Autumn migration has taken many of our birds south for the winter, especially the little forest birds known as wood-warblers. But one, the Yellow-rumped Warbler (Dendroica coronata) will stick around if conditions are right.
The Yellow-rumped Warbler is one of 53 species of wood-warbler found in North America. Small, insectivorous birds of our woodlands, shrubby areas and wetland edges, wood-warblers thrill us with their colorful breeding plumage and their mass migrations in the spring and fall. Equally, they confound and frustrate us with their drabber, hard-to-identify fall plumage, and with their penchant to feed and flit about high in the trees. “Warbler neck” is a well-known discomfort that afflicts those who spend too much time peering up into a tree’s dense foliage in search of these little avian wonders. Thankfully, the Yellow-rumped is always ready to accommodate – it is common, easy to identify, and tends to hang out on lower vegetation.
As their insect prey disappears in the fall, many warbler species fatten up on fruits to fuel them on their migration south. And all of them, except the yellow-rumped, will continue south and out of our area. But the Yellow-rumped has a neat trick that allows it to stay through the winter: it has the ability to feed on and digest the waxy fruits of the bayberry. It possesses the enzymes required to digest the waxy coating on the fruits and to glean nutrients from the wax. (Also known as wax myrtle or myrtle, there are six species of bayberry that are native to the East Coast of the United States. These evergreen shrubs in the genus Myrica bear wax-coated fruits that are eaten by many bird species, but only one warbler – the Yellow-rumped.)
This cheery bird is also known as the Myrtle Warbler in the East, and Audubon’s Warbler in the West. Our eastern subspecies has a white throat while the western bird’s throat is yellow. The Myrtle Warbler breeds throughout Alaska and Canada, as well as in the northern states in the eastern U. S. In Connecticut, it can be found nesting in coniferous forests in the northwest corner of the state. Eastern birds spend the winter along the coast of the Northeast, south through the Southeast and into Central America. Those remaining in our area can be found flocking together in open, brushy areas where bayberry, juniper, and other fruiting shrubs are found.
During spring migration and throughout the breeding season the Yellow-rumped Warbler is a lovely gray-blue bird with a white belly, white throat and white wing bars. A black mask surrounds its eyes and black streaking runs down its breast and back. In the fall and winter its plumage, like so many other warblers’, becomes subtler, taking on a brown overtone and losing the sharp contrasting black and white. But one thing it doesn’t lose is the brilliant flash of yellow on the sides of its chest and, of course, on its rump. That yellow rump inspires many a bird watcher to affectionately refer to this friendly warbler as a “butter butt.” Would a flitting flock of Yellow-rumped Warblers be considered a “churning of butter butts?”