THE LATE BIRD SLEEPING IN MOVIE

Expanded views (bottom) show wakefulness characterized by low-amplitude, high-frequency EEG activity in both hemispheres, infrequently punctuated by isolated high-amplitude, slow waves (*), and SWS characterized by continuous high-amplitude, slow waves, in this case, primarily in the left hemisphere. Brief episodes of dropping (green bars) occur after this episode of sleep. ( a) Recording of head acceleration in three dimensions (sway, surge and heave) and electroencephalogram (EEG) activity from the left (L) and right (R) hemispheres showing the transition from wakefulness to SWS following the cessation of flapping (red bars). ( e) Altitude, ground speed and airspeed (computed from the GPS data in ( d)), tangential and centripetal (radial) low-pass filtered acceleration, and the absolute value of total acceleration (measured by an accelerometer) for the flight in ( d).

THE LATE BIRD SLEEPING IN MOVIE

( d) High temporal resolution (1 Hz) 10 min flight trajectory recorded with GPS from a frigatebird (see Supplementary Movie 1 for 3D visualization) showing the circling (soaring) and straight (gliding) flight modes typical of Fregatidae (Methods). Ocean depth (m) is coded with grey scale. The Galapagos Islands are outlined with black lines and the study site (Genovesa) is marked by a star. ( c) All GPS tracks for individual birds coded with different colours. ( b) Overhead view of a great frigatebird skull showing (1) the position of the cranial bulge (shaded grey) overlying the hyperpallium of each hemisphere, (2) the position of the epidural electrodes (red dots, EEG green dot, ground) and (3) the data logger (black rectangle) just posterior to the naso-frontal hinge (arrow).

A back-mounted GPS logger recorded position and altitude. ( a) Great frigatebird with a head-mounted data logger for recording the electroencephalogram (EEG) from both cerebral hemispheres and head acceleration in three dimensions.

The late bird sleeping in