Adelie Penguin Pygoscelis adeliae

The Adelie Penguin Pygoscelis adeliae occurs throughout Antarctica and the subantarctic islands, limited in distribution by shelf ice to the south and pack ice to the north (seldom found in open water). The Ross Sea area has the largest estimated breeding population at one million pairs; the total estimated population is 2,610,000 breeding pairs and ten million immature penguins. Breeding colonies are found on rocky islands, peninsulas, beaches and scree slopes wherever ice-free and accessible from the ocean. Adelie Penguins eat mainly euphausids (over 70% of diet) as well as some fish and squid. They catch their prey by diving in pursuit at ten to forty meters depth with an average dive duration of 1.4 - 1.9 minutes; they can dive down to a maximum depth of 170 meters. The average swimming speed on an Adelie Penguin is 2.2 - 4.6 kilometers per hour.

Adelie Penguins return to their breeding colony from September to October with egg laying occurring in October to November. Shallow nests lined with pebbles are built by both parents. Two eggs are laid with peak egg laying from November 10 - 15. Eggs are incubated by alternating parents for thirty-five days. After egg laying, the female leaves to forage and the male sits on the egg. The egg will be left to die by the male if the female doesn't return from her first foraging trip in time to relieve the male. Peak egg hatching is December 10 - 15. After hatching, chicks are brooded in the nest for 22 days, guarded by a parent. Then the chicks leave the nest to form small creche groups while awaiting the return of parents from feeding forays. When possible, skuas will attack and kill Adelie Penguin eggs and chicks; 9% of the eggs were lost to predation in one year at Cape Bird. At the Cape Bird rookery where these pictures were taken during the egg incubation period, Adelie Penguins make long foraging trips averaging 9-25 days in duration and up to one hundred kilometers away. During the chick rearing period, they make much shorter trips in duration and distance. Chicks are fed by their parents every 1-2 days until they depart from the colony at two months of age. The chicks molt by early February and then leave. 60-70% of the mating pairs retain the same partner each year. Adelie Penguins tend to be faithful to a specific nest site; males are 99% faithful to the nest site with females less so.

Adelie Penguins are most active between 4 am and 10am. Those in the Ross Sea Are have an annual mortality of 20%. Penguins were first discovered in 1520 during Magellan's circumnavigation; the expedition historian, Pigafetta, called them "strange geese"; the Adelie Penguin was first described in 1841.

1: The Penguins, Spheniscidae. TD Williams. Oxford: Oxford University Press, 1995. pp.169-178; 2: Penguin Biology. LS Davis & JT Darby. San Diego: Academic Press, 1990

Text ©Peter Brueggeman. Photographs ©Peter Brueggeman. Photographs may not be used in any form without the express written permission of Peter Brueggeman.