The neretic krill Euphausia crystallorophias and the ice fish Pleuragramma antarcticum contribute more than 95%, by mass, to the diet of Adélie penguins breeding on Ross Island. Occasionally Adélies also feed on amphipods and pelecypods.
Results show that diet varies during the year, from year to year, and is related to the percentage of foraging area covered by sea ice. Euphausia crystallorophias was consumed predominantly in a year of heavy pack-ice cover, and P. antarcticum was the most important prey in years, or periods within years, when little pack ice was present.
- Percent fish varied among years (F6,56 = 15.96, r2 = 0.544, P < 0.0001) and increased within year (by week, F1, 56 = 5.85, r2 = 0.033, P = 0.019)
- Percent fish was also related to the percent of the foraging area covered with pack ice (F1, 56= 4.36, adj r2 = 0.025, P = 0.041)
Fish is 20% more energetically valuable than krill and the increase in fish in the diet during chick raring may also indicate that the birds are actively targetting fish to meet the energy demands of their chicks, if the sea ice conditions are favourable.
For more information:
Ainley DG, Ballard G, Barton KJ, Karl BJ, Rau GH, Ribic CA, Wilson PR 2003. Spatial and temporal variation of diet within a presumed metapopulation of Adelie Penguins. Condor 105: 95–106 .
Ainley DG, Wilson PR, Barton KJ, Ballard G, Nur N, Karl B 1998. Diet and foraging effort of Adélie penguins in relation to pack-ice conditions in the southern Ross Sea. Polar Biology 20: 311–319.