Emperor Penguins of Cape Crozier and Beaufort Island, Antarctica
Emporer penguins breed in traditional rookeries located on annual sea ice along the Antarctic coast. Unique among birds, they commence their reproductive cycle in winter in regions that are the coldest and windiest on the planet while in the dark 24 hours a day. Emporer penguins begin nesting in midwinter so that their chicks fledge before the breakup of the annual ice. This study reviews survey data for the Cape Crozier and Beaufort Island rookeries from 1902 to 1975, and then reports the results of the 1976 to 1977 censuses. Researchers found evidence that at least 26 adult Emporer penguins were killed by land slides and falling rocks. During their census, rocks were constantly falling from the crumbling overhead cliffs. The census also found 54 dead chicks, most of which were in good physical condition and had full stomachs which suggest they died of exposure. The Beaufort Island rookery was more productive than Cape Crozier. The concern was that Emporer penguins are known to tolerate high chick mortality, but high adult mortality may be disasterous for smaller rookeries like Cape Crozier. There was no evidence that human disturbance contributed to penguin mortality.
Todd, F.S. Factors Influencing Emperor Penguin Mortality at Cape Crozier and Beaufort Island, Antarctica. Le Gerfaut. 70: 37-49. 1980.