Monday, August 29, 2016

Frigatebirds Sleep While Flying

Scientists have recently determined that frigatebirds (Frigata magnificens), those acrobatic thieves of the tropical oceans, actually sleep while flying.  This explains in part how these birds are able to fly over vast expanses of water without landing.  Their feathers are not waterproof, so resting on the ocean's surface is not an option.  Frigatebirds can stay aloft for up to two months!  That is an impressive feat in itself, but hardly the record for avian aviation.  The Alpine Swift holds the record for longest recorded time in the air, an amazing 200 days as it hunts insects over West Africa, its winter range.  The albatross is also an accomplished long distance flyer, able to circle the globe in just forty-six days.  How these birds managed to accomplish such energetic feats of endurance was a mystery, but scientists suspected the birds are somehow able to sleep on the wing.  A study published this month in Nature Communications provides the hard data to support this hypothesis.

The frigatebirds on the Galapogos Islands are habituated to humans by now, so they are easy to capture for study.  Neils Rattenborg of the Max Planck Institute for Ornithology and his colleagues went there and captured fifteen birds in the interests of science.  Miniature electroencephalographs were implanted in the birds skulls that relayed brainwave activity to recorders.  From this data researchers could determine if the birds was asleep or fully awake.  An implanted accelerometer also told the researchers if the bird was moving or at rest.  What they found is even more stunning than the old lore about albatrosses being able to eat, drink and mate on the wing, landing only to lay their eggs

Frigatebirds sleep in short bursts of ten seconds throughout a day for a total of only 45 minutes while airborne over water.  On land they sleep an average of 12 hours each day.  While sleeping on the wing, frigatebirds do not completely shut down their brains.  Just as dolphins do, they keep half of their brains active apparently to avoid mid-air collisions.  Frigates are also careful to confine their sleep patterns to ascents on warm air thermals.  When descending they are wide awake.   Humans experience something similar when they have difficulty sleeping in unfamiliar surroundings like hotel rooms.  The brain does not completely shut off as an evolutionary adaptation against predators.  What research such as this shows is the importance and necessity of sleeping in general.  Even the great polymath Leonardo DaVinci allegedly slept 90 minutes a day in fifteen minute bursts every four hours.