Research Objectives:
This group investigates the mechanisms responsible for the geographic structuring, the founding of new colonies, and the recent population expansion of the Adélie penguins of Ross and Beaufort Islands. Similar expansion has been occurring throughout the Ross Sea, where 30 percent of the world population of this species resides, and is in some way related to ameliorating climate. So far they have been examining:
+ The relative importance of resources that constrain colony growth (the amount of nesting habitat versus access to food)
+ Aspects of natural history that might be affected by exploitative or interference competition among neighboring colonies (breeding success and foraging effort)
+ Climatic factors that influence the latter, especially extent and concentration of sea ice
+ Behavioral mechanisms that influence colony growth as a function of initial size and location, emigration, and immigration.
None of the colonies are limited by nesting space, and the researchers have shown how sea ice extent and concentration affect diet, foraging effort, and winter survival. In addition, large colonies affect the foraging patterns of smaller ones within range and, perhaps, ultimately their size. The rate and direction of emigration also appear to be constrained by sea ice conditions, with reasonable concentrations of ice favoring growth of smaller colonies where foraging competition is minimal. Yet to be determined is the demographic mechanism of colony growth (or decline). Reproductive success does not appear to be important, however.
Using seven cohorts of marked penguins from each colony, researchers will assess juvenile survival, recruitment age, and age-specific fecundity and subsequent survival. These data will be compared with another demographic study, the only one for this species, conducted at Cape Crozier during the 1960s and 1970s when populations were declining.
Information will be related to sea ice as quantified by satellite images. Global climate is changing fastest in the polar regions. The Adélie penguin is tied to sea ice, a primary factor in rapid polar climate change (less sea ice, less reflection of solar energy). The extreme sensitivity of these penguins to climate change has been often noted. Understanding the demographic mechanisms behind this sensitivity will contribute greatly to knowledge of the effects of climate change on antarctic marine organisms.
