Postnuptial Molt Research Articles

Survival Strategies and Seasonal Size Variations of Feather Mites Proctophyllodes megaphyllus on their Host Alpine Accentor Prunella collaris

Compared to chewing lice, symbiotic and studies on their biology, ecology and survival strategies are still rare. To describe the ecology and morphology of the mite species Proctophyllodes megaphyllus, a symbiont of the alpine accentor Prunella collaris, 150 accentors were captured in the West Carpathian Mountains of Slovakia. The mites extracted from the birds were sexed and their specific body structures were measured. In total 2144 individuals of P. megaphyllus were collected from 100 accentors. Male mites collected in autumn, after the bird's postnuptial moult, reached the largest size. At the same time, mite prevalence reached maximum while the mean intensity of infestation was at its lowest. Our results suggest that mites preferred newly coated feathers after a moult and radiated horizontally, infesting birds at shared roosting sites where alpine accentors tend to reoccur. This study is one of the few evaluations of seasonal variation in ecology and morphology of feather mites in alpine conditions.

Adaptive Plasticity in Insect Parasites – Philopterus Lice and their Accentor Passerine Hosts

One hundred and five alpine accentors Prunella collaris (Scopoli, 1786) and ninety four dunnocks Prunella modularis (Linnaeus, 1758) were captured in the West Carpathian Mountains of Slovakia in order to compare the morphology of their Ischnoceran parasites Philopterus emiliae Balat 1985 and Philopterus modularis (Denny, 1842), respectively. In the case of both host species, the largest bodied lice occurred in winter, before the beginning of the host breeding season. Lice collected during the host breeding season were smaller in size than those collected in winter. Lice collected in the autumn, following postnuptial molt were even smaller in size. The largest lice were found on the bodies of host individuals with relatively long wings. The lice Ph. emiliae also differed in shape. In winter, the relative size of the head was large, while in the autumn, the head was proportionately smaller in size, compared to other body regions. Adult lice Ph. modularis also tended to have larger heads in April than in July. Measurements of lice over an eleven year period from the same site yielded differences in shape, but not in size. This study is one of the first assessments of seasonal variation in morphology of lice.

Subspecies-specific features of molt in the common chiffchaff (Phylloscopus collybita L.) from Europe and Western Siberia

The patterns of molt in the chiffchaffs of the nominotypical subspecies from central Europe and eastern European subspecies from the Ladoga region are compared with that of the Siberian subspecies from the lower Ob region. The onset dates of postjuvenile molt in the Siberian subspecies are controlled endogenously, while in the nominative and, probably, eastern European subspecies they are under photoperiodic control. The molt of chiffchaffs from central Europe is no less complete than in birds from the Ladoga region and more complete than in Siberian birds. The individual duration of molt is the shortest in Siberian birds and the longest in central European birds, being intermediate in birds from the Ladoga region. Differences in the pattern of postnuptial molt between chiffchaffs from the Ladoga and Ob regions concern its duration and completeness. The completeness of molt proved to be reduced in half of examined birds from the Ladoga region and in some birds from the Ob region. The duration of complete molt in birds from the Ob region is smaller (40 days vs. 60 days in birds from the Ladoga region) at a longer daylight period, which is evidence for a higher rate of feather growth. The completeness and timing of prenuptial molt do not differ between the subspecies.

ЖЕЛТОСПИННАЯ МУХОЛОВКА FICEDULA ZANTHOPYGIA (HAY, 1845) У СЕВЕРНОЙ ГРАНИЦЫ АРЕАЛА НА БУРЕИНСКОМ НАГОРЬ

The Yellow-rumped Flycatcher is distributed in Priamurye to the North up to 53°NL, and in Bureinsky uplands up to 51°07’ by NL. In the subboreal zone of uplands it gets into mountains not higher than 200-250 m a.s.l., and in the boreal – to 450-500 m a.s.l. Migrations in all the areas of uplands happen approximately at the same time: the spring one – in mid or late May, the autumn one – in the second decade of August. In the subboreal zone of uplands (southeast part) the highest number is observed in the broad-leaved and mixed woods. In the boreal zone of uplands the highest number is observed in an anthropogenous landscape of internal areas in the secondary slope woods. Look number in the northern part of the geographic range (Priamurye) is higher, than in its southern part (Primorye). The northern border of the range is characterized by the overlap of initial stages of a post-nuptial molt with the period of feeding of nested baby birds. The beginning of a post-juvenile molt is shifted, apparently, for later term. The penetration into internal areas of uplands which is observed in the last 80-100 years is the consequence of the current climatic changes as well as the anthropogenous transformation of the environment.

Ecological and life history correlates of changes in avian migration timing in response to climate change

Spring migration of birds in many parts of the world has advanced as the climate has become warmer. Variation in advancement among species has been proposed to correlate with geography and life history features, but individual studies have reported variable results, and general patterns have been elusive. In a quantitative review of data from 389 bird species sampled at 69 European and 23 North American localities, we evaluated associations between change in the timing of migration and life history (body size, molt, broodedness), ecology (habitat, diet, nest position), and geography. We confirmed that spring migration advanced: -0.214 d yr-1 (95% CI: -0.266, -0.162) for first-arriving individuals and -0.104 d yr-1 (-0.139, -0.071) for the median date of passage. The rate of change in autumn was more variable: 0.090 d yr-1 (0.002, 0.176) delay for median passage and 0.019 d yr-1 (-0.175, 0.204) delay for the date of last departure. The response during spring was weaker in the far north and in species that migrate long distances to the wintering area. Autumn migration became increasingly delayed in species that are large-bodied, molt before departure, and that feed on seeds, insects, or fruits. Variation among species, especially during autumn, was associated in part with constraints surrounding the timing of the postnuptial molt. The results suggest that ecological and life history features of species may influence their ability to respond to climate change.

Contrasting Trans-Atlantic Migratory Routes of Nearctic Purple SandpipersCalidris maritimaAssociated with Low Pressure Systems in Spring and Winter

Bird migration is generally scheduled to avoid other energetically expensive events in the annual cycle (e.g. moult) and seasons when survival can be difficult (e.g. northern winters). Purple Sandpipers winter at relatively high latitudes compared to other waders. It is suspected that the majority that winter in Britain and Ireland originate from Canada, but there is no primary evidence of their breeding grounds and migratory routes. These birds, characterised by their long bills, start to arrive in Britain and Ireland in late October/early November, after completing their post-nuptial moult at an unknown location. Fifty geolocators were attached to Purple Sandpipers in northern Scotland and southwest Ireland and we established for the first time their Canadian origin (Baffin Island and Devon Island), migration routes and post-nuptial moulting areas. Spring departure from Scotland and Ireland took place mainly in late May, followed by staging in Iceland and/or southwest Greenland before reaching the breeding grounds. Those that staged in Iceland departed earlier than those that flew directly to Greenland. Post-nuptial moulting areas were in southern Baffin Island, northern Quebec/Labrador (the Hudson Strait), and southwest Greenland. Migration from Baffin Island and Labrador took place during late October – early November, and during mid to late December from Greenland, usually in a single trans-Atlantic flight. Therefore, this migration was scheduled at a time when most other wader species are already on their wintering grounds. No birds staged in Iceland on the return trip. The flight from Baffin Island to Scotland and Ireland was accomplished in about 2.5 days at an average speed of about 1400 km per day. Freezing of coastal waters may be the reason for the eventual departure from the Hudson Strait. The more northerly route via Iceland, taken in spring by most birds, and the more southerly route in early winter were associated with seasonal shifts in the Atlantic low pressure systems (depressions) whose anti-clockwise wind-flows would have assisted flights.

An infradian rhythm of changes in the thyroxine level and related periodicity in feather replacement during passerine bird molting

The blood serum thyroxine and corticosterone levels of molting starlings (Sturnus vulgaris) were determined daily by enzyme immunoassay over 15 days. A 3-day rhythm for changes in the thyroxine content and a 4-day rhythm for corticosterone were observed, taking place synchronously in different individuals. The beginning of new flight feather growth coincided with maximal thyroxine concentration in the blood serum and also displayed a 3-day periodicity. A 3-day rhythm was also observed in the feather replacement dynamics of free-living passerines (Passer montanus, Parus major, and Chloris chloris). This rhythm was synchronous in the examined species, although they differed in the timing of their postnuptial molt. A synchronous manifestation of a 3-day rhythm of changes in the thyroxine level and feather replacement by molting in individuals of both the same and different passerine species has been observed.

Photoperiodic regulation of seasonal reproduction, molt and body weight in the migratory male yellow-breasted bunting (Emberiza aureola)

Photoperiod has been shown to be a major source of temporal information regulating reproduction and associated functions in a number of avian species. We studied seasonal cycles of testicular volume, molt and body weight in natural and temperature-controlled conditions and under different artificial photoperiods in the yellow-breasted buntings. Buntings posses seasonal cycles of testicular volume, molt, body weight and fattening with no major difference between natural and temperature-controlled conditions. These cycles follow an annual solar cycle suggesting the possibility of their photoperiodic control. To confirm this, photosensitive birds were studied under 9L/15D (close to shortest day length), 12L/12D (equinox day length) and 14L/10D (close to longest day length) for 18 months. Buntings showed testicular growth followed by regression and development of photorefractoriness; molt and body weight change only under 12L/12D and 14L/10D but not under 9L/15D. Reinitiation of above responses did not occur following initial cycles under stimulatory photoperiods precluding the possibility of circannual rhythm involvement. Birds exhibited an incomplete prenuptial molt of body feathers during gonadal stimulation under long days followed by complete postnuptial molt of body and primary feathers that progressed with gonadal regression. Exposure of photosensitive birds to light–dark cycles constituting 9–16h of light/day suggested that daily photoperiod of about 12h or more is essential in inducing testicular growth and function. These results clearly indicate that buntings are capable of fine discrimination of photoperiodic information and use annual changes in day length as an environmental factor to time their seasonal responses.

The use of tongue spots for ageing and wing length for sexing Skylarks Alauda arvensis – a critical evaluation

The Skylark Alauda arvensis is a European passerine species lacking plumage dimorphism and having a complete post-nuptial moult in adults, and a complete post-juvenile moult in young birds. Tongue spots were thought to allow age discrimination after moult. Based on data from a study population in the Netherlands, where the age of many birds was known, we show that tongue spots are not useful for ageing Skylarks. Some nestlings lack tongue spots and half of all birds had tongue spots when three years or older. Regarding sex discrimination, males and females can usually be distinguished from a bimodal wing length distribution, but the threshold and amount of overlap in wing length between sexes vary greatly between studies. Here, we show that 98% of all individuals from our Dutch breeding population could be sexed correctly by wing length. However, during migration and winter, when populations from other regions co-occur in the same area, molecular analyses revealed that the overlap in wing length between sexes increased. Therefore, ringers need to be cautious when assigning sex, and small males especially are often misclassified. For example, based on criteria used in France, 14% of Dutch male Skylarks, which are partial migrants, would be misclassified as females.

A tropical bird can use the equatorial change in sunrise and sunset times to synchronize its circannual clock

At higher latitudes, most organisms use the periodic changes in day length to time their annual life cycle. At the equator, changes in day length are minimal, and it is unknown which cues organisms use to synchronize their underlying circannual rhythms to environmental conditions. Here, we demonstrate that the African stonechat (Saxicola torquatus axillaris)-an equatorial songbird-can use subtle solar cues for the annual timing of postnuptial moult, a reliable marker of the circannual cycle. We compared four groups that were kept over more than 3 years: (i) a control group maintained under constant equatorial day length, (ii) a 12-month solar time group maintained under equatorial day length, but including a simulation of the annual periodic change in sunrise and sunset times (solar time), (iii) a 14-month solar time group similar to the previous group but with an extended solar time cycle and (iv) a group maintained under a European temperate photoperiod. Within all 3 years, 12-month solar time birds were significantly more synchronized than controls and 14-month solar time birds. Furthermore, the moult of 12-month solar time birds occurred during the same time of the year as that of free-living Kenyan conspecifics. Thus, our data indicate that stonechats may use the subtle periodic pattern of sunrise and sunset at the equator to synchronize their circannual clock.

Wing length as a predictor of body size in the Willow Tit Poecile montanus

In a subalpine mixed forest in central Norway, I measured the wing length, tail length and tarsus length and recorded the body mass of 48 male and 43 female first-year Willow Tits Poecile montanus. Some of these were retrapped in the following years and measured again after they had moulted. The wing length of first-year birds was significantly correlated (Pearson) with tail length (males: p<0.01; females: p<0.05) and tarsus length (males: p<0.05; females: p<0.05) but not with body mass. After their postnuptial moult in July-September, i.e. from their first-year to adult stage, the mean wing length of males increased significantly: 0.82 mm from their first to their second year and 0.37 mm from their second to their third year. Also the mean wing length increase in females was marked from first to second year (0.24 mm), but not for the following years. In adult Willow Tits, i.e. two years or older, the wing length was significantly correlated with only tarsus length (p<0.05) in males and tail length (p=0.01) in females. Thus, while wing length apparently is an appropriate measure of body size of first-year Willow Tits, it seems to give an uncertain reflection of the size in adult birds.

Non-breeding feather concentrations of testosterone, corticosterone and cortisol are associated with subsequent survival in wild house sparrows.

Potential mechanistic mediators of Darwinian fitness, such as stress hormones or sex hormones, have been the focus of many studies. An inverse relationship between fitness and stress or sex hormone concentrations has been widely assumed, although empirical evidence is scarce. Feathers gradually accumulate hormones during their growth and provide a novel way to measure hormone concentrations integrated over time. Using liquid chromatography-tandem mass spectrometry, we measured testosterone, corticosterone and cortisol in the feathers of house sparrows (Passer domesticus) in a wild population which is the subject of a long-term study. Although corticosterone is considered the dominant avian glucocorticoid, we unambiguously identified cortisol in feathers. In addition, we found that feathers grown during the post-nuptial moult in autumn contained testosterone, corticosterone and cortisol levels that were significantly higher in birds that subsequently died over the following winter than in birds that survived. Thus, feather steroids are candidate prospective biomarkers to predict the future survival of individuals in the wild.

Sexually Selected Male Plumage Color Is Testosterone Dependent in a Tropical Passerine Bird, the Red-Backed Fairy-Wren (Malurus melanocephalus)

BackgroundSexual signals, such as bright plumage coloration in passerine birds, reflect individual quality, and testosterone (T) may play a critical role in maintaining signal honesty. Manipulations of T during molt have yielded mixed effects on passerine plumage color, in most cases delaying molt or leading to production of drab plumage. However, the majority of these studies have been conducted on species that undergo a post-nuptial molt when T is low; the role of T in species that acquire breeding plumage during a pre-nuptial molt remains largely unexplored.Methodology/Principal FindingsWe experimentally tested the effects of increased T on plumage color in second-year male red-backed fairy-wrens (Malurus melanocephalus), a species in which after-second-year males undergo a pre-nuptial molt into red/black (carotenoid and melanin-based) plumage and second-year males either assume red/black or brown breeding plumage. T treatment stimulated a rapid and early onset pre-nuptial molt and resulted in red/black plumage acquisition, bill darkening, and growth of the sperm storage organ, but had no effect on body condition or corticosterone concentrations. Control males molted later and assumed brown plumage. T treated males produced feathers with similar but not identical reflectance parameters to those of unmanipulated after-second-year red/black males; while reflectance spectra of red back and black crown feathers were similar, black breast feathers differed in UV chroma, hue and brightness, indicating a potentially age and plumage patch-dependent response to T for melanin- vs. carotenoid-pigmentation.Conclusions/SignificanceWe show that testosterone is the primary mechanism functioning during the pre-nuptial molt to regulate intrasexually variable plumage color and breeding phenotype in male red-backed fairy-wrens. Our results suggest that the effects of T on plumage coloration may vary with timing of molt (pre- vs. post-nuptial), and that the role of T in mediating plumage signal production may differ across age classes, plumage patches, and between pigment-types.

Role of gonadal and adrenal steroids and thyroid hormones in the regulation of molting in domestic goose

Plasma levels of testosterone (T), 17-β-estradiol (E2), progesterone (P4), dehydroepiandrosterone (DHEA), corticosterone (B), thyroxine (T4) and triiodothyronine (T3) were monitored during postnuptial and the prenuptial molt in domestic goose (Anser anser domesticus) in both sexes. 1. At the beginning of postnuptial molt (when the old, worn dawny-, and cover feathers' loss starts) in ganders, the levels of T, E2, P4 decrease while DHEA and B significantly increase. The elevated levels of T4 and low T3 concentrations characteristic of the last phase of the reproduction, remain unchanged. In layers, similar changes were observed, however, B decreases. 2. In the early phase of outgrowth of wing and cover feathers, plasma levels of T, E2 and P4 are low. Elevated B, DHEA and T4 concentrations decrease in ganders, while in layers DHEA increases and B and T4 levels remain unchanged. T3 increases in both sexes. 3. The subsequent intensive outgrowth period of wing- and cover feathers both in ganders and in layers is characterized by very low levels of T, E2, DHEA and T4, but P4 increased, and T3 concentration remain high. 4. At the end of postnuptial molt - when the outgrowth of dawny, cover-, and wing feathers stops - very low T, E2, P4, DHEA and T4 levels and and high T3 plasma levels were found in both sexes. Fast increase of plasma B was detected in ganders, while in geese, B concentration remain high. 5. During prenuptial molting (outgrowth of contour and tail feathers) low E2, P4 and T4, increasing T and DHEA, but very high T3 and B plasma concentration were measured in ganders. In layers, very low T, E2, P4, DHEA and T4 levels, and very high B and T3 levels were found. 6. At the beginning of the fall-winter sexual repose (postmolting stage) T, E2, P4, DHEA and T4 levels increase, T3 and B declines in both sexes. 7. In the subsequent phase of fall-winter period (preparatory stage) there is a further increase in T, P4 and T4, a fast increase of B and a decrease of E2, DHEA and T3 in ganders. In layers, T, P4 and DHEA decrease, B increases and the T4 and T3 do not change. 8. At the beginning of reproduction high T level, unchanged DHEA, slightly declined P4, and decreased E2, T4, T3 and a strong decline of B concentrations occur in ganders. In layers, T is further increased, E2 and P4 shows high levels, and, at the same time DHEA and T3 remain unchanged, while B and T4 decrease.

Residence Time and Movements of Postbreeding Shorebirds on the Northern Coast of Alaska

Abstract. Relatively little is known about shorebird movements across the coast of northern Alaska, yet postbreeding shorebirds use this coastline extensively prior to fall migration. We deployed 346 radio transmitters on 153 breeding and 193 postbreeding shorebirds of five species from 2005 to 2007.We examined two hypotheses regarding postbreeding shorebirds' movements: (1) whether such movements reflect ultimate routes of southbound migration and (2) whether migration strategy (length of flights) or timing of molt in relation to migration (molt occurring in breeding or winter range) are more influential in determining postbreeding shorebirds' behavior. Semipalmated Sandpipers (Calidris pusilla) moved east, consistent with the direction of their ultimate migration, but patterns of other species' movements did not reflect ultimate migration direction. Timing of postnuptial molt appeared to have more influence over residence time and movements than did migration strategy. Postcapture residence time for the...

Exposure of Dunnocks (Prunella modularis) to their Previous Wintering Site Modifies Autumnal Activity Pattern: Evidence for Site Recognition?

We caught dunnocks at a wintering site near Pisa/Italy prior to their departure for breeding territories and held them indoors north of this site (Andechs/Germany) on a simulated photoperiod of 52.5 °N. After birds had gone through a reproductive cycle and postnuptial moult they developed migratory restlessness in autumn. At this time one group was transferred back to the previous wintering site (Pisa) where birds were held in individual activity cages in an outdoor aviary, allowing them to perceive as much environmental information as possible. A second group was transferred to a control site near Tour du Valat/France of approximately the same latitude and climate, but different longitude and held in an identical aviary. The diurnal activity pattern changed after transfer back to the previous wintering site, but not after transfer to the control site. Specifically, the amount of morning activity was reduced while afternoon activity was increased. This effect was restricted to those individuals that had been developing nocturnal migratory restlessness the previous spring. It was absent in individuals without migratory restlessness in spring, indicating that the different patterns were not due to unspecific effects from the testing sites. These results are consistent with the hypothesis that birds were able to derive information about their locality and to recognize their previous wintering site, resulting in suppression of migratory state by experience. The results are not definitely conclusive, however, because of several difficulties in the interpretation of perch-hopping activity, which are discussed in detail.

Seasonal changes in concentrations of plasma LH and prolactin associated with the advance in the development of photorefractoriness and molt by high temperature in the starling

In a study on starlings ( Sturnus vulgaris) kept on a simulated annual cycle in photoperiod, temperature had no effect on the timing or rate of testicular maturation but high temperature resulted in an advance in the timing of testicular regression and molt ( Dawson, 2005). This study asks whether the earlier gonadal regression in response to higher temperature represents a central neuroendocrine response to temperature, and secondly, whether prolactin plays a role in the earlier regression. Castrated starlings were kept on a simulated annual cycle of photoperiod at either 8 or 18 °C. Circulating LH and prolactin concentrations were measured and the progress of the post-nuptial molt was recorded as an external indicator of the development of photorefractoriness. Additionally plasma prolactin was measured in samples taken from intact male and female starlings in the 2005 study. In castrated birds, LH concentrations decreased three weeks earlier at 18 °C. These birds also showed the same three week advance in molt as males and females in the earlier study. This demonstrates that the advance in regression caused by higher temperatures probably results from a central neuroendocrine mechanism, i.e., an advance in photorefractoriness, rather than an effect at the level of the gonads. Temperature had a highly significant effect on the changes in prolactin – peak prolactin occurred three weeks earlier at 18 °C. However, there was no clear consistent significant difference in prolactin between the two temperatures in advance of the onset of photorefractoriness, so the advance in photorefractoriness may not be mediated by prolactin. The higher temperature resulted in a significantly earlier decrease in prolactin and this may be causally related to the advance in molt.

Seasonal phenomena of the year cycle of the whitethroat (Sylvia communis) in the south of West Siberia

The data for many years were used to study the migration, nesting and molt of the whitethroat in the Baraba forest-steppe (south of West Siberia). The parameters of reproduction as the basis for adaptation of the species to the habitat conditions were studied in detail. Variability of the reproductive parameters of the whitethroat living in the south of West Siberia is relatively low and comparable to the reference data on the other parts of its range. The shortage of time in the nesting places, which is due to climate and their remoteness from the wintering places, is covered primarily at the expense of completeness of postnuptial molt and its overlapping with the start of autumn migration.

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.

MIGRATION TIMING OF CANADA WARBLERS NEAR THE NORTHERN EDGE OFTHEIR BREEDING RANGE

Abstract Canada Warblers (Wilsonia canadensis) are one of the last warblers to arrive in breeding areas in northern Alberta and one of the first to depart in autumn resulting in a condensed breeding chronology relative to other locally breeding wood warblers. Males arrived before females during spring migration, while in autumn, adult females departed prior to males. Second-year males arrived later (P = 0.029) than after-second year males. Adult males departed later (P = 0.015) than adult females. Hatch-year birds departed after adult females but prior to adult males. Female Canada Warblers remained in breeding areas for 62 days while males remained 72 days. These data provide the shortest documented breeding site occupancy estimate for any bird that shows a post-nuptial molt. The short time spent in breeding areas may impose energetic constraints that influence breeding, molt, and survival, particularly for females.