Many birders find identifying fall warblers to be a tricky proposition. One good species to start with is the Yellow-rumped Warbler (Dendroica coronata) since it is probably the most common fall warbler in our area.
The most consistently distinctive feature of this species’ appearance is, as its name suggests, its yellow rump patch. This patch is present in all plumages except the juvenile plumage, which is held only from about May to August, and mostly on the breeding grounds to our north. The rest of the bird’s upperparts are mostly brown to gray, with most fall birds tending to be brownish. The bird has fine, dark streaks over the background color going down the back. The wings and tail are grayer than the rest of the upperparts, and there are two white wingbars. The head is brown to gray, and grayer birds have a dark to black auricular (ear) patch. It has a broken white eyering, interrupting a white to whitish eyeline. (The eyeline is not present on duller-plumaged birds.) The Yellow-rump’s underparts are white to pale tan, the throat being the lightest. It has heavy to light dark streaking from the breast down to the sides where the streaking is the heaviest. The sides also sport a small yellow patch, visible on all but the dullest birds. Two small white patches at the corners of the upper surface of the tail are visible in flight.
In the spring and summer, the song is a high, loose, warbling trill, whereas the usual vocalizations we hear in the fall are a clipped “check” call note and a high-pitched, ascending “sweet” flight note, especially familiar sounds along the coast in October, when the species can be impressively abundant.
Though insects make up most of its diet in summer, this species is unique among warblers in its ability to subsist almost wholly on fruit, especially bayberries, which hold high concentrations of energy-giving lipids (fats). This adaptation allows the Yellow-rumped Warbler to winter much farther north than our other warblers, being regularly found in winter as far north as Nova Scotia. In the more northern parts of its winter range, the Yellow-rumped Warbler is usually found close to the coast, almost inevitably near stands of Northern Bayberry (Morella pensylvanica). The fruits of Poison Ivy (Rhus toxicodendron) and Eastern Red Cedar (Juniperus virginiana) are also sometimes part of its diet.
In summer, the species frequents conifer woods mostly in boreal forests from Alaska to the Maritimes. In the northeast its breeding range extends south to central New England and New York. In the south, it also breeds at high elevations in the Appalachians to West Virginia. Most of the time when we see yellow-rumps in our area, they are in transit between their breeding and wintering grounds. During this time, they can be found in almost any habitat, from forests to fields, foraging for insects and berries.
Support Yellow-rumped Warblers during fall migration and winter by planting Northern Bayberry, Eastern Red Cedar, and other native berry-producers.