Wildlife Watching Wednesday: The Yellow-Rumped Warbler

By: Tom Berg

Yellow-rumped warblers are fairly large when compared to other warblers, since they have a wingspan of up to nine inches. But, of course, they are small when compared to many other birds. The males are very colorful during spring migration and the breeding season, with a mixture of bright yellow, white, gray and black. The signature yellow patch on their rump helped give them the name “butter-butts”. They also have bright yellow patches on their sides and the top of their heads. Females are a bit duller in coloration.

Large numbers of yellow-rumped warblers migrate north in the springtime as they head for Canada, Alaska and the mountains out west. The coniferous forests in Colorado, Wyoming, Montana and other western states play host to many breeding yellow-rumped warblers. Great flocks of them also go north along the east coast and stop in our northeastern states like Maine, Vermont, New Hampshire and New York.

Like most warblers, the yellow-rumped “butter-butts” love to eat insects. Flying insects, crawling insects like beetles and caterpillars, spiders – it doesn’t matter to them. They are even pretty adept at flying out from a stationary perch and catching flying insects in midair. But when insects are in short supply, they are just as happy to eat a variety of small fruits and berries.

Speaking of berries, yellow-rumped warblers are the only species of warbler able to eat and digest the natural waxes found in bayberries and wax myrtle berries. These waxy berries were traditionally boiled down and used as candle wax by early colonists, but the butter-butts can eat them!  They also eat grapes, juniper berries and the berries from poison ivy vines.

Yellow-rumped warblers often flit from branch to branch in search of insects, and unlike some other warblers that prefer to hunt in the upper canopy of the trees, they tend to stay in the lower and middle branches. Spider webs are attractive to them, and they will even pick insects out of the webs to eat. If a spider comes out to investigate, they will catch and eat it, too!

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