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...

SUMMARYPelagic birds, which wander in the open sea most of the year and often nest on small remote oceanic islands, are able to pinpoint their breeding colony even within an apparently featureless environment, such as the open ocean. The mechanisms underlying their surprising navigational performance are still unknown. In order to investigate the nature of the cues exploited for oceanic navigation, Cory's shearwaters, Calonectris borealis, nesting in the Azores were displaced and released in open ocean at about 800km from their colony, after being subjected to sensory manipulation. While magnetically disturbed shearwaters showed unaltered navigational performance and behaved similarly to unmanipulated control birds, the shearwaters deprived of their sense of smell were dramatically impaired in orientation and homing. Our data show that seabirds use olfactory cues not only to find their food but also to navigate over vast distances in the ocean. Supplementary material available online at

We report the first successful use of miniature Global Positioning System loggers to track the ocean‐going behaviour of a c. 400 g seabird, the Manx Shearwater Puffinus puffinus. Breeding birds were tracked over three field seasons during the incubation and chick‐rearing periods on their foraging excursions from the large colony on Skomer Island, Pembrokeshire, UK. Foraging effort was concentrated in the Irish Sea. Likely foraging areas were identified to the north, and more diffusely to the west of the colony. No foraging excursions were recorded significantly to the south of the colony, conflicting with the conclusions of earlier studies based on ringing recoveries and observations. We discuss several explanations including the hypothesis that foraging may have shifted substantially northwards in recent decades. We found no obvious relationship between birds’ positions and water depth, although there was a suggestion that observations at night were in shallower water than those during the day. We also found that, despite the fact that Shearwaters can be observed rafting off‐shore from their colonies in the hours prior to making landfall at night, breeding birds are usually located much further from the colony in the last 8 h before arrival, a finding that has significance for the likely effectiveness of marine protection areas if they are only local to the colony. Short sequences of precise second‐by‐second fixes showed that movement speeds were bimodal, corresponding to sitting on the water (most common at night and around midday) and flying (most common in the morning and evening), with flight behaviour separable into erratic (indicative of searching for food) and directional (indicative of travelling). We also provide a first direct measurement of mean flight speed during directional flight (c. 40 km/h), slower than a Shearwater's predicted maximum range velocity, suggesting that birds are exploiting wave or dynamic soaring during long‐distance travel.

Mate choice for major histocompatibility complex (MHC) compatibility has been found in several taxa, although rarely in birds. MHC is a crucial component in adaptive immunity and by choosing an MHCdissimilar partner, heterozygosity and potentially broad pathogen resistance is maximized in the offspring. The MHC genotype influences odour cues and preferences in mammals and fish and hence olfactorybased mate choice can occur. We tested whether blue petrels, Halobaena caerulea, choose partners based on MHC compatibility. This bird is long-lived, monogamous and can discriminate between individual odours using olfaction, which makes it exceptionally well suited for this analysis. We screened MHC class I and II B alleles in blue petrels using 454-pyrosequencing and quantified the phylogenetic, functional and allele-sharing similarity between individuals. Partners were functionally more dissimilar at the MHC class II B loci than expected from random mating (p ¼ 0.033), whereas there was no such difference at the MHC class I loci. Phylogenetic and non-sequence-based MHC allele-sharing measures detected no MHC dissimilarity between partners for either MHC class I or II B. Our study provides evidence of mate choice for MHC compatibility in a bird with a high dependency on odour cues, suggesting that MHC odour-mediated mate choice occurs in birds.

Petrels, albatrosses and other procellariiform seabirds have an excellent sense of smell, and routinely navigate over the world's oceans by mechanisms that are not well understood. These birds travel thousands of kilometres to forage on ephemeral prey patches at variable locations, yet they can quickly and efficiently find their way back to their nests on remote islands to provision chicks, even with magnetic senses experimentally disrupted. Over the seemingly featureless ocean environment, local emissions of scents released by phytoplankton reflect bathymetric features such as shelf breaks and seamounts. These features suggest an odour landscape that may provide birds with orientation cues. We have previously shown that concentrated experimental deployments of one such compound, dimethyl sulphide (DMS), attracts procellariiforms at sea, suggesting that some species can use it as a foraging cue. Here we present the first physiological demonstration that an Antarctic seabird can detect DMS at biogenic levels. We further show that birds can use DMS as an orientation cue in a non-foraging context within a concentration range that they might naturally encounter over the ocean.

SUMMARYDynamic soaring is a small-scale flight manoeuvre which is the basis for the extreme flight performance of albatrosses and other large seabirds to travel huge distances in sustained non-flapping flight. As experimental data with sufficient resolution of these small-scale movements are not available, knowledge is lacking about dynamic soaring and the physical mechanism of the energy gain of the bird from the wind. With new in-house developments of GPS logging units for recording raw phase observations and of a dedicated mathematical method for postprocessing these measurements, it was possible to determine the small-scale flight manoeuvre with the required high precision. Experimental results from tracking 16 wandering albatrosses (Diomedea exulans) in the southern Indian Ocean show the characteristic pattern of dynamic soaring. This pattern consists of four flight phases comprising a windward climb, an upper curve, a leeward descent and a lower curve, which are continually repeated. It is shown that the primary energy gain from the shear wind is attained in the upper curve where the bird changes the flight direction from windward to leeward. As a result, the upper curve is the characteristic flight phase of dynamic soaring for achieving the energy gain necessary for sustained non-flapping flight.