Dartford Warbler

Listen to example recordings of the main vocalisations of Dartford Warbler, provided by xeno-canto contributors.

This species can be found on the following statutory and conservation listings and schedules.

UK Birds of Conservation Concern	Amber listed
Species of European Conservation Concern	Near Threatened
IUCN Red List of Threatened Species (global)	Near Threatened
Schedule 1 license required (to disturb)	Yes
Birds Directive Annex 1	Yes
Listed on the Annexes of	WCA(I,IV),WBD(I), Bern(III), Bonn(II)

The Dartford Warbler was first recorded breeding in the UK in 1773 near Dartford and numbers have subsequently fluctuated reaching a low point of 11 pairs in the early 1960s following two successive severe winters (Tubbs 1967). Since then numbers have increased substantially with an estimate of 3,214 breeding pairs at the time of the last national survey in 2006 (Wotton et al. 2009). The breeding range has recently expanded into East Anglia, central England and Wales (Balmer et al. 2013). Numbers again fell dramatically after the severe winters of 2008/09 and 2009/10 (Clark & Eyre, 2012) and after the 'Beast from the East' in 2018 (Eaton et al. 2020). Recent figures from the RBBP suggest that the population has not yet recovered to the levels seen in 2006, with 1,450 territories counted in 2019, although this count is likely to be slightly low as coverage is incomplete (Eaton et al. 2021).

Breeding Dartford Warblers are confined to southern Britain, in both coastal and inland locations. The latter comprise lowland heathlands but also upland sites on the moorland fringes. Breeding abundance is greatest on heathlands in Hampshire, Surrey and Dorset. Breeding range expansion beyond southern England has been recent and rapid, including the colonisation of Wales, central England and East Anglia.

From 1968–72 to 1988–91 the Dartford Warbler's range expanded by 52%. Since then it has expanded by 198%, accompanied by an increase in the proportion of occupied tetrads in core areas.

Dartford Warbler is a localised resident and recorded consistently throughout the year in suitable habitat.

View a summary of recoveries in the Online Ringing Report.

View number ringed each year in the Online Ringing Report

Maximum Age from Ringing	3 years 8 months 8 days (set in 1986)
Typical Lifespan	2 years with breeding typically at 1 year
Adult Survival	0.5±0.083

Wing Length	Adults	53.4±1.5 | Range 51–56mm, N=198
	Juveniles	65.3±1.4 | Range 63-67mm, N=38
	Males	53.8±1.4 | Range 52–56mm, N=137
	Females	52.3±1.4 | Range 50–54mm, N=53

Body Weight	Adults	9.40±0.7 | Range 8.40–10.4g, N=173
	Juveniles	12.3±1.9 | Range 9.50–16.1g, N=36
	Males	9.30±0.6 | Range 8.30–10.1g, N=120
	Females	9.60±0.8 | Range 8.50–11.0g, N=45

Feather measurements and photos on featherbase

Ring size	A
Field Codes	2-letter: DW | 5-letter code: DARWA | Euring: 12620

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Causes of change

It is likely that loss and fragmentation of heathlands has contributed to historical declines (Wotton et al. 2009). The recent range expansion of the Dartford Warbler is likely to have been aided by climate change, which may have enabled it to occupy sites further north and also at higher altitudes (Wotton et al. 2009, Bradbury et al. 2011). However, the species also remains highly susceptible to to population crashes caused by severe winter weather (Tubbs 1967, Clark & Eyre 2012). Surviving birds following the population crash on the Thames Basin and Wealden Heaths in 2008/09 and 2009/10 were in areas containing extensive dense gorse; hence habitat management could potentially influence the severity of population crashes (Clark & Eyre 2012), although this is speculative. Short-term recovery immediately after a population crash in central western France in 2008–09 only occurred on heathland and did not occur in nearby early-growth forest habitats (Jiguet & Williamson 2013), further highlighting the importance of core heathland habitats as a factor influencing population trends for this species.