Blackbirds and greenfinches have been identified as the next native birds likely to suffer a devastating population slump.

An evolutionary family tree has shown they are closely related to species of birds that have already undergone a severe decline.

Animal family trees have been shown previously to pinpoint amphibian species at risk but it is the first time that one has been created for British birds.

Despite being common today, much like the house sparrow 40 years ago, blackbirds are at risk of a downturn in fortunes because they have strong genetic similarities to starlings and song thrushes, which have recently declined in number.

Greenfinches are at risk because they are closely related to the linnet and bullfinch, which have both suffered severe declines. Ptarmigan are also in danger because they are related to the struggling black grouse and grey partridge.

Gavin Thomas, of Imperial College, London, drew up the evolutionary chart. He said that being closely related meant that animals shared similar physical traits, such as habitat preferences or reproductive rates, that could make them more vulnerable to environmental changes.

He said the phylogenic chart, which covered 249 species of birds in Britain — more than 93 per cent of the breeding and winter species — offered an early warning of future population crashes.

In his report, published in the journal Proceedings of the Royal Society B: Biological Sciences, he concluded: “The species that are threatened due to population declines are phylogenetically more closely related than expected by chance alone.”

Further analysis should, he said, enable conservationists to identify the factors that prompt declines.

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