Dull greenish-brown "Old World warbler", not related to other more colorful "New World warblers." A Eurasian species that extends its range into Alaska. Breeds in shrubby willow thickets on Arctic tundra. Look for faint wingbars (sometimes just one) and narrow pale eyebrow. Whitish throat and pale buffy belly. Not likely to be confused within limited range. Song is a chattery trill, reminiscent of Palm Warbler or Common Redpoll.