About Phylloscopus trochilus (Linnaeus, 1758)
The willow warbler, Phylloscopus trochilus (Linnaeus, 1758), is a typical leaf warbler in overall appearance. It measures 11–12.5 cm (4.3–4.9 in) in length and weighs 7–15 g (0.25–0.53 oz). Its upperparts are greenish brown, and its underparts range from off-white to yellowish. The plain greenish-brown wings have no wingbars. Juvenile willow warblers have yellower underparts than adult birds. This species is very similar in appearance to the chiffchaff. Non-singing willow warblers can be told apart from chiffchaffs by several features: paler pinkish-yellow legs (chiffchaffs have dark brown to blackish legs), a longer paler bill, a more elegant body shape, and a longer primary projection on the wingtip. The willow warbler's song is a simple repetitive descending whistle. Its contact call is a disyllabic 'hoo-eet', which is distinct from the more monosyllabic 'hweet' contact call of chiffchaffs.
