When I traveled to the Galapagos last year, I finally got to see a frigatebird (!!!), and I was disturbingly excited. Shortly after my trip (sadly), I came across a publication that documented great frigatebirds in Galapagos sleeping mid-flight (Evidence that birds sleep in mid-flight)! There is also a supplementary video to the publication, which shows footage of a frigatebird power napping mid-flight and a 3D flight trajectory animation. I thought that this article by Audubon, Scientists Finally Have Evidence That Frigatebirds Sleep While Flying, culled down the scientific article well.
Despite spending so much time near the water, frigatebirds cannot actually swim. They would drown if they tried to rest on the water. Hence, while at sea, these birds can end up staying airborne for up to two months! When do they let their brains recharge? Apparently, mid-flight! Researchers humanely implanted electroencephalographs into frigatebird skulls and measured the birds’ brain activity. Evidently, while flying, the birds can rack up about 45 minutes of sleep each day by taking ten-second power naps. On land, they bump up their naps to one minute at a time over the duration of the day, clocking in approximately 12 hours every day. Frigatebirds are able to sleep in the air because they frequently use “unihemispheric slow-wave sleep,” where one hemisphere of the brain is sleeping and the other is in a conscious/awake state. This type of sleep pattern is also seen in dolphins because they have to consciously breathe and monitor their environment for predators. However, bizarrely, frigatebirds can also shut off both sides of their brain while sleeping in the air but only for a few seconds at a time. I think this behavior is the one portrayed in the supplemental video file that I linked above because the duration of the bird’s fall is so short. Here is a Discovery News video, How Can Birds Sleep While They’re Flying?, that does a great job summing up the topic.
One of the most interesting things that I learned from researching frigatebird sleep patterns was that humans can utilize a semi-unihemispheric sleep pattern as well: Sleeping with Half a Brain. Scientists investigated the “first-night effect” seen in travelers. You are probably already familiar with this effect. It is the feeling of waking up groggy and unsatisfied after spending the night in an unfamiliar place. Essentially, research showed that part of the left hemisphere does not reach the same “depth” of sleep as the right hemisphere because it invokes a “vigilance response.” This study shed light on some of my sleep problems and hopefully yours too! Although you might be groggy, try appreciating the evolutionary history of your brain and that it was just trying to keep you from being eaten by a bear. 😀 I wish you a sleepy Sunday!