Birdfeeder evolution.

Wired reveals one strange way humans are changing the natural world – by accidentally creating new species:

“This is reproductive isolation, the first step of speciation,” said Martin Schaefer, a University of Freiburg evolutionary biologist.

Blackcap migration routes are genetically determined, and the population studied by Schaefer has historically wintered in Spain. Those that flew north couldn’t find food in barren winter landscapes, and perished. But during the last half-century, people in the U.K. put so much food out for birds that north-flying blackcaps could survive.

About 30 percent of blackcaps from southern Germany and Austria now migrate to the United Kingdom, shaving 360 miles from their traditional, 1,000-mile Mediterranean voyage….

From these groupings, subtle differences are emerging. The U.K. birds tend to have rounded wings, which sacrifice long-distance flying power for increased maneuverability. Now that they don’t need wide bills to eat Mediterranean olives in winter, their bills are becoming narrower and better-suited to summer insect diets. They’re also slightly darker.

Schaefer thinks it unlikely that humans will keep feeding the blackcaps long enough for them to become truly separate species, but it’s possible.

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