Page last updated at 00:50 GMT, Wednesday, 11 June 2008 01:50 UK

Bird family trees predict decline

By Richard Black
Environment correspondent, BBC News website

Blackbird. Image: John Harding / BTO
With starlings declining, the work hints at problems for the blackbird

A new genetic family tree of the UK's birds may help predict which will see their populations decline in future.

The family tree - or phylogenetic map - shows how closely species are related.

The scientist who compiled it, Gavin Thomas, found that populations of closely related species tend to undergo declines more or less in step.

Writing in the Royal Society's journal Proceedings B, he suggests that an apparently healthy species may be at risk if its relatives are disappearing.

So the decline in the song thrush, mistle thrush and starling could suggest problems ahead for the blackbird, which is currently thriving.

Likewise, falling numbers of linnets and bullfinch might suggest that the greenfinch is not as safe as its numbers would imply.

"This hasn't been tested on the ground, so we don't know at the moment whether the inferences we're making turn out to be true," Dr Thomas told BBC News.

It's going to be incredibly helpful in terms of doing some of our analyses
Rob Robinson, BTO
"And it could be some years before we do know - but I think it could be a kind of early warning system."

The population biologist from Imperial College London found that genetic sequences from almost all of the UK's birds had already been analysed and made public.

His study includes 249 species, 93% of those that breed or winter in the country.

The result is a giant family tree documenting where the various evolutionary lineages emerged and diverged and how closely individual species are related today.

"As far as I can tell, this is the first time that anyone has attempted a complete phylogeny, and I was quite surprised - you'd think that they'd be one of the first groups of animals to be done because of all the interest there is in them, at least in Britain," said Dr Thomas.

Bunting out

One of the organisations serving the UK public interest in birds is the British Trust for Ornithology (BTO), whose senior population biologist Rob Robinson described the phylogenetic tree as "a fantastic piece of work".

"It's going to be incredibly helpful in terms of doing some of our analyses," he said.

Segment of phylogenetic map. Image: Gavin Thomas / Royal Society
The phylogenetic map plots relationships between the 249 species
But he was less sure about the idea that a species' place on the evolutionary tree indicated its susceptibility to decline.

"The buntings, which are all declining, all live on farmland so you would think that anything that affects farmland would affect them all.

"But I'm not convinced that the decline in thrushes implies trouble for blackbirds, which appear more adaptable in terms of food supply."

The BTO is about to embark on a major study of UK blackbirds, which might shed more light on the true status of these apparently versatile feeders.

Numbers have been steady over the last 35 years, whereas starlings have declined by 70%, mistle thrushes by 40% and song thrushes by 50% (though numbers of the last may be recovering now).

Gavin Thomas agrees that this kind of research - on the ground, examining the habitats, the food and the behaviour - is top of the tree when it comes to forecasting prospects for birds.

But these days, in some countries, it may be easier to obtain genetic data than to find the resources and expertise to run the ground-level surveys.

In these cases, he believes, the genetic tree would not show conservation agencies when to begin remedial measures - but it might show them which species they should be keeping a closer eye on.

Richard.Black-INTERNET@bbc.co.uk



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