Bird Files: Yellow-rumped Warbler a Smart Forager

  • That's not butter on my butt, but the yellow spot is why I'm called a butter-butt and Yellow-rumped Warbler. Photo: Alan D. Wilson,

October 17, 2014

If someone calls you a butter-butt, that may sound like an insult. But it turns out that the butter-butt (the colloquial name for the Yellow-rumped Warbler), is one smart cookie. This warbler has strategic eating habits.

This time of year, the Yellow-rumped Warbler is mostly brown and streaked with a touch of yellow on the sides. Not the most brightly colored bird, especially when compared with other warblers. However, there’s  more to the Yellow-rumped Warbler than meets the eye.

During fall migration and winter, the Yellow-rumped Warbler’s diet expands from insects, which is the typical warbler fare. The addition? Many servings of fruit—especially bayberries. Unlike any other warbler, Yellow-rumps are able to digest the waxes in bayberries. This high-energy food allows them to overwinter much farther north than other warblers—wherever the bayberries grow. The birds have been found wintering as far north as Atlantic Canada. This is remarkable, as most warblers spend the chilly months in the tropics or the southern U.S.

Yellow-rumped Warblers use feeding strategies that are unlike other members of their warbler family. While they do search for insects along tree branches like most warblers, they’ve also been known to forage by fly-catching, and even feeding on the ground.

From autumn to spring, Yellow-rumped Warblers form large flocks with their species and other warblers. They fill the woods with flitting wings and a hard 'chip' sound.

So if you’re out in the woods this fall and you hear a distinctive chipping, look closely—you might just see a Yellow-rumped Warbler.

Bird calls for this segment come courtesy of the Macaulay Library at the Cornell Lab of Ornithology, recorded by Nicholas D. Sly and Michael J. Andersen.