Body Moult Research Articles

Molt and migration inCinnyricinclus leucogaster

The sequence of molt inCinnyricinclus leucogaster differs markedly from that in most passerine birds. Instead of having body molt proceed concurrently with that of wing and tail, the main body molt begins only after wing and tail molt are complete. Within the wing molt, the sequence of primary molt is normal descending, but that of secondary molt is peculiar. In most passerine bird, the three inner secondaries (nos. 7–9, the “tertials”) start the secondary molt followed by the six outer secondaries, but inCinnyricinclus the tertials do not begin molting until secondary 3 is growing. Secondaries 5 and 6, which are replaced in other Songbirds at the time of the last primary, are delayed until the time of body molt. This delayed molt of contour feathers and inner secondaries has the adaptive advantage of permitting the male to enter courtship activities with the maximum amount of violet gloss.

The White-Headed PetrelPterodroma Lessoniat Macquarie Island

The breeding cycle and habits of the White-headed Petrel, Pterodroma lessoni, have been observed over parts of two nesting seasons at Macquarie Island. These birds are strictly nocturnal on land and are the commonest burrowing species on the island. Their numbers appear to be declining and factors responsible fur this include predation by feral cats, competition with rabbits for burrows, and loss of soil cover through rabbit-induced erosion. The White-headed Petrels arrive at the island from the third week of August after an absence of about 11 weeks. There is a long re-occupation period. The same individuals may breed in the same nest during successive seasons. Egg-laying occurs between November 24 and December 16, incubation being undertaken by both sexes in turn and extending over eight to nine weeks. The chicks are unguarded when two to three days old and are fed rather irregularly by both parents. One chick flew when it was about 102 days old. The chicks threaten intruders by lunging and by spitting stomach oil but this ability declines with increasing age. Adults undergo a body moult while breeding, but wing moult is delayed until nesting is over.

THE MOULT OF THE BULLFINCH PYRRHULA PYRRHULA

SUMMARYThe distribution of feather tracts and their sequence of moult in the Bullfinch is described. The adult post‐nuptial moult, which is complete, lasted 10–12 weeks, and the post‐juvenile moult, which is partial, 7–9 weeks. Adult moult began with the shedding of the first (innermost) primary and ended with the replacement of the last. Variations in the rate of moult in the flight feathers were mainly achieved, not by changes in the growth rates of individual feathers, but in the number of feathers growing concurrently. The primaries were shed more slowly, and the onset of body moult delayed, in birds which were still feeding late young.In 1962, the onset of moult in the adults was spread over 11 weeks from thc end of July to the beginning of October, and in the two following years over the six weeks, from the end of July to the beginning of September. The onset of moult was delayed by late breeding, which itself occurred in response to a comparative abundance of food in late summer, markedly in 1962. In all years, the first juveniles to moult started at the end of July, and the last, three weeks after the latest adults. Juveniles moulting late in the season retained more juvenile feathers than those moulting earlier.During moult, adult and juvenile Bullfinches produce feathers equivalent to 40% and 33% respectively of their dry weights. In both, for much of the moult, an average of nearly 40 mgm. of feather material—some 0.6% of their dry‐weight–is laid down each day. The remiges of the adult comprise only a seventh of the weight of the entire plumage, and it is suggested that their protracted moult results not so much from their energy requirements, as from the need to maintain efficient flight. Variation in the rate of moult in the remiges was much less pronounced than in the body feathers. Bullfinches were less active during moult than at other times of the year. The weights of both adults and juveniles increased during moult.The food during the moult period is described. In all years, most Bullfinches finished moulting just before food became scarce, even though this occurred at different times in different years. In one year, adults moulting latest in the season probably survived less well than those moulting earlier; the same was apparently true of the juveniles in all years. The timing of moult in the Bullfinch, and the factors initiating it, are discussed in relation to the breeding season and foodsupply near Oxford.

The molting of young Gray Starlings

1. The molting to adult plumage of three hand raised young Gray Starlings Sturnus cineraceus was observed.2. The plumage of the young is first grayish and turns brownish or even rustic before molting begins, which is about 40 day after hatching and about 20 days after leaving the nest.3. The wing quills of both sides are usually shed at the same time.4. The primaries molt from innermost (I) to outer ones, and the last one (IX) was shed 84 days after the first primary (in bird A). Possibly normal molting intervals were: more or less a week for I-II, III-IV, IV-V, V-VI, (VI-VII on one side) and about two weeks for II-III and (VI-VII on one side), VII-VIII and VIII-IX.5. The maximum body weights (measured in the evening) markedly increased before the molting of primaries, but minimum body weights (measured in the early morning) were rather constant. Thus the increased body weights have possibly been used for growing new quills (see Fig. 2).6. In the female observed which was rather ill-nourished, remolting of the primaries began in the regular sequence (with an overlap of the first and second molting). The intervals from the first molting of I primary to its second molting were 52 (left) and 54 (right) days.7. primaries was unsheathed after about a week of shedding and was completely grown in about 20 days. The rates of growth of unsheathed feathers were average 0.2mm per hour and 4-5mm per day.8. The primary coverts molted 2-8 days after the primaries with which they are growing together.9. The bustard wing molted during the later part of the molting period of the primaries.10. The molting of secondaries occurred 35-40 days after the shedding of I-primary and during the molting of V, VI primaries. Molting proceeds slowly from inner to outer secondaries, with the intervals of about 20 days (though within 10 days between III-IV) in an observed case, and two months from the molting of I-secondary to V-secondary.11. The tertiaries were shed after the molting of I-secondary, in a sequence of II-III-I, the interval having been 21 days for II-III and 10 days for III-I.12. The greater wing-coverts molted at the same time and irregularly, with no relation with the secondaries.13. The tail molt was commenced by the 4 central feathers and proceeded to outer ones.14. The main molting of body plumage began about 70 days after hatching and 30 days after the shedding of I-primary, first on the flanks and lower back. The molting of the crown to fore-neck and upper scapulars delayed most. The body molting was completed at about 120 days after hatching, but the last primary and secondary were completed at 130 and 140-150 days after hatching.15. No marked difference was noticed in the speed of molting by early (early July) and later (early August) young birds in captivity.

Moult Adaptation in Relation to Long-Distance Migration

Marshall and Serventy1 have recently directed attention to moult adaptation in the short-tailed petrel, Puffinus tenuirostris, of Tasmanian waters. In this species post-nuptial head and body moult takes place in the breeding quarters while moult of tail- and wing-feathers is postponed until the bird has arrived at its northern non-breeding quarters. From this the authors decide that “from the … data there emerges clear evidence of the evolution of a moult adaptation related to the migratory requirements of species that undergo a long post-nuptial migratory movement”. That moult adaptation in relation to long-distance migration need not be a general phenomenon, and probably has only taken place in certain families of birds, is indicated by the following observations on two species of long distance passerine migrants. In April 1953 a large number of swallows, chiefly consisting of the European swallow, Hirundo rustica, and the European house martin, Delichon urbica, perished in the neighbourhood of Cape Town, due to a short spell of adverse weather conditions. Of the thirty-five H. rustica examined, 99.1 per cent showed moulting flight-feathers, 65.7 per cent had moulting tail-feathers and 8.6 per cent had moulting body- and head-feathers. Of fifty-two D. urbica, 40.4 per cent had moulting wing-feathers, 75 per cent moulting tail-feathers and 94.2 per cent moulting body- and head-feathers2.

Molting and Growth of Individual Feathers in Turkeys Exposed to 10 or 24 Hours of Daily Light

Mueller et al. (1951), observing Broad Breasted Bronze turkeys, found that restricting light to 12 hours daily from 4 to 16 weeks of age and to 10 hours daily from 17 to 28 weeks of age reduced molting of the first postjuvenile plumage. These birds, when dressed, exhibited fewer pin-feathers and had higher market grades than birds of the same age and origin reared under natural daylight or provided 15 hours of light daily. At 20 weeks of age, when the first classifications of body and wing molt were made, there were slight differences in wing molt among poults in pens receiving different amounts of light, and these differences increased between 20 and 28 weeks of age. No consistent between-treatment differences were observed in body molt until after 22 weeks of age. The present experiment was designed to provide more critical information on the progress of molting in body feathers …