If those conditions--especially the first three--change sufficiently, then the birds will abandon a colony and establish themselves elsewhere.
Emslie said data collected by his team allow him to make a strong case that Adelies abandoned the entire southern Ross Sea for almost 1,000 years, from roughly 2000 to 1000 years ago. The analysis also indicates that the large Adelie penguin colonies that now exist on Ross Island in McMurdo Sound likely were established only 500 to 600 years ago.
Emslie also noted that a "natural experiment" seems to be underway in Antarctica today that confirms the idea that Adelie populations can rapidly adapt to changing conditions. But it also helps illuminate the difficulties in interpreting the climate record.
Iceberg B-15A, an enormous piece of ice that broke away from the Ross Ice Shelf in March of 2000, has caused much more ice than usual to accumulate for a number of years in eastern McMurdo Sound, essentially cutting off large Adelie colonies at Cape Royds, Cape Crozier, and Cape Bird. Another enormous berg, called C-16 has exacerbated the ice build up.
The bergs prevented Ross Sea currents from breaking up sea ice every year, as they normally would, instead allowing the ice to accumulate and thicken and forcing the birds to travel farther to reach open water.
While the icebergs now appear to be breaking up, the numbers of breeding pairs of birds in those colonies, which already were experiencing some declines, have dropped dramatically in the past three years and, if the unusual conditions produced by the icebergs conditions p
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Contact: Peter West
pwest@nsf.gov
703-292-7761
National Science Foundation
8-Dec-2003