Watching wandering winter warblers – which warbler is which?

In autumn and winter, rare warblers on migration turn up, mostly along the coast, but often inland. Without their spring songs they are difficult to identify.

Our familiar leaf or Phylloscopus warblers are summer visitors, but often overwinter. There are over 80 species in this genus of birds in Europe and Asia.

Our common chiffchaffs are greenish brown above with paler underparts, a pale eyebrow stripe and (usually!) dark legs. They can often be spotted in winter for example at Logan’s Meadow and Paradise nature reserve and can be located by their soft “hweet” call. Sometimes a Scandinavian race, which is much greyer, may be seen. Willow warblers are greenish above with yellower underparts and (usually!) pale legs, but they rarely overwinter.

This is where it gets more complicated. The rare greenish warbler is greener than the willow warbler, has a single pale wing-bar and a pale eyebrow stripe. Beware though the very rare green warbler, which is greener than the greenish warbler, and the two-barred greenish warbler which is green and has two pale wing-bars.

There are more! The Arctic warbler is like the greenish warbler but with a dark stripe through its eye and a contrasting pale eyebrow stripe. Occasionally, wood warblers that breed in Welsh oak woods pass through. These are green above and whitish below, with a clear yellow upper breast. Phew!

Now it gets easier. The yellow-browed warbler has a distinct yellow eyebrow stripe and two yellowish wing-bars, and then there is Pallas’s warbler with its bright yellow eyebrow and central crown stripe, two bright wing-bars and a yellow rump. But beware a yellow-browed warbler with a pale central crown stripe which just might be a very rare eastern crowned warbler…

When they turn up in the UK on migration most of these warblers feed in trees and shrubs, often associating with flocks of long-tailed tits. There are two leaf warblers that feed in low bushy scrub - the dusky warbler and Radde’s warbler. Greenishness is replaced by brownness, both have pale whitish eyebrows and can be especially told apart by their calls, but Radde’s warbler is more olive brown! Dusky warbler has a distinct “tak” call rather like a wren, and Radde’s warbler a softer “chett”. Easy!

I’ll stop there!

Most of these warblers nest in the taiga forests of north-east Russia, east of the Ural Mountains, and winter in south-east China, the Himalayan foothills, India, and Malaysia. Some, such as yellow-browed, Pallas’s and possibly dusky warblers, may undertake a “reverse migration” in autumn which directs them to western Europe. Some now overwinter in the UK and have been seen in Cambridge and nearby.

This reverse migration may be linked to extending their breeding ranges or is just vagrancy associated with adverse autumn weather in far-eastern Asia.

Yellow-browed warblers can be located and recognised by their distinct call - a penetrating “sweet” which is remarkably loud for such a small bird weighing about 12gms. In 2021-2022 one overwintered at Milton Country Park and in the last few years they have been seen along the riverside at Stourbridge Common, Newmarket Road and Pound Hill, and last October in trees bordering Coe Fen, and in November in Histon Road cemetery.

In late November to December 2019 a Pallas’s warbler was found at Paradise local nature reserve. The only previous Cambridgeshire record was, sadly, a dead bird that had flown into a window in Peterborough in October 1998. Recently, a dusky warbler was found overwintering in Aldreth.

These birds could turn up anywhere, including in gardens around feeders but more often in trees and shrubs near water. Watch and listen out for them, especially yellow-browed warblers in mixed flocks of roving tits and goldcrests.

There was an unprecedented arrival of American warblers in the UK last autumn associated with Hurricane Lee carrying migrating birds across the north Atlantic. It’s a sad story as those seen were perhaps just the few survivors of many hundreds or thousands that perished at sea. Those that arrived here will probably continue a north/south migration that is doomed to fail.