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85680a6
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It can be difficult to accept the fact that a lot of birds have to be identified as "possible" or "probable." --
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David Allen Sibley |
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c051fb3
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Many species undergo an additional partial molt each year, involving just some head and body feathers. This most often occurs in the late winter or early spring and is called the pre-alternate molt, resulting in the alternate plumage. Many species, but not all, have an alternate plumage. Because this is only a partial molt (not involving all feathers), the new feathers of the alternate plumage are worn alongside the older feathers of the ba..
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David Allen Sibley |
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eeca8be
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The H-P system indicates the age of the bird in essentially the same way as the Life-Year system. The bird is considered to be in its first year (with plumages labeled first basic and first alternate) from hatching until the prebasic molt a year later, in its second year from that time until the following prebasic molt, and so on.
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David Allen Sibley |
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ddbb035
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One clue, which applies to virtually all species and can be very useful in late summer and fall, is that juveniles, having just fledged, are then in very uniform fresh plumage, while adults are actively molting or showing a mixture of old and new plumage.
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David Allen Sibley |