Buzz
Migrating birds can travel non-stop for days, sometimes crossing vast oceans with no chance to rest. For years, it was only a theory that these birds manage to sleep during their journey, but now, scientists have observed migrating birds taking mid-flight naps, proving they don’t stay awake throughout their entire long-haul journey.
In a study published in Nature Communications, researchers investigated the brain activity of nine frigatebirds from the Galápagos Islands, a species that spends weeks or even months flying over the ocean without stopping. They attached specialized sensors, originally designed for homing pigeons, to each bird to track brain-wave activity using an electroencephalogram test and to monitor head movements with an accelerometer. The study followed the birds for a span of 10 days.
Much like dolphins, birds are capable of sleeping with one eye open and keeping half of their brain active, a behavior known to scientists for over ten years. This study has now shown that birds can also put part of their brain to sleep while flying.
Although the birds typically slept with only one hemisphere of their brain at a time, they sometimes allowed both hemispheres to rest while still in flight. When they did sleep mid-flight, it was usually at higher altitudes and in rising air currents, causing them to ascend as they snoozed. However, the ability to sleep doesn't necessarily mean they always do.
On land, these birds sleep about 50 percent of the time, both during the day and night. When flying, they typically sleep only at night for less than an hour, and their rest is lighter compared to when they're on solid ground. This is likely because, during migration, they need to stay alert for potential threats and food sources, prioritizing these over rest.
