Human exploitation is the primary reason penguins are endangered. The decline of the Humboldt penguin began in the mid-19th century when the intensive activity of guano collectors disturbed and damaged nesting areas. Guano, the excrement of animals such as birds and bats, is much sought after for fertilizer.

Penguins were heavily hunted for their meat, oil, and skins. Adult penguins and chicks were captured for zoos and private collectors. People also collected penguin eggs. 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. A recent fire swept through a breeding colony, killing several hundred birds.

Macaroni penguins are similar to the Royal penguins. They both have the yellow and black plumes joining on the top of the head. The difference is that the Macaroni has solid black feathers on the cheeks and under the chin on the throat, while the Royal penguins have white chins. There are large breeding colonies of Macaroni penguins on the sub-Antarctic Islands of South Georgia, Crozet, Kerguelen, Heard & McDonald Islands. Colonies are also located on the small islands off the southern tips of South America and Africa.

There are an estimated total population of 12 million breeding pairs of Macaroni penguins. They stand about 28 inches (71 cm) tall and weigh 11 to 13 lbs. (5 to 6 kg). This penguin was named by the early English explorers. In the mid 18th century, a young man who wore flashy feathers in his hat was called a "Macaroni". This is also the origin for the words to "Yankee Doodle" sung during the Revolutionary War to poke fun at the poorly dressed Continental Army. The English explorers thought the yellow feathers of this penguin was like a fancy young man called a "macaroni".

Macaroni penguins build a crude nest by scraping a shallow hole in mud or gravel among rocks. The first egg laid is smaller and less likely to hatch. It is often lost to predators and fighting that occurs in the large breeding colonies. The second egg is larger and more likely to hatch. The incubation, keeping the egg warm, is done by both male and female in long shifts. The egg usually hatches within 33 to 37 days.

The male cares for the newly hatched chick for 23 to 25 days while the female brings food daily. At this time chicks have a down covering and they form groups with other chicks called "crèches" for warmth and protection. The parents will feel them every 1 to 2 days until they have their adult feathers and are ready to go on their own. This takes place in about 60 to 70 days. Macaroni penguins eat mostly krill with small amounts of squid.

Unlike most other birds, penguins can't fly. They waddle on land and swim in the sea. When swimming fast, they jump out of the water every few meters, just like dolphins do. This is called porpoising.

On ice there is another method penguins sometimes use: tobogganing. They lie down on their belly and glide along like a tobogan, using their flippers and feet to push themselves forward.

The top layer of a penguin's skin is made of thousands of small, stiff feathers. The air between the feathers is good insulation. To make their 'coat' even more water- and windproof penguins spread some oil on it (this oil comes from a gland above their tail). Below the feathers is a thick layer of blubber to keep the penguins warm.

Once a year, penguins shed their feathers and grow new ones. This is called molting. The old feathers come off in patches and at the same time new feathers grow. This takes about three weeks and during this period the penguins do not eat nor swim.

All penguin backs are black and all bellies are white. This has to do with swimming camouflage: the black back looks like the bottom of the ocean and the white belly looks like the water surface. Some species, like king and emperor penguins, have yellow, orange or red areas on their head or neck.

When penguins are too warm they spread their flippers to release body heat. They can also ruffle their feathers to break up the insulating air layer.
When Emperor penguins are too cold they huddle together.