Length: 11 cm.
The male and female have like plumage.
Voice: A bright ‘hooeet’.
Song: Resembling that of the chaffinch but a softer and more rippling ‘sooeet-sooeetoo’.
Size of Egg: 13.2—18.8 x 10.9—13.8 mm.
The loud rippling song of the willow warbler can be heard in April when it returns from its winter quarters in tropical and southern Africa, in thick deciduous or mixed woods with thick undergrowth, less often in coniferous forests. It is a small bird and is distributed throughout Europe, except the southern parts and the Balkans, though in the
east its range extends as far as northeast Siberia.
It hops about and flits restlessly from branch to branch, collecting small insects and their larvae, as well as small spiders. In the warm days of May or June, the female builds a neat dome-shaped nest in a clump of grass, or close above the ground in a blueberry bush or heather.
The nest is made of grass stems, dead leaves, moss and lichens and lined with fine materials. The entrance is located
at the side so that the clutch is out of sight. The 6 to 7 eggs are incubated by the hen alone, usually for 13 days, but the male helps share the duties of rearing the young. They leave the nest after 12 to 16 days, but continue to be fed by the parents for a further 14 days. The diet consists mainly of small insects and their larvae.
The cuckoo often lays its eggs in the willow warbler’s nest, and on hatching the young cuckoo is often reared by the willow warblers and fed by them for far longer than their own nestlings. In September or October, the willow warbler leaves the nesting grounds for its winter quarters. It is one the most plentiful species of woodland birds.