Cool critters: The butterbutt of autumn is bound for berries

Editor’s Note: This story was supposed to run in last Sunday’s Northwest section. However, due to a mix-up, a different story was re-rerun instead.

A bright yellow patch flashes from a tree canopy and then vanishes. Was it an autumn leaf jostled by a sudden breeze? How about a yellow-rumped warbler?

Affectionally known as butterbutts, these small songbirds are eye-catching and energetic this time of year.

As millions of birds take to the skies for their journeys south, the yellow-rumped warbler – named for the cheery cluster of yellow feathers on its rump – stays in the Inland Northwest until late autumn, while some never leave.

In contrast to its streaky grayish-brown body feathers, yellow patches are also found on the bird’s throat, crown and sides. But its rump flares the brightest.

There are roughly 50 warbler species in North America, most of which have begun their fall migration to warmer climates. The butterbutt is unique among them.

“While most of its relatives migrate to the tropics in fall, the yellow-rump are able to live on berries, commonly remains as far north as New England and Seattle,” according to the National Audubon Society. “It is the main winter warbler in North America.”

Each year at this time, groups of yellow-rumps (known as bouquets) congregate outdoors around Alan McCoy’s Spokane-area home. As usual, his fall-time visitors are “really jittery” and hard to photograph, he said.

“They’re in the shrubs and treetops. They’re on the ground. They’re at my birdbaths. And they rarely hold still,” said McCoy, president of the Spokane Audubon Society and a chapter member for more than 40 years.

Whether the butterbutts are fueling for fall migration or bulking up to spend winter in our region, “this is a critical time for them as they build energy reserves,” he explained.

Which means, these diminutive birds weighing little more than a standard penny are moving hurry-scurry as they catch insects from mid-air and drink from birdbaths and other water sources.

But with cooler weather sweeping the region, it will not be long before insects enter a dormant stage or die. How, then, do wintering yellow-rumps survive?

The bug-chomping songbird switches its diet, which literally takes guts to accomplish, according to the online Audubon Field Guide.

“High levels of bile salts allow them to digest the wax found in the coating of berries from a variety of plants, including bayberry, juniper, wax myrtle, and poison ivy,” the organization states, adding that this special adaptation enables them to winter farther north than other warbler species. It also helps that the warblers grow an extra layer of feathers and cluster together on frigid nights to share warmth.

Consequently, McCoy is able to enjoy the birds’ buttery warmth year-round, even though their numbers are considerably smaller in winter than during summer.

“Their soft ‘chep’ call often alerts me where to look for them,” he said.

Though the species’ yellow patches begin to fade in autumn, their sunny-colored rumps are still easy to spot as the bird flits about on bare branches or against backdrops of wintertime gray.

Even in the dead of winter, “they’re pretty and flitty,” McCoy explained

Meaning that the yellow-rump remains cheery, yet challenging to photograph.

“It’s a fun bird,” he said, “but not very cooperative.”