This is the largest and brightest of the three common leaf or green warblers. It is distinguished from the Willow Warbler and Chiffchaff by the bright yellow stripe over the eye, dark green stripe running through the eye, its yellow cheeks and throat (more extensive on the male) and gleaming white underparts.
However. it is most easily encountered in its breeding habitat by its characteristic call – a short metallic tick that accelerates into a trill that is reminiscent of a coin spinning and falling to rest. Despite this, it is a difficult species to actually see because of its habit of feeding within trees, where its combination of colours blend with dappled sunlight on leaves. A little patience is worthwhile, as a singing bird is fascinating to watch as it vibrates its whole body as it gives forth its trill.
It is a species that has suffered worrying declines in recent years, for reasons that are not well understood, and all records should be reported. It has the very precise breeding requirements of tall trees with open spaces and dead leaf litter on the ground (see photo from the southern tip of Grizedale Forest). It builds its domed nest amongst the leaf litter and is badly affected if the ground scrubs over. Incubation takes up to a fortnight and the young are feed for a month, so only one brood is raised, making the species vulnerable to poor spring weather.
Cumbria still has quite good numbers of Wood Warblers in its Oak and Beech woods. Although never widespread, it occurs in good numbers in Lakeland valleys when the habitat is most suitable. Strongholds are the mature woodlands around Loweswater, Nether Wasdale, Elterwater, Torver and Grizedale.
In autumn Wood Warblers migrate (like Lesser Whitethroats) via Italy to central and east Africa.