Willow Warbler (Ceolaire sali)

Phylloscopus tochilus

Though unfamiliar to most people, the Willow Warbler is actually an extremely common bird in Ireland. Indeed, it is our most numerous summer migrant, with around two million individuals making the journey here each spring; they begin to leave for their west African wintering grounds in August, staging in Iberia en route. The species occurs in all counties, and despite its name is not confined to willows, nesting also in a wide range of young deciduous trees and bushes, woodland edges and scrubland.
At 11cm in length, the Willow Warbler is about the same size as a Blue Tit, though with a somewhat slimmer build. It specialises in eating small flies, spiders, caterpillars and other invertebrates, and can frequently be seen busily flitting around in trees gleaning these from the underside of leaves; when available, berries will also be consumed. The upperparts are buffish-brown, while the underparts are yellowish, gradually becoming paler through the summer. It also has a dark stripe through each eye, bordered thinly above with yellow.

The above description also fits perfectly for another closely-related warbler species, the Chiffchaff, itself a common summer visitor, and the two birds can be very difficult to separate. Willow Warblers have slightly longer wings and almost always have pale pinkish legs, whereas the legs of the Chiffchaff are always dark brown or blackish. In addition, Chiffchaffs are a bit duller overall on average, but these slight differences can be difficult to pick out in the field. By far the easiest way to tell these two warblers apart is by their songs. The song of the Willow Warbler consists of a series of soft melodic descending notes, while that of the Chiffchaff is strikingly different: a repetitive rhythmic series of 'chiff chaff' notes that give it its name – one of the easiest Irish bird songs to identify.

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