Willow Warbler

The Willow Warbler is a bird slightly larger than the Chiffchaff, but more slender and paler. The upper parts are a pale brown tinged with olive. The wings and tail are darker, but the light fringes of the feathers are of the same colour as the coverts. The underparts are white, tinted with yellow to yellow-olive mainly on the chest and flanks.
Now let's take a look at the specific identification criteria of the adult of the nominate subspecies of Middle Europe (vs the Chiffchaff):
- Primary projection: The Willo Warbler has the long wing of a long-distance migrant. The tips of the primaries protrude significantly more from the tertiaries than in the Chiffchaff.
- Leg colour: It is quite variable, yellowish, reddish, pale brown, with the foot of a more marked hue, but never dark brown to blackish like the Chiffchaff.
- The head: A clear and long pale yellow eyebrow, sometimes yellow in front and white behind, outlines the eye. Its sharpness makes the pale orbital ring less visible than in the Chiffchaff. The beak is long and tinged with yellow along the commissure (fine and dark in the Chiffchaff). Finally, the ear coverts are beige (brown in the Chiffchaff).
The juvenile is characterised by a much yellower plumage which makes it resemble for example a Subalpine Warbler. The voice and silhouette are different. The Subalpine Warbler often bristles the feathers of the crown and has light lores, while the Willow Warbler has a clear dark loral line.
The adults of the northern European subspecies acredula are paler, more grey-brown on the upper parts, with a more discreet yellow on the head and on the chest.
Finally, the adults of the central and eastern Siberian subspecies yakutensis have a grey-brown upper part without olive (except on the fringes of the remiges) and a white underside, tinted with greyish on the chest.The yellow only occurs on the undersides of the wings and is not visible. The very prominent brow is white.