moult control. We successfully classified moult phenotypes according to nine moult patterns described in the literature and found an uneven distribution between the preformative and the prealternate moult. Moult patterns were phylogenetically conserved for the preformative but not for the prealternate moult. Our results suggest differential seasonal control of bird moult with preformative moults being associated with (evolutionarily conserved) somatic demands, whereas prealternate moults are probably associated with (rapidly evolving) signalling functions.     

Sociable Weaver biometrics and primary moult

The biometric and primary moult data housed at the South African Bird Ringing Unit (SAFRING) were analysed for the Sociable Weaver Philetairus socius. The average body mass and wing length was 27.9g (SD = 2.2) and 74.1mm (SD = 2.5), respectively. Variation in these parameters is not clearly correlated with region, season or climate, other than a negative correlation of body mass with average annual water deficiency. Body mass of Sociable Weavers near Kimberley showed a longterm decrease of 2.9g, probably due to stabilising selection on mass. Primary moult duration varied from 152 days to 169 days and started between 26 January and 31 December in two populations (socius and South African eremnus respectively). Individual primaries moulted mainly one at a time, each taking 20–28 days to grow fully. Prolonged moult duration in this species is probably an adaptation to reduce energy expenditure, and to grow more durable feathers due to abrasion in entering the nest. The lack of clear patterns of geographical variation in biometrics indicates that the contiguous populations of Sociable Weaver should belong to the nominate species. The biometric and primary moult data housed at the South African Bird Ringing Unit (SAFRING) were analysed for the Sociable Weaver Philetairus socius. The average body mass and wing length was 27.9g (SD = 2.2) and 74.1mm (SD = 2.5), respectively. Variation in these parameters is not clearly correlated with region, season or climate, other than a negative correlation of body mass with average annual water deficiency. Body mass of Sociable Weavers near Kimberley showed a longterm decrease of 2.9g, probably due to stabilising selection on mass. Primary moult duration varied from 152 days to 169 days and started between 26 January and 31 December in two populations (socius and South African eremnus respectively). Individual primaries moulted mainly one at a time, each taking 20–28 days to grow fully. Prolonged moult duration in this species is probably an adaptation to reduce energy expenditure, and to grow more durable feathers due to abrasion in entering the nest. The lack of clear patterns of geographical variation in biometrics indicates that the contiguous populations of Sociable Weaver should belong to the nominate species.     

Reproductive phenology of a natural population of Armadillidium pelagicum Arcangeli, 1955 (Isopoda, Oniscidea)

Armadillidium pelagicum, the most abundant species of the genus in Tunisia is endemic to the North of Tunisia and the circumsicilian islands. In the laboratory and under the natural conditions of temperature and photoperiod, virgin females of A. pelagicum exhibit a spontaneous ovarian maturation, followed by a parturial moult. Nevertheless, the onset of reproduction is greatly accelerated by the presence of a male. In fact, mating shortened the lag time (from the beginning of experiment to the parturial moult) by reducing the number of normal moult preceding the first parturial moult and the duration of the preparturial intermoult. In this species, only one mating is enough to ensure the fertility for several egg layings. Otherwise, it has been shown that A. pelagicum has a reproductive period rather than a reproductive activity and that mating females have a longer reproductive period than virgins. Like several species of terrestrial Isopods, the duration of the gestation period is temperature-dependent.     

Aggression in shorebirds in relation to flock density and composition

The aggressive interactions of Turnstones and Purple Sandpipers feeding in wintering mixed-species wader flocks could be classified into those involving food and those involving space. All observed interspecific encounters were of short duration and were initiated and won by the larger species; the majority did not involve food and were resolved by low-intensity displays. Intraspecific interactions (a greater proportion of which involved food) were also resolved quickly and were usually won by the initiator. Space-related encounters between conspecifics were more likely to be resolved than food-related encounters just by threat displays. Aggression rates increased with flock densities. However, the increase in aggression with density was dependent on the species composition of the flock: both Turnstones and Purple Sandpipers were more likely to be involved in fights (both over food and over space) with conspecifics than with other species, indicating that the aggression costs of flocking were less in mixed-species flocks.