Ynghylch

Yellow-browed warblers are small leaf warblers, related to chiffchaffs and willow warblers. They breed in taiga forests in Siberia and spend the winter in Southeast Asia. Migration between the two regions shouldn't bring them anywhere near the UK, but each autumn sees large numbers recorded here, particularly along eastern coasts. Over the last 50 years they've become much more common, rising from a handful of records each year to well over a thousand.

At first it was assumed that these birds were just wayward strays (known as vagrants), which took a wrong turn and are doomed never to return to their breeding grounds. More recently, scientists are theorising that we may be seeing a new migration route developing, with yellow-browed warblers migrating between western Siberia and an unknown wintering area in West Africa.

In the UK, yellow-browed warblers are most common in October. They're usually found in coastal trees and scrub, particularly in sycamores. They often give away their presence with their distinctive call. Like goldcrests, they're restless and rarely stay still for long. Most records come from the north and east, but they can turn up almost anywhere, with a few inland records each year. Occasionally they spend the winter here, or appear in spring.