Wintering Warblers

Spring is in the air, at last! For birdwatchers, one welcome sign is the sound of Chiffchaffs piping up during March. ‘Chiffchaff’ is onomatopoeic – the bird declares its own name. It does so in a quite clear, cheerful-sounding way but with more hesitant delivery than the strident ‘Tea-cher, Tea-cher’ of a Great Tit, regularly getting ‘stuck’ on the same note. By the end of the month, the first few Blackcaps will have reappeared too, and they will have started giving their much more complex, fast-paced, sometimes almost tropical-sounding song. Although their names don’t give any clue, Chiffchaffs and Blackcaps are members of the warbler family, a group of birds often associated with summer.

Although many warblers are summer visitors to our area, a few species now spend the winter here, and one fairly recent colonist stays in the UK year-round: the secretive but explosive-sounding Cetti’s Warbler. This species first reached Britain in 1961, and it took another decade before they began breeding in southeast England. It didn’t become established as a breeding species at BTO’s Nunnery Lakes until as recently as the mid 2000s. Chiffchaff and Blackcap are migratory species, with the most of those that breed here heading to sub-Saharan Africa (Chiffchaff) and the Mediterranean basin (Blackcap) in winter. Small numbers of each now winter in the UK. Research using BTO Garden BirdWatch data has revealed that ‘our’ wintering Blackcaps are actually birds from the central European breeding population that have changed their migration routes. The origin of our winter Chiffchaffs isn’t as well studied but may involve some UK-bred birds but probably many more from Scandinavia and elsewhere in northern Europe. Blackcaps are scarce around Thetford in winter but occasionally visit garden feeders. Two or three Chiffchaffs spent last winter at the Nunnery Lakes reserve. The reserve hosted a fourth warbler in winter 2021: a rare Dusky Warbler. Weighing less than a 50p piece, this insect-eating bird breeds no closer than Tomsk in Russia, a cool 3,000 miles from Thetford, and should have been spending the winter in southeast Asia! Unfortunately it favoured an area well away from the permissive paths but if it is still there when lockdown ends, BTO might be able to organise small group visits to look for it.

Nick Moran, BTO

'Dusky Warbler’ at the Nunnery Lakes by Neil Calbrade / BTO

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