Abstract: Although penguins are key marine predators from the Southern Ocean, their migratory behavior during the inter-nesting period remains essentially unknown. Here, we report for the first time the winter foraging movements and feeding habits of a penguin species by using geolocation sensors fitted on penguins with a new attachment method. We focused on the macaroni penguin Eudyptes chrysolophus at Kerguelen, the single largest consumer of marine prey among all seabirds. Overall, macaroni penguins performed very long winter trips, remaining at sea during ~6 months within the limits of the Southern Ocean. They departed from Kerguelen in an eastward direction and distributed widely, over >3.106 km². The penguins spent most of their time in a previously unrecognized foraging area, i.e. a narrow latitudinal band (47-49°S) within the central Indian Ocean (70°-110°E), corresponding oceanographically to the Polar Frontal Zone. There, their blood isotopic niche indicated that macaroni penguins preyed mainly upon crustaceans, but not on Antarctic krill Euphausia superba that does not occur at these northern latitudes. Such winter information is a crucial step for a better integrative approach for the conservation of this species whose world population is known to be declining.

Abstract: Among procellariiform seabirds, many burrowing petrels show good olfactory abilities especially in recognising their nest. In particular, it has been reported that Antarctic prions (Pachyptila desolata) discriminate their own and their mate’s odours and, in Y-maze experiments, prefer the odour of a conspecific bird to their own. While traditionally examined from the perspective of homing mechanisms, these recent results have drawn attention to the possible use of chemical signals in birds’ social behaviours. Indeed, the life history of petrels suggests that a mate choice mediated by olfactory mechanisms may have evolved in this group to ensure genetic compatibility. This study was undertaken to validate and extend results obtained on petrels’ olfactory discrimination capabilities. Following the Y-maze experiment protocol, blue petrels (Halobaena caerulea) were offered three different choices: (1) mate versus conspecific’s odour, (2) own versus mate’s odour and (3) own versus conspecific’s odour. We discovered that birds prefer the odour of their mate not only when presented against conspecific’s odour but also against their own. We further verified that blue petrels also avoid their own odour when presented against conspecific’s odour. Our results confirm that olfactory discrimination in burrowing petrels goes beyond selfrecognition and that self-odour avoidance may be widespread. We use two mutually non-exclusive behavioural frameworks for the interpretation of our results, homing and mate choice, and explain why homing mechanisms cannot account for all of our observations. This study opens the door to further research on olfactory mechanisms that, in petrels, might mediate individual recognition and mate choice.