Upper plumage bright yellowish green; a broad streak of sulphur-yellow over the eye; sides of the head, throat, insertion of the wings and legs bright yellow; rest of the under plumage pure white; second primary equal to the fourth, third and fourth with the outer web sloped off at the extremity; legs pale brown. Length five inches and a half; breadth eight and three quarters. Eggs white, speckled so thickly with purplish brown as almost to conceal the ground.
The Wood-warbler, Willow-warbler, and Chiff-chaff resemble each other so closely in size, colour, and habits, that except by a practised observer, they are likely to be mistaken for one another. In song, however, they differ materially, and as this is begun early, and continued till very late in the season, it affords ready means of discriminating the species. The Wood-warbler, or Wood-wren as it is now called, arrives in England towards the end of April, and betakes itself to woodland districts, where it spends the greater portion of its time among the upper branches of lofty trees, constantly moving from place to place with rapid irregular flight, and frequently repeating its short and peculiar song. It feeds exclusively on insects, which it occasionally catches on the wing. Its song is difficult to describe. The name by which it is popularly known in some parts of France, _Touïte_, is derived from the syllable '_tweet_', which, rapidly and continuously repeated many times, constitutes its song. These notes are uttered in a sweet tone, and with a tremulous accent, and are unlike those of any other bird. Gilbert White, who appears to have been the first who noticed the bird, describes it as "joyous, easy, and laughing". The last notes of its strain are accompanied by a quivering of the wings and tail, which accounts for their tremulous sound.
The Wood-warbler is much less frequent than either the Willow-warbler or Chiff-chaff, and on a close inspection may be distinguished by its superior size, by the pure white of its under tail-coverts, and by the bright yellow line above the eye. The nest is composed of grass, ferns, and moss, and lined with fine grass and hair; it is covered with a dome, an entrance being left sufficiently large to allow its contents to be seen, and is placed on the ground, in or near a wood, among thick herbage, or against the stump of a tree. The eggs are from five to seven in number, almost round, and so thickly spotted with purple-brown that the ground is almost invisible.