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Résumé :
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[(1) The food of grey-faced petrels in December comprises approximately 58% Cephalopoda, 28% fish, 12% Crustacea and 2% Tunicata by weight. Little seasonal variation was found but data on this aspect were very limited. Over 95% of the food is taken beyond the continental shelf. The presence of remains of big squid (> 1 kg) and big fish in samples indicates that it scavenges, but at least 90% of cephalopods weighed less than 200 g and were probably taken alive. Of prey presumed captured, few would be available in daylight at the sea's surface where these petrels obtain their food. (2) This petrel apparently takes 80% or more of its food at night, including nearly all live-captured prey. Of the pelagic families identified thirteen of the fourteen cephalopod, five of the six fish (three tentative) and six of the eight crustacean families do not normally occur within 150 m or more of the surface by day. They belong to, or are associated with, the acoustic (deep) scattering layers which have a diurnal vertical migration, ascending towards or into surface waters at dusk and descending at dawn. (3) A number of these prey, especially some squids and crustaceans, have not so far been detected vertically migrating or coming right to the surface at night. Many species of Cephalopoda taken have yet to be collected in the south-west Pacific, and two Crustacea have been added to the regional list. (4) About 90% of its prey are bioluminescent. An even higher proportion of those likely to be captured at night can emit light, which may well be an important means of detection. (5) Adults may forage up to 600 km or more from the breeding colony while obtaining food for chicks. (6) Comparisons with what little is known of the diet of other Procellariiformes of similar size indicate many similarities among Pterodroma and Fulmarus species, but some contrasts with Puffinus species.]
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