The dark, long-tailed, vinous-breasted, resident Dartford Warbler is a rare breeding bird in Britain, with a population of less than 2,000 pairs. It inhabits heathland with gorse and heather. Although skulking within such habitat it does occasionally sing from the tops of gorse sprays. The nest is concealed within deep cover.
Historically Dartford Warblers have been confined to southern England, mostly found in Hampshire and Dorset, where numbers were reduced during severe cold winters but recovered in milder following years. The successive “Arctic” winters of 1961–62 and 1962–63 drastically reduced the population, with only 11 pairs known to have survived. The mild winters which have since prevailed enabled them not only to steadily increase but also to expand their range, principally to the west.
In Wales they were breeding in Gwent by 1998, in Glamorgan by 2000 and in the first year of the Pembrokeshire Breeding Birds Survey of 2003-07 up to six pairs were confirmed to be breeding at one locality. By the end of 2007 they had been found in eight tetrads, with a total population of 13 – 15 pairs. All were in lowland areas, none having yet been found in uplands as has been the case in Somerset, Devon and the Brecon Beacons.
Graham Rees
Fieldwork 2003-07 (based on 490 tetrads)
Red = breeding confirmed
Orange = breeding probable