Moult

This paper presents an overview of patterns in the primary moult of waders using the Eurasian–African migration
system and updates earlier summaries with results obtained from the Underhill–Zucchini moult models (1988,
1990). Recent applications of these models allow researchers to examine moult timing down to the progress
of an individual feather in a tract and to determine the effects of environmental factors on moult. Waders
present a wide variety of inter- and intra-specific strategies for their primary moult, an energy-costly activity
they must fit in with breeding and migration, the other main energy-demanding events in their life cycle. Here
I present the moult strategies of waders in the context of their age, size, sex and annual variation in breeding
success, seasonal food abundance, the latitude where they moult, the distance they migrate, the habitats they
use, and the rainfall patterns and temperatures at their moulting grounds. I also discuss how moult is adjusted
to these factors. This overview emphasises the flexibility of many waders’ moult strategies as an adaptation
to the unpredictable food supply provided by ephemeral inland wetlands and compares these strategies with
those of populations that use predictable coastal habitats. Discovering the mechanisms that allow waders to
adjust their genetically controlled and hormonally regulated moult to proximate factors is suggested as one of
the challenges in further studies of moult.

The Lovely Fairy-Wren (Malurus amabilis) is endemic to the wet tropics of Australia and is one of 11 species in the genus Malurus. Despite the large number of studies on fairy-wrens, little is known about the Lovely Fairy-Wren. This study provides the first detailed description of its ecology, behaviour, and breeding biology. Lovely Fairy-Wrens displayed breeding behaviour characteristic of tropical birds, with groups maintaining territories and breeding year-round, small clutch size (two to three eggs), long juvenile dependence (2 months) and high adult breeder survival (86%). They breed cooperatively, and groups formed when male (but not female) offspring delayed dispersal and remained in their natal group as subordinates. Groups were typically small (2.5 ± 0.8 individuals), possibly because productivity was low: 29% of the monitored groups produced at least one fledgling per year. Males provided high levels of parental care and this, together with low extra-pair courtship and petal displays, suggests that this species may not be as promiscuous as other fairy-wrens. Unlike other Australian fairy-wrens, males maintained their brightly coloured adult plumage year-round after initial acquisition. This lack of seasonal moult into dull plumage, coupled with the unusually colourful plumage of females in this species, suggests that the impact of natural selection on the plumage colour of both sexes may be lower in this species than in their congeners. We discuss similarities and differences in life-history and morphological traits between the Lovely Fairy-Wren and other Malurus species.

Inter-individual differences in the extent of post-juvenile moult of migratory birds are usually attributed to energetic or time constraints related to different geographic origins. In addition to these factors, recent research has stressed the importance of food availability for the process of moult and the migratory strategy of individuals. Consequently, individual quality and foraging ability would account for both moult extension and body condition. We hypothesized that both variables may be influenced by the same factors and would be correlated in winter. We therefore tested whether the extent of post-juvenile moult was associated with body condition (body mass, muscle and fat scores) and related variables (tarsus and bill length) of forty-six Common Chiffchaff Phylloscopus collybita males wintering in the Mediterranean area. We found no correlation between moult extension and body mass. Nevertheless, Common Chiffchaffs with longer bills and that showed a higher fat score were in better body condition and moulted a larger number of flight feathers. The number of flight and contour feathers moulted increased as the season proceeded, whereas body mass varied on a daily temporal scale. Our results support the idea that individual quality influences post-juvenile moult and winter performance, and suggest that juvenile Common Chiffchaffs with longer bills may display different foraging strategies that lead some individuals to improve their performance.

Decapod crustaceans show proliferation of the nerve cells in the olfactory lobe throughout their lives. However, the regulation of this process is still poorly understood, since it may vary with endogenous and exogenous factors. The objective of the present investigation was to quantify the proliferation of nerve cells and number of nerve cells with ecdysone receptors in the clusters of the central olfactory system in Neohelice granulata, according to moult stages and in different seasons (summer and winter). Three injections of bromodeoxyuridine (BrdU) were administered to the crabs. Brains were sectioned by microtome and fixed on slides for immunohistochemistry with anti-BrdU and anti-EcR antibodies. The proliferation of nerve cells was higher in winter than in summer, probably because in winter the crabs do not breed and the premoult and postmoult periods are longer. Crabs in postmoult exhibited more BrdU-labelled cells than crabs in premoult or intermoult in winter, because of a greater number of mitoses related to an increase in body size and addition of olfactory receptor neurons. The number of EcR-labelled cells was higher in premoult than in postmoult or intermoult in winter. The proliferation of nerve cells is regulated seasonally and according to moult stages.

Changes in mass during moult were investigated by analysis of data recorded on standard moult cards by members of the British Trust for Ornithology Ringing Scheme. In the analysis of post juvenile moult, all available cards that presented wing length, mass and time of capture were used. The analysis of adult post-nuptial moult was restricted to cards from a single year. Juvenile mass correlated strongly with body size, time of day and the number of greater coverts being replaced. After controlling for the effects of size and time of day, mass was found to increase with date except in those individuals in which all juvenile greater coverts were retained. In these birds residual mass declined with date. In adult males, mass increased with both date and moult scores of primary, secondary and tertial remiges and of rectrices but because of the strong correlations between moult scores and date, the true relationship was not clear. In adult females, mass declined with date before increasing again. Unlike the males, female moult scores did not predict body mass. However, the timing of moult was a strong predictor of body mass. The differences between age and sex groups are discussed in relation to the nutritional demands of moult.

Delayed plumage maturation (DPM) of young males in sexually dichromatic birds has been explained under the female mimicry hypothesis (FMH) or the subordination signalling hypothesis (SbSH), among other adaptive ideas proposed. In this study, we tested in the Eurasian kestrel, Falco tinnunculus, the predicted sexual deception and aggressiveness under the FMH and SbSH to explain DPM in birds. We analysed aggressive and courtship behaviour of breeding males and females in the presence of adult male, adult female and 1-year-old male natural decoys. We designed two different treatments: one presenting un-moulted 1-year-old males and a second presenting partly moulted 1-year-old males, as observed in nature. Males attacked adult male decoys more frequently than 1-year-old male and female decoys in both moulted and un-moulted treatments and no sexual displays were observed. Females were more aggressive towards female and 1-year-old male decoys as compared to male decoys in the un-moulted treatment. In the moulted treatment, females were more aggressive towards female decoys as compared to both male decoys. In addition, females solicited copulas from moulted, but not from un-moulted, 1-year-old male decoys. Our results suggest that FMH can be a mechanism which explains DPM in un-moulted 1-year-old males. However, when they show moulted plumage (more than 80% in the studied population during the spring), the SbSH seems to be the mechanism that better explains sexual and agonistic behaviour from adults towards 1-year-old males.