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Weighing only a few ounces, warblers are not known for their winter hardiness, but the yellow-rumped, or myrtle, warbler is one tough bird. As warblers go, this species is just a little larger, a little heavier and a little bulkier than its kin. They can be downright abundant in the late fall landscape, darting through the thinning tree branches, or even shaking off the season’s first snowflakes. The yellow-rumped warbler (Setophaga coronata) overwinters farther north than any other North American wood warbler, and is very hardy. Butter butts, as birders call them because of the bright yellow patch above their tails, are just beginning to show up in our local woodlands as their passerine brethren abandon the cold Northeast for the warmth of Central and South America. The birds are official New Yorkers throughout the winter months.

Few insects are active during an average New York winter, so the yellow-rumped warbler has evolved to capitalize on other foods for winter survival. It is one of only a handful of birds or other vertebrates able to digest wax. In our area, the fragrant bluish fruit of the northern bayberry (Myrica pensylvanica) is covered in a thick waxy coating the birds find ideal. In fact, they are so reliant upon bayberry (and relatives like wax myrtle in the Southeast) that their ranges coincide almost identically on both the Atlantic and the Pacific coasts.

Until recently the East and West Coast populations of the yellow-rumped warbler were segregated into two closely related but separate species, Audubon’s warbler on the West Coast and the myrtle warbler in the east. Despite obvious differences (for example, Audubon’s warblers sport a yellow throat; the myrtle’s is white), DNA testing has revealed that both birds represent one variable species with an extensive range across North America. Hybrids also occur where the two varieties’ ranges overlap.

Myrtle warblers are wonderful trail companions; always good company as they flit through the outer branches of trees and shrubs, their slight chirping calls the perfect complement to the sound of rustling leaves. Gregarious and inquisitive, they often gather in large flocks to feed on bayberries and other ripe winter fruits. The birds will sometimes land within an arm’s length of a quiet hiker.

During the fall and winter months, the myrtle warbler is a streaky warm gray, marked with what seem like randomly placed bright yellow patches. But as days lengthen and spring arrives, the birds color until their random yellow marks are framed by sharp black and white patterns. Then, almost overnight, they’re off, on a migration that will deliver them, in full color, to mates in the north woods.

In Brooklyn, Floyd Bennett Field’s North 40 or the Saltmarsh Nature Center’s trails are great places to observe these winter residents. In Queens, Fort Tilden offers acres of quiet bayberry shrub land for winter hiking. Pelham Bay Park in the Bronx and Battery Park in Manhattan also offer suitable habitats for these adaptable urban birds.