Timing Of Moult Research Articles

Evolution of long-term coloration trends with biochemically unstable ingredients

The evolutionarily persistent and widespread use of carotenoid pigments in animal coloration contrasts with their biochemical instability. Consequently, evolution of carotenoid-based displays should include mechanisms to accommodate or limit pigment degradation. In birds, this could involve two strategies: (i) evolution of a moult immediately prior to the mating season, enabling the use of particularly fast-degrading carotenoids and (ii) evolution of the ability to stabilize dietary carotenoids through metabolic modification or association with feather keratins. Here, we examine evolutionary lability and transitions between the two strategies across 126 species of birds. We report that species that express mostly unmodified, fast-degrading, carotenoids have pre-breeding moults, and a particularly short time between carotenoid deposition and the subsequent breeding season. Species that expressed mostly slow-degrading carotenoids in their plumage accomplished this through increased metabolic modification of dietary carotenoids, and the selective expression of these slow-degrading compounds. In these species, the timing of moult was not associated with carotenoid composition of plumage displays. Using repeated samples from individuals of one species, we found that metabolic modification of dietary carotenoids significantly slowed their degradation between moult and breeding season. Thus, the most complex and colourful ornamentation is likely the most biochemically stable in birds, and depends less on ecological factors, such as moult timing and migration tendency. We suggest that coevolution of metabolic modification, selective expression and biochemical stability of plumage carotenoids enables the use of unstable pigments in long-term evolutionary trends in plumage coloration.

Does Water Temperature Affect the Timing and Duration of Remigial Moult in Sea Ducks? An Experimental Approach.

Aquatic birds have high cost of thermoregulation, especially during the moulting period, yet the effect of water temperature on the moulting strategy of aquatic birds has rarely been studied. Our general hypothesis is that energy savings associated with lower thermoregulation costs would be allocated to moulting processes. We predicted that aquatic birds moulting in warm water would have a higher level of body reserves, a faster growth rate of feathers, and an earlier remigial moult onset compared with birds moulting in cold water. We used the common eider (Somateria mollissima dresseri), a large sea duck, as the model species. Captive individuals were experimentally exposed to warm (18°C) and cold (8°C) water treatments during a three year period with individuals swapped between treatments. We found a similar feather growth rate for the two water temperature treatments and in contrast to our predictions, eiders exposed to warm water had a lower body mass and showed a delayed onset of remigial moult of approximately 7 days compared with those exposed to cold water. Our data indicate that body mass variations influence the timing of moult in unexpected ways and we suggest that it likely controls the occurrence of wing moult through a hormonal cascade. This study emphasizes the importance of improving our knowledge of the effects of water temperature on remigial moult of aquatic birds, to better assert the potential effects of global warming on their survival.

Demographic variation in timing and intensity of feather molt in migratory Fork‐tailed Flycatchers (Tyrannus s. savana)

Understanding the annual cycle of migratory birds is imperative for evaluating the evolution of life-history strategies and developing effective conservation strategies. Yet, we still know little about the annual cycle of migratory birds that breed at south-temperate latitudes of South America. We aged, sexed, and determined the progression and intensity of body, remige, and rectrix molt of migratory Fork-tailed Flycatchers (Tyrannus s. savana) at breeding sites in southern South America and at wintering sites in northern South America. Molt of both body and flight feathers occurred primarily during the winter. In early winter, a similar proportion of young and adult flycatchers molted remiges and rectrices, but remige molt intensity (number of remiges molting) was greater and primary molt progression (mean primary feather molting) more advanced in adults. In late winter, remige molt intensity and primary molt progression did not differ between age groups. We found no difference between males and females either in the proportion of individuals molting in winter or in the intensity or progress of remige molt. Our results suggest that the nominate subspecies of Fork-tailed Flycatcher undergoes one complete, annual molt on the wintering grounds, and represents the first comprehensive evaluation of molt timing of a migratory New World flycatcher that overwinters in the tropics. Given that breeding, molt, and migration represent three key events in the annual cycle of migratory birds, knowledge of the timing of these events is the first step toward understanding the possible tradeoffs migratory birds face throughout the year. © 2016 Association of Field Ornithologists.

Age and sex determination of Mallards Anas platyrhynchos in autumn

Male and female mallards Anas platyrhynchos are easily told apart, whereas ageing is problematic, due to individual timing of moult and lack of easily defined age criteria. From examination and photographic documentation of mallards caught at Ottenby Bird Observatory (56°12′N, 16°24′E), we describe nine characters of plumage and bare parts to be used for ageing in autumn. The reliability of these characters was tested by letting experienced bird ringers determine putative age of birds from photos. Age determination from any single character proved to be uncertain, as correctly assigned mallard photos of each character was in the range of 51–85% for males and 48–89% for females. For both sexes, the lowest figure represented post-humerals and the highest represented tertials. Rectrices, tertial coverts, and greater coverts had high scores (71–85%). Using all characters, 91% of the males and 95% of the females were correctly aged. As young mallards, with the progress of pre-breeding moult (completed from October onwards), acquire tail and tertials identical to adults, untypical individuals are better not assigned to an age category.

Carry‐over effects provide linkages across the annual cycle of aNeotropical migratory bird, theLouisianaWaterthrushParkesia motacilla

Population limitation models of migratory birds have sought to include impacts from events across the full annual cycle. Previous work has shown that events occurring in winter result in some individuals transitioning to the breeding grounds earlier or in better physical condition than others, thereby affecting reproductive success (carry‐over effects). However, evidence for carry‐over effects from breeding to wintering grounds has been shown less often. We used feather corticosterone (CORTf) levels of the migratory Louisiana WaterthrushParkesia motacillaas a measure of the physiological state of birds at the time of moult on the breeding territory to investigate whether carry‐over effects provide linkages across the annual cycle of this stream‐obligate bird. We show that birds arriving on wintering grounds with lowerCORTfscores, indicating reduced energetic challenges or stressors at the time of moult, occupied higher quality territories, and that these birds then achieved a better body condition during the overwinter period. Body condition, in turn, was important in determining whether adult birds returned the following winter, with birds in better condition returning at higher rates. Together these data suggest a carry‐over effect from the breeding grounds to the wintering grounds that is further extended with respect to annual return rates. Very few other studies have linked conditions during the previous breeding season with latent effects during the subsequent overwintering period or with annual survival. This study shows that the effects of variation in energetic challenges or stressors can potentially carry over from the natal stream and accumulate over more than one life‐history period before being manifested in reduced survival. This is of particular relevance to models of population limitation in migratory birds.

Moult Strategies Affect Age Differences in Autumn Migration Timing in East Mediterranean Migratory Passerines.

Adult passerines renew their flight feathers at least once every year. This complete moult occurs either in the breeding areas, just after breeding (summer moult), or, in some long-distance migratory species, at the non-breeding areas, after arrival to the southern wintering area at the end of autumn migration (winter moult). The aim of this study was to relate moult strategies with the DMD, the difference in median migration date, through Israel, between juveniles and adults. Our data on autumn migration timing in juveniles and adults was based on ringing data of 49,125 individuals belonging to 23 passerine species that breed in Europe and Western Asia and migrate through Israel. We found that DMD was associated with moult timing. In all species that perform a winter moult, adults preceded juveniles during autumn. Among migrants who perform a summer moult, we found evidence of both migration timing patterns: juveniles preceding adults or adults preceding juveniles. In addition, in summer moulters, we found a significant, positive correlation between mean breeding latitude and DMD. Although previous studies described that moult duration and extent can be affected by migration, we suggest that moult strategies affect both migration timing and migration strategy. These two moult strategies (summer or winter moult) also represent two unique migration strategies. Our findings highlight the evolutionary interplay between moult and migration strategies.

Dietary flavonoids advance timing of moult but do not affect redox status of juvenile blackbirds (Turdus merula).

Flavonoids are the most abundant plant polyphenols, widely occurring in fruits and berries, and show a strong antioxidant activity in vitro Studies of avian species feeding on berries suggest that dietary flavonoids have health-promoting effects and may enhance the expression of melanin-based plumage traits. These effects are probably mediated by the antioxidant activity of flavonoids. However, the effect of dietary flavonoids on oxidative status has never been investigated in any bird species. We analysed the effects of dietary flavonoids on blood non-enzymatic antioxidants and protein oxidative damage of juvenile European blackbirds (Turdus merula). In addition, we analysed the effects of flavonoid-enriched diet on body condition and on the timing of moult from juvenile to adult plumage. Dietary flavonoids did not significantly affect redox status but significantly advanced the onset of moult, hastening plumage development. Moulting birds showed higher protein oxidative damage compared with those that had not yet started moulting. The probability of initiating moult after 40 days of dietary treatment was higher for birds with low circulating levels of oxidizing agents and high glutathione concentration. The metabolization of flavonoids could have altered their redox potential, resulting in no net effects on redox status. However, flavonoid consumption before and during moult may contribute to enhance plumage development. Moreover, our findings suggest that moulting feathers may result in redox imbalance. Given their effect on moult and growth of melanin-rich feathers, fruit flavonoids may have contributed to shape plant fruiting time in relation to fruit consumption preferences by birds.

Transcriptional regulation of insect steroid hormone biosynthesis and its role in controlling timing of molting and metamorphosis.

The developmental transition from juvenile to adult is often accompanied by many systemic changes in morphology, metabolism, and reproduction. Curiously, both mammalian puberty and insect metamorphosis are triggered by a pulse of steroid hormones, which can harmonize gene expression profiles in the body and thus orchestrate drastic biological changes. However, understanding of how the timing of steroid hormone biosynthesis is regulated at the molecular level is poor. The principal insect steroid hormone, ecdysteroid, is biosynthesized from dietary cholesterol in the specialized endocrine organ called the prothoracic gland. The periodic pulses of ecdysteroid titers determine the timing of molting and metamorphosis. To date, at least nine families of ecdysteroidogenic enzyme genes have been identified. Expression levels of these genes correlate well with ecdysteroid titers, indicating that the transcriptional regulatory network plays a critical role in regulating the ecdysteroid biosynthesis pathway. In this article, we summarize the transcriptional regulation of ecdysteroid biosynthesis. We first describe the development of prothoracic gland cells during Drosophila embryogenesis, and then provide an overview of the transcription factors that act in ecdysteroid biosynthesis and signaling. We also discuss the external signaling pathways that target these transcriptional regulators. Furthermore, we describe conserved and/or diverse aspects of steroid hormone biosynthesis in insect species as well as vertebrates.

Ancient Murrelets Molt Flight Feathers After the Precocial Young Become Independent

Abstract Knowledge of timing and pattern of wing molt is important for explanations of post-breeding movements and inland vagrancy in Ancient Murrelets (Synthliboramphus antiquus). Examination of specimens coupled with observations of family groups and recently independent young suggests that chick rearing and wing molt probably occur separately in adults, although it may commence before the last chicks of the season become independent. An adult Ancient Murrelet beached in September 1976 (Alaska Peninsula) and a probable second-year murrelet beached in July 1987 (Oregon) were synchronously molting remiges. Adults in family groups, collected in July 1920 (southeast Alaska) and July 1948 (British Columbia), and observed in July 2009 (British Columbia), were not molting remiges, although an adult observed with a family group on 18 July 1971 (British Columbia) may have commenced molt. Family groups immediately moved offshore from colonies on Langara Island, Haida Gwaii (Queen Charlotte Islands), British Colum...

SURVIVAL AND RESPONSE MOLTING OF MUD CRAB (Scylla olivacea) INJECTED WITH MURBEY (Morus spp.) LEAVE EXTRACT

The soft shell crab productivity has been hampered due to the long rearing time and unsimultaneous molting of the crab. This study aimed to determine the effect of murbey (Morus spp.) leave extract as molting stimulant on Scylla olivacea and its best extract dosage to be applied in soft shell crabs production technology. Application of murbey extract was conducted by using injection method with 5 treatments such as (a) 0 ppm (as control); (b) 100 ppm; (c) 125 ppm; and (d) 150 ppm for 12 individual per treatment. The results showed that the highest molting percentage (50%) was obtained at the concentration of 100 ppm. Meanwhile, the control (0 ppm), 125 ppm, and 150 ppm treatments displayed the same molting response (33.3%). The fastest latent molting time (29 days) was found at the treatment of 125 ppm and the slowest one of 44 days at 100 and 150 ppm treatments. The best growth of crabs injected with murbey leaves extract was at the concentration of 100 ppm with the carapace width of 6.0 mm and the body weight of 32.98 g, while the lowest was obtained at the concentration of 150 ppm with the carapace width of 3.8 mm and the body weight of 25.43 g. Crabs treated with murbey extract at the concentrations of 100, 125, and 150 ppm exhibited survival rate of 91.7 % vs. the control of 83.3%. Murbey leaves extract have been proven to be effective in stimulating molting mud crab (Scylla olivacea). The 100 ppm exhibited the best response for growth and molting percentage, while the 125 ppm showed the best performance for latent period molting of the crab. Keywords: molting response, survival rate, Scylla olivacea, murbei leaves, Morus spp.

Responses of growth and hemolymph quality in juvenile Chinese horseshoe crab Tachypleus tridentatus (Xiphosura) to sublethal tributyltin and cadmium.

Responses of growth endpoints and hemolymph constituents in juvenile Chinese horseshoe crab Tachypleus tridentatus under treatments of 0.01 and 0.1 mg/l tributyltin (TBT) and 0.1 and 1 mg/l cadmium (Cd) were examined in a 12-week experiment. A significant decline in final body weight, final prosomal width, percentage of individuals molted and mean molting time was detected under TBT exposures. While morphological abnormalities of the juveniles between TBT treatments and the control were statistically indistinguishable, significantly higher occurrences of carapace erosion and appendage loss were noted under 0.1 and 1 mg/l Cd exposures. Various hemolymph quality indicators, including hemolymph plasma protein level, amebocyte viability and percentage of granular-spherical state of amebocytes of the juveniles exposed to TBT or Cd were significantly lower than the control. Such a decrease in hemolymph quality suggested deleterious effects of metal contaminant-induced stressors on the health status of the juveniles even at low exposure levels (i.e., 0.01 mg/l TBT and 0.1 mg/l Cd). Changes of hemolymph parameters in juvenile horseshoe crabs were more sensitive than growth performance as well as morphological abnormalities in response to metal stressors, and can be used as an indicator to reflect habitat conditions and contaminant levels.

Does prolactin mediate parental and life-history decisions in response to environmental conditions in birds? A review

This article is part of a Special Issue “Parental Care”. In vertebrates, adjustments of physiology and behavior to environmental changes are often mediated by central physiological mechanisms, and more specifically by hormonal mechanisms. As a consequence, these mechanisms are thought to orchestrate life-history decisions in wild vertebrates. For instance, investigating the hormonal regulation of parental behavior is relevant to evaluate how parents modulate their effort according to specific environmental conditions. Surprisingly and despite being classically known as the ‘parental hormone’, prolactin has been overlooked in birds relative to this context. Our aim is to review evidence that changes in prolactin levels can mediate, at least to some extent, the response of breeding birds to environmental conditions. To do so, we first examine current evidence and limits for the role of prolactin in mediating parental behavior in birds. Second, we emphasize the influence of environmental conditions and stressors on circulating prolactin levels. In addition, we review to what extent prolactin levels are a reliable predictor of breeding success in wild birds. By linking environmental conditions, prolactin regulation, parental behavior, and breeding success, we highlight the potential role of this hormone in mediating parental decisions in birds. Finally, we also review the potential role of prolactin in mediating other life history decisions such as clutch size, re-nesting, and the timing of molt. By evaluating the influence of stressors on circulating prolactin levels during these other life-history decisions, we also raise new hypotheses regarding the potential of the prolactin stress response to regulate the orchestration of the annual cycle when environmental changes occur. To sum up, we show in this review that prolactin regulation has a strong potential to allow ecological physiologists to better understand how individuals adjust their life-history decisions (clutch size, parental behavior, re-nesting, and onset of molt) according to the environmental conditions they encounter and we encourage further research on that topic.

The flight feather moult pattern of the bearded vulture (Gypaetus barbatus)

Moult is an extremely time-consuming and energy-demanding task for large birds. In addition, there is a trade-off between the time devoted to moulting and that invested in other activities such as breeding and/or territory exploration. Moreover, it takes a long time to grow a long feather in large birds, and large birds that need to fly while moulting cannot tolerate large gaps in the wing, but only one or two simultaneously growing feathers. As a consequence, large birds take several years to complete a full moult cycle, and they resume the moult process during suboptimal conditions. A clear example of this pattern is the Bearded Vulture (Gypaetus barbatus), which needs 2–3 years for changing all flight feathers. Here we describe the sequence, extent, and timing of moult of 124 Bearded Vultures in detail for the first time. We found that extent and timing of flight feather moult was different between age classes. Subadults (from 3rd to 5th calendar year) started moult, on average, in early March, whereas adults only started moult, on average, in late April, possibly due to breeding requirements. Second calendar year individuals delayed onset of moult until the middle of May. In general, the moult lasted until November, and although adults started to moult later than subadults, they moulted more feathers. Subadults needed 3 years for moulting all flight feathers, whereas adults normally completed it in 2 years.

The time scale of isotope signals in spiders: molting the remains of a previous diet

AbstractStable isotope analysis (SIA) has emerged as an important tool for understanding consumer diets and diet shifts. However, although the general idea behind SIA is clear, the interpretation of data is often fraught with problems because tissue turnover and fractionations are not known. We investigated shifts in stable isotope composition of spiders following a diet shift, using mealworms fed either maize (C4) or wheat (C3) flour. Mealworms had different carbon isotope composition depending on their diet and this difference was reflected in spider body parts. In the experiment, we first fed the spiders on a diet of either maize‐fed or wheat‐fed mealworms and then switched diet at the time of the second molt. Spiders were then sampled repeatedly until the next molt. We sampled both legs and abdomens, as these are presumed to have different turnover of tissue, and also molt remains were sampled when this was relevant. The data indicated that the spider legs had a turnover of about 20 days, whereas the spider abdomens had a turnover of about 8 days. Molt remains had the slowest turnover and reflected the diet at the previous molt, when the exoskeleton was formed. Both these observations indicate that SIA may be successfully used for elucidating diet shifts. More problematic was the fact that fractionation of carbon isotope ratios varied with body parts and diets. When spiders were fed maize‐mealworms then the fractionation was larger for abdomens, but when the spiders were fed wheat‐mealworms then the fractionation was larger for legs. The mechanisms underlying this pattern are unclear and deserve further attention.

Timing and duration of moult in relation to weather conditions in four montane passerine species at the Gran Sasso, Central Italy

Summer primary and secondary moult were investigated in four species of passerines, Northern Wheatear Oenanthe oenanthe, Black Redstart Phoenicurus ochruros, Linnet Linaria cannabina and Water Pipit Anthus spinoletta, in a mountain environment in central Italy. For each species we determined mean starting date and duration of both primary and secondary moults, and whether factors such as spring precipitation or temperature affected the timing or the duration of each moult. Northern Wheatear, the only long-distance migrant among the study species, was the first to start and to complete its moult. Furthermore, this species was the only one to moult earlier in years with warmer springs and with less snow, as predicted. Black Redstarts, on the other hand, started to moult later in warmer years, possibly because a greater proportion of pairs produced a second brood. In each of the species with distinguishable sexes, moult began later in females than in males. In Linnets, females finished primary moult on average two days earlier than males, due to a shorter moult duration. Similarly, Black Redstart females finished their secondary moult exactly at the same time as males, despite a later start.

White tail spots in breeding Barn SwallowsHirundo rusticasignal body condition during winter moult

The determinants and function of pigmentation of feathers and other tissues have been the focus of a large number of studies, particularly with respect to socio‐sexual communication. However, many birds exhibit depigmented white spots or bars on their feathers whose function is poorly understood. Here we assess whether white feather spots reflect phenotypic condition at the time of moult by investigating the covariation between spot size or shape and condition‐dependent feather growth rate, as gauged by width of the growth bars on the tail feathers of Barn Swallows. We found that feathers with higher growth rates had larger, less rounded white spots. In addition, variance in spot perimeter for a given spot area was larger in males than in females. This study is the first to provide evidence that features of white markings on feathers directly reflect body condition at the time of moult and can therefore reliably signal phenotypic quality in the context of socio‐sexual communication. In addition, the study highlights the potential communication function of the shape and not just the size of colour signals.

Comparative analysis points to functionally significant variation in wing feather structure among a large and diverse sample of modern birds

Comparative analysis points to functionally significant variation in wing feather structure among a large and diverse sample of modern birds

Life history and multiscale habitat preferences of the red-listed Balkan Goldenring, Cordulegaster heros Theischinger, 1979 (Insecta, Odonata), in South-Hungarian headwaters: does the species have mesohabitat-mediated microdistribution?

Life cycle and microdistribution patterns of Cordulegaster heros, a charismatic species for nature conservation, are poorly known. Life history characteristics and multiscale habitat preferences of the larvae were followed for one year in monthly intervals by systematic samplings in eight headwaters, which resulted in data on 2562 individuals. We hypothesized that meso- and microhabitat complexity play an important role in forming the population structure and microdistribution of the species. Based on the distribution of the consecutive larval instars, duration of later stages and time of molt and emergence, the larval development of C. heros in the Mecsek Mountains lasts for at least three, but with a maximum of four years. All three levels of the multi-habitat structure [habitat (sites), and meso- (riffle/pool sequence) and microhabitats (biotic and different particle-sized abiotic types)] have significant effects on the spatial distribution of the larvae. Densities and population structures vary among the sites, but mesohabitat type and microhabitat diversity (heterogeneity within a pool or riffle) govern the microdistribution. C. heros prefers pools with small or medium microhabitat heterogeneity and higher proportion of small particle-sized substrates, especially in younger stages. Older larvae are less sensitive for these effects.

Population dynamics of thrushes and seasonal resource partition

We studied seasonal population dynamics in birds using four thrush species from the Yenisei middle taiga region as an example. Long-term data on bird route censuses, capture-mark-recapture, and nest observa- tions were incorporated in the analysis. Particularly, methodological problems that complicate a direct comparison between assessed numbers at different phases of the annual cycle are considered. The integrated analysis of the results allowed comparing changes in numbers, energy expenditure, age structure, migrating status, and density distribution of selected populations during the snowless period and relating them to seasonal changes in food resource abundance. Thrush population numbers within the breeding range, and their energy consumption in the Yenisei middle taiga proportionately reflect the seasonal change in abundance of food resources. The compliance between resource intake and carrying capacity of the environment is attained by: timing of arrival and departure regarding to the species' range of tolerance; change in numbers as a result of reproduction and mortality; change in numbers due to habitat changes and long-distance movements; increasing energetic expenditures during reproduction and molt; timing, intensity and replication of nesting attempts; timing of molt and proportion of molting individuals in a population; individual variations of the annual cycle. Reproductive growth of local bird populations is not fast enough to catch up with seasonal growth of ecosystems productivity. Superabundance of invertebrates at the peak of the season offers a temporal niche which, on the one hand, is suitable for species capable of diet switching, while, on the other hand, may be used by specialized consumers, namely tropical migrants for whom, at high resource level, a shortened breeding period suffices.

Migration distance and breeding latitude correlate with the scheduling of pre-alternate body moult: a comparison among migratory waders

Moult is an important maintenance activity that should be carefully timed within the annual cycle. Many birds perform a pre-alternate moult of body feathers some time prior to the breeding season. In migrants, the timing of the pre-alternate moult coincides with the migration from wintering to breeding areas. In this study, we used visual plumage scores collected on the Continental Black-tailed Godwit Limosa limosa limosa in Portugal and The Netherlands to establish that the pre-alternate body moult of these birds during the northward migration between West Africa and The Netherlands takes place only in staging areas in the Iberian peninsula from late January to late February. A comparison of the moult strategy of these godwits with that of 20 other migratory wader populations (13 species) revealed that the former had a rather uncommon moult schedule which was more characteristic of populations with rather short migrations that breed at lower latitudes. We argue that this unusual moult schedule can be explained by a combination of ecological opportunity and proximate and ultimate trade-offs (hormonal incompatibly and maximization of plumage quality vs. time spent on migration, respectively).