Warming blamed for bird breeding errors

Netherlands researchers say climate change is leading birds to breed during periods of food shortages, causing population declines.

The study by scientists at Groningen University in Haren, Netherlands, centered on the migratory pied flycatcher, Ficedula hypoleuca. It found a large drop in bird population when prey and predator species vary in the rate at which they adapt to warmer conditions.

The pied flycatcher is a long-distance migratory bird, spending the spring breeding in the Netherlands, where caterpillars make up the bulk of its chicks' diet.

Lead author of the study, Christiaan Both, and colleagues looked at the effects earlier peaks in the caterpillar population, induced by higher temperatures, have had on the birds.

The researchers found pied flycatcher populations declined by approximately 90 percent in areas with the earliest food peaks, compared with 10 percent in areas with the latest food peaks. They attribute that decline to birds breeding during periods when food is scarce.

The authors suggest the mistiming is a result of the inability of the birds to adapt their rigid migratory journey to higher temperatures. The populations of other long-distance migrants might suffer similar effects, they added.

The study appears in the journal Nature.

Copyright 2006 by United Press International