Moult-breeding Overlap Research Articles

A higher incidence of moult–breeding overlap in great tits across time is linked to an increased frequency of second clutches: a possible effect of global warming?

The rise of temperatures due to global warming is related to a lengthening of the breeding season in many bird species. This allows more pairs to attempt two clutches within the breeding season, thus finishing their breeding activity later in the season and therefore potentially overlapping these with post–breeding moult. We tested whether this occurred in two Spanish great tit Parus major populations. The proportion of pairs laying second clutches increased from 1 % to 32 % over the study period in one of the populations (Sagunto, 1995–2019), while it did not change in the other (Quintos, 2006–2019; mean 5 %). We did not find any temporal trend for moult start date of late–breeding birds in any population. The proportion of individuals of both sexes that overlapped moult and breeding increased in Sagunto. For this latter population, sex and age, but not clutch type, contributed to the variability in the probability of overlapping in late–breeding individuals, this being higher for first–year males and lower for older females.

Differences in tail feather growth rate in storm-petrels breeding in the Northern and Southern hemisphere: a ptilochronological approach.

Moulting and breeding are costly stages in the avian annual cycle and may impose trade-offs in energy allocation between both stages or in their timing. Here, we compared feather growth rates (FGR) of rectrices in adults between two pairs of small pelagic Procellariiformes species differing in moult-breeding strategies: the European storm-petrel Hydrobates pelagicus and Leach’s storm-petrel Oceanodroma leucorhoa breeding in the Northern Hemisphere (Faroe Islands), showing moult-breeding overlap in tail feathers; and the Wilson’s storm-petrel Oceanites oceanicus and black-bellied storm-petrel Fregetta tropica, breeding in the Southern Hemisphere (South Shetlands), temporally separating moult and breeding. We used ptilochronology (i.e., feather growth bar width) to reconstruct FGR reflecting relative energy availability during moult. Based on previous research, we expected positive correlations between feather length (FL) and FGR. Additionally, we expected to find differences in FGR relative to FL between the moult-breeding strategies, where a relatively higher FGR to FL indicates a higher energy availability for moult. To investigate if energy availability during moult in the studied species is similar to species from other avian orders, we used FGR and FL found in literature (n = 164) and this study. We fitted a phylogenetic generalized least squares (PGLS) model to FGR with FL, group (i.e., Procellariiformes vs. non-Procellariiformes) and the interaction FL * group as predictors. As it has been suggested that Procellariiformes may form two growth bars per 24 h, we fitted the same model but with doubled FGR for Procellariiformes (PGLSadj). The group term was significant in the PGLS model, but was not in the PGLSadj model, confirming this suggestion. Individually predicted FGR by the PGLSadj model based on FL, showed that the Southern species have a significantly higher FGR relative to FL compared to the Northern species. Additionally, we found no correlation between FL and FGR in the Northern species, and a positive correlation between FL and FGR in the Southern species, suggesting differences in the trade-off between feather growth and size between species from both hemispheres. The observed differences between the Northern and Southern species may be caused by different moult-breeding strategies. The Southern species may have had more energy available for moult as they are free from breeding duties during moult, while the Northern species may have had less free energy due to a trade-off in energy allocation between breeding and moulting. Our study shows how different moult-breeding strategies may affect relative nutritional condition or energy allocation during moult of migratory pelagic seabirds.

Timing manipulations reveal the lack of a causal link across timing of annual-cycle stages in a long-distance migrant.

Organisms need to time their annual-cycle stages, like breeding and migration, to occur at the right time of the year. Climate change has shifted the timing of annual-cycle stages at different rates, thereby tightening or lifting time constraints of these annual-cycle stages, a rarely studied consequence of climate change. The degree to which these constraints are affected by climate change depends on whether consecutive stages are causally linked (scenario I) or whether the timing of each stage is independent of other stages (scenario II). Under scenario I, a change in timing in one stage has knock-on timing effects on subsequent stages, whereas under scenario II, a shift in the timing of one stage affects the degree of overlap with previous and subsequent stages. To test this, we combined field manipulations, captivity measurements and geolocation data. We advanced and delayed hatching dates in pied flycatchers (Ficedula hypoleuca) and measured how the timing of subsequent stages (male moult and migration) were affected. There was no causal effect of manipulated hatching dates on the onset of moult and departure to Africa. Thus, advancing hatching dates reduced the male moult-breeding overlap with no effect on the moult-migration interval. Interestingly, the wintering location of delayed males was more westwards, suggesting that delaying the termination of breeding carries over to winter location. Because we found no causal linkage of the timing of annual-cycle stages, climate change could shift these stages at different rates, with the risk that the time available for some becomes so short that this will have major fitness consequences.

Passerine phenology in the largest tropical dry forest of South America: effects of climate and resource availability

ABSTRACTIn tropical dry areas, rainfall is predicted to be the most important climatic variable influencing bird phenology because it triggers food and foliage production. In addition, because resources are scarce, the moulting and breeding seasons are not expected to overlap. We conducted a 2-year study on the phenology of passerine birds at one site in Caatinga, South America’s largest dry forest region to: (a) evaluate the contributions of climate, foliage cover, and food abundance to the onset of the breeding and moulting seasons, (b) assess the duration of the breeding and moulting seasons, and (c) measure the frequency of the bird moult–breeding overlap. Birds can use rainfall or humidity as environmental cues to start their breeding seasons. The effects of water availability are mediated by both foliage cover and food abundance, but foliage cover is more important to the onset of the bird breeding season than food abundance. In contrast, both foliage cover and food abundance equally influence the timing of the primary moult. Because we found several cases of moult–breeding overlap, we suggest that some passerine species adapt that strategy to adjust the timing of their life history stages to the relatively short period of abundant resource availability.

Differences in the timing and extent of annual moult of black-browed albatrosses Thalassarche melanophris living in contrasting environments

Moult entails costs related to the acquisition of energy and nutrients necessary for feather synthesis, as well as the impact of reduced flight performance induced by gaps in the wing plumage. Variation in moult strategies within and between populations may convey valuable information on energetic trade-offs and other responses to differing environmental constraints. We studied the moult strategies of two populations of a pelagic seabird, the black-browed albatross Thalassarche melanophris, nesting in contrasting environments. According to conventional wisdom, it is exceptional for albatrosses (Diomedeidae) to moult while breeding. Here we show that black-browed albatrosses breeding on the Falklands regularly moult primaries, tail and body feathers during chick-rearing, and the majority of those at South Georgia show some body feather moult in late chick-rearing. The greater moult-breeding overlap at the Falklands allows the birds to annually renew more primary feathers than their counterparts at South Georgia. The results of the present paper, pooled with other evidence, suggest that black-browed albatrosses from South Georgia face a more challenging environment during reproduction. They also serve to warn against the uncritical acceptance of conventional ideas about moult patterns when using feathers to study the ecology of seabirds and other migrants for which there is scant information at particular stages of the annual cycle.

Regular moult-breeding overlap in the Pale-winged Starling Onychognathus nabouroup

Regular moult-breeding overlap in the Pale-winged Starling Onychognathus nabouroup

A record of breeding–moulting overlap in the Common Redstart Phoenicurus phoenicurus

Capsule Moult-breeding overlap in a male Common Redstart feeding a second brood may reflect time pressure to fit moult between the completion of breeding and migration.

Moult strategies of Cory’s Shearwaters Calonectris diomedea borealis: the influence of colony location, sex and individual breeding status

The replacement of old feathers is essential for birds, but it is also an energy-demanding task. As moult usually does not coincide with other stressful events in its annual cycle, such as reproduction and migration, the bird can optimise its use of time and energy allocated to different activities. There are very few studies comparing the moult strategies of populations with similar breeding calendars but occurring in areas of different habitat quality. Cory’s Shearwaters Calonectris diomedea have a partial moult–breeding overlap, an unusual phenomenon among pelagic seabirds. We have compared the moult schedules in Cory’s Shearwater colonies located in distinct environments (pelagic vs. coastal) and show that moult–breeding overlap is less extensive on Selvagem Grande, situated in deep oceanic waters, than on Berlenga, situated on the continental shelf. Colony attendance of failed breeders, most of which were moulting, was lower at Selvagem Grande than at Berlenga, which suggests that the feeding areas of birds from the former site are more distant from the colony. Failed breeders started to moult earlier than individuals still raising a chick, and breeding status had a stronger influence on determining the onset of wing-feather moult than colony location. Despite published evidence that internal circannual rhythms and external cues, such as variation in daylength, are important factors regulating moult schedules, it is clear that birds retain a considerable flexibility that allows them to respond to external factors in order to strategically manage time and energy in a way that is thought to maximise their fitness.

Early moult improves local survival and reduces reproductive output in female pied flycatchers

Overlapping moult and reproduction might be crucial for long-distance migratory birds, which are time-constrained to complete these energy-demanding functions before the onset of migration. However, proximate factors modulating the potential trade-off between moult and breeding, such as haemoparasite infection and stress, have not been studied in wild avian populations. We investigated the occurrence of moult-breeding overlap in females of a Spanish population of pied flycatchers (Ficedula hypoleuca) and its association with female age, haemoparasite prevalences, physiological stress, and condition at initial (incubation phase or beginning of the nestling period) and final breeding stages (days11'12 of the nestling period). Late-breeding females were more likely to show a moult—breeding overlap than early-breeding females. Female age was not associated with moult status when taking into account laying date and study year. A higher proportion of females infected by Haemoproteus at initial breeding stages showed a moult—breeding overlap. Haemoproteus prevalences at final breeding stages did not differ according to moult status. Females with a moult—breeding overlap also showed better condition and lower stress levels (HSP60 levels) at the end of the season. A higher proportion of moulting females returned to the breeding grounds in the following season compared with non-moulting ones. Conversely, moulting females showed reduced hatching success and numbers of hatchlings and fledglings. Overlapping moult and breeding might be the expression of a shift in resource allocation between present and future reproduction, towards increased self-maintenance and reduced reproductive investment.

A trade‐off between two resource‐demanding functions: post‐nuptial moult and immunity during reproduction in male pied flycatchers

Summary Costs of reproduction might be mediated by a resource‐allocation trade‐off between immunity and reproductive effort. Recent studies have suggested that the moult–breeding overlap observed mainly in males may affect this trade‐off. In order to test whether increased investment in immunity may affect the onset of moult or reproductive output in a species with moult–breeding overlap, we immunized breeding male pied flycatchers Ficedula hypoleuca (Pallas) with a non‐pathogenic antigen (sheep red blood cells) in the first week post‐hatching and compared their moult score, parental effort and reproductive success shortly before fledging with that of control males injected with sterile phosphate‐buffered saline. Immunized males provisioning nestlings delayed the onset of post‐nuptial primary moult compared to control males. The experimental activation of the immune defence of males affected their stress levels (heterophile/lymphocyte ratio, heat‐shock proteins) on day 13 after chicks hatched. An activated immune response tended to depress reproductive output, although the experimental design was not efficient enough to find a significant effect because the manipulation was not performed early enough in the nestling period. The results suggest that experimental activation of the males’ immune system decreased the resources necessary for initiating post‐nuptial moult. The trade‐off between immunity and moult onset may imply costs of delayed moult in cases of infection and may interact with reproductive immunosuppression in cases of moult–breeding overlap. Moult, immunity and reproduction are locked in a three‐way interaction which may markedly affect avian life histories.

Daily energy expenditure and cell-mediated immunity in pied flycatchers while feeding nestlings: interaction with moult

Ecological immunology posits a trade-off between parental effort and immunocompetence underlying the cost of reproduction. The moult-breeding overlap observed in several bird species represents a conflict in resource allocation between two energy-demanding processes. Moult processes have been associated with enlargements of immune system organs. In the present study. we measured simultaneously daily energy expenditure (DEE) and the T-cell-dependent immune response of pied flycatchers, Ficedula hypoleuca, caring for grown nestlings. We used the doubly labelled water technique and the phytohaemagglutinin (PHA) injection assay on both males and females, while recording provisioning rates and moult scores. DEE and the PHA response were negatively correlated for females, but not for males. A significantly higher proportion of males than females initiated moult. Provisioning rates were strongly correlated with DEE for females but only for non-moulting males. The DEE of moulting males was marginally correlated with moult score. For moulting males, there was a marginally significant positive correlation between moult score and immune response. The trade-off between DEE and immunity for females could underlie the cost of reproduction. However, the moult-breeding overlap found in males may offset this trade-off, thereby reducing the implications of immunosuppression for parental survival.

Effects of latitude on the trade-off between reproduction and moult: a long-term study with pied flycatcher.

Long-distance migratory passerine birds are generally time constrained by reproduction and moult, which need to be completed before migration. Breeding and post-nuptial moult may overlap especially under time-constrained conditions (northern latitudes). Here, we analysed the timing of adult moult in relation to latitude, timing of breeding and reproductive effort in pied flycatchers (Ficedula hypoleuca) breeding in four widely separated populations (40-68°N). In males but not females, the proportion of moulting birds while provisioning nestlings increased with increasing latitude. This may suggest that a moult-breeding overlap is a strategy employed by male pied flycatchers to adjust to the short breeding season at northern latitudes. However, the moult-breeding overlap was more pronounced among males in the southernmost study population (Spain). In this population, males may decide not to invest more in reproduction, and start moulting at earlier breeding stage than in northern populations,or, alternatively, birds in the Mediterranean region are time constrained by the hot and dry summer. The trade-off between breeding and post-nuptial moult may be more important in some populations than in others, depending on the latitude of the breeding site. Our results show that a moult-breeding overlap imposes a fitness cost on males in terms of fecundity and breeding success.

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

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

Trade-off between reproduction and moult - a comparison of three Fennoscandian pied flycatcher populations.

Organisms that reproduce at high latitudes are assumed to have evolved several adaptations to the short summer. For birds, and especially for long-distance migrants, there is a time constraint because both reproduction and moult must be completed before autumn migration. It has therefore been assumed that birds at northern latitudes must initiate their moult during reproduction more often than birds at low latitudes. To investigate how passerine birds breeding at different latitudes allocate their time between reproduction and moult, we compared timing of these activities during three consecutive breeding seasons in three widely separated populations of the pied flycatcher Ficedula hypoleuca. Our results show that the frequency of individuals with moult-breeding overlap, and moult initiation in relation to breeding stage, varied considerably among populations and years. In all three populations, female moult initiation was restricted to the late nestling period. The males had a more pronounced moult-breeding overlap than the females, but its duration was similar in all three study areas. Thus, there was no evidence for a more pronounced moult-breeding overlap at high compared with low latitudes. These results suggest that pied flycatchers sometimes accept a moult-breeding overlap, but that the time gained by having too extensive an overlap between reproduction and moult does not outweigh the associated costs. Long-distance migrants breeding at northern latitudes apparently experience a trade-off between reproduction and somatic investment during moult. We therefore suggest that a pronounced moult-breeding overlap is not a typical strategy used by long-distance migrants to adjust to the short breeding season at northern latitudes.

A sexual conflict in collared flycatchers, Ficedula albicollis: early male moult reduces female fitness

A sexual conflict over levels of parental care occurs in most animals with biparental care, and studies of sexual differences in levels of parental care have usually focused on its intra-annual fitness consequences. We investigated inter-annual fitness consequences of a sexual difference in timing of feather replacement (moult) in collared flycatchers (Ficedula albicollis). In this study, males overlapped reproduction and moult more often than females, they also initiated their moult at an earlier stage of breeding than females. Females mated to males with a moult-breeding overlap had significantly lowered survival chances than females mated with males initiating moult after breeding. Furthermore, females mated with moulting males risked a lowered future fecundity in terms of a delayed start to breeding in the following season. However, early moulting males achieved a similar reproductive success as males initiating moult after breeding. Likewise, male survival probability to the following breeding season did not differ between early and late moulting individuals, nor was there any evidence that males gained or lost in future mating advantages by moulting early. These results show not only that a sexual conflict over timing of moult may operate, but also that it can impose severe fitness consequences, in terms of reduced future fecundity and survival probability, upon the 'losing' sex.

Costs of overlapping reproduction and moult in passerine birds: an experiment with the pied flycatcher

The process of moult in birds requires the investment of substantial amounts of energy and nutrients in feather production and attendant processes. Flight performance may be reduced during the moult of the wing feathers, and moulting birds may suffer from an increased predation risk. These factors may explain why the moult is usually separated in time from other energetically demanding processes, such as reproduction. In this study, we investigated the importance of the temporal separation of moult from breeding activities in the pied flycatcher Ficedula hypoleuca. We induced a moult-breeding overlap by removing the two innermost primaries on both wings, thus imitating the natural loss of these feathers during the initial stage of the moult. The experiment probably did not stimulate feather regrowth, but may have reduced flight performance. Just before fledging of the young, manipulated males and females, as well as the fledglings, had a lower body condition than control birds. The return rate of adult males in the year following the manipulation was significantly lower for males in the manipulated group than for control males. The return rate of females was lower than that of males, but there was no difference between the two female groups. The number of nestlings recruited in the year after the manipulation was significantly lower for the group with an induced moult-breeding overlap than for the control group. The reproductive performance in recruited and returning old females was independent of the manipulation, and in returning adults and recruits the feather quality in terms of number of barbs/mm was independent of the manipulation. These results suggest that a moult-breeding overlap induces fitness costs in terms of reduced recruitment rate and adult survival in a long-distance migrant.