Scientists meeting at Boston's New England Aquarium say most penguin colonies - except for five in Antarctica - have declined in the past few years.

They blame the decline on warmer temperatures brought by the El Nino weather system as well as the effects of pollution and tourism.

A combination of these factors has created a scarcity of food for the penguins, impeded their breeding habits, and left them open to disease.

Penguins Sinclair and Good Hope were brought out to illustrate the scientist's message

Most concern centres on the plight of the Erect-Crested and the Galapagos penguins, which are considered endangered - meaning they have an estimated 20% chance of extinction in the next 20 years.

But other species in South America are also considered vulnerable.

Researchers say the unusually warm weather brought on by El Nino could have affected the penguins' breeding and feeding.

"It's important to know that penguins do not adapt like other birds, such as gulls," said South Africa-based researcher, Robert Crawford.

"They can't fly and they can't feed behind boats. They're affected by what happens on land, as well as what happens in the sea."

Environmental warning

Changing sea currents have altered the location of fish stocks and many penguin colonies have gone hungry.

Scientists say environmental changes have interfered with breeding patterns

But scientists say penguins, which are easy to see and count, are also a good indicator of how other species are being affected by climatic and environmental change.

"Things happening to penguins are a foretaste of things to come," says Susie Ellis of the World Conservation Union.

Pollution and human contact have also taken their toll.

In 1994, 10,000 penguins off the coast of Cape Town died following an oil spill.

The penguins' popular appeal has also proved damaging, with growing numbers of tourists visiting penguin colonies and unwittingly disrupting their delicate habitat.

And since last year the Antarctic's colonies of Emperor and Adelie penguins have both succumbed to a poultry virus brought by humans.