Changes in king penguin breeding cycle in response to food availability
From 1991 to 1996 we investigated how the breeding cycle of King Penguins Aptenodytes patagonicus, in a small colony at South Georgia, was affected by variation in food availability between years. During the first (1992) and third (1996) of the three successful cycles studied, food was plentiful, whereas food availability was lower during the second cycle (1994). We found (1) the duration of breeding was longer (455 days) in 1994 compared to 1992 (437 days) and 1996 (438 days), (2) fewer birds made late breeding attempts in 1994 (38%) than in 1992 (88%) and 1996 (70%), and (3) those birds that made late attempts laid their egg later in 1994 (mean 16 March) compared to 1992 (19 February) and 1996 (21 February). We conclude that the breeding timetable changed in response both to the reduced availability of food in 1994 and to the subsequent improved conditions in 1996. This suggests that annual versus biennial breeding in King Penguins is dependent on the availability of food and the condition of the birds.