Central Feathers Research Articles

Adaptive fault bar distribution in a long-distance migratory, aerial forager passerine?

Fault bars are translucent bands produced by stressful events during feather formation. They weaken feathers and increase their probability of breakage, and thus could compromise bird fitness by lowering flight performance. It has been recently suggested (‘fault bar allocation hypothesis’) that birds could have evolved adaptive mechanisms for reducing fault bar load on the feathers with the highest function during flight. We tested this hypothesis by studying first-year individuals of the long-distance migratory, aerial forager barn swallow Hirundo rustica . We predicted that fault bars should be less abundant on the outermost wing and tail feathers, but more frequent on the tail than on the outermost wing feathers. Accordingly, we found that fault bars occurred more often in tertials than in primaries or secondaries. Tail feathers had fewer fault bars than tertials, but more than primaries. Within the tail, the distribution pattern of fault bars was W-shaped, with the highest fault bar load occurring on the streamers and on the two central feathers. Because streamers are the most important tail feathers for flight performance, this finding seems to contradict the ‘fault bar allocation hypothesis’. However, flight performance is much less sensitive to changes in the shape of the tail than of the wings, which could explain why evolutionary forces have not counteracted the increase of fault bars associated with feather elongation during the recent evolution of streamers in the tail of hirundines. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 455‐461.

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.