A small American songbird. It is somewhat warbler-like but not closely related to the New World warblers (Parulidae). It is common across its vast range. This bird, not always seen, may sing for long periods of time; it appears to be endlessly repeating the same question and answer. It holds the record for most songs given in a single day among bird species. More than 20,000 songs in one day.
13 - 14 cm in length. Adults are mainly olive-green on the upperparts with white underparts; they have a red iris and a grey crown edged with black. There is a dark blackish line through the eyes and a wide white stripe just above that line. They have thick blue-grey legs and a stout bill. They are yellowish on the flanks and undertail coverts (though this is faint in some populations).
The breeding habitat is open wooded areas.