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Tweet of the Day is the voice of birds and our relationship with them, from around the world.

Liz Bonnin presents the eastern orphean warbler in an olive grove near Athens. Until recently there used to be just a single species of Orphean Warbler; a summer visitor to southern Europe, North Africa and western Asia: a handsome bird much like a large blackcap with a white throat and greyish-brown back. But across the wide breeding range which stretches from Portugal to Pakistan some orphean warblers look and sound different. Those east of Italy tend to be subtly greyer above and paler beneath. And the songs of birds from Greece eastwards are longer and richer, often including the richness of nightingale like notes. These slight differences have persuaded many ornithologists that the Eastern Orphean warbler is a different species to the Western Orphean Warbler. Biologists call this "splitting "although exactly where these new species boundaries lie is a moot point.

Producer : Andrew Dawes