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The process of moulting in birds is as follows: First, the bird begins to shed some old feathers, then pin feathers grow in to replace the old feathers. As the pin feathers become full feathers, other feathers are shed. This is a cyclical process that occurs in many phases. It is usually symmetrical, with feather loss equal on each side of the ...
Unmated males without family responsibilities often start losing feathers earlier in the year. Their moult follows a pattern similarly prolonged as that of the female. The first sign that the male is moulting is often when a tail feather has been dropped at the roost. [43] A consequence of moulting is the loss of thermal insulation.
By 12 days old, contour feathers are well developed in areas except for the head. At 15 days, facial feathers show the dark eyestripe against the white throat and cheek. [ 19 ] They jump from the breeding cliffs at 20–21 days old, long before being fully fledged, and are cared for by the male parent at sea.
Moulting occurs once a year in late summer after the breeding season has finished; the fresh feathers are prominently tipped white (breast feathers) or buff (wing and back feathers), which gives the bird a speckled appearance. The reduction in the spotting in the breeding season is achieved through the white feather tips largely wearing off.
The American goldfinch undergoes a molt in the spring and autumn. It is the only cardueline finch to undergo molting twice a year. [14] During the winter molt it sheds all its feathers; in the spring, it sheds all but the wing and tail feathers, which are dark brown in the female and black in the male. [13]
Moulting behaviour is divided into two types – adult post-breeding and post-juvenile. [9] For adults, promptly after the breeding season comes to an end, they begin to moult by discarding older, rundown feathers to make way for the newer, unblemished feathers. This process takes place between late summer up until autumn.
This resulting covering of feathers, which will last either until the next breeding season or until the next annual moult, is known as the basic plumage. Many species undertake another moult before the breeding season known as the pre-alternate moult , the resulting breeding plumage being known as the alternate plumage or nuptial plumage.
Feather variations. Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates [1] [2] and an example of a complex evolutionary novelty. [3]