Annual Moult Research Articles

A ptilochronological study of carry‐over effects of conditions during wintering on breeding performance in the barn swallowHirundo rustica

The ecological conditions that a bird experiences during any stage of its life cycle may have consequences that become manifested at later life stages, and these ‘carry‐over effects’ may be major components of variance in individual performance. Condition‐dependent feather growth rate, as assessed by growth bars width (GBW), provides a unique, though largely under‐exploited tool to investigate carry‐over effects of ecological conditions and individual physiological state during molt. In this study of breeding barn swallowsHirundo rustica, which undergo a single complete annual molt of tail and wing feathers during wintering in sub‐Saharan Africa, we first show that old (≥ 2 yr) females have larger GBW than old males and yearlings. GBW was smaller with larger infestations by common ectoparasites of barn swallows, independent of the swallows’ age or sex, and larger GBW was associated with a higher index of body condition during the breeding season in males. Larger GBW predicted higher seasonal reproductive output of older males, but not reproductive output of younger males or females of any age class, with this higher reproductive output of older males mediated by higher offspring fledging success. However, no relationship with GBW was observed for seasonal reproductive output of males in the spring preceding the winter when the feathers were grown. Hence, this study suggests that the analysis of the rate of feathers growth (‘ptilochronology’) has a larger potential to serve as a powerful tool in the study of carry‐over effects than has been appreciated to date. Specifically, the present results support the idea that conditions experienced during wintering in Africa and proximately reflected by GBW have carry‐over effects on body condition and breeding success. These effects are sex and age specific, being more pronounced in older males, possibly as a consequence of differences in annual time routines and susceptibility to extrinsic factors among sex and age classes.

Do single point condition measurements predict fitness in female pronghorn (Antilocapra americana)?

Condition is frequently used in evolutionary studies as an estimator of fitness. Broad theoretical interpretations of condition include many different attributes that can influence fitness, but in practice, researchers commonly employ condition measures (e.g., body-fat scores or size-adjusted body mass) that have uncertain relationships with reproductive success. In addition, researchers typically rely on condition estimates that are made once. Empirical studies investigating the relationship between condition and fitness are nearly absent. We examined the effect of maternal condition on current and future reproductive success in a wild population of pronghorn ( Antilocapra americana (Ord, 1852)). We used body condition scoring and date of annual molt to measure female condition, and mass–size residuals to measure offspring condition at birth. We found that current reproductive success lowered female condition, and that poor condition reduced subsequent prenatal growth rates. However, poor condition did not reduce postnatal offspring condition or future reproductive success. We suggest that the elapsed time should be taken into consideration when making predictions based on single point condition measures. The assumption that condition predicts fitness requires further empirical test.

Towards a unification of movement ecology and biogeography: conceptual framework and a case study on Afrotropical ducks

AbstractAim We present elements of a new conceptual framework for the unification of biogeography and movement ecology, and demonstrate the value of the new framework using a case study of two species of Afrotropical duck (Anatidae) across a latitudinal gradient.Location Southern Africa.Methods The first part of the paper rests on logic and philosophy. For the second (case study) section, we used data from up to 3 years of satellite telemetry for 26 individuals of two species of Afrotropical duck, the Egyptian goose (Alopochen aegyptiaca) and red‐billed teal (Anas erythrorhyncha), from three different populations with moulting sites spread across 17 degrees of latitude. We compared quantitative measures of movement patterns using principal components analysis and boxplots.Results We argue that unpacking the concept of dispersal into the fundamental elements of movement (internal drivers, external drivers, navigation capacity, and motion capacity) provides a more solid basis for contrasting competing hypotheses in biogeographical studies. We found, surprisingly, that red‐billed teal, a ‘highly nomadic’ species, moved with a relatively high degree of consistency at each of our three study latitudes, while Egyptian geese, a ‘resident’ species, showed latitude‐dependent variation in their movements. However, much of the latitude‐related variation for Egyptian geese was driven by their annual moult migrations, rather than directly by fluctuations in resource availability. Internal factors appear to dominate movements and probably determine the species ranges of both of our study species.Main conclusions The integration of biogeography and movement ecology, through a more sophisticated view of mechanisms formerly lumped together under ‘dispersal’, offers a fertile area for further research. The biogeography of Afrotropical ducks appears to be strongly influenced by internal factors. Biogeographical patterns in this taxon may thus be best understood (and modelled) as a long‐term response to environmental stochasticity, rather than as a deliberate selection of optimal habitat. Latitudinal comparisons emerge as a valuable way of gaining insights into the drivers of movement for widespread species.

Evidence of cryptic individual specialization in an opportunistic insectivorous bat

Habitat use and feeding behaviors of cryptic animals are often poorly understood. Analyses of stable isotope ratios in animal body tissues can help reveal an individual's location and resource use during tissue growth. We investigated variation in stable isotope ratios of 4 elements (H, C, N, and S) in the hair of a sedentary species of insectivorous bat (Eptesicus fuscus) inhabiting a chemically complex urban landscape. Our objective was to quantify population-level isotopic variation and test for evidence of resource specialization by individuals. Bats were sampled over 3 annual molt cycles at maternity roosts in buildings and variance components analysis was used to test whether intraindividual isotopic variation among molts differed from interindividual variation, after controlling for year and roost-group effects. Consistent with prior evidence that E. fuscus is opportunistic in its habitat use and foraging at the population level, we observed wide population-level variation for all isotopes. This variation likely reflects the chemical complexity of the urban landscape studied. However, isotopic variation among years within marked individuals was lower than variation among marked individuals within year for all isotopes, and carbon signatures indicated resource specialization by roost groups and individuals. This is the 1st study to examine variation in stable isotope ratios of individual wild bats over multiple years. Although our results suggest this population tends toward opportunistic habitat use or prey selection, or both, during molt periods, results also indicate that individuals and groups of bats composing the population might be habitat or dietarv specialists—a novel finding for insectivorous bats.

Seals like it hot: Changes in surface temperature of harbour seals (Phoca vitulina) from late pregnancy to moult

The annual moult in harbour seals (Phoca vitulina L.) follows a few weeks after the end of lactation and is characterised by a progressive loss and regrowth of hair which is apparent over a 4–6 week period. It is thought that during the moult harbour seals increase the time spent ashore as an adaptation to avoid additional energy costs associated with blood flow to the skin surface. The aim of this study was to determine the extent to which harbour seals regulated their surface temperature in order to maximise hair regrowth during the moult. The surface temperatures of two female harbour seals were recorded in captivity from late pregnancy to completion of the moult using infrared thermography. In this study, animals hauled out (exited the water onto land) more frequently during lactation and throughout the moult. Compared to the premoult period the temperature difference between body surface and air temperature (dT¯) showed a ∼10°C elevation at the peak of the moult. Also, during the moult dT¯ reached a higher maximum at a faster rate over a two hour haul-out period. Heat loss was estimated to increase during the moult and was equivalent to an approximate doubling of resting metabolic rate. It was therefore evident that harbour seals minimise the energetic cost of the moult by hauling out so that they can maintain optimal high skin surface temperature for hair growth. Human disturbance at haul-out sites that causes animals to enter the water during the moult may have consequences for harbour seals for two reasons. Firstly, reduced time spent ashore in optimal conditions for hair regeneration may prolong the duration of the moult and secondly, repeatedly forcing animals into the water when their skin temperature is high will incur an energetic cost.

Contour-feather moult of Bar-tailed Godwits (Limosa lapponica baueri) in New Zealand and the northern hemisphere reveals multiple strategies by sex and breeding region

The extreme long-distance migration of Alaskan breeding Bar-tailed Godwits (Limosa lapponica baueri) may present severe constraints on annual moult, and high individual variation in plumage and migration timing suggests that multiple strategies by sex and breeding region may exist. We used digital photography of free-living Bar-tailed Godwits to describe the timing and extent of pre-basic and pre-breeding contour-feather moults in New Zealand, and used plumage of breeding birds in Alaska to infer the proportion of moults occurring in Alaska and Asia. These data demonstrated that: (1) Godwits conducted overlapping pre-alternate and pre-supplemental moults; (2) pre-basic and pre-breeding moults were scheduled differently in relation to southbound and northbound migration respectively; (3) northern and southern Alaskan breeding Godwits of each sex were distinguishable by plumage differences throughout the non-breeding season; and (4) males and northern breeders achieved more extensive breeding plumage by spending longer in pre-breeding moult in New Zealand, rather than through faster moult rates or greater investment in moult during migratory stopover in Asia. The existence of a ventral pre-supplemental moult implies that contemporary selection for red breeding plumage overrides older selection for barred alternate plumage. Our use of individual-based data revealed a continuum of annual moult strategies within the population, which may reflect individual differences in any combination of sex, size, migration distance or breeding location. Even within the highly constrained annual cycle of extreme long-distance migrants, differential selection influences how individuals manage trade-offs among non-breeding activities such as moult, fuelling and migration.

Climate change and the long-term northward shift in the African wintering range of the barn swallow Hirundo rustica

ABSTRACT: Recent, unprecedentedly rapid climate change has frequently been invoked as thecause of changes in the phenology of bird migration as well as population decline. Birds would beexpected to respond to milder climatic conditions at their breeding grounds by reducing the lengthof their migration. Here, we exploit the largest ringing recovery database available for a long-distance migrant passerine bird, the barn swallow Hirundo rustica , spanning 1912−2008 and includ-ing recoveries from sub-Saharan Africa, to show that this species has shifted its wintering groundsnorthwards at a rate of 3 to 9 km yr −1 . This shift occurred consistently in the 2 geographical clustersof barn swallows that could be identified on the basis of their migratory connectivity and could be-detected after accounting for possible differential changes in recovery probability among geograph-ical areas. Analyses of trends in climatic conditions at the wintering grounds, based on time series ofrainfall and temperature anomalies, showed that this northward shift should have caused a progres-sively larger proportion of barn swallows to winter in drier or warmer areas, i.e. where primary pro-ductivity is lower and therefore ecological conditions for wintering are less favourable. This shift,which may have contributed to the general decline in breeding barn swallow populations, may bedue to the combined effects of selection for earlier arrival at the breeding grounds because of milderclimatic conditions in the breeding areas, and constraints in other stages of the annual life cycle (e.g.timing of the annual moult) that prevent earlier departure from the wintering grounds.KEY WORDS: Barnswallow·Birdmigration·Connectivity·EURINGswallowproject·Phenology·Winteringrange

Optimal bird migration revisited

Using optimality perspectives is now regarded as an essential way of analysing and understanding adaptations and behavioural strategies in bird migration. Optimization analyses in bird migration research have diversified greatly during the two recent decades with respect to methods used as well as to topics addressed. Methods range from simple analytical and geometric models to more complex modeling by stochastic dynamic programming, annual routine models and multiobjective optimization. Also, game theory and simulation by selection algorithms have been used. A wide range of aspects of bird migration have been analyzed including flight, fuel deposition, predation risk, stopover site use, transition to breeding, routes and detours, daily timing, fly-and-forage migration, wind selectivity and wind drift, phenotypic flexibility, arrival time and annual molt and migration schedules. Optimization analyses have proven to be particularly important for defining problems and specifying questions and predictions about the consequences of minimization of energy, time and predation risk in bird migration. Optimization analyses will probably also be important in the future, when predictions about bird migration strategies can be tested by much new data obtained by modern tracking techniques and when the importance of new trade-offs, associated with, e.g., digestive physiology, metabolism, immunocompetence and disease, need to be assessed in bird migration research.

Indications of phenotypic plasticity in moulting birds: captive geese reveal adaptive changes in mineralisation of their long bones during wing moult

Bone is continually undergoing cycles of apposition and resorption referred to as adaptive remodelling. We tested the hypothesis that captive moulting Barnacle Geese (Branta leucopsis) would show adaptive bone mineralisation during the flightless period of their annual flight feather moult, despite having never flown. The three leg bones showed selective changes in mineralisation in terms of mass and mineral content, while the wing bones did not change in mass or mineral content. The tibia/fibula was the only bone to also undergo significant changes in mass, increasing as moult progressed then decreasing significantly towards the end of moult. This was not a response to changing body mass. Instead, we propose that this is a response to the requirement for increased strength brought about by the significant increase in the force producing muscles that attach to the tibia. The femur and tarsometarsus showed the opposite trend, with mineral content decreasing significantly during mid-moult before increasing again at the end. These changes were also independent of changing body mass, suggesting instead that the calcium, or rather calcium derivatives, were mobilised for feather regrowth. This study demonstrates significant and selective adaptive natural changes in bone mass and mineralization that have not been previously demonstrated. That they should also occur in captive birds which show a decrease in locomotion during the wing moult period, suggests a high endogenous capacity for these changes.

Inexplicable Inefficiency of Avian Molt? Insights from an Opportunistically Breeding Arid-Zone Species, Lichenostomus penicillatus

The majority of bird species studied to date have molt schedules that are not concurrent with other energy demanding life history stages, an outcome assumed to arise from energetic trade-offs. Empirical studies reveal that molt is one of the most energetically demanding and perplexingly inefficient growth processes measured. Furthermore, small birds, which have the highest mass-specific basal metabolic rates (BMRm), have the highest costs of molt per gram of feathers produced. However, many small passerines, including white-plumed honeyeaters (WPHE; Lichenostomus penicillatus), breed in response to resource availability at any time of year, and do so without interrupting their annual molt. We examined the energetic cost of molt in WPHE by quantifying weekly changes in minimum resting metabolic rate (RMRmin) during a natural-molt period in 7 wild-caught birds. We also measured the energetic cost of feather replacement in a second group of WPHEs that we forced to replace an additional 25% of their plumage at the start of their natural molt period. Energy expenditure during natural molt revealed an energy conversion efficiency of just 6.9% (±0.57) close to values reported for similar-sized birds from more predictable north-temperate environments. Maximum increases in RMRmin during the molt of WPHE, at 82% (±5.59) above individual pre-molt levels, were some of the highest yet reported. Yet RMRmin maxima during molt were not coincident with the peak period of feather replacement in naturally molting or plucked birds. Given the tight relationship between molt efficiency and mass-specific metabolic rate in all species studied to date, regardless of life-history pattern (Efficiency (%) = 35.720•10−0.494BMRm; r2 = 0.944; p = <0.0001), there appears to be concomitant physiological costs entrained in the molt period that is not directly due to feather replacement. Despite these high total expenditures, the protracted molt period of WPHE significantly reduces these added costs on a daily basis.

Intra-sex dimorphism in crayfish females

A unique cycle of female form alternation has been revealed in an experimental population of Orconectes limosus during a year-long observation. Significant cyclic changes observed in chelae length, width, and robustness, as well as in abdomen width, demonstrated a form alternation similar to that in conspecific males. Small females alternate between sexually active and sexually inactive forms with a short time interval between successive molts as well as different growth patterns of some body parts. Form alternation efficiently produces larger chelae, abdomen, and body dimensions, especially the molt to form I (sexually active). Larger females that undergo only a single annual molt do not alter between forms and are sexually active. They grow slowly and lose chelae robustness. The cycle of form alternation, consisting of two molts per year, may facilitate the effective utilization of resources to increase the size of body parts important to survival and reproduction.

The status of harbour seals (&lt;i&gt;Phoca vitulina&lt;/i&gt;) in the United Kingdom

The UK holds approximately 40% of the European harbour seal population, with the majority found around the coasts of Scotland. Harbour seal populations in the UK have been monitored through a series of repeated aerial surveys of animals hauled out during the annual moult in early August. This moult count is used as a consistent index of population size. Survey methods and frequencies vary. The Scottish and English east coast populations mainly haul out in tidal estuariesand are surveyed annually, using fixed wing aircraft and digital photography. Populations in north and west Scotland often haul out on rocky shores and are surveyed less frequently, using helicopters fitted with thermal imagers. Overall, the most recent minimum estimate of the UK harbour seal population is 24,250 seals of which 19,800 are in Scotland, 3,200 in England and 1,250 in Northern Ireland. The results show that the number of harbour seals in eastern Englandwas increasing before the 1988 and 2002 phocine distemper (PDV) epizootic but has not increased since the end of the 2002 epizootic. There is also evidence of a general decline in most of the large harbour seal colonies around Scotland. The populations along the north and northwest mainland coast were an exception, with numbers appearing to be stable. Between 2001 and 2008, the population in Orkney declined by 67% and Shetland declined by 40%, indicating harbourseals in these areas experienced substantially increased mortality or very low recruitment over this period. The widespread declines, ranging from Shetland to The Wash, suggest that the causes may have been present over a large part of the North Sea and waters off western Scotland.

The status of the harbour seal (&lt;i&gt;Phoca vitulina&lt;/i&gt;) in Ireland

The status of Ireland’s harbour seal population and its relationship with that of Britain and Western Europe are poorly understood. Prior to 2003, limited research efforts and poor co-ordination of survey methods fell short at providing an accurate assessment of overall distribution and population size on a regional or national scale. However, in August 2003, the Republic of Ireland’s harbour seal population was assessed by means of a geographically extensive survey conducted during the annual moult, providing an up-to-date minimum population estimate and a reliable baseline for future surveys. Trends on a national scale could not be assessed due to absence of a reliable historic population estimate; however there is some evidence of local decreases and increases in harbour seal numbers in Northern Ireland and southwest Ireland respectively. Research effort to date on aspects of the ecology of the harbour seal in the Republic of Ireland is reviewed and current research and management priorities highlighted.

Notes on the Breeding Biology of the White-Throated Swift in Southern California

Reproductive activities of White-throated Swifts (Aeronautes saxatalis) were examined from 1997 to 2006 at two nest sites in a human-made structure in southern California. The start of egg-laying was from 27 April to 30 May and hatching of the first chick ranged from 21 May to 23 June; all chicks had fledged by late July, 42–43 days after hatching. The annual molt of adults began in early June and broadly overlapped with the chick-rearing period. Year to year adult survival was minimally 73.9% and nesting pairs showed strong mate and nest site fidelity; pairs reused nests up to five consecutive years. The composition of the arthropod food (insects and spiders) brought to nestlings was different in the periods 1997–2000 and 2001–2004 but prey size was similar in both periods. The onset of breeding was more varied from year to year than the start of the primary feather molt suggesting differing environmental stimuli for these important components of the annual cycle.

Regional patterns in moult and sexual dimorphism of adult Southern Red Bishops Euplectes orix in southern Africa

Using the SAFRING database and the Underhill-Zucchini model of primary moult, we analysed the timing of wing moult in Southern Red Bishops Euplectes orix in relation to sex and geographical region. Birds from the winter rainfall region in the south-western sector of the Western Cape start the annual moult more than two months before any other population, but there were no significant differences in starting date within the summer rainfall region. There were striking differences in the estimates of moult duration (62–114 d), which did not follow a consistent pattern in relation to sex or geography; annual variation within a region may be an additional factor. Throughout southern Africa, both sexes showed a trend for longer-winged birds to take more time to complete their moult. We suggest that sex, geographical area and possible annual environmental variations may all influence the timing of moult in local populations. In this sexually dimorphic species, males are consistently longer-winged and heavier than females.

Bill color, not badge size, indicates testosterone-related information in house sparrows

The honesty of ornamental signals of quality is often argued to be enforced via costs associated with testosterone. It is still poorly understood, however, how seasonal variation of testosterone within individuals is related to the timing and extent of ornament development. Here, we studied inter- and intra-individual variability of plasma testosterone levels in a population of 150 captive male house sparrows (Passer domesticus) through the course of a full year. We further analyzed the relationship between plasma testosterone levels and two sexually dimorphic ornaments: badge size and bill coloration. Also, because of a known negative relation between molt and circulating testosterone levels, we analyzed the relationship between ornamentation and molt status during the fall. We found that testosterone levels increased towards the breeding season and decreased before the onset of annual molt. However, within individuals, relative testosterone titers demonstrated low repeatability between seasons. Plasma testosterone levels were not correlated with badge size in any season but were correlated strongly with bill coloration during all periods, except the breeding season when variation in bill color was low. Finally, we found that bill coloration strongly correlated with molt status during fall. Our results indicate that bill coloration, not badge size, is the best ornamental indicator of a “running average” of male testosterone in house sparrows and therefore the best potential indicator of qualities and/or behavioral strategies associated with testosterone.

Optimizing survey design for Scandinavian harbour seals: population trend as an ecological quality element

Abstract Teilmann, J., Rigét, F., and Harkonen, T. 2010. Optimizing survey design for Scandinavian harbour seals: population trend as an ecological quality element. – ICES Journal of Marine Science, 67: 952–958. To be successful, conservation and management programmes require accurate data on abundance and population trends. Noise caused by within- and among-year variance should be minimized to optimize the statistical power for detecting changes in abundance. A total of 30 years of monitoring data from seven distinct subpopulations of harbour seals (Phoca vitulina) in southern Scandinavia was used to investigate the relative contributions of factors affecting the power to detect trends in abundance. The power is typically doubled under the conditions tested when carrying out annual surveys compared with every second year. The power also increases substantially when carrying out replicate surveys during the annual moult. The gain in power increases steeply up to three annual replicates, but then levels off, and it is further increased when the mean of the two highest counts of three annually repeated counts is used. We propose that harbour seal haul-out sites are surveyed every year during the moult, with at least three replicate surveys per year. This would provide robust data for analyses of population trends, facilitating management and identification of potential influences of diseases and anthropogenic activities.

Flight feather shaft structure of two warbler species with different moult schedules: a study using high‐resolution X‐ray imaging

Plumage constitutes a significant component of the somatic investment of birds. A detailed investigation of feathers and moult can help to uncover trade-offs involved in somatic investment decisions, the sources of some of the costs birds have to pay and the potential fitness consequences. We used micro-computed tomography imaging to study the second moment of area, a structural parameter that is one determinant of bending stiffness and the cortex volume of flight feather shafts of two sister taxa, the willow warbler Phylloscopus trochilus, a migratory species with two annual moults, and the chiffchaff Phylloscopus collybita, a migrant with one annual post-nuptial moult. Juvenile and adult willow warbler and chiffchaff feathers, all grown on the breeding grounds, are structurally very similar to each other. Willow warbler feathers grown during moult on the wintering grounds, however, have a significantly higher second moment of area and a significantly larger cortex volume than all the other feather types. We discuss the possibility that the seasonal variability of willow warbler feathers may be an adaptive structural reflection of a moult-migration strategy that has allowed this species to occupy large breeding and wintering ranges.

Long-range migration of a chinstrap penguin from Bouvetøya to Montagu Island, South Sandwich Islands

AbstractWe describe a long-range migration of a pre-moulting adult chinstrap penguin from Bouvetøya, a small relatively recently established colony, to the South Sandwich Islands, where large, established colonies of this species reside. The trip lasted around three weeks, covered ∼3600 km, and the time of arrival was consistent with the annual moult. The bird did not travel along the shortest path or along a constant bearing, but instead followed what appeared to be a series of two or three rhumb lines of constant bearing. Small southward and northward deviations from the general path were consistent with local water currents. Travel speeds were high during daylight but decreased at night, suggesting that resting or opportunistic feeding occurred preferentially at night. While long-range winter migrations of chinstraps to feeding areas in the vicinity of distant colonies have been previously described, this is the first observation of such a trip during the period between breeding and moulting, and the first record of an individual actually arriving at one of these distant colonies. This has implications for understanding population structure and management of this important Southern Ocean predator.

Intra-archipelago moult dispersion of southern elephant seals at the Prince Edward Islands, southern Indian Ocean

During three summer surveys at Prince Edward Island (PEI), southern Indian Ocean (2001, 2004 and 2008), 416 southern elephant seals Mirounga leonina were inspected for identification tags. In all, 42 seals that had been tagged as weaned pups at their natal site were found on Marion Island (MI), 38 of which could be individually identified by resighting their tag numbers. The majority of the MI-tagged seals were yearlings or subadults, and all but one were hauled out at PEI for the annual moult. The attendance rate of the known individuals at their natal island during the annual moult was only 40%, based on their resighting histories. This was significantly lower than the 77 ± 6% moult attendance rate estimated for a random MI population sample drawn from the same cohorts (based on 10 000 replications). Annual resight probabilities (considering all haulout phases) was 58% per annum for the MI seals seen at PEI, and 80 ± 4% for the simulation. Seasonal and annual absences of seals from MI violate the ‘homogeneity of capture’ assumption of mark-recapture models. When multiple sightings during any year are treated as a single sighting, resights during other haulouts (e.g. breeding) compensate only partially for absences during the moult. Therefore, mark-recapture studies undertaken in archipelagos should ideally include both marking and resighting of individuals on all islands which will allow discrimination between mortality and local migration.