Warming Throws Bird’s Timing Off

A tiny black-and-white songbird that flies from West Africa to the Netherlands to lay its eggs in mid-April is arriving too late for dinner, in what may be one of the subtler consequences of global warming, a new study says.

The number of European pied flycatchers has dropped 90% in some areas because the supply of caterpillars is peaking earlier, leaving the birds with no food for their chicks, according to results in this week’s issue of the journal Science.

Climate change may upset the ecological balance that supports commuters like pied flycatchers, which migrate 2,796 miles, the scientists said.

“We think this is the first time that people really have shown that climate change leads to population decline in such a bird species,” said Christiaan Both, lead investigator and a postdoctoral fellow at Groningen University in the Netherlands. “The ecosystems are getting mistuned.”

The researchers used annual population counts from 1987 to 2003 at 10 Dutch nest boxes.

The birds now lay their eggs 10 days earlier than they did two decades ago, but they still miss the caterpillar population’s height by six days, a previous study showed.

The birds are about 5 inches long and weigh about as much as three Hershey’s Kisses chocolates. They lay five to nine eggs that incubate for a little less than two weeks.

Both said the scientists were looking at how the flycatchers might adapt to a change in their food supply.

“If the birds in the Netherlands would arrive too late to profit from the short period of food availability,” he said, “they may continue migration to the north, say to Scandinavia, until they meet a site where their timing of arrival and breeding is still pretty much tuned to the timing of the caterpillar peak.”