Foraging behaviour during chick rearing of sympatrically breeding Humboldt and Magellanic penguins in southern Chile


A. Raya Rey, Puetz K., Hiriart-Bertrand L. et al 2010. 7 International Penguin Conference (Oral).

Humboldt and Magellanic penguins breed sympatrically at Puñihuil Islets in Chile. As these are two closely related species with comparable food requirements, we studied the degree of resource partitioning. Sex- and species-specific foraging areas and diving behaviour were investigated during the chick-rearing period using GPS-TDlog and TDRs. Penguins performed mainly daily foraging trips close to the colony. Maximum distance to the colony did not significantly differ between species and sexes (average 8.8 ± 3.2 km). Foraging trip and diving characteristics also revealed no significant interspecific differences. The major differences observed were sex-specific, independently of species. Trip duration (range: 2.3 to 26 hs) was shorter in females while the diving rate (range: 13 to 48 dives per hour) was higher than in males. Mean dive duration (range: 45 to 91sec) was higher in males than in females which is in accordance with the slight sexual dimorphism found in these species. Mean dive depth ranged from 9 to 37 m, maximum depth attained was 70 meters and maximum dive duration recorded was 270 s. Interestingly, all birds showed a high value of intra depth zone dives (more than 70%), indicative of benthic feeding. In contrast to these findings, previous studies indicated a high amount of pelagic fish in their diet. Magellanic penguin’s males performed less intra depth zone dives, this being the only sex-species difference. In conclusion, in areas where food is not limited, variations in the diving behaviour are likely to be more sex-specific rather than interspecific.