13 September 2011 – Ruby-throated Hummingbird

I often leave hummingbirds in place to check scavenging rates, but this one was so fresh I decided to pick it up and really study it.  Of course, hummingbird identification, ageing, and sexing can be pretty tricky, and it’s taken me nearly an hour to figure out this bird with confidence.  I learned a bit along the way, however, so that’s my reward.

OK, it’s a small green hummingbird in the eastern U.S. that is whitish below with some subtle streaking on the throat.  That means it’s most likely a Ruby-throated Hummingbird. On the folded wing, I can see that primaries 1–6 are closer together than primaries 7–10.  That, and some of the other measurements I took, ruled out Black-chinned Hummingbird.

It could be a female (HY or AHY) or an HY male.  A closer look reveals a single gorget feather that has come in red.  Case closed!  It’s a HY male, right?

Well, not quite.  Some AHY females can have a red gorget feather or two, so I had to be more careful in my identification.  I needed to determine the age of this bird, definitively.

Some of the contour feathers on the crown and back were edged in brown.  That should be indicative of an HY bird, but that’s a subjective criterion.  It turns out that the most common technique hummingbird banders use for ageing is to look for “corrugations” on the surface of the bill.  These are faint wrinkles on the bill that fade or smooth out as the bird ages.  Did this bird on my desk have corrugations?

 

OK, kind of, I guess.  But my inexperience with this character still made me suspicious.  I could, however, determine the sex of this bird – definitively – by looking at the shape of the tip of primary #6 (visible in the top photo).  In males, p6 is almost concave and sweeps up to an attenuated point; in females, that shape really isn’t there and the tip of p6 is more truncate or even rounded.

I see the attenuated p6.  Now I’m convinced, it’s a HY male, Ruby-throated hummingbird.

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