Among birds, the Procellariiform seabirds (petrels, albatrosses, and shearwaters) are prime candidates for using chemical cues for individual recognition. These birds have an excellent olfactory sense, and a variety of species nest in burrows that they can recognize by smell. However, the nature of the olfactory signature--the scent that makes one burrow smell more like home than another--has not been established for any species. Here, we explore the use of intraspecific chemical cues in burrow recognition and present evidence for partner-specific odor recognition in a bird.

The distribution of foraging activity for female Antarctic fur seals was investigated at Cap Noir (49°07' S, 70°45' E), Kerguelen Island in February 1998. Eleven females were fitted with a satellite transmitter and time-depth recorder. The 2 data sets were combined in order to locate diving activity of the seals. The occurrence of fish in the diet of the seals was investigated by the identification of otoliths in 55 scats collected at the breeding colony during the study period. Oceanographic variables were measured simultaneously by direct sampling and satellite remote sensing. The mesopelagic fish community was sampled at 20 stations along 4 transects, where epipelagic trawls were conducted at night at 50 m depth. We then investigated, using geographic information systems, the relationship between the spatial distribution of diving activity of the seals and oceanographic variables (sea surface temperature, surface chlorophyll concentration, prey distribution and bathymetry) at the same spatio-temporal scale. An inverse relationship was found between the main fish species preyed on by the fur seals and those sampled in trawl nets. However, diving activity of the seals was significantly related to oceanographic conditions, forage fish distribution and distance from the colony, although these relationships changed with the spatial scale investigated. A probabilistic model was developed for the distribution of diving activity, which predicted where females should concentrate their foraging activity according to the oceanographic conditions of the year, and where breeding colonies should be located.

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 Ϫ1 (average ϭ 2.6 Ϯ 0.7 km hour Ϫ1 ) indicating that birds were sitting on the water (59.5% of foraging time) and speeds ranging between 18 and 135 km hour Ϫ1 (average ϭ 54.5 Ϯ 4.5 km hour Ϫ1 ) when birds are in flight. When in flight, birds frequently attained (8.2% of time) ground speeds higher than 85 km hour Ϫ1 , 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 ϭ 0.72 to 0.280, with 1.0 being a straight-line course). The ratio was not affected by wind direction with respect to overall route direction because birds always have a zigzagging flight when they move with head, cross, or tail winds [F ( 2,15 ) ϭ 0.893, P ϭ 0.429]. Predators foraging in a heterogeneous environment are expected to adjust their search pattern (e.g., the straightness of their route, the flight speed, and/or turning rate) to increase the probability of encountering prey (8), but this prediction is generally impossible to test on marine animals. We tested whether birds modified the straightness of their movements according to the season or the marine habitat visited. The straightness index of the track was lower during the brooding period (0.41 Ϯ 0.1), when birds are searching for food close to the colonies (9), compared with the incubation period (0.588 Ϯ 0.09; Kruskal-Wallis, U ϭ 4.0, P ϭ 0.028), when birds are only moving away from the shelf a...