The adult has a plain grey-green back, green-toned rump and wings and whitish underparts. The bill is small and pointed and the legs brown. The sexes are identical, as with most warblers. The western Bonelli's warbler has a browner tinge to the upperparts than eastern Bonelli's warbler; the latter sometimes has a greenish tinge instead.
Habitat and Distribution
The species is migratory, wintering in sub-Saharan Africa. It is a rare vagrant in Northern Europe.
Like most warblers, western Bonelli's is insectivorous.
4?6 eggs are laid in a nest on the ground.
Calls and Songs
The song is a fast monotone trill, only slightly different from eastern Bonelli's, and also some similarity to wood warbler. The call of the western Bonelli's warbler is a disyllabic hu-it, differing from that of eastern which is a completely different hard chup, reminiscent of a crossbill or a house sparrow.