Date: 10/5/25 4:53 am From: <lehman.paul...> via groups.io <lehman.paul...> Subject: [SanDiegoRegionBirding] Ruby-throated Hummingbird Sex Change! (and feeding behavior)
Due to the presence of stippling on the throat, we first thought the Carlsbad Ruby-throated Hummingbird was a young male. But it turns out that females have not only clean whitish throats but they can also have lightly/partially stippled throats. Also, most young males by early October would seemingly be showing the first few larger gorget feathers with adult color on them, which this bird does not. (A couple noticeable dark blobs along the lower edge of the throat on this bird are not larger gorget feathers appearing but are actually small gaps in the feathering resulting from presumed missing feathers.) Whether or not the bird is a female or young male can actually be important, as that would influence such characters as the exact shape of P10 and P6 and play a role in bill length. (This bird being a female would help better match P10 and P6 as Ruby-throated. And females of many hummer species have longer bills than the males, so if a female then the bill on the Carlsbad bird better fits Ruby-throated rather than the longer-billed female Black-chinned.) We sent a photo taken of the spread wing, showing the shape of P10 and other P's to a seasoned hummingbird bander in Louisiana, and he wrote back that it looks just fine to him for Ruby-throated. He also wrote that the shape of P5 (not a feather I knew to study) indeed makes the bird a FEMALE.
Anyway, everyone, including me, who included in their eBird details that the bird is a young male, needs to change that to female, or leave unspecified.
Lastly, a character I was able to study, but is very difficult to see from the path because the bird is mostly hidden while feeding, is that when the bird is flying around amongst the hedge looking for the appropriate blossoms, it is moderately pumping the tail (slightly less emphatically than a Black-chinned) but the moment it sticks its bill in a flower, the pumping stops and it just lightly jiggles of shivers the closed tail, and then it immediately starts pumping the tail again when the bill is removed from the flower. In contrast, Black-chinneds keep pumping the tail. This matches perfectly with what we are told by hummingbird experts that the two species do.
--Paul Lehman, San Diego
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