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In spring, it is easy to age and sex Ruby-throated Hummingbirds (Archilochus colubris). Then, all the males are adults with red gorgets, and all the females are adults with plain, white throats. After about mid-May--when the first hatchlings begin to fledge--things get complicated because young males lack the distinctive red throat. (They may, however, have some streaks of dark green or black on the throat.) At this time, a bird without a red throat could be an adult female, a young female, OR a young male. To better understand population dynamics, it is important to know the percentages of males and females, so it's fortunate that young birds can be sexed by looking at the sixth primary (flight feather) on the wing. In Ruby-throated Hummingbird males of any age this feather is sharply tapered to a point, while in females it is not tapered and the tip is usually rounded.
© Bill Hilton Jr.
The sixth primary feather on the wing of female Ruby-throated Hummingbirds (red pointer in left photo) is rounded and untapered, while that of males is tapered and pointed (right).
Ageing hummingbirds can be even more difficult, but perhaps the best way to determine age is to look at the bill with a hand lens. In young birds, the sides of the upper bill are marked by fine etchings, while in adults the mere action of sticking the bill into flowers typically wears these etchings smooth by the time the bird migrates away and returns in the spring; thus, a smooth-beaked bird is an adult. Young birds also have a yellowish-colored gape (corner of the mouth). Body plumage differences--including the amount of streaking on the throat--are often very subtle and shouldn't be used as the sole criterion to determine age.
© Bill Hilton Jr.
Although it is difficult to illustrate photographically, the upper bill of a young Ruby-throated Hummingbird (above left) has tiny etchings that make it appear rough. After several months, the mere action of probing flowers wears away the etchings so that the bill of the adult (right) is smooth. Some researchers believe the bill appears smoother in adults because an increased flow of blood "plumps up" or "fills in" the etchings.
Back to How Hummingbirds are Banded; forward to Measuring Hummingbirds
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