What they eat
Stomach contents from breeding Adélie penguins are collected each breeding season to work out the type and amount of food eaten. They eat a mixture of
- krill (Euphausia superba, E. crystallorophias)
- fish (mainly Pleuragramma antarctica) and
- amphipods
The food collected differs according to the location it is captured. Local meals (those within 20km of the colony) consist mostly of fish, amphipods and 'crystal krill' (E. crystallorophias), while offshore meals consist of mainly 'Antarctic krill' (E. superba) (Clarke et al. 1998). Meal sizes range from about 300g to 650g depending on the size of the chicks.
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 Adélie penguin with small chicks Photo: Lyn Irvine |
When the chicks are small, they are protected in the adult's brood patch, thus restricting foraging to one parent at a time. During this stage one parent is always attending the nest, while the other parent is at sea foraging for the chick's next meal. The chicks are fed an average of 300 g of food per meal at this time. Both local and offshore trips are conducted, delivering a mixture of fish, amphipods and krill to the chicks. Males frequently feed within 20 km of the colony where they collect fish, amphipods and 'crystal krill'. Most of the females travel offshore, to the edge of the continental shelf, and catch 'Antarctic krill'.
Large chicks (the crèche stage)
When the chicks are larger and no longer need the protection of their parents, they form groups called crèches. This allows both parents to forage simultaneously, providing more food for the chicks. Chicks in crèches receive an average of 650 g of food per meal. Most of these meals are 'Antarctic krill' that has been caught offshore at the edge of the continental shelf. If food is not found here, the adults will search further afield to collect food for their chicks.
 Adélie penguin with large chick Photo: Lyn Irvine |
The chicks' diet varies between the brood and crèche stages due to differing needs of the chicks as they grow. The diet also varies between seasons, according to food availability in the penguin foraging grounds. In some seasons there is a lack of food within the penguins' foraging range, causing meal sizes to be small. In other seasons, more fish and less krill are eaten because fish are easier to find. These changes can be caused by natural variations in the Southern Ocean ecosystem or man-made causes, such as harvesting of krill.
Seasons with high meal mass and a high percentage of krill in the diet are the most successful seasons for the penguins. Stomach content analysis over successive seasons allows us to investigate annual variations in diet and the effects of this on the breeding success of the birds.
