Frigatebirds can sleep in flight
AI-generated conceptual natural-history image of a frigatebird gliding over the ocean at dusk. It does not depict an observed subject or prove sleep state. Prompt: “Vertical 4:5 natural history illustration of a great frigatebird soaring above the Pacific ocean at dusk, long narrow wings outstretched, forked tail and distinctive hooked bill, wind currents suggested subtly. Educational museum illustration with realistic bird anatomy, atmospheric sky and ocean. Do not depict it asleep, with closed eyes, or with brain imagery; it is a conceptual scene only. No text, labels, numbers, map, tag, or tracking device. Not documentary evidence.” Generated 2026-10-29; no external source or documentary role.
In a 2016 study, researchers recorded the brain activity of great frigatebirds flying over the Pacific Ocean. The birds could sleep with one brain hemisphere at a time or with both at once; in flight, they slept an average of about 0.69 hours per day—roughly 41 minutes. This result applies to the frigatebirds studied, not to all birds.