Moult Scores Research Articles

Primary moult of adult Laughing Doves Spilopelia senegalensis: introduction of the relative duration index and a comparison of moult indices

A new moult index, the relative duration index (RDI), was developed to quantify progress through moult using the Underhill–Zucchini model of primary avian moult, with the Laughing Dove Spilopelia senegalensis as a case study. The RDI weights individual primaries in accordance with their estimated relative moult durations in the same way that proportion feather mass grown (PFMG) weights primaries in accordance with their relative masses. A sample of 1 893 moult records of adult Laughing Doves was used to study their primary moult. Moult parameters were estimated for three moult indices: the traditional moult score (TMS), PFMG and the RDI, and for each of the 10 primaries. Comparing the moult parameter estimates of each of the three indices to their respective cumulative growth curves obtained from the progression of moult of individual primaries, PFMG had the closest fit. However, any of the three moult indices would give satisfactory results for the Laughing Dove. Laughing Doves had an estimated primary moult duration of 215 days, with mean start and end dates of 3 November and 6 June, respectively. The standard deviation parameter was 66 days, which implies a lack of synchronisation of moult in adult doves. It was hypothesised that the RDI might be an appropriate moult index for species that moult one feather at a time and for which the individual moult durations are not proportional to their mass, as seen in Laughing Doves. However, this was not the case as PFMG provided the best fit. The RDI might also prove to be an appropriate moult index for species that moult multiple feathers simultaneously during part of the moult period and these feathers grow more slowly than when fewer feathers are moulting simultaneously.

Using banding data to estimate primary feather molt and hatch chronology of white‐winged doves in Texas

AbstractBanding data are commonly used to estimate vital rates for migratory game bird management. We used white‐winged dove (Zenaida asiatica) banding data to estimate molt and hatch chronology in Texas. We used Texas Parks and Wildlife Department's long‐term, state‐wide banding data (71,675 banded individuals) from 1 June to 15 August 2007–2016 to investigate primary feather molt and hatching in white‐winged doves in Texas. We estimated primary feather molt and used individual recapture data to determine reliability of models predicting primary feather molt rates. For hatching, we used primary feather molt scores of captured hatch‐year doves to backdate to an estimated hatch date. Our modeling predicted mean after‐hatch‐year primary feather molt rate of 13.21 ± 0.93 days. We predicted 95% of adult white‐winged doves began molting between 7 April to 8 July and completed molt between 17 August to 17 November. Across all years, white‐winged doves hatched as early as 6 January and as late as 27 July, with 95% of all hatching occurring between 22 March and 18 June and peaking on 4 May. Primary feather molt initiation peaked 16 days after the peak of hatching, suggesting that white‐winged doves delay the onset of primary molt until reproductive activity slows. Secondary data collected during banding operations on migratory game birds may be used to understand additional life processes without the requirement to initiate additional survey efforts.

Non-breeding behaviour in the Brown Skua (Stercorarius antarcticus lonnbergi): insights from modelling moulting patterns and stable isotope analyses

ABSTRACT Long-term changes in the life history and behaviour of seabirds during the non-breeding season can reflect shifts in environmental conditions. However, long-term marine studies are scarce, particularly on southern hemisphere seabirds. Here, we used moult scores from 86 Brown Skuas (Stercorarius antarcticus lonnbergi), a large predatory seabird breeding on the Chatham Islands, Aotearoa/New Zealand to model both the timing and duration of primary feather moult. In addition, we analysed stable isotope values (δ13C and δ15N) from 62 modern (2014–16) and ten museum tail feathers. These data provide insights into the non-breeding behaviour of Brown Skua. Interestingly, our results show that the primary feather moult occurred prior to birds departing the colony, starting on average on 2 January ± 5 days (SE). The average start of primary feather moult occurred five days prior to the end of breeding (7 January ± 10 days (SD)) and 42 days before the birds departed the colony (13 February ± 11 days (SD)). The average duration of primary feather moult was 189 ± 14 days (SE). Importantly, low δ13C values in four females suggested that tail feather moult might also occur while skuas are at the colony. There was no difference in tail feather δ13C and δ15N values between any pairwise comparison of modern and museum years. However, values of δ15N from tail feathers sampled in 2014 were different from those sampled in 2015 and 2016. This large annual variation in δ15N values from tail feathers over such a short period makes long-term comparisons difficult to interpret, particularly between years with low sample sizes. While the stable isotope analyses of tail feathers are informative, we recommend future studies of skuas sample the primary coverts rather than tail feathers.

An experimental study of trade‐offs between brood size and moult in the blue tit (Cyanistes caeruleus)

Life‐history theory predicts that whenever expensive activities overlap, there will be a trade‐off between the activities. In a field study of Blue TitsCyanistes caeruleusin Norway, we tested whether parental energy expenditure during reproduction affected timing of moult of primary feathers. Five days after hatching, we manipulated broods to contain either two (n = 10 broods) or 9–12 nestlings (n = 13). In contrast to previous studies, we measured stage of moult at two time points during the nestling period (7 and 14 days after hatching). The onset of moult in the male but not in the female was strongly affected by a reduction in brood size. Stage of moult did not differ between the experimental groups 7 days after hatching, but did after a further week. This difference was also evident when considering only males that had started moulting on day 7. Male moult score was not related to male age (yearling or older), body size (wing length, tarsus length) or hatching time (calendar date) of the brood. However, body condition, expressed as residuals of the regression of body mass on wing length, tended to be greater for parents of both sexes attending small broods than large broods. None of 23 females had initiated moult 7 days after hatching, and only two had done so by day 14. Surprisingly, moult did not seem to affect food provisioning by males relative to females. These results confirm previous studies of passerine birds, namely, that males may start moulting before females and that the moult can quickly be adjusted to the demands of brood‐rearing. The novel result in this case was that such demands affected not only the timing of moult onset but also its speed once it had started.

Moult chronology and strategies of sympatric Great (Ardenna gravis) and Sooty (A. grisea) Shearwaters based on stable isotope analysis

Moult is an energetically demanding period, during which flight may be impaired and foraging ranges may become constrained. During the non‐breeding period, GreatArdenna gravisand SootyArdenna griseaShearwaters migrate from South Atlantic breeding colonies to aggregate at North Atlantic feeding grounds. We investigated whether both shearwater species used coastal Newfoundland, Canada, as a moulting area and used stable isotope ratios (δ15N, δ13C) of recently moulted primary feathers (P1, P5, P10) to infer moult location/diet for both species. Moult scores indicated that both species finished their moult (i.e. P6–10) in coastal Newfoundland, which was further corroborated with similar stable isotope ratios for Great (δ15N = 15.17 ± 1.13‰; δ13C = −18.66 ± 0.54‰) and Sooty Shearwaters (15.54 ± 0.74‰; −18.43 ± 0.78‰); however, Sooty Shearwater moult was more advanced relative to that of Great Shearwater. In contrast, isotopic ratios of P1 and P5, which were grown before arriving in coastal Newfoundland, differed between and within species, suggesting divergent locations/diet during early moult. For Great Shearwaters, P1/P5 isotopic ratios were more variable (broader niche breadth) than P10, suggesting that some individuals started moulting in the South Atlantic prior to trans‐equatorial migration, whereas others start moulting in the North Atlantic Ocean. Sooty Shearwaters had two distinct groupings of either higher or lower δ15N in P1/P5, suggesting that individuals began moulting either on the Newfoundland Shelf or further offshore based on comparisons to reference shearwater feathers grown in known locations. These findings illustrate distinct locations and/or diets at the start of primary feather moult, both within and between species, but diets converged when aggregated together at the end of moult in coastal North America, where growing feathers of both species were sampled. More importantly, we identified an important area for both Sooty and Great Shearwaters to complete their moult in coastal Newfoundland. Protecting this moulting area would minimize disturbance and the impacts of threats (e.g. by‐catch) to both species during this energetically demanding period. The area has been suggested previously to be an important candidate area for protection due to annually persistent prey aggregations that can be spatiotemporally delimited based on specific prey habitat requirements.

Body condition and molt chronology of waterfowl in east central Texas

Waterfowl undergo changes in body condition during migratory and wintering periods that can affect survival and reproduction. Understanding how condition varies among age and sex cohorts and temporally can inform habitat management during the post- and pre-breeding period. We examined changes in body composition and molt of three waterfowl species migrating and wintering in managed moist-soil units in east central Texas and determined the influence of season, age, and sex using Analysis of Variance. We examined age, sex, and season effects on body condition indices (body mass divided by wing chord) using mixed-effects models and determined the influence of molt score on body condition using linear regression. For specimens collected from 2004–2007, we found differences in body composition among age and sex groups for Blue-winged Teal (<em>Spatula discor</em>), a migrant through this study area, and for Green-winged Teal (<em>Anas crecca</em>), and Northern Shoveler (<em>Spatula clypeata</em>), which are wintering species. We found a mid-winter decline in body condition for Green-winged Teal. Blue-winged Teal were in worse condition in spring than in fall, which could be due to differences in energy accumulation prior to departure to wintering grounds in fall and post-arrival in spring. We did not find an effect of season for Northern Shoveler. For all species, adults were in better condition than juveniles. Molt score was greatest in late-winter for all species combined (x̄ = 11.60, SE = 2.45). We did not find an effect of molt score on body condition for any species. Wintering waterfowl in east central Texas appear to be in good condition and did not show molt-induced stress during the migratory and wintering periods. Changes in condition among specimens and across seasons indicate that there should be consideration in the timing and quality of management in regional approaches to moist-soil management for migrating and wintering waterfowl.

Low asymmetry of primary moult in Dunlins Calidris alpina alpina migrating to wintering grounds

The Dunlin is one of very few wader species that moults primaries when migrating to its wintering grounds. In our study, a total of 68.2% of immatures and 26.6% of adults underwent their primary moult when passing through the southern Baltic in autumn. More than 30% of moulting birds revealed differences in moult scores of left and right wings. However, 13% of Dunlins showed differences between the left and right wing not greater than 1%, and 50% of individuals showed differences between the two wings that were lower than 3% of the total mass of all primaries. The probability of asymmetry during the primary moult increased over time and decreased with the advancement of the primary moult. Sex and age of birds had no significant effect on the occurrence of moult asymmetry. The level of asymmetry in the primary moult increased in the following days of autumn migration and with the advancement of the primary moult. The mean index of primary moult asymmetry (the absolute value of the difference in moult advancement between the left and right wing) was lower in immature Dunlins than in adults, and in females compared to males. Hence, sex (males) and age classes (adults) that spend a longer time on the breeding grounds revealed a higher index of primary moult asymmetry, most probably as a result of higher levels of physiological stress. However, the low proportion of birds showing large asymmetry suggests that this is strongly constrained by selection for aerodynamic efficiency, as asymmetry in primaries affects aerodynamic stability, take-off costs, manoeuvrability and agility in birds with flapping flight.

Assessing the impact of extreme adverse weather on the biological traits of a European storm petrel colony

AbstractClimate change affects the climatic disturbance patterns and regimes and is altering the frequency and intensity of subtropical cyclones. These events can affect population dynamics of seabirds (e.g., survival, reproduction). In this work we tested the effect of adverse weather on a colony of European storm petrels (Hydrobates pelagicus) located in a small islet (Aketx) in northern Spain. Over a long‐term monitoring period (1993–2014) we ringed 3728 petrels. From 2003 onwards we also monitored breeding success, the percentage of immature individuals and moult scores. We used Cormack‐Jolly‐Seber models and Underhill and Zucchini models to analyze the effects of climatic conditions on a number of biological traits (survival, breeding parameters, moulting patterns). Our analyses revealed a constant value of adult survival over the 26‐year monitoring period. Recapture probability, however, tended to be positively influenced by NAO conditions in spring, and negatively influenced by NAO conditions in winter (although this would only affect to a fraction of first‐captured birds). Moreover, the impact of adverse weather, especially in 2011 and 2014, resulted in an increasing proportion of yearlings in the breeding population, a lower breeding success and a delayed onset of moult. These effects were similar to those observed during the Prestige oil spill catastrophe.

Patterns of Molt in Long-Tailed Ducks (Clangula hyemalis) during Autumn and Winter in the Great Lakes Region, Canada

Molt and migration can coincide in Arctic nesting waterfowl because they have little time between fledging and the severe weather that precipitates migration. Objectives were to observe how patterns in autumn and winter molt by Long-tailed Ducks (Clangula hyemalis) were influenced by nutrient reserves or seasonal life-cycle events. Molt scores and nutrient reserves were determined for birds salvaged during autumn 2011 (n = 79) and collected during winter 2002–2004 (n = 255). Differences in molt among sex-age classes and correlation between molt and nutrient reserves were determined. It was predicted that adult females and juveniles of both sexes suspended molt during autumn migration to limit energetic overlap; however, greater molt in juveniles during autumn than winter was detected. Correlation between molt and nutrient reserves were not detected. Molt was less in adult males than females and juveniles during winter, which may suggest that the effects of reproduction (females) and growth (juveniles) extended their molt into winter. Observed molt patterns are consistent with fixed cues associated with the timing of seasonal life-cycle events of this species. This could have important implications in understanding the life-cycle events of Long-tailed Ducks and provide novel explanations of seasonal molt.

Photoperiodic regulation of seasonal responses in Indian weaver bird (Ploceus philippinus)

Photoperiod (=day length) is the vital factor for the regulation of behavioral and physiological activities in many avian species. This study investigated the seasonal cycles of testicular growth and secondary sexual characteristics of Indian weaver bird under natural day length (NDL) and the effects of duration and intensity of light on photoperiodic induction. In the first experiment, groups of birds (n = 7 each) were exposed to under NDL in April 2008 and May 2009 for 8 and 12 months, respectively. In second and third experiment, birds (n = 6 each group) were exposed to different photoperiods (11.5L:12.5D, 12L:12D, 13L:11D, and 15L:9D) at the same (500 lux) light intensity, and to 13L:11D at different light intensities (10-, 50-, 500-, and 800-lux). Observations on testis size, molt, and plumage score were recorded 2-week (molt and plumage) or at 4-week intervals (testes). Both the NDL groups showed similar seasonal cycles of testicular growth-regression and secondary sexual characteristics. Second and third experiments suggest that the photoperiodic induction was depending upon duration and intensity of the light. Birds showed testicular growth-regression cycle followed by molt and plumage color change only under 13L:11D and 15L:9D and only 500- and 800-lux under 13L:11D photoperiod but not under 11.5L:12.5D and 12L:12D and 10- and 50-lux light intensities. Pre- and post-nuptial molting on body feathers were progressed with gonadal stimulation–maturation and regression cycle under 13L:11D and 15L:9D. Results under different light–dark cycles suggest that day length of about 12 h or more and above the threshold level of light intensity are essential for the induction of photoperiodic responses.

Flexibility in the timing of post‐breeding moult in passerines in the UK

Higher temperatures resulting from climate change have led to predictions that the duration of the breeding season of many temperate bird species may be changing. However, the extent to which breeding seasons can be altered will also depend on the degree of flexibility in processes occurring at other points in the annual cycle. In particular, plasticity in the timing of post‐breeding moult (PBM) could facilitate changes in the timing of key events throughout the annual cycle, but little is known about the level of within‐ and between‐species plasticity in PBM. As part of the British Trust for Ornithology (BTO) Ringing Scheme, many ringers routinely record moult scores of flight feathers, and these can be used to provide information on the annual progression of PBM for a range of species. Here we use ringing data to investigate patterns of PBM in 15 passerines, as well as data from the BTO Nest Record Scheme to relate these differences to the timing of breeding of these species across the UK. We find considerable variation in both the mean start (19 May–29 July) and duration (66–111 days) of PBM between species, but find no evidence that species starting PBM later in the season complete it any faster. However, there is considerable within‐species variation in PBM, particularly for multi‐brooded species; PBM starts later and is completed in less time when the duration of the breeding season (difference between first and last nests) is longer. This implies that a later end to breeding can be compensated for by faster PBM, and that advances in breeding could lead to earlier and slower PBM. Our findings suggest that adaptation of PBM in response to climate‐mediated changes in the timing and duration of the breeding season is possible. However, the requirement to complete PBM prior to migration or the onset of winter might constrain the extent to which breeding seasons can lengthen, especially for later nesting species.

Climate Change and Advanced Primary Moult in Eurasian Golden PloversPluvialis apricaria

We measured primary moult scores of 1051 Eurasian Golden Plovers Pluvialis apricaria staging in pastures in The Netherlands from 1978 to 2011. We hypothesized that moult may have advanced due to earlier breeding resulting from global climate change. At the same time, intensification of agricultural practices has changed the environment on which the Golden Plovers depend during migration and staging, which may have affected their condition and moult schedule.Primary moult has advanced by 8 days from 1990 to 2011, without visible changes preceding 1990. This suggests that long-term changes in weather might have caused the change in moult timing. In the absence of the variable year, the North Atlantic Oscillating (NAO) index, averaged over September–October, significantly correlated with timing of moult. However, this was a weaker relationship than that of year and timing of moult. Apparently, year correlates better with relevant weather parameters than NAO. Because moult speed at the staging areas has not changed from 1978 to 2011, the birds must have started moult earlier. Advanced breeding has been shown to have occurred in several bird species breeding in northern temperate latitudes. Golden Plovers start to moult during breeding, and therefore we think that the advancement of moult has been the result of an earlier start of breeding and not of changes in agricultural practice in The Netherlands.

Corticosterone mediated costs of reproduction link current to future breeding

Life-history theory predicts that costs are associated with reproduction. One possible mediator of costs involves the secretion of glucocorticoid hormones, which in birds can be measured in feathers grown during the breeding period. Glucocorticoids mediate physiological responses to unpredictable environmental or other stressors, but they can also function as metabolic regulators during more predictable events such as reproduction. Here we show that corticosterone (“Cort”) in feathers grown during the breeding season reflects reproductive effort in two Antarctic seabird species (giant petrels, Macronectes spp.). In females of both species, but not males, feather Cort (“fCort”) was nearly 1.5-fold higher in successful than failed breeders (those that lost their eggs/chicks), suggesting a cost of successful reproduction, i.e., high fCort levels in females reflect the elevated plasma Cort levels required to support high metabolic demands of chick-rearing. Successful breeding also led to delayed moult prior to winter migration. The fCort levels and pre-migration moult score that we measured at the end of current breeding were predictive of subsequent reproductive effort in the following year. Birds with high fCort and a delayed initiation of moult were much more likely to defer breeding in the following year. Cort levels and the timing of moult thus provide a potential mechanism for the tradeoff between current and future reproduction.

Moult and body condition in Long-tailed Tits Aegithalos caudatus

Moult is a key life-cycle event associated with reduced flight performance and high energetic demands. Juvenile Long-tailed Tits Aegithalos caudatus have a complete post-juvenile moult so that both adults and juveniles will be undergoing a full moult at similar times of year. Given lower foraging experience and developmental immaturity of juveniles, we might predict differences between adults and juveniles in moult parameters and the effect of moult progression on body mass. The aim of this study was to test these predictions by analysing moult data for Long-tailed Tits in the northeast of England. Juveniles started moult 12 days later than adults but the duration of moult was similar. The timing of moult varied between years; correlations between year-to-year change in moult timing and spring temperatures suggest that the timing of moult and breeding are linked. Raggedness scores, a measure of moult speed, remained relatively constant during the central phase of moult and were independent of moult score. Although wing length made the greatest contribution to body mass, the best statistical model included raggedness as a factor contributing to variation in body mass, suggesting that faster moulting may be associated with lower body mass. The analysis did not support the prediction that age is a significant factor affecting body mass during moult.

Timing, Duration, and Intensity of Molt in Birds of a Neotropical Savanna in Brazil

Abstract. While researchers have made great progress investigating the molt of temperate-zone birds, few studies have examined the molt of tropical birds. We carried out this study in 2009 and 2010 in the cerrado biome, Distrito Federal, Brazil. On the basis of 334 birds captured with mist nets, we describe the timing, duration, and intensity of the flight-feather molt in eight species. Molt scores indicated the direction of replacement and points where molt series started and ended. The innermost primary usually was the first flight feather to drop, and primaries were replaced proximal to distal. Secondaries were replaced in two series, and S6 or S5 typically was the last remex to complete growth. Rectrices were replaced in a single series on each side, from R1 (central) to R6 (lateral). All species replaced their primaries according to the rules followed by most passerines. The White-eared Puffbird (Nystalus chacuru: Galbuliformes) was an exception; it replaced primaries in two molt series and possibly ...

Moult and mobility of the Aquatic Warbler Acrocephalus paludicola on the West African non-breeding grounds

The globally threatened Aquatic Warbler Acrocephalus paludicola is a Palearctic–African long-distance migrant that undergoes a complete moult while wintering in Africa. Little is known about the timing of moult and the birds’ mobility during moulting periods. We conducted the first study on the moult of Aquatic Warblers, in the Djoudj area of Senegal, West Africa. Wing moult scores from 36 to 90 and raggedness scores from 0 to 25 were recorded in December and January. No moulting Aquatic Warblers were caught after January. Body-feather moult was observed during and shortly after wing moult until January. We conclude that Aquatic Warblers follow the typical sequence of passerine moult, with remige moult starting in October or November. To find out how moult affects their mobility, we measured the net distance that Aquatic Warblers equipped with radio transmitters travelled in 15-min intervals. In our small sample of eight birds, the mean path length was 34 m, and there was no obvious difference between the path lengths in moulting and non-moulting individuals. We conclude that, possibly, moult does not affect the mobility and flight ability of Aquatic Warblers in general. Further research is needed to locate other wintering grounds, e.g. in the Inner Niger Delta, and reproduce our study in other populations.

Plasticity of moult and breeding schedules in migratory European StonechatsSaxicola 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 StonechatSaxicola 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 inc.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.

Timing and duration of moult in the Bullfinch Pyrrhula pyrrhula: an appraisal of different analytical procedures

The method most commonly used to assess the timing and duration of moult in birds is based on the moult scores of individuals caught in moult, while non-moulting individuals caught at the same time are ignored. Underhill and Zucchini (1988) produced a statistical model of avian moult which incorporated data from non-moulting birds and which could be used to produce potentially more reliable estimates of the key parameters. They distinguished three types of moult data Our aim was to evaluate the Underhill-Zucchini model, using records of Bullfinch Pyrrhula pyrrhula moult. We found that only data incorporating observations of non-moulting as well as of moulting birds (but without individual moult scores) gave unbiased estimates of moult rate (and duration) as judged from rates obtained from recaptures of the same individuals. Using such data, the estimated mean starting date of moult in adult Bullfinches near Oxford varied between 10 and 18 August in four years, the standard deviation in starting dates between 11 and 14 days, and the mean moult duration between 67 and 77 days. Only mean starting date differed significantly between years.

Moult in adult Fiery-necked Nightjars Caprimulgus pectoralis ringed on Ranelia Farm, Cashel, Zimbabwe

Nothing has been published on the moult of the Fiery-necked Nightjar Caprimulgus pectoralis in Zimbabwe. However, most of the birds handled on Ranelia Farm, Cashel, during a study of nightjar breeding biology over four seasons, were examined for moult. Fiery-necked Nightjars were examined on over 70 occasions. Their annual moult occurs between late October and early March, commencing with the primaries, which moult descendantly. The secondaries, which moult ascendantly, follow after P5 has been shed, and so do the rectrices, which moult centrifugally, but R5 precedes R4. Body moult, which starts about the time that R1 is shed, progresses from the head across the neck to the rest of the dorsal plumage, and then over the throat and flanks to the ventral surface. The rictal bristles moult descendantly in time with the primaries. Several birds, some with primary moult scores as high as 18, had commenced moult while still tending young from the first brood, or incubating the eggs of a second, or replacement, clutch. The moult season overlaps the breeding season by about two months.

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.