The Great Frigatebirds are some of the most iconic inhabitants of the Galapagos Islands, especially when dramatically inflating their red gular sacs to attract mates. When not breeding or caring for young, however, they can be well out of sight — soaring up to 2.5 miles high in the air!
This would be impressive for any seabird, but the truly amazing fact is that frigatebirds have been tracked by GPS flying continuously (without any rest) for 56 days! Averaging 260 miles per day with 400 miles possible in perfect conditions, that would be a global round-trip in 95 days.
Most seabirds (albatrosses, petrels, etc.) glide for maximum efficiency. A frigatebird’s heart rate when soaring at altitude, flapping once every 6 minutes, is similar to when resting in a nest. Updraft currents allow them to ride upwards before swooping, in rollercoaster fashion.
Their fantastic flight durations are due to an extremely low wing load (body weight distributed across wing area) and the probable ability to sleep with only half a brain. Even fully asleep, they would glide 22 meters for every meter of descent, so just need to doze off at a sufficient height.
As for nutrition, such effortless travel requires so little energy that frigatebirds can go months without food. Hunting is usually done at the water’s surface, taking care not to wet their wings (or risk drowning). They can also nimbly snatch food from the mouths of other birds, in flight!