Yellow-rumped (Audubon’s) warbler just south of Grand Teton National Park, fall 2026.
It has one of the better nicknames in the birding world: butterbutt.
It makes perfect sense too because the yellow butt is a key field mark. Of course, it’s the yellow-rumped warbler, one of New England’s most commonly seen warblers. There are fall days when I’ll see dozens of butterbutts and hardly anything else, except for maybe a few palm warblers.
Yellow-rumped warblers can be tricky in the fall, however, as the flocks are a mixed bag of adult males and females and first-year males and females. All four varieties look fairly similar this time of year.
In the spring, we have adult males and adult females coming up from the south, and they look completely different from each other with males sporting an attractive mix of bluish gray, white, black and yellow. In the fall, they are all much duller than they are in the spring.
Their trademark and namesake is the yellow patch on their rump, which is visible at rest and in flight in all seasons. They also have small yellow patches on their sides. The western subspecies also has a yellow throat while the eastern subspecies sports a white throat.
The yellow-rumped warbler is an interesting study in bird names and splits. It used to be considered two separate species: Audubon’s warbler and myrtle warbler, which are now each considered subspecies of the yellow-rumped warbler. That change took place in 1973. There has been talk for years about splitting them again, but that hasn’t happened yet.
To add to the confusion, there are two more forms of the yellow-rumped warbler: black-fronted from Mexico and Goldman’s of Guatemala. I’ve never seen one in person, but from photos, the Goldman’s form looks like a really cool bird that is mostly black with yellow and white markings.
To add even more confusion, the Audubon’s and myrtle subspecies interbreed where their ranges cross somewhere around the Rocky Mountains. It was there where I saw dozens of yellow-rumps during a recent trip to Grand Teton National Park. It being fall, it was difficult to tell males from females and adults from immatures, but they were definitely yellow-rumped warblers. Whether they were the Audubon’s or myrtle subspecies is another question. I believe they were Audubon’s based on the yellow throats.
Who knows when or if the split will take place again. In the last few years, the American Ornithologists’ Union seems to be on a splitting kick. I wrote recently about the splitting of the warbling vireo, house wren and yellow warbler ─ all common New England birds.
In a way, I’d prefer the bird to remain a single species. Yellow-rumped warbler is much more fun to say than Audubon’s warbler or myrtle warbler. Either way, butterbutt remains a fitting nickname, so there’s that.
