Willow Warbler

The Willow Warbler is a small, slender leaf warbler with soft greenish-olive upperparts and pale, yellowish-white underparts that can vary in brightness between individuals and populations. A pale supercilium (eyebrow stripe) runs from the bill to just behind the eye, and the overall plumage is fresh and clean-looking, especially in spring.

It is virtually identical in plumage to the Common Chiffchaff, and the two are among the classic identification challenges of European birding, best separated by leg colour and, especially, by voice.

One of the most numerous and widespread summer migrants in Europe, the Willow Warbler's gently descending, wistful song is a defining sound of birch woods, scrub, and hedgerows in spring and early summer.

Key field marks

• Greenish-olive upperparts, often brighter than Chiffchaff
• Pale, yellowish-white underparts
• Pale supercilium above the eye
• Pinkish-brown or pale flesh-coloured legs (key difference from Chiffchaff)
• Longer wings than Chiffchaff, giving a slightly more elongated shape

Similar species

• Common Chiffchaff: virtually identical in plumage but has dark, blackish legs (versus Willow Warbler's pale legs), a duller and browner tone, and a completely different "chiff-chaff" song.
• Wood Warbler: brighter yellow throat and breast with a sharply demarcated white belly, and a longer, more contrasty supercilium.
• Chaffinch and other finches: much stockier with conical bills, unlike the Willow Warbler's thin insectivorous bill.

Willow Warblers breed across almost the entire temperate and subarctic zone of Europe and northern Asia, occupying open woodland, birch and willow scrub, young plantations, heathland edges, and large gardens with scattered trees and shrubs.

They are long-distance migrants, wintering in sub-Saharan Africa, and are among the most abundant migratory songbirds crossing between Europe and Africa each year.

The species arrives on breeding grounds from April, with its cascading song often the first confirmation that spring migration is well underway.

Voice

The song is a gentle, sweet, descending cascade of clear notes, often likened to a wistful, tumbling melody that fades away at the end. The call is a soft, disyllabic "hoo-eet," softer than the Chiffchaff's sharper "hweet."

Feeding

Willow Warblers glean small insects and spiders from leaves and twigs, often flitting actively through foliage and occasionally hovering briefly to pick prey from leaf surfaces.

Nesting and breeding

The nest is a domed structure built on or near the ground, hidden among grass or low vegetation, with a side entrance. Clutches typically contain six to seven eggs, among the larger clutches of European warblers.