- Migratory birds travel vast distances as they move between
their summer and winter homes. Songbirds make the feat all the more impressive,
traveling mostly at night yet remaining active during the day, thereby
cutting back on opportunities for sleep. Research published today in the
journal PLoS Biology indicates that during migration season the creatures
manage to survive on less shuteye without deleterious effects often observed
in other sleep-deprived animals.
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- In the wild, white-crowned sparrows travel some 2,700
miles between Alaska and Southern California twice annually. Ruth Benca
of the University of Wisconsin at Madison and her colleagues observed captive
animals for a year, tracking their sleeping patterns and movements. During
migratory season, the caged birds became restless and exhibited increased
hopping and wing flapping. In addition, the creatures slept only about
a third as much as usual and entered REM sleep--the type associated with
dreaming in humans--more quickly than they did during other times of the
year. At night, while their free-living counterparts were flying, the captive
animals were fully awake and performed normally on learning tests, which
suggests that the birds don't "sleepwalk" during their migrations.
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- The scientists determined that lack of sleep during nonmigration
seasons does negatively affect the birds, however. This suggests that they
have an unprecedented ability to reduce sleep specifically during migration
without deficits in their cognitive function. Just how the creatures accomplish
this remains unclear. The authors note that "understanding the mechanisms
that mediate migratory sleeplessness may provide insights into the etiology
of changes in sleep and behavior in seasonal mood disorders, as well as
into the functions of sleep itself."
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