Active Moult Research Articles

Complete Moult of an Undescribed Resident Taxon of the Reed WarblerAcrocephalus scirpaceus / BaeticatusComplex in the Smir Marshes, Northern Morocco

A complete moult north of the Sahara has never been reported conclusively in the Reed Warbler Acrocephalus scirpaceus complex. During a ringing program carried out in the Smir marshes (northern Morocco) 140 adults and 292 juvenile Reed Warblers were examined during four autumns in the period 2004–2008. Of these birds, 8.9% of juveniles were either in active moult (n = 17) or had completed moult (n = 9) and 48.6% of adults were either in active moult (n = 32) or completely moulted (n = 22). At least some of the moulting birds were of local origin (i.e. Smir breeding population), since 14 males and one female were captured in autumn and later recaptured in spring showing signs of breeding activity, or captured in spring and recaptured moulting in autumn. Also, one juvenile captured in May was recaptured in November while moulting. Capture history of some moulting birds indicate that they over-winter locally and others most likely winter somewhere else in Morocco (i.e. north of the Sahara). Therefore, we report the discovery of a (partly) sedentary population of an as yet undescribed taxon of Reed Warblers in Smir marshes, Morocco. The relationship of these to the Eurasian A. scirpaceus and African A. baeticatus Reed Warblers remains to be investigated.

Midgut and fatbody mitochondrial transhydrogenase activities during larval-pupal development of the tobacco hornworm, Manduca sexta

Midgut and fatbody mitochondria from fifth larval instar Manduca sexta display a membrane-associated transhydrogenase that catalyzes a reversible hydride ion transfer between NADP(H) and NAD(H). The NADPH-forming activity occurs as a nonenergy- or energy-linked activity with energy for the latter derived from either electron transport-dependent NADH or succinate utilization, or ATP hydrolysis by Mg ++-dependent ATPase. During the ten-day developmental period preceding the larval-pupal molt (fifth larval instar), significant peaks in the mitochondrial transhydrogenase activities of midgut and fatbody tissues were noted and these peaks were coincident with the onset of wandering behavior and with the fifty-fold increase in ecdysone 20-monooxygenase (E20-M) activity previously reported for M. sexta midgut. Since E20-M preferentially uses NADPH in catalyzing ecdysone conversion to the physiologically active molting hormone, 20-hydroxyecdysone, the physiological and developmental significance of the mitochondrial, NADPH-forming energy-linked transhydrogenations were made apparent. Moreover, that the increases in all transhydrogenase activities resulted from de novo enzyme synthesis were indicated by the cycloheximide-dependent reductions in these activities.

Population structure, biometrics and moult of migrant Purple Sandpipers Calidris maritima in southwest Iceland in spring

Capsule Iceland is a stop‐over site for a population of Purple Sandpipers that winter in Britain. Here, they accumulate fuel loads for onward migration along with birds that have wintered in Iceland. Aims To establish whether Purple Sandpipers from Britain stop‐over in Iceland during spring migration and, if so, to describe their population structure, changes in mass and moult. Methods Purple Sandpipers were cannon‐netted on the coast of the Reykjanes Peninsula in southwest Iceland during May 2003 and 2005. Birds were aged, sexed (some by DNA) and standard biometric measurements made. Active body moult was scored. Results Bill and wing lengths showed that the Purple Sandpipers we caught were similar to one of the populations that winter in Britain rather than Icelandic breeding birds. There were more males than females throughout the migration period (63% males for first‐year‐birds and 67% for adult birds). Accounting for a bias due to a higher percentage of males in a less usual habitat (muddy/sandy bays), the values for rocky sites were 52% males for first‐year birds and 62% for adults. The percentage of first‐year birds was 19% in 2003 and 32% in 2005, though the latter figure was biased by catches in muddy/sandy bays where there was a higher percentage of young birds. The percentage of first‐year birds was 25% on just the rocky shores in 2005. Many birds were in latter stages of body moult, and males were slightly in advance of females. Increasing mass showed that they were preparing for onward migration. The average increase of 0.58 g per day was similar to the rate measured in Orkney at an earlier point on the migration route. However, a high turnover of birds could be the reason for these low values. By late May, and close to the assumed departure date, the Purple Sandpipers of the different age/sex classes had fuel indices of 24–29% (33–42% of the lean mass). This was lower than that for the high Arctic sandpipers (Knots and Sanderlings) leaving southwest Iceland for Greenland and Canada. Conclusions Our study confirmed that Purple Sandpipers do stop‐over in Iceland, and the possible lower rate of fuel accumulation and smaller amount stored, compared with Knots and Sanderlings, suggests a different migration pattern.

Studies on the black box: Incorporation of 3-oxo-7-dehydrocholesterol into ecdysteroids by Drosophila melanogaster and Manduca sexta

It has long been hypothesized that the oxidation of 7-dehydrocholesterol (7dC), made from dietary cholesterol (C), to 3-oxo-7dC (3-oxo-Δ 5,7C) immediately precedes the unknown “Black Box” oxidations that lead to the formation of the first up-stream intermediate exhibiting the highly characteristic ecdysteroid structure of the steroid molting hormone of insects, crustaceans and some other arthropods. Perhaps rate-limiting and under the control of the prothoracicotropic hormone (PTTH), the biosynthesis of 3-oxo-7dC and its subsequent oxidative modifications have been difficult to study because of their apparent instability, i.e. no intermediates between 7dC and the diketol (3-oxo-25,22,2-trideoxyecdysone) have ever been observed or identified in insect prothoracic gland incubations with radiolabelled precursors. However, we show that 3-oxo-7dC can be converted into lipophilic, photosensitive, ketone-blocked (PSKB) ketal derivatives which will release 3-oxo-7dC when and where desired following brief irradiation with innocuous long-wave (365 nm) UV-light both in vivo and in vitro. In this manner, 3-oxo-7dC is quickly and efficiently incorporated into ecdysteroids by adult male and female Drosophila raised on a diet containing the PSKB ketals and in prothoracic glands of Manduca sexta incubated with the ketals emulsified into media. The instability of 3-oxo-7dC and its spontaneous transformation into extensively electron-delocalized intermediates will be discussed in relation to a possible mechanism of the Black Box oxidations eventually leading to the production of the active molting hormone 20-hydroxyecdysone (20E).

A PRIMER ON SUMMARIZING MOLT DATA FOR FLIGHT FEATHERS

Abstract Once established with reliability, the rules of flight feather replacement become an important component of comparative life-history studies. Here I illustrate the form of tables that should be used to describe the pattern and intensity of flight feather molt. Using a subset of original data summarizing primary, secondary, and rectrix molt in Western Kingbirds (Tyrannus verticalis), I show how to assign scores indicating direction of replacement and points where waves of molt started or will stop. Combining these scores across birds yields a molt summary table, the starting point for determining the rules of feather replacement. This raw summary table is then iterated to show breaks between molt series and how summary scores around these breaks are reassigned to acknowledge series breaks. Molt summary tables also give sample sizes, because the rules of flight feather replacement cannot reliably be inferred unless birds in active molt are available for all the feathers being considered.

Primary moult patterns and morphometrics in the Green-winged Pytilia Pytilia melba

We investigated primary moult and morphometrics in the Green-winged Pytilia Pytilia melba during a six-month period (May–October) in central South Africa. A total of 157 pytilias were captured; 80 (51.0%) of these were in active primary moult during all months of the study. The Underhill-Zucchini model was not applicable for determining moult duration (start and end dates) due to the great variation in moult timing and because moulting may often be suspended. We suggest that this is due to factors other than low food availability.

Large-scale variation in flight feather molt as a mechanism enabling biennial breeding in albatrosses

Laysan and black-footed albatrosses, Phoebastria immutabilis and P. nigripes, exhibit both annual and biennial breeding frequencies, and annually replace flight feathers in patterns that can be described as large, small or medium in extent. Large molts are temporally incompatible with successful breeding. Small molts are temporally compatible with the longest breeding seasons. Medium molts are compatible with shorter, but still successful breeding seasons. On average, large and small molts combined replace the same feathers with the same frequencies as two medium molts combined. Thus, large and small annual molt patterns combined provide a mechanism for ‘‘transferring time from one year to another’’ enabling extended breeding seasons every other year, and thus biennial breeding. Medium-sized molts are compatible with annual breeding. Among multiple albatross species, large-scale, annual molt patterns can shift in response to shifting breeding frequencies, but there may be a time lag in the response. A newly identified period of rapid fattening following molt termination and preceding colony arrival suggests albatrosses maintain low fat stores throughout active molt to reduce wing-loading, intensifying temporal trade-offs between flight feather molt and breeding.

Biometrics and Primary Molt of Common Tern and Sandwich Tern in Autumn in Puck Bay, Southern Baltic

Abstract Data were collected at one of the important stop-over sites in the southern Baltic between 1989 and 1995. Sandwich Terns were not only more advanced in primary molt than Common Terns, but also replaced their flight feathers faster due to larger number of primaries growing simultaneously. All caught adult Sandwich Terns were in active molt, whereas over 21% Common Terns either had not started primary molt or suspended it. The difference in migration strategy may be the main reason for the discrepancy between these two species in molt advancement. Biometrical analysis showed that juveniles of both species did not reach adult size at this stage of migration. Sandwich Terns caught in late summer in northeast England had shorter wings than birds from Puck Bay probably due to different origin of birds caught at these two sites. Common Terns caught in Puck Bay were larger than birds from German and Scottish breeding colonies and also from birds measured in northeast England. Moreover in Puck Bay, 84% of...

Applying fenoxycarb at the penultimate instar triggers an additional ecdysteroid surge and induces perfect extra larval molting in the silkworm

When the juvenile hormone analog fenoxycarb was topically applied to the silkworm Bombyx mori at the beginning of the 3rd or 4th (penultimate) instar, an extra larval molt was induced. The 5th instar period was shortened to about 5 days and the extra 6th instar ranged from 8 to more than 20 days, depending on the dose applied. Starvation before fenoxycarb treatment strongly enhanced the incidence of extra molting up to 100%. When 1 ng was applied in the 4th instar after a 2-day starvation, most larvae underwent an extra molt, metamorphosed to pupae, then to fertile adults. Combining starvation and fenoxycarb application thus induces a perfect extra molt efficiently. In perfect extra molting larvae, profiles of total ecdysteroid titer during the 4th and 5th instars were similar to that during the 4th instar in the control, and the ecdysteroid profile during the extra 6th instar was similar to that during the control 5th (last) instar. At ecdysteroid peaks, 20-hydroxyecdysone (20E) and ecdysone (E), generally regarded as the active molting hormone and its precursor, had similar titers in the 6th instar, whereas E was much less than 20E in the 4th and 5th instars in the extra molting larvae. E was also abundant only in the last larval instar in the control. These results suggest that both 20E and E contents are important for regulation of larval molt and metamorphosis in silkworms and that fenoxycarb triggers the extra molt by inducing an additional larval molt type of ecdysteroid surge before the last larval instar.

Moult and ageing of storm petrels hydrobates pelagicus

Current published ageing criteria for Storm Petrels, Hydrobates pelagicus appear to be unreliable, so fledged birds are not aged to a high degree of accuracy, restricting the scope of age‐specific studies. Analyses of moult and feather wear were carried out on 28 specimens of Storm Petrels which were washed ashore on the southern coast of Portugal during January 1996, and on a further 780 live individuals which were trapped during May‐July 1998, also on the southern coast of Portugal. Differences in the pattern of wear and bleaching of the primary feathers between those grown simultaneously in the nest and those grown sequentially over a long period by older birds, allows fledged individuals to be aged as in their first year, or older. Using primary wear to age individuals, the shape of the outermost long primary feather can then also be shown to be a reliable ageing criterion. Some birds in active primary moult can be aged even more specifically by a combination of primary wear and the shape of the outermost primary.

MOLT DURING SPRING MIGRATION: A COMPARISON OF FOUR SPECIES OF RAPTORS

We quantified the extent of molt in Steppe Buzzards (Buteo buteo vulpinus), Marsh Harriers (Circus aeruginosus), Levant Sparrowhawks (Accipiter brevipes), and Eurasian Sparrowhawks (A. nisus) caught during spring migration 1985–1988 in Elat, southern Israel. Ten percent of yearling Steppe Buzzards (58 of 550) and four percent of yearling Marsh Harriers (3 of 77) were actively molting their remiges while on migration. These findings are contrary to suggestions that birds do not molt their flight feathers during migration when they should avoid extra energy expenditure and maintain flight performance. Active molt of primaries and secondaries, however, was not found among adult buzzards and harriers, or in any individual of the two Accipiter species. Molt strategies may be related to differences in flight mode during migration between species that primarily soar (buzzards and harriers) and species that flap more (sparrowhawks). Body condition was not related to the state of molt. This, and the fact that only yearling birds were in active molt of remiges, suggest that a delay in arrival on the breeding grounds may be a significant cost of molt during spring migration.

Breeding plumage honestly signals likelihood of tapeworm infestation in females of a long-distance migrating shorebird, the bar-tailed godwit

The indicator mechanism for sexual selection proposed by Hamilton and Zuk (i.e. that sexually selected ornaments signal parasite resistance) has received rather little observational support, and none in the case of long-distance migrant birds. Here we present a test by examining the association between helminth infestations and breeding plumage quality in bar-tailed godwits Limosa lapponica taymyrensis during their spring staging period in the Wadden Sea, The Netherlands. After a non-stop flight from West Africa, these shorebirds refuel in the Wadden Sea in preparation for a second flight to the central Siberian Arctic breeding grounds. Earlier studies have shown that only relatively heavy and well ornamented birds carry out a "top-up" moult during stopover, in which part of the contour feathers recently grown in West Africa are replaced by even fresher ones. Active body moult was therefore taken as the primary indicator of ornament quality. Of 78 birds collected between 1992 and 1997, 42% carried helminths, including four species of digenean trematodes (flukes), three species of cestodes (tapeworms) and an acanthocephalan (spiny-headed worm). Faecal samples examined for helminth eggs in another 92 birds in 1998 and 2000 showed similar rates of infestation. Actively moulting bar-tailed godwits were confirmed to be heavier and to show more extensive breeding plumage than non-moulting birds. In females, but not in males, active moult was associated with fewer cestodes and acanthocephalans. Also, breeding plumage and presence of cestodes were negatively associated in females. We argue that the quality of the breeding plumage reliably indicates parasite resistance in female godwits. The repeatability of plumage scores of females between years is consistent with such resistance having a heritable component. In contrast, male ornaments may demonstrate other qualities, e.g. an ability to combine adequate fuelling and flight performances with moult during the time-stress of migration.

Post‐breeding and post‐juvenile moult of House Martins Delichon urbica at colonies in Spain

House Martins Delichon urbica were examined for moult in autumn at breeding colonies on a north/south transect in W Spain. Adults and some early‐brood juveniles had started flight feather moult; most were in active moult immediately prior to migration. Estimates were made of the start dates of the laying of first clutches at various latitudes.

Migration patterns and moult of Common Terns Sterna hirundo and Sandwich Terns Sterna sandvicensis using Teesmouth in late summer

Count, recovery and biometric data were analysed to assess the conservation status and use of Teesmouth by Common Terns Sterna hirundo and Sandwich Terns Sterna sandvicensis in late summer. The recognition of the international importance of Teesmouth to migratory Sandwich Terns was endorsed. Peak late summer counts for 1990–1997 averaged 1,835, over 1% of the international population. Analysis of information from both Common and Sandwich Terns ringed or recovered in late summer at Teesmouth identified the existence of a trans‐Pennine migratory pathway of Common Terns between Teesmouth and Merseyside. Trans‐Pennine migration of Sandwich Terns is also suspected from visual observations of departures from Teesmouth. 55% of adult Common Terns using Teesmouth have yet to initiate primary moult. This, and the recovery patterns, are consistent with the involvement of a substantial Baltic contingent of non‐moulting adults amongst the late summer Teesmouth population. Of those adults in active wing moult, primary moult had progressed less far than for birds in the Wadden Sea at the same time of year. This suggests a cline through northern European breeding populations in the timing of moult. Visible migration, retrap data, arrival dates of different populations and the progression of primary moult, all identify rapid turnover amongst the late summer Common Tern population at Teesmouth, suggesting that over 1% of the UK breeding population, with their young, migrate through Teesmouth

Cloning of a Novel Cytochrome P450 (CYP4C15) Differentially Expressed in the Steroidogenic Glands of an Arthropod

Biosynthesis of ecdysteroids, arthropod steroid molting hormones, proceeds from dietary cholesterol through a complex and still incompletely elucidated pathway. Most of the known steps are catalyzed by cytochrome P450 enzymes (CYPs) but none of their genes has yet been identified. We have established a cDNA library of crayfish steroidogenic glands (Y organs). A full length CYP-cDNA was characterized containing a 1539 bp open reading frame encoding a predicted protein of 513 amino acid residues. This novel CYP was assigned to the CYP4 family and designated CYP4C15. Northern blots demonstrated predominant expression of this gene in the active molting glands, suggesting a role in ecdysteroid biosynthesis rather than detoxification.

Frequency of complete moult in adult and juvenile Great Reed Warblers(Acrocephalus arundinaceus) in Spain

We examined a large data set of adult and juvenile Great Reed Warblers (Acrocephalus arundinaceus), caught over five years, to study the occurrence of complete moult in a Spanish population. A total of 27 adults and 5 juveniles were in active moult. The proportion of birds moulting each year varied between 0.03 and 0.19. Nearly half the adults were finishing moult. At least one bird was certainly of local origin, rather than on passage, and four more were moulting when retrapped in subsequent years, suggesting that they too were resident breeders in the area. Some other birds were probably resident also, because they were in moult when caught at the beginning of August. Two of the five juveniles finished their moult in the area. In conclusion, our data seem to show that complete moult before departure to the wintering quarters is a regular process undertaken by some of the breeding population of Great Reed Warblers in north-east Spain.

Geographical variation in pre‐migratory condition of Swallows Hirundo rustica in Italy

In order to investigate pre‐migratory strategies of Swallows in Italy, simultaneous ringing activities were carried on during three focal days (September 6–8 1996) at 24 different roosts scattered across the Italian peninsula and main islands. A total of 8,771 Swallows was ringed, out of which 81.8% were juveniles and 18.2% adults. Among the latter, 28.3% were classified as males and 71.7% as females. Most birds had already completed their body moult; a higher fraction of birds still in active moult was found among adults. The frequency of adults with active primary moult was intermediate between the values reported for Northern‐Central and Southern Europe respectively. Mean body mass values were higher in adults, which were also fatter than juveniles. Both in adults and juveniles, fat score was significantly lower in moulting birds. A high variability in mean body mass values and frequency of fat birds was found between roosts. The mean body mass of the 25% heavier birds corresponded to 24.1% and 30.5% of the lean body mass for juveniles and adults respectively. The situation observed in early September does not indicate a clear north‐south gradient in the average physical conditions of pre‐migratory Swallows, suggesting the use of roosts as sites of concentration of birds staging and fattening in the surrounding areas. The observed latitudinal gradient in the frequency of adults at the roosts might be related to earlier southward movements of more northern birds.

Catching bias in cannon and mist netted samples of Redshanks Tringa totanus on the Inner Moray Firth

A series of five cannon and nine mist net catches in a small area of the Inner Moray Firth during the autumn of 1994 provided the opportunity to examine the differences in the proportions of juvenile and moulting and non‐moulting adult Redshanks caught by the two methods. This comparison showed significant differences with mist nets apparently catching a higher proportion of juveniles. This difference was highly significant for early autumn (13 August to 15 October) catches, when adults were undergoing active wing moult, but was no longer significant for late autumn (17 October to 24 December) catches when moult had been completed. The proportion of juveniles caught in cannon nets remained similar at 42.9 and 45.6% during the early and late periods. During the early period 67.6% of the birds caught by mist netting were juveniles, but this reduced to 43.9% in the late period, similar to the proportion found by cannon netting. It is suggested that in the situation on the Moray Firth the cannon netting techniques used were giving a representative sample of the population present. It also appeared that the number of juveniles caught by mist netting was proportional to the number of juveniles present in the population, but this appeared to be biased in the catch make‐up because mist netting failed to catch a representative proportion of the moulting adults present. The significance of the difference between the proportions of moulting adults caught by the different catching techniques remained very high for the early autumn period but reduced for the late autumn from mid October onwards. It is suggested that the bias against catching moulting adults in mist nets was related to the progress of moult, and that once this had been completed there was little or no evidence for a bias against catching adidts. This suggests that the apparent bias in mist netting towards juveniles noted by previous workers is not related to any lack of experience or flying ability on the part of young birds, but is caused by some difference in the behaviour of moulting adults.

Ageing Immature Black-browed and Grey-headed Albatrosses Using Moult, Bill and Plumage Characteristics

SummaryWe describe how to age immature Black-browed Diomedea melanophris and Grey-headed Albatrosses D. chrysostoma up to age 6 years (when they have usually acquired adult characteristics), from a combination of the age and pattern of moult of flight feathers, bill colouration and certain plumage characteristics. This is based on known-age birds retrapped at colonies during the breeding season. Ageing of immatures at other times may be complicated by them being in active moult; we provide further guidance for these circumstances.

Is ecdysone involved in the moult cycle of the terrestrial crustaceanOrchestia cavimana(Amphipoda)?

Summary We have tested several labelled ecdysteroids as possible precursors of moulting hormone biosynthesis in Orchestia cavimana, a terrestrial Amphipoda. Ecdysone, known to be a prohormone in many classes of Arthropods, was never converted into 20-hydroxyecdysone when injected in this animal in vivo, though 20-hydroxyecdysone has been previously shown to be the predominant ecdysteroid. On the contrary, C-2 hydroxylation was evidenced by the conversion of 2-deoxy-ecdysteroids into 2-hydroxylated compounds. The surprising failure of ecdysone conversion was corroborated by its absence of effect on protein synthesis in an ecdysteroid target tissue, the calcium storage organ of O. cavimana. Our results are in agreement with the previously reported findings that 20-hydroxyecdysone is the active moulting hormone in O. cavimana. However, ecdysone does not appear to be its natural precursor.