During the course of our study we have learned a lot about Adélie penguins. Below is a summary of our key findings.
- The Ross Sea is one of the most biologically productive regions of the Southern Ocean. More than 38% of all Adélies are found here, even though this region has less than 10% of the total Antarctic coastline.
- There are 38 Adélie penguin colonies in the Ross Sea region, 11 previously unreported, with over one million breeding pairs of Adélie penguins.
for more information on Adélie penguin census data
- The distribution of Adélie colonies in the Ross Sea Region is controlled by the location of polynyas. These ice-free areas allow access to breeding sites and also provide food early in the spring when the sea is still frozen.
- Our population monitoring indicates Adélie penguins are increasing in the Ross Sea region and that there is considerable annual variation in numbers attempting to breed.
- Modelling our data has indicated that the number of breeding pairs is inversely related to the maximal sea ice, with a 5-year lag. If winter sea ice is too extensive, young birds don't survive. Therefore in 5 years when they would normally enter the breeding population, the number of breeding pairs is lower.
- The percentage increase at each colony is inversely proportional to the initial colony size. This could be the result of a relaxation of natal philopatry in larger colonies, with more birds emigrating from larger to smaller colonies, or a higher rate of recruitment in small colonies.
- Both sea-ice extent and concentration affect diet, foraging effort and ultimately chick growth and survival.
- Adélies feed mainly on one species of krill, Euphausia crystolloporphias, and one species of fish, Pleuragramma antarcticum.
- Adélies forage optimally on feeding trips lasting up to 2 days, with both body weight and the amount of food bought back to chicks increasing. On trips longer than 2 days, adults lose condition and the amount of food bought back to the chicks decreases.
- Dive duration and depth, as well as trip distance, increase during the breeding season at all colonies. Dives at Cape Crozier, the largest colony, were deeper, longer, and more frequent than at the smaller colonies, indicating prey depletion was affecting foraging at Cape Crozier.
- Chick condition is dependent on feeding trip duration.
- Our results offer evidence that competition may be important in metapopulation structuring (i.e. the large colony affecting the size and location of foraging areas of smaller colonies located within foraging range).
- Breeding success is affected by competition - a function of colony size. If large and small colonies have equal access to food, chicks at the smaller colonies are in better condition.
- Adélie population parameters are sensitive indicators of both annual and long-term climate change.
- Our study using mark-recapture methodologies, in conjunction with RFID tags, is the first to model band effects in regard to sighting probability, sex, time or environmental variation. Using other comparisons between banded and unbanded RFID-tagged birds in the WB subcolonies, we have also begun to measure effects of bands on foraging trip duration (detectable, but with significant annual variation) and meal sizes (no detectable effect).