The nests they build on icebergs are roughly circular consisting of stones and are typically 40 cm in diameter and up to 15 cm high. Chinstrap penguins usually lay two eggs, generally two to four weeks later than other pygoscelid species in the same area. The Chinstraps complete their breeding cycle by February or March and go back to the pack ice during winter. The eggs are hatched by both parents in shifts of 5 to 10 days. After 33 to 35 days the chicks hatch and they stay in the nests for 20 to 30 days before joining their crèches (groups of young penguins huddling together for warmth and protection). At 50 to 60 days of age, after molting, the chicks finally go to sea (Barham and Barham 1996, Hale 1999).