Brain sensors measure their sleep patterns continuously during migratory and non-migratory periods. During "migrating" times, they slept about one-third as much as usual and moved more quickly into REM sleep, marked by rapid eye movements. At night, when the birds were active, the brain recordings showed they were fully awake, and they did not appear to make up their lost nocturnal sleep with increased napping during the day.
Cognitive tests showed that, during the migration periods, the birds performed normally -- or even improved their ability to learn -- on little sleep; but during other times, sleep deprivation hurt their performance. The researchers theorize that migrating songbirds have developed the ability to apparently reduce their need for sleep temporarily, without suffering the consequences of sleep deprivation. While the researchers do not know how the birds do what they do, they are convinced that the birds' behavior sheds light on sleep processes in general and on some human disorders as well.
The Wisconsin researchers are also affiliated with the UW HealthEmotions Research Institute, created to study the scientific basis of emotion and health.