Seabirds can potentially feed over a wide range at sea. Recently, feeding area fidelity and individual differences in feeding area have been reported in several species of inshore and offshore feeding seabirds. Environmental factors and proximate mechanisms inducing these behaviors were reviewed. Feeding area fidelity has been reported among seabirds feeding at stable and suitable feeding sites such as upwelling areas caused by fronts, tidal cycles or sea bottom topology. Birds feeding on predictable demersal fish also seem to show feeding area fidelity. Individual birds tend to visit the same site during consecutive foraging trips, indicating that the birds use memory to locate feeding sites. The hypothesis predicting that individual feeding area fidelity promotes high feeding efficiency hence high reproductive success has to be tested. To examine how spatial and temporal prey predictability affect variation in feeding area and its fidelity, scale dependent and comparative studies based on appropriate statistical techniques to evaluate feeding area fidelity are required.

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Technical development such as radiotelemetry, data logger and stable isotope analyses have enabled studies of individual variation in foraging ecology of seabirds. Individual variation in dive depth, foraging site, diet and foraging habitat are often observed in Phalacrocoracidae. Individuals feed solitarily but sometimes join large foraging groups. Some birds migrate but others are resident. Individual birds show high flexibility in foraging behaviour according to food availability. Thus foraging site fidelity and flexible foraging behaviour are both important aspects of cormorant foraging ecology. The stable isotope ratio in appropriate tissues gives us useful information on the food cormorants ate during certain time windows. To understand individual-based foraging strategies and population dynamics, and also to provide adequate plans for conservation and management of cormorants, further research is necessary on the factors determining individual variation in foraging ecology.

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Seabirds usually rely on food resources that are distant from their breeding colony, yet they have to return to the colony regularly for breeding. Due to this basic constraint on foraging and reproduction, the individual variation in foraging ecology of seabird parents, such as diet choice, foraging effort or efficiency, may have profound consequences in their reproductive performance. Studies examining the link between seabird foraging and reproduction at the individual level are briefly reviewed in this paper. The diets of individual seabirds have been examined by using conventional food/pellet sampling or direct observation techniques, but also recently by using stable-isotope analysis. Individuals feeding more on energy-rich prey tend to have higher reproductive output although studies have been conducted mostly on gulls and further work is required on other groups of seabirds. The behaviour of individual seabirds foraging at sea has been studied recently by using animal-borne electronic devices, such as time-depth recorders or satellite/ VHF telemetry. Recent studies have quantified individual variation in the foraging effort of two species of penguins and found no effects of foraging effort on the growth rate of chicks, suggesting the importance of individual variation in foraging efficiency for reproductive success. Studies on both diet and behaviour of individual seabirds suggest that foraging efficiency, rather than foraging effort, is the key to high reproductive performance of individual seabirds. Sources of individual variation in foraging efficiency may include differences in morphology, learning histories or competition with other individuals. Further studies on foraging ecology of individual seabirds in relation to their energy allocation and reproductive performance will make it possible to explore the connection between foraging and life-history strategies of seabirds.

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Sixteen Osprey Pandion haliaetus nests were found during the 2002 breeding season in eastern Kagawa Prefecture (34°15-24′N, 134°5-17′E), Shikoku, Japan. Fourteen nests were situated on or near the tops of dead or alive pine trees Pinus spp, and two on the flat tops of radio towers. Thirteen of them were found within a small (4.5×2.5 km) hilly area.

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Streaked Shearwaters Calonectris leucomelas breed along the northwest Pacific coast, and winter in Australia and Southeast Asia. Previous studies at nesting sites on islands off the Japanese coast have indicated that males and females give different mating calls. This research, implemented at a breeding colony on Kanmuri Island, Kyoto Prefecture, showed that there were differences in the external measurements of Streaked Shearwaters giving low-pitch and high-pitch vocalizations. A discriminant function: D=216.400-2.318×THL-4.074×BW+2.007×NAL-1.929×BD, where THL is total head length, BW is width of bill at anterior edge of nostril, NAL is nalopsi and BD is depth of bill at anterior edge of nostril, was derived from external measurements of adult shearwaters giving low-pitch (41 birds) and high-pitch (41 birds) calls. D was positive for the birds with low-pitch calls and negative for the birds with high-pitch calls. This function proved reliable for 97.6% of the low-pitch individuals and for 95.1% of the high-pitch individuals, thus vocalization may be a useful means of sex identification in the field.

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