British Wildlife of the Week

Dartford Warbler

Britain is home to many small, skulking, inconspicuous warblers that superficially look very similar to one another. Drab, nondescript and unmemorable, they are the ultimate ‘little brown jobs’ – small seed- or bug-eating passerines of unexceptional shape or colouring. The wood warbler, willow warbler and chiffchaff, in particular, are very hard to tell apart from their physical appearance alone, providing a challenge for even expert birdwatchers. In fact, these three birds were once thought to be one species – the willow wren – until the 18th-century naturalist, Gilbert White, realised otherwise, based mainly upon their different and rather distinctive songs.

The Dartford warbler, however, is more attractive and much more recognisable: slate-grey above and deep red below, with a long tail that is often held cocked at a jaunty angle (the female is similarly patterned, but duller overall). Whereas most of our warblers are summer visitors, the Dartford warbler is one of just a handful that stays here year-round. The very first pair to be officially identified was shot on Bexleyheath, near Dartford, Kent, in 1773 – hence the bird’s name. The population there became extinct in the early 20th century, but the name nonetheless stuck.

The Dartford warbler is a strict specialist of lowland heaths, a habitat that is now much reduced and fragmented. Here in Britain, it was once found mainly in the heather-strewn landscapes of Dorset and Hampshire, but more recently it has expanded its range to Somerset, Devon, Cornwall, Norfolk, Suffolk and South Wales. It has even returned to Kent – though, sadly, not yet in Dartford.

However, southern England and Wales are at the very northern limit of this splendid warbler’s range. Essentially a bird of Mediterranean climes, it does not cope well with cold weather – and that can be problematic here in Britain. It suffers badly during prolonged periods of snow and ice, with local populations sometimes being wiped out altogether if the weather becomes too severe. In fact, the species almost died out in our country completely during the particularly harsh winter of 1962-63, when the national population dropped to less than a dozen pairs.

Although the Dartford warbler is still considered a rare British bird, its population in recent years has increased to more than 3,000 pairs, thanks to generally milder winters. In addition, many of the heathlands it occupies are now protected and often actively managed to help protect the species. Well-managed areas of gorse are very important for this bird as they provide cover for it to forage and shelter during cold weather. If you’re in the correct location and habitat, it often isn’t hard to spot a Dartford warbler, particularly in spring, when males can sometimes be clearly seen singing from the top of a gorse bush. In fact, given the bird’s attachment to this plant, and its current, inaccurate name, perhaps it would make more sense if it was called the ‘gorse warbler’ instead.

In the next British Wildlife of the Week, as we approach Easter, we’ll be looking at an animal that, over the centuries, has gone from being a major economic asset to being viewed as a serious pest – the rabbit.