Willow warbler

The willow warbler is a leaf warbler in the family Phylloscopidae, formally described by Carl Linnaeus in 1758 as Motacilla trochilus. Three subspecies are recognized, showing a gradual reduction in green and yellow plumage tones from west to east across the range. It is a small warbler, 11 to 12.5 centimeters long and weighing 7 to 15 grams, with greenish brown upperparts, pale underparts, plain wings without bars, and a longer bill and paler legs than the similar chiffchaff. The species breeds throughout northern and temperate Europe from Ireland east to eastern Siberia, occupies open woodlands with birch, alder and willow, and builds its nest close to the ground. Almost the entire population winters in sub-Saharan Africa, with the easternmost subspecies making one of the longest migrations of any bird its size, up to 12,000 kilometers. It feeds exclusively on insects.