A vulnerable bird is experiencing an extraordinary population revival in the UK, RSPB figures have indicated.
Restoring heathlands is vital to the warblers' recovery, say the RSPB
The latest survey of Dartford warblers shows that numbers have soared by 70% since the last count in 1994.
The bird is vulnerable to changes in climate and two harsh winters left just 11 pairs of the bird in 1963.
It has returned to Wales, the Midlands and East Anglia and now there are more than 3,000 pairs - the highest tally for more than 40 years.
The Royal Society for the Protection of Birds says the recent rise in numbers - to an estimated 3,208 pairs from 1,890 in 1994 - is due both to milder winters and improvements in the conservation of heathland habitats.
But campaigners say more work is needed to protect and restore heathlands in order to cement the warbler's recovery.
"This survey is fantastic news for a very vulnerable bird, particularly because it has moved to higher ground not used by Dartford warblers for many years," said Simon Wotton, research biologist at the RSPB.
The warbler has been returning to its former ranges
"Warmer winters mean the birds are likely to push even further north but they can only do that if there are heathland sites available, which are protected from development.
"If the government is to help wildlife adapt to climate change it should be assigning more land for the creation of habitats to help birds like these."
But the bird remains vulnerable in some areas of its range and, on the Thames Basin heaths in Berkshire, Hampshire and Surrey, numbers fell by 40% from 2005 to 2006. The reasons for this remain unclear.
The RSPB said the losses emphasised the importance of protection and management of the warbler's existing strongholds.
It says the creation of new heathland sites is vital to help Dartford warblers expand their range.
The Dartford warbler survey was a joint effort between the RSPB, Natural England, Forestry Commission England and The British Trust for Ornithology.