Mr. Underhill, who holds the unusual title of avian demographer, has been charting the penguin population for years.

Since then the penguin population has been increasing.

African penguin populations, which breed in Namibia and South Africa, have declined by 95 percent since preindustrial times.

Around the world, many penguin populations are declining, researchers say, and evidence is mounting that global warming, whether natural or human-induced, is a prime cause.

The deployment of Maremma sheepdogs to protect the penguin colony has deterred the foxes and enabled the penguin population to rebound.

Because the poles reflect changes in temperature and climate faster than anywhere else, penguin populations rise or fall equally dramatically.

They also visit islands noted for their abundant penguin populations.

He estimated the size of the penguin population in Antarctica, and the effect of repealing the motorcycle helmet law in the United States.

So, the researchers point out, the size of penguin populations appears to be linked to climate.

Home to bull elephant seals and the wandering albatross, this stark, snowy land boasts the world's largest penguin population.