Breeding dynamics of a gentoo penguin Pygoscelis papua population at cierva point, Antarctic Peninsula

Abstract

Aspects of the breeding biology of the Gentoo Penguin Pygoscelis papua were studied at Cierva Point, Antarctic Peninsula (64°09'S, 60°57'W). From a breeding population of 1044 pairs (85% with two eggs), 83% raised at least one chick to fledging. Survival in different subcolonies was neither correlated with perimeter-area ratio nor with distance to the sea. Chick mortality at the end of January 1993 was 23.9%, whereas for the 1991/92 breeding season it was 14.0%; for 1993/94, 23.9%; for 1994/95, 33.0% and for 1995/96 24.3%. By 17 February 1993, chick mortality was 32.3%. Chick survival was regressed against time for nine selected subcolonies, showing a high correlation between them. Covariance analysis among the regression line slopes showed a non-significant result (F = 0.42, P > 0.05). No significant differences were also observed when Tuckey's multiple contrasts test was performed on the proportions of surviving chicks in-between weeks (P > 0.05), showing a gradual mortality of chicks from egg-laying to créching. These results show that the Gentoo Penguin colony at Cierva Point contains a higher proportion of pairs rearing two chicks and a lower mortality rate than does the species at other maritime Antarctic sites. Average annual growth of the colony increased by 5.7% from 1991 to 1996, in contrast to the period 1954-1958 when the colony decreased by -2.3%. The low impact of the Argentinean station near the study area could account for this fact.