The birds drastically reduced how long they slept during the times they would be migrating without any deterioration in their ability to function. I(n fact, that ability seemed to improve. However, if the birds were deprived of sleep at a time when they wouldn't be migrating, performance was impaired.
Another discovery made during the study was that sleep changes during the migratory period resembled sleep patterns experienced by people suffering from depression or bipolar disorder.
"We already know from human studies that people with severe depression and mania show characteristic changes in their sleep patterns, such as having insomnia and entering REM (rapid eye movement) sleep (the dream stage) too quickly after falling asleep," says Ruth Benca, professor of psychiatry at the University of Wisconsin Medical School and principal investigator of the study. "Finding this same pattern in the birds offers us an intriguing model for studying mechanisms for seasonal mood disorders, such as bipolar illness."
The researchers studied captive white-crowned sparrows and found that, during normal migration seasons, the birds became very restless and active in their cages, moving around and flapping their wings. Brain sensors showed the birds slept about one-third as long as usual. The brain recordings revealed the birds were fully awake at night and didn't appear to make up for the lost sleep during the day.
The next step will be to determine just how the birds accomplish the long flights on little sleep. Then, perhaps, researchers can determine a way for this ability to be of benefit to people suffering from sleep deprivation or who are victims of significant sleep problems.
