Migrating Birds Forgot about Their Trip

A common migratory bird slightly smaller than a sparrow, known as the pied flycatchers, hasn't made the trip back to Europe soon enough to catch its spring meal. This is a result of climate change. The discovery shows how complicated the effects of shifting seasons are and how they impact on predators and prey.

The migratory birds fly thousands of kilometers each spring from Africa to Europe, where they breed. In 2001, scientists with the Netherlands Institute of Ecology had found that the flycatchers arrived in Europe too late to have much time to breed. Now, Christiaan Both, an evolutionary ecologist from University of Groningen, and his colleagues measured how many caterpillars were available for the birds to eat by weighing the insects' droppings. Scientists found that due to the earlier springs, the number of caterpillars peaked 16 days earlier than usual.

But some of the birds are breeding only a week earlier than they used to - and thus their young are missing out on many meals. "It's impossible for them to predict when the spring starts in Europe," says Both.

Researchers studied nine flycatcher populations over 20 years and found that their numbers declined by a stunning 90%. Other better-synchronized groups of birds have declined only by 10%. Insofar nobody knows why some of the pied flycatchers are leaving Africa sooner than the others. Both also wants to track the birds to see if they are adapting by migrating to northern parts of Europe.