ANTARCTIC RESEARCH SERIES, VOL. 70, PP. 257-272, 1996
Factors controlling the distribution of seabirds: Winter-summer heterogeneity in the distribution of adélie penguin populations
Recent and historical data on the distribution of Adélie Penguins in the western Antarctic Peninsula region were analyzed
to examine and detect patterns and causes of heterogeneity, and to relate these to long-term population changes. Adélie Penguins
are one of the dominant components of the region's seabird community in terms of biomass, but not in numerical abundance.
Approximately 308,300 pairs breed in the region, 80% of which are found in five colony clusters. These colony clusters are
associated with deep canyons and basins that intersect the continental shelf. Adélie Penguins confine foraging activities
to regions over these deep features that are within 20–50 km from colony clusters. Winter distributions in the Weddell and
Bellingshausen Seas exhibit similar spatial heterogeneity and also occur in association with anomalies in bottom topography.
Available daylight in winter restricts available foraging time, an analog to summer conditions when similar restrictions occur
due to the need to provision chicks. It is hypothesized that summer and winter heterogeneity in the distribution of Adélie
Penguins is maintained by behavioral mechanisms, but is causally linked to the juxtaposition of suitable bottom topography,
nesting habitat, pack ice and available daylight, features associated with high prey availability. Changes in the spatial
and temporal juxtaposition of some of these features over ecological and geological time due to climate change are likely
to drive changes in the populations of Adélie Penguins. Different regions of the Antarctic appear to be out of phase with
each other from the standpoint of climate change for reasons that are not yet clear. As a result, trends in Adélie Penguin
populations are not synchronized, but instead reflect region-specific changes in climate.
Citation: Fraser, W. R., and