Date: 5/12/19 8:03 am
From: Spector, David \(Biology\) via CTBirds <ctbirds...>
Subject: Re: [CT Birds] Eli Whitney mystery warbler and confusing age terminology
There is a lot of confusion in ageing terminology, which is reflected in people identifying the mystery male American Redstart as "first year" or "second year," meaning the same thing.

As with a few other male song birds (e.g., Red-winged Blackbird), male American Redstarts take a bit over a year to reach full ("definitive") male plumage, with variation among individual males in the first year of life (some looking more "female-like" and others looking more "male-like").

The bird in question is roughly 11 months old. He is in his first breeding season (thus the label "first year") and in its second calendar year (thus the label "second year," or "SY"). If everything goes well for this bird he will molt into his definitive adult male plumage at the end of this breeding season, and by the fall migration (when it will be roughly 15 months old) he will probably be indistinguishable from older males. Although it takes a little over a year to grow full adult plumage, a male does not appear in breeding season in adult plumage until he is nearly two years old (in his third calendar year--thus the impression that it takes three years to appear adult).

The word "yearling" for such individuals might reduce confusion.

David

David Spector
Belchertown, Massachusetts

P.S. Feather generation terminology adds another level of potential confusion. The bird in question probably has two or three generations of feathers. The primaries, secondaries, tail feathers, and primary coverts are probably "juvenal" (or "juvenile"), most of the rest of the feathers are probably "first basic" (or "formative"), and some feathers might be "first alternate."
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