title: Evidence that birds sleep in mid-flight.
abstract: Many birds fly non-stop for days or longer, but do they sleep in flight and if so, how? It is commonly assumed that flying birds maintain environmental awareness and aerodynamic control by sleeping with only one eye closed and one cerebral hemisphere at a time. However, sleep has never been demonstrated in flying birds. Here, using electroencephalogram recordings of great frigatebirds (Fregata minor) flying over the ocean for up to 10 days, we show that they can sleep with either one hemisphere at a time or both hemispheres simultaneously. Also unexpectedly, frigatebirds sleep for only 0.69 h d(-1) (7.4% of the time spent sleeping on land), indicating that ecological demands for attention usually exceed the attention afforded by sleeping unihemispherically. In addition to establishing that birds can sleep in flight, our results challenge the view that they sustain prolonged flights by obtaining normal amounts of sleep on the wing.
authors.affiliation: Avian Sleep Group, Max Planck Institute for Ornithology, Seewiesen 82319, Germany.
authors.forename: Niels C
authors.initials: NC
authors.lastname: Rattenborg
authors.affiliation: Avian Sleep Group, Max Planck Institute for Ornithology, Seewiesen 82319, Germany.|California Academy of Sciences, San Francisco, California 94118, USA.
authors.forename: Bryson
authors.initials: B
authors.lastname: Voirin
authors.affiliation: Department of Migration and Immuno-Ecology, Max Planck Institute for Ornithology, Radolfzell 78315, Germany.
authors.forename: Sebastian M
authors.initials: SM
authors.lastname: Cruz
authors.affiliation: Avian Sleep Group, Max Planck Institute for Ornithology, Seewiesen 82319, Germany.
authors.forename: Ryan
authors.initials: R
authors.lastname: Tisdale
authors.forename: Giacomo
authors.initials: G
authors.lastname: Dell'Omo
authors.affiliation: Institute of Anatomy, University of Zurich, Zurich 8057, Switzerland.|Institute of Evolutionary Medicine, University of Zurich, Zurich 8057, Switzerland.|School of Laboratory Medicine and Medical Sciences, Department of Physiology, Kwazulu-Natal University, Durban 4000, South Africa.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Lipp
authors.affiliation: Department of Migration and Immuno-Ecology, Max Planck Institute for Ornithology, Radolfzell 78315, Germany.|Department of Biology, University of Konstanz, Konstanz 78457, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wikelski
authors.affiliation: Institute of Neuroinformatics, University of Zurich and Swiss Federal Institute of Technology (ETH), Zurich 8057, Switzerland.
authors.forename: Alexei L
authors.initials: AL
authors.lastname: Vyssotski
mesh_terms: D000818:Animals; D001717:Birds / Q000502:physiology*; D001921:Brain / Q000502:physiology; D004569:Electroencephalography; D005260:Female; D005426:Flight, Animal / Q000502:physiology*; D012890:Sleep / Q000502:physiology*