UW-Madison Scientists Find Sleep Changes During Migration Make Birds Hyperactive
Madison, Wisconsin - Birds in the wild can fly long distances on very little sleep during the spring and fall migrations, but they also become more impulsive.
University of Wisconsin School of Medicine and Public Health researchers, writing in the open access journal BMC Neuroscience, found that during the migratory seasons, sparrows become much less able to resist temptation.
During migratory periods, the birds slept very little - as much as 60 percent less than normal - and became more impulsive. But Benca says sleep loss itself was not entirely to blame for their impulsivity.
"In the laboratory, we've previously found that birds in the migratory state can learn to peck at a switch for food just as well as birds during non-migratory periods," she writes. "In contrast, in this study we demonstrate that, relative to birds in the non-migratory state, they struggle to learn when not to peck."
The study looked at the effects of migratory status and sleep deprivation on the ability of a group of sparrows to master the urge to peck at a food-giving button. If they were able to delay pecking for a 20-second interval, they were rewarded with food.
Birds that were deprived of sleep or were on a summer schedule, during which they also naturally sleep less, mastered the correct response. But birds on a migratory sleep schedule could not learn the task and pecked impulsively at the button.
This apparent hyperactivity during the migratory period may be linked to the fact that the migrating birds' sleep periods become divorced from the light/dark cycle they follow during the non-migratory seasons of summer and winter. Separate experiments showed that sleep deprivation alone does not cause this loss of control. Short sleep duration in the summer is also not associated with increased impulsivity.
"It is conceivable that the fragmentation of migratory sleep plays a role in these birds' loss of inhibition," Benca says. "Whether the inability to inhibit pecking is related to a general failure of inhibition, a distorted sense of time, inattention to salient cues, or some other underlying mechanism is not entirely clear."
Benca, a professor of psychiatry and psychology who also treats people with sleep disorders, concludes, "the observed seasonal changes in sleep patterns and behavior in the migratory sparrow raise interesting questions regarding possible correlates of these behaviors in other species, including humans. Some of the seasonal changes we see in the sparrows are similar to those in humans with bipolar disorder, for example."
Date Published: 07/28/2010