Western Bonelli's Warbler vs Willow Warbler

In short

Western Bonelli's Warbler and Willow Warbler can be distinguished by their plumage and vocalizations. Western Bonelli's Warbler has a brighter green edging on wings and tail, and silky white underparts, while Willow Warbler is generally paler with a yellowish wash. The vocalizations differ, with Western Bonelli's Warbler having a descending trill and Willow Warbler a more melodic, varied song.

Identification tips

1. Look for the bright green edgings on the wings and tail of Western Bonelli's Warbler. 2. Check the underparts: Western Bonelli's Warbler has silky white underparts, while Willow Warbler has a yellowish wash. 3. Listen for the descending trill of Western Bonelli's Warbler versus the melodic song of Willow Warbler.

Plumage

Western Bonelli's Warbler has a greenish-yellow rump and bright green edgings on wings and tail, with silky white underparts. In contrast, Willow Warbler is paler overall with a yellowish wash on the underparts and lacks the bright green wing edgings.

Voice

Western Bonelli's Warbler produces a descending trill that is quite loud at the start but diminishes, with a metallic quality. Willow Warbler has a more melodic and varied song, lacking the metallic quality.