Sailors on the southern seas regarded penguins as a welcome, easy meal. Penguin eggs were so prized in the Falkland Islands that the country declared National Penguin Day, a holiday when even school children were given the day off to collect eggs. More recently, penguins have been drowning in fishing nets and on long line fishing gear. Commercial fishing also has reduced prey availability. In addition, penguins are threatened by oil spills from ships and tankers rounding the treacherous waters of the Cape of Good Hope at the tip of Africa and Cape Horn at the tip of South America.
Penguins also are vulnerable to climate variations.
The occurrence of El Nino from 1982 to 1983 is thought to have caused the loss of some 65 percent of the Peruvian population of Humboldt penguins. The arrival of this unusually warm ocean current may have killed or driven away the penguins' prey species. One of the rarest of all penguins is the yellow-eyed species of southeastern New Zealand with fewer than 4,000 birds remaining. The yellow-eyed penguin is threatened by introduced predators like weasels, dogs, and cats. Destruction of forests and human disturbance have reduced the quality of their breeding areas.