for National Geographic News
After a century-long population crash, African penguins face a tough road to recovery, conservationists say. The birds face problems old and newfrom the lingering aftereffects of a 19th-century guano craze to modern woes like oil pollution and a dwindling food supply.
"Before artificial fertilizers were invented, guano [bird excrement] was the best source of nitrogen. [It was] white gold," said Les Underhill, the director of the avian demography unit at the University of Cape Town in South Africa.
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Seabird dung was heavily harvested by 19th-century European and North American traders and sold to farmers to replenish exhausted soils. The islands off the coast of South Africa were waist deep in the stuff. Resident penguins burrowed into the guano to make nests.
Today the islands are largely denuded of guano. As a result, penguins are often forced to nest out in the open, where they are exposed to the elements, according to Rob Crawford. Crawford is a marine conservationist with South Africa's Department of Environmental Affairs and Tourism in Cape Town.
"Many of the islands have no, or very few, bushes and no sand to burrow into, hence birds nest on the surface," he said. He noted that burrows offer penguins favorable conditions, "with less extreme fluctuations in temperature."
African penguins are known as jackass penguins for their donkeylike braying. Most of the birds take up residence on their nesting islands in Aprilautumn in the Southern Hemisphere. Breeding tails off in October.
However, some early nesters arrive on their nesting islands off the South African coast in January and Febrarymid-summer in the Southern Hemisphere.
Jackass penguins will abandon their nests for cool ocean waters when the air temperatures begin to rise above 80 degrees Fahrenheit (27 degrees Celsius). Such hot days usually occur in the summer and, as a result, tend to impact early nesting penguins.
When temperatures climb, early nesters desert their eggs to avoid heat stress and dehydration. The penguins typically return about six weeks later, when temperatures have dropped. In the birds' absence, kelp gulls eat most of the penguins' eggs.
"Whenand ifthis happens, desertion is a gradual process, over days, and unless the hot weather is in the early autumn, not a large proportion of the population is impacted," Underhill, the University of Cape Town researcher, said.
He added that heat waves are natural today and that current global warming is having no impact on the penguin populations.
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