DARTFORD WARBLER (Sylvia undata)


This small, long-tailed Warbler has a very restricted range in the UK and is only found in small populations in Southern Wales and England. The Dartford warbler is dependent on low-lying, dry heathland with dense vegetation, such as gorse, for surviving cold winters. It is most often seen or heard singing a rattly, scratchy song from the top of gorse bushes.

Discover our Promises

Alert Status:


Estimated number of UK breeding

pairs: 2200

Listen to Dartford Warbler song:


The Dartford warbler is a small, long-tailed bird with a grey head and upper parts and red breast. It has a distinctive red ring around its eyes and white streaking can sometimes be seen on the throat. It blends in well with heathland vegetation but can be spotted at the top of gorse bushes while it sings during the breeding season. Males and females of this species look alike.

Average Length: 12-13 cm

Average Lifespan: 2 Years

Average Wingspan: 13-18 cm

BACK to a-z

Dartford Warbler diet

Dartford warblers eat mainly invertebrates but will eat berries outside of the breeding season when insect numbers are low. They will visit garden feeders if you live near a population.

How to feed: On garden feeders or tables.

What to feed: As they are insectivores, mealworms are the best thing to feed them.

Dartford warbler breeding and nesting information

The breeding season of Dartford Warblers starts in mid-march and lasts until mid-August and in many cases, they are monogamous, breeding with the same individual each year. They are a ground-nesting species and will often nest under the protection of dense heathland vegetation within 60cm of the ground. In this nest, the female will lay 3 or 4 eggs and incubate them for 12-14 days. Once hatched the chicks are fed by both parents until they fledge after 2 weeks. Once fledged the chicks will be looked after by their parents for a further fortnight. They will often produce 2 or 3 broods before the breeding season ends.

Threats to Dartford Warblers

Dartford warblers are very susceptible to cold weather and cold winters and low temperatures in 2009, 2010, and 2018 dramatically reduced the population. Climate change and unpredictable weather patterns could be detrimental to these birds as successive cold winters could lead to their extinction in the UK. This highlights the importance of building a large healthy population. While wildfires create an ideal habitat for this species, the increased frequency and intensity of these fires, due to climate change, could have detrimental impacts on the population. Large continuous areas of heathland are essential for the survival of this species and the loss of this heathland to fire and human expansion not only directly reduces the population but impacts its ability to recover. This species, as with many ground-nesting birds, is also negatively affected by disturbance, especially from walkers and their dogs.

How you can help

Keep your dogs on a lead, especially during the breeding season.

Avoid using harsh chemicals to remove insects from your garden.

Protect heathlands by petitioning to stop development and being very careful when walking in heathlands during the drier months.  

Fascinating Fact

A severely harsh winter in 1962/63 almost drove this species to extinction in the UK, with only 10 surviving pairs left.
Download Fact Sheet
Discover our Promises


BirdLife International (2023) Species factsheet: Curruca undata. Downloaded from http://datazone.birdlife.org/species/factsheet/dartford-warbler-curruca-undata. (Accessed: 21/08/2023)

British Trust for Ornithology (no date) Dartford warbler | BTO - British trust for ornithology. Available at: https://www.bto.org/understanding-birds/birdfacts/dartford-warbler (Accessed: 21/08/2023).  

Jiguet, F., & Williamson, T. (2013). Habitat-dependent population recovery in the Dartford Warbler Sylvia undata following a severe winter episode. Bird Study, 60(3), 391–398. https://doi.org/10.1080/00063657.2013.811463

Murison, G., Bullock, J. M., Underhill-Day, J., Langston, R., Brown, A. F., & Sutherland, W. J. (2007). Habitat type determines the effects of disturbance on the breeding productivity of the Dartford Warbler Sylvia undata. Ibis, 149(SUPPL. 1), 16–26. https://doi.org/10.1111/J.1474-919X.2007.00660.X

Van Den Berg, L. J. L., Bullock, J. M., Clarke, R. T., Langston, R. H. W., & Rose, R. J. (2013). Territory selection by the Dartford warbler (Sylvia undata) in Dorset, England: the role of vegetation type, habitat fragmentation and population size. Retrieved August 14, 2023, from www.elsevier.com/locate/biocon

mag glass