The reproductive isolation between these populations, which live together for part of the year, is now stronger than that of other blackcaps
that are always separated from one another by distances of 800 kilometers or more, according to the researchers.
migrate to Iberia or north-west Africa for the winter, and haven't suffered the declines of warblers that winter south of the Sahara.
An RSPB spokesman said: "The blackcap
species in particular, a warbler, which would have migrated to southern Europe 20 years ago, is staying throughout winter.
A Richard's Pipit at Rhoscolyn was a good find, while the three Firecrests at RSPB Conwy have proved popular; Blackcap
and Chiffchaff were spotted too.
Twitchers, including 86,000 children, reported seeing a wide range of birds, from the common blackbird to the more unusual blackcap
in Conwy was a recent arrival from central Europe, but a ringer in Rhos on Sea reports fewer than usual so far this winter.
The thickets become home to linnets, yellowhammers and a whole range of warblers, including blackcap
, whitethroat, garden and willow warblers.
By examining clippings, Dr Stuart Bearhop of Queen's University, Belfast, showed how the European blackcap
could become two different species.
However, given the limited manpower to cover the area, high demand and the huge blackcap
population, the industry will continue to flourish without harsher punishments.
Birds which feature in the Dawn Chorus exhibition include swallow, chiffchaff, robin, blackbird, wren, yellowhammer, linnet, song thrush, chaffinch, pheasant, blue tit, and blackcap
Birdwatch has also shown that milder weather is encouraging more unusual species such as the blackcap
and chiffchaff to winter in North-East gardens," said RSPB regional spokesman David Hirst.
Good numbers of sand martins are passing through, with the first sedge warbler and blackcap
5 million birds were caught and killed by poachers in 2009, noting that between one and three other birds such as rare shrikes, small owls and hawks are killed for every blackcap
hopping around a Rhos-on-Sea garden last week wore a small aluminium ring on its leg.
Nick Walton, a promising engineering student, of Blackcap
Close, Washington, was just 17 when he was hit by the virus, which inflames the lining of the brain, for the second time in two years just two months ago.