Breeding biology of Magellanic penguins Spheniscus magellanicus at Golfo San Jorge, Patagonia, Argentina

YORIO, P.; GARCÍA BORBOROGLU, P.; POTTI, J.; MORENO, J.

Marine Ornithology

African Seabird Group

Año: 2001 vol. 29 p. 75 - 79

1018-3337

We studied the breeding biology of the Magellanic Penguin Spheniscus magellanicus at Golfo San Jorge, Argentina, during 1999. Egg-laying was relatively synchronous, with 88% of eggs being laid during the first two weeks of the laying period. Median laying date of the first egg was 14 October (range 6 October–1 November). Mean female mass at egg-laying was 3.54±0.35 kg. Mean clutch size was 1.91±0.29 eggs/nest and mean calculated egg volume was 227±21 cm3. The volumes of both eggs were positively correlated with female body condition at laying. The length of the incubation period was 39.8±1.7 days. Of the 280 eggs laid, 101 (36%) were lost and hatching success was 1.23±0.85 eggs per nest. Female body condition during egg-laying at nests where two eggs hatched was significantly higher than that at nests where only one or no eggs hatched. Chicks started to hatch on 15 November. No significant differences were found between sibling mass or morphological measurements at hatching. Ninety-one (53%) of the 171 hatched chicks were lost and breeding success was 0.56±0.67 chicks per nest. The mass of first chicks at 60 days of age was 15% larger than for second chicks (2.67±0.49 vs 2.32±0.63 kg). Female body condition and egg volume of both eggs were significantly correlated with laying date. Nests with no, one or two hatched eggs differed significantly with respect to laying date. Both clutch size and breeding success were not significantly associated with laying date.