Suspended Moult Research Articles

Estimation of moult duration in birds with suspended moults: the case of the Red Crossbill and its relation to reproduction

Suspended moult is a relatively common phenomenon in birds, but it has remained relatively ignored for a long time in studies dealing with moulting process. Furthermore, the new and increasing number of models used to estimate moult duration systematically omit the fact that suspended moults can occur and that they significantly alter parameter estimates. Taking suspended moults into account is critical to obtain reliable moult-associated parameter estimates, which is fundamental given the demographic and evolutionary consequences of moult in birds. The main goal of this work is to develop a standardised method useful for characterising the main moulting parameters (such as the duration and starting date) of bird species that perform suspended moults. Additionally, with the aim of delving into our understanding of when and why suspended moults happen, we study their relationship with the occurrence of second breeding attempts in summer. We used data obtained from a Red Crossbill population in the Pyrenees during a period of 17 years. We observed that the percentage of crossbills undergoing suspended moult was approximately 50% during summer (July–August) and that moult suspension ultimately gives rise to a lengthened moulting period. Underhill–Zucchini models assume a time-linear replacement of feathers, overestimating the moult duration. Based on these same modelling approaches, we proposed a method to calculate the real moult duration after removing the time during which the moult was suspended. We also obtained evidence supporting the idea that crossbills suspend their moult as a strategy that could increase their breeding output in summer. The method proposed here can be used as a tool for working with species that undergo suspended moults.

Flight feather moult in Western Marsh Harriers during autumn migration

BackgroundMost of long-distance migratory raptors suspend moult during migration but detailed information is patchy for most of the Palearctic species. The aim of this research is to verify if active moulting in migrating Western Marsh Harriers occurs and to quantify the extent of moulting along the season focusing on primary feathers.MethodsDuring a whole post-breeding migration at the Strait of Messina in Southern Italy, we gathered information about symmetrical flight feather moult from 221 adults by taking pictures of raptors passing at close range.ResultsWe found active moulting primaries during autumn migration in 48.4% of our samples. Slight differences on the extension and timing among sex classes were recorded during the season, with adult females showing a more advanced moult stage than adult males.ConclusionThe finding that the extension of the suspended moult was already defined in migratory individuals might be explained as an adaptation to minimize the energy required for moulting during migration.

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

ABSTRACTCapsule: 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.

Moult in the Loggerhead Shrike Lanius ludovicianus is influenced by sex, latitude and migration

We investigated moult strategies in Loggerhead Shrikes by examining first prebasic or preformative moult patterns and by assessing the general location where individual feathers were grown using stable hydrogen isotope (δ2H) analysis. We tested the relative importance of factors known to impact moult timing and pattern, including age, sex, body size, food availability and migration. Migratory Shrikes showed evidence of suspended moult, in which feathers are moulted on both the breeding and the non‐breeding grounds with a suspension of moult during migration. Extent of moult was best explained by sex, longitude, migratory behaviour and breeding‐ground latitude. Male Hatch Year (HY) Shrikes replaced more feathers on the breeding grounds prior to migration than did HY females and moulted more extensively on the breeding grounds than did females. Non‐migratory HY Shrikes underwent a more extensive preformative moult than migratory HY Shrikes. Individuals in more southerly migratory populations moulted more extensively on the breeding grounds than did those breeding further north. Our data also indicate that individuals in the northeastern populations moulted more extensively on the breeding grounds than did those in the north and southwest. Our study underlines the complex structure and variation in moult possible within species, revealing surprising levels of differentiation between sexes and age cohorts, linked to environmental factors on the breeding grounds. Our study highlights the utility of an intrinsic marker, specifically δ2H analysis, to test hypotheses regarding the evolutionary and ecological forces driving moult. Although the methodology has not commonly been applied to this area of research, our results indicate that it can provide unprecedented insight into inter‐ and intra‐specific adaptive response to constraints, whereby individuals maximize fitness.

Atypical moult of the secondary feathers in Spectacled Warbler Sylvia conspicillata

Moult of Spectacled Warbler Sylvia conspicillata was studied in central Spain. Between April 2010 and August 2013, 136 adult birds were captured and 43 of these were moulting. Of the moulting birds, 30% had atypical moult of secondary feathers, indicative of suspended moult and the retention of old feathers.

Seasonal patterns of breeding, moulting, and body mass variation in Pyrenean Common Crossbills Loxia curvirostra curvirostra

The aim of this study was to investigate the relationship between breeding, moulting and fuel load of Common Crossbills Loxia curvirostra curvirostra inhabiting a Scots pine Pyrenean forest. Data were collected from two locations (Sierra de Uztarroz and Bigüezal) in northern Iberia by systematic mist netting between 2000 and 2008. Breeding females were detected in most months of the year except June, October and November, and with two main peaks, one in late winter (March), and another in the summer (August). Between years, reproduction was more variable in some months than in others, particularly in summer months. This suggests that breeding during the summer was more likely to be influenced by external factors and relatively opportunistic compared to winter breeding. Moulting adults of both sexes were captured during almost every month with a unimodal pattern peaking in June, similar to the pattern described for Mediterranean Crossbills. Moulting did not overlap with breeding, and our data do not support suspended moult patterns. Mean fat scores overall were low and, as was the case for body mass, showed little month-to-month variation.

Primary moult, body mass and migration of Grey Plovers Pluvialis squatarola in Britain

Long‐distance migrants have evolved complex strategies for the timing of their annual moult, fattening and migration cycles. These strategies are likely to vary at different stages of a bird's life. Ringing data on 6079 Grey Plovers Pluvialis squatarola, caught on the Wash, England, between 1959 and 1996, were analysed to relate migratory strategies to patterns of primary moult and body mass changes. Adults returning from breeding grounds had a shorter and delayed primary moult (duration 90 days, starting date 19 August) in comparison with over‐summering birds (duration 109 days, starting date 5 June). Three categories of migrant adults were identified on the basis of primary moult and body mass: (1) birds which did not moult, but increased body mass and migrated further south; (2) birds which moulted 1–3 inner primaries, suspended moult, increased body mass and migrated; and (3) birds which completed or suspended moult and wintered locally. In birds of the second category, timing of primary moult and body mass increase overlapped. Among wintering birds, 38% were in suspended moult. Ninety‐six per cent of birds that suspended moult at the beginning of winter were males and almost all completed moult in spring. Grey Plovers which left Britain in autumn had an average body mass of 280 g, enough to reach southern Morocco without refuelling. Both wintering adults and first‐year birds showed a prewinter body mass increase, peaking in December. Adults had a synchronized premigratory body mass increase in May, which suggested a negligible presence of African migrants. The average departure mass for spring migration, estimated at 316 g, would allow birds to fly non‐stop to the Siberian breeding grounds in western Taymyr.

Fifteen years of the Common Snipe (Gallinago gallinago) study at the Jeziorsko reservoir with some notes about weight and moult

Fifteen years of the Common Snipe (Gallinago gallinago) study at the Jeziorsko reservoir with some notes about weight and moult The Students's Section from University of Łódź organises ringing camp at the dam reservoir every year. The aim of the camp is wader and duck ringing. One of the most numerous species of bird ringed is the Common Snipe. During 15 years (1989-2003) of studies 4142 individuals of this species were ringed. Age ratio differed among years, but every year young birds represented more that 80% of all ringed individuals. Snipes caught in September caused problems with age identification and that impeded to obtain correct age ratio each year. Analysis of weight of caught birds revealed between-years variation in juvenile birds, adults were excluded from analysis due to small sample size. Throughout the autumn months the increase in mean body mass in young birds was observed. Data about moult suggest that adult birds show two main strategies of primary moult: traditional moult and suspended moult. Both of them are of the same frequency. Tail feathers are moulted by juveniles as well as by adults simultaneously.

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.

Factors influencing the onset of post‐nuptial moult in Willow WarblersPhylloscopus trochilus

A long‐term study (1975 to 1989) on a population of Willow Warblers showed that in each year the majority of male birds commenced post‐nuptial moult before females. It is suggested that this was due, in part, to an annual rhythm in moult onset and was fine‐tuned, in both sexes to different degrees, during their first summer by other endogenous factors possibly linked to breeding. The majority of males commenced moult in June, regardless of whether replacement or second broods were being reared in July, but females synchronised onset of moult to the independence of their young. Two late breeding females suspended moult until their young were independent. Photoperiod alone probably had no bearing on the onset of moult in the majority of birds, but this factor may influence the rate of moult in late moulting individuals. Suspension of moult before migration probably involves late breeding females, and is discussed speculatively.

On the Control of Suspended Moult in an European Trans-Saharan Migrant, the Orphean Warbler

Suspended moult is a special adaptive moult strategy which is widespread in long-distance migrants. The replacement of remiges and rectrices in this type of moult starts before migration but then is interrupted during migration. So far, it has virtually not been investigated experimentally. We carried out an investigation on the Orphean Warbler, Sylvia hortensis, an European trans-Saharan migrant known commonly to suspend its moult. We studied 15 trapped adults and 8 handraised young individuals, which were kept in light conditions simulating those to which freeliving conspecifics are normally exposed in the course of a year. In the first experimental year, the adults, caught during breeding, all suspended their moult and retained some old primaries, secondaries, and tertials. In the second experimental year, when the same birds were prevented from breeding, they moulted weeks earlier, and, as a result, completed their moult before the migratory period. Similarly, the handraised birds showed a complete moult in their second year. Thus, the suspended moult of the Orphean Warbler is not based on strictly endogenously controlled moult programs with preprogrammed moult pauses. Moult in this species can be adapted on a facultative basis to various conditions experienced. The course of the moult and its suspension appear to be linked to the preceeding individual breeding season, and some conceivable control mechanisms are discussed in detail.

The suspension of moult by trans-Saharan migrants in Crete

A higher incidence of suspended moult is found among trans-Saharan migrants on passage in Crete than in Iberia. Evidently east European birds have less time to complete their moult before autumn migration, and this is probably linked to later breeding seasons.