Dartford Warbler

Another Schedule 1 bird the Dartford Warbler Sylvia undata named after the county which it was first discovered and where I was raised Kent. It was first identified in the 18th century near Dartford and is one of the few warblers to remain in it's breeding territory year-round. These birds are predominantly found in the south of the UK often in lowland heathland amongst gorse and heather. They are an illusive bird with a distinctive long tail dark grey slate body and reddish brown chest. The most striking characteristic has to the be it's red eyes surrounded by a pale ring. The BTO code for this species is an easy one it is DW. The best chance to see these birds is during the breeding season. They can often been seen flitting between shrubs perching on top of gorse bushes to sing. Their song is distinctive a rapid scratchy song (XC54914 Dartford Warbler (Curruca undata) :: xeno-canto). Defending their territory is key to breeding success, so they are very territorially and males will aggressively chase rivals away. 

Dartford warbler singing in a young holly tree

Dartford Warblers tend to nest between April and July in heathland shrubs and scrub. Their nests are small and cup-shaped, often well hidden in dense vegetation. They typically lay 3-5 eggs which are incubated for around 12-14 days. Both parents continue to feed the chick after they hatch until they fledge after 12-14 days. They feed primarily on spiders, insects and other invertebrates. In winter months, they have occasionally been recorded consuming berries and seeds. 

Dartford warbler with a spider in its mouth

Populations of Dartford warbler have fluctuated significantly due to habitat loss and harsh winters historically. At one point it was thought they were down to a few pairs left in the UK in the 1960s, however, numbers since have started to increase. However, it is still listed as Amber on the Birds of Conservation Concern (BoCC) 5 and it is a Schedule 1 bird so, their nests are protected from disturbance as well as destruction. Conservation efforts have sought to prevent further declines by restoring heathland and improving management of lowland areas within the UK. Heathlands important for wildlife are also popular amongst recreational users therefore, it is important that there are managed paths to prevent tramping and disturbance to these and other birds. Many heathlands have enforced leash laws to prevent the wild running of dogs during the breeding season. 

Dartford warbler in lowland heathland

If you are in the south of the UK and have heathland on your site chances are that Dartford warbler are also there. This means that if you are impacting their nesting and foraging habitat that you will need to undertake targeted surveys to determine territories present. Following Gilbert et al., 1998, three visits should be undertaken one in April to Mid-May, one in mid-late May and one in June for an hour after dawns onwards. See here for more information (Dartford-warbler-Gilbert-et-al.pdf) Following these the results of which can help inform the mitigation. Firstly you should encourage the developer/client to preserve the heathland which is the Dartford Warblers primary habitat. As well as restoring degraded heathland by removing invasive species and managing vegetation and restoring structural biodiversity. This can be done by creating a mosaic of gorse, heather and open areas to meet the species nesting and feeding requirements. It's important that these habitats are not fragmented and that populations do not become isolated from each other. 

Dartford warbler in calling in it's territory