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How innocent garden feeders are altering birds' evolution
By Daily Mail Reporter
Last updated at 9:19 PM on 03rd December 2009

One population of blackcaps has already begun to split into two separate species because of kindly British bird-lovers, scientists have found. One population of blackcap birds has already evolved into two different species
Over less than 30 generations, birds visiting UK gardens in winter have evolved different-shaped wings and beaks.
In time, they could eventually become a distinct species, say researchers - although in practice this was unlikely.
The birds breed side-by-side in the same central European forests, but began to follow different winter migration routes after some discovered rich pickings in the UK.
Eventually they divided into two reproductively separate groups.
One continued to fly south for the winter, migrating to Spain to forage for olives and other fruits.
The other got into the habit of flying a shorter distance north-west to the UK. Despite being colder, this had the advantage of a ready supply of food from garden bird tables and feeders, and meant a quicker journey.
Dr Martin Schaefer, from the University of Freiburg in Germany, who led the study, said: 'The new north-west migratory route is shorter, and those birds feed on food provided by humans instead of fruits as the birds that migrate south-west do.
'As a consequence, birds migrating north-west have rounder wings, which provide better manoeuvrability but make them less suited for long-distance migration.'
They had also developed longer, narrower bills adapted to bird feeder food from pet shops and less suited to fruit-eating.
'Our study documents the profound impact of human activities on the evolutionary trajectories of species,' said Dr Schaefer. 'It shows that we are influencing the fate not only of rare and endangered species, but also of the common ones that surround our daily lives.
'This is a nice example of the speed of evolution. It is something that we can see with our own eyes if we only look closely enough. It doesn't have to take millions of years.'

The research is published today in the journal Current Biology.

Dr Schaefer thought it unlikely that the two groups of blackcaps would ever actually become separate species, because the habits of humans tended to change over time.
However the findings showed the initial steps of speciation could occur very quickly in migratory birds.
The blackcap, Sylvia atricapilla, is a warbler with a distinctive black or red-brown crown and forehead. It is a little smaller than a house sparrow.
During the breeding season the birds root around shrubs and trees for insects, spiders and caterpillars, but at other times they normally feed on fruit.
Although blackcaps are mostly summer visitors, increasing numbers are now overwintering in the UK.
Experts believe both milder winters and an abundance of food have drawn the birds to Britain.
Wintering in the UK instead of Spain or Africa uses up less energy and allows the birds to return to their breeding grounds sooner.
Blackcaps enjoy bird feeder balls and bars made from suet, seeds, nuts and cereals, especially those impregnated with dried flies.