Every spring and fall, billions of songbirds migrate thousands of miles. Most fly by night, yet are active during the day as well, raising the question of how they cope with little sleep. A new study, published online in the open-access journal PLoS Biology, suggests such nocturnally migrating songbirds simply skimp on sleep--but without the disastrous effects of sleep-deprivation seen in other animals. If researchers discover the mechanisms behind the birds' feat, it could prove useful for people that need to stay awake for long periods, such as pilots, and could shed light on mood disorders that disrupt sleep.

In the study, led by Ruth Benca of the University of Wisconsin, Madison, captive white-crowned sparrows were studied over the course of a year. These songbirds normally migrate approximately 2,700 miles each spring and fall between Alaska and Southern California, with flights typically occurring at night. In laboratory cages, during migratory seasons the birds get restless, with lots of hopping around and wing flapping. The researchers tracked the birds' movement in the cages and placed sensors on their brains to monitor their sleep patterns across the seasons. During the times the birds would normally be migrating, they slept about a third as much as usual and entered more quickly into REM sleep, the stage of sleep typically associated with dreaming in humans. At night, when the birds were active, the brain recordings showed they were fully awake. The researchers also put the birds through tests of their learning ability. During the migration periods, the birds performed normally on little sleep, but during the times of year when they were not migrating, sleep deprivation seemed to hurt the birds' performance.

These results suggest that migrating songbirds simply slash their sleep time rather than "sleepwalking" through their migrations. The mechanisms underlying the birds' ability to forego sleep are unknown, but further studies could shed
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Contact: Hemai Parthasarathy
hemai@plos.org
415-624-1205
Public Library of Science
13-Jul-2004

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