British gardens are in danger of losing one of their most tuneful visitors, the blackbird.
Although their numbers are plentiful now, blackbird populations may dwindle in the future, scientists believe.
The evidence comes from a new "family tree" showing how different bird species are related to each other.
Researchers found that British birds now in decline were clustered close together on the same branches of the tree.
Species not under threat today could face an uncertain future if they sit next to other species on the tree that are declining, say experts.
This is because closely related species share similar physical traits, some of which may make them less able to cope with climate change or changes to their habitat.
Lead researcher Dr Gavin Thomas, from the NERC Centre for Population Biology at Imperial College London, said: "This study threw up some interesting results. Numbers of the common blackbird are currently not perceived as threatened at all, however it has several close relatives, including the song thrush, that are experiencing severe levels of population decline.
"This could mean that populations of blackbirds in the UK are at risk of declining in the future." He said the family tree could act as an early warning for conservationists.
Dr Thomas added: "Pulling together the family tree was an important task as we now have a clearer insight than ever before into the evolutionary relationships of bird in Britain.
"The data clearly show a link between closely related birds and chances of population decline which could be useful for conservationists, although they will always need to take other factors, such as range contraction, into account."
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