Developments in satellite telemetry have recently allowed considerable progress in the study of long-range movements of large animals in the wild (1), but the study of the detailed patterns of their foraging behavior on a small to medium scale is not possible because of the imprecision of satellite telemetry systems (2). We used a miniaturized Global Position System (GPS) that recorded geographic position at 1-s intervals (3) to examine the exact flight pattern and foraging behavior of free-ranging wandering albatrosses (Diomedea exulans).

We deployed GPS loggers on breeding birds (3) either starting a long foraging trip in ocenic waters during the incubation period or searching for food close to the colony during the chick brooding period (Fig. 1, A and B, respectively). The distribution of ground speeds measured between 924,712 GPS locations was bimodal, with speeds varying from 0 to 9 km hour 1 (average 2.6 0.7 km hour 1) indicating that birds were sitting on the water (59.5% of foraging time) and speeds ranging between 18 and 135 km hour 1 (average 54.5 4.5 km hour 1) when birds are in flight. When in flight, birds frequently attained (8.2% of time) ground speeds higher than 85 km hour 1, the maximum travel speed predicted for wandering albatrosses (4, 5). Small-scale flight paths show typical zigzag patterns with continuous changes in flight speed according to the position of the bird with respect to wind (Fig. 1C). Because they rely extensively on wind conditions to reduce flight costs (4–6), wandering albatrosses have to adjust their searching behavior according to wind conditions, but at the same time they must adjust their foraging movements to increase the probability of encountering prey. The zigzagging small-scale movements added to the larger scale changes in overall direction affect overall the sinuosity of the track. The straightness index of the path, as measured by the ratio of straight-line distance between the initial and final positions of two consecutive landings relative to the actual path (7), was on average 0.512 (range 0.72 to 0.280, with 1.0 being a