The effect of nest size on stone-gathering behaviour in the chinstrap penguin

Stone-collecting behaviour was studied in a colony of chinstrap penguins (Pygoscelis antarctica), to explore the likely importance of nest size. We randomly categorised nests as control or experimental. All nests were weighed at the beginning of the incubation period. In the experimental nests we removed stones constituting 50% of their initial weight, while in the control nests all the stones were returned after weighing. All nests were weighed again either prior to or just after hatching to determine likely changes in their weight. The mean weight increase of experimental nests was significantly higher than the mean weight increase of control nests. Size represents a property of the nest which individuals continuously monitor throughout the incubation/brooding period, reacting to changes in it by appropriate changes in stone-collecting rate. Accepted: 8 February 1999