Brainy Birds Stay Behind

How can warblers and other long-distance migrants fly so far with such tiny brains? Some Blackpoll Warblers travel 10,000 miles from Alaska to Brazil and back each year. It may seem that their navigational abilities would require incredible intelligence. However, a recent study suggests that resident birds may have even more smarts than migratory birds since they have figured out how to find food year-round despite dramatic seasonal changes.

Resident songbirds have larger brains than long-distance migrants, according to the study by McGill University researcher Daniel Sol and colleagues (Proceedings of the Royal Society, June 2005). The researchers also found that the resident birds were more inventive foragers, suggesting a possible link between bigger brains and the ability to find food in northern winters.

The study suggested that resident songbirds have relatively large brains?perhaps because they must be innovative to find food during northern winters.

Although long-distance migrants must navigate across thousands of miles, they have smaller brains than resident songbirds with similar body size.

Sol and collaborators compared data on the brain sizes of 105 songbird species from Europe, the Middle East, and North Africa. After adjusting for the birds? body size, they found that long-distance migrants have smaller brains than short-distance migrants. Resident birds have the biggest brains of all.

The researchers also found that long-distance migrants tended to be less innovative in their foraging behaviors than short-distance migrants and residents. These results were based on data from 68 common breeding birds in the British Isles, where scientists have recorded extensive observations about the variety of foods the birds eat and their innovative approaches to finding food?such as using a twig to clear snow from a food source.

Sol et al. suggested that big-brained resident birds are able to develop new foraging techniques to help them find food in a wider variety of places than migratory birds. They point out that it is not yet known which came first—migration strategies or smaller brain size.

The bigger brains and behavioral flexibility of resident birds may be what enabled them to avoid traveling thousands of miles each year in search of food. The researchers speculate that innovative abilities may also make resident birds more resilient against environmental changes, such as habitat destruction or global warming.