The majority of warblers who summer in New England or points north have fled south by early November. The occasional Pine, Palm, Nashville, Orange-crowned, or less common vagrant Warbler may linger well into the new year (or even overwinter), but odds are if you see a warbler in late fall or winter, you're probably along the coast, and the bird is most likely a Yellow-rumped Warbler.
Yellow-rumps are insect eaters, but also seek fruit in fall, like that of Small Bayberry (Morella caroliniensis) and Poison-ivy (Toxicodendron radicans, see Quiz #30). Aside from their bright yellow-rumps (which account for their nickname "Butter-butts"), fall birds tend to be drab with streaked chests and yellow sides of variable brightness. In spring, adult males have a black mask and bright yellow sides, rump and crown. As they forage, Yellow-rumped Warblers give frequent call notes, which are most often what alert me to their presence.