The penguin species with the highest population is the Macaroni penguin with 11,654,000 pairs. The species with the lowest population is the endangered Galapagos penguin with between 6,000-15,000 individuals.
When in the water, penguins may be eaten by leopard seals, fur seals, sea lions, sharks, or killer whales. On land, foxes, snakes, and introduced predators such as feral dogs, cats, and stoats (members of the weasel family) prey on eggs and chicks of some penguin species, including the yellow-eyed and Galapagos penguins.
Both parents take turns incubating the egg. The incubation period lasts from 4 weeks (Erect-Crested penguins) to 66 days (Emperor penguins). Chicks first occur by poking a small hole in the egg and they require attentive parents for survival. Once a chick has fledged, it is able to swim and becomes independent of its parents.
Penguins stand upright while incubating a single egg on the tops of their feet under a loose fold of abdominal skin. Under this loose fold is a featherless patch of skin called a brood patch, which occurs in all incubating birds. The brood patch contains numerous blood vessels, that, when engorged with blood, transfer body heat to the eggs.
There are some great qualities of penguins found in their reproduction process. They can mature for reproduction from about 4 to 8 years of age. Generally the smaller species of penguins will mature at a younger age than the larger ones. However, the smaller ones also seem to have a life span that is much shorter. A number of species only mate with the same partner year after year.
Penguins are among the most social of all birds. All species are colonial. Penguins usually associate in small groups while at sea, but often gather by the thousands when nesting on land. Penguins are among the most social of all birds. Penguins may swim and feed in groups, but some may be solitary when diving for food. Emperor penguins have been observed feeding in groups with coordinated diving. During the breeding season penguins come ashore and nest in huge colonies called rookeries. Some rookeries include hundreds of thousands of penguins and cover hundreds of square kilometers.
Only a few penguins live in the warmer parts of the southern oceans. The Galapagos Penguin, breeding in the Galapagos region, may even breed a little north of the equator, and the Jackass Penguin (or African Penguin) may range as far north as the equator. These penguins have special ways of keeping cool and live in places where cold ocean currents cool the immediate environment—the Humboldt Current in the eastern Pacific, and the Benguela and Agulhas Currents off South Africa. They are non-migratory species, so they’re not likely to stray too far north. Most other species never come further north than 45°S latitude. Specially adapted for life in cold places, they don’t wander into warm water.
A penguin’s diet can range from small fish to shrimps, small crayfish, barnacles and many other small shellfish. A penguin’s beak is very tough so it can remove the barnacles from the rocky surface of the sea bed. The penguin’s speed is fast enough to catch small fish swimming at their top speed along with other foods they like. Many penguins spend days out at sea eating many of their favourite foods, so that when they return to their colony they will be able to feed their young and their mate. Their mate would have spent the last few days caring for their younger penguins as they cannot fish for their own food yet. The penguin that has been out at sea regurgitates the food for their partner and children to eat.
Penguins are champion swimmers and divers. But they are not fish and they are not aquatic mammals such as dolphins. Penguins are birds because they have feathers, and only birds have feathers. Like birds, they lay their eggs and raise their chicks on land. But they seem to fly through the water, and they spend much of their lives at sea.
By 55 million years ago, penguins were already flightless and were completely adapted to a life in the ocean. Scientists believe that these flightless seabirds arose even earlier than this from an ancestor which could fly and that the transition took place somewhere in the southern hemisphere roughly 65 million years ago, about the same time the dinosaurs disappeared.