The Flightless Birds Called Penguins
They include the tiny blue penguins of Australia and New Zealand, the majestic emperor penguins of Antarctica and king penguins found on many sub-Antarctic islands, the endangered African penguins and the Galápagos penguins—the only penguins to be found north of the equator.
Though they are birds, penguins have flippers instead of wings. They cannot fly, and on land they waddle walking upright—though when snow conditions are right they will slide on their bellies. They spend about half of their lives on land and half in the oceans. In the water they are expert swimmers and divers, and some species can reach speeds of up to 15 miles per hour. The penguin’s distinctive coloring—black body with white belly—helps camouflage the bird in the water as it searches for meals of small shrimp, fish, crabs and squid. Larger penguins inhabit colder regions, while smaller penguins are generally found in temperate or even tropical climates.
Penguins for the most part breed in large colonies, the exceptions being the yellow-eyed and Fiordland species; these colonies may range in size from as few as 100 pairs for gentoo penguins, to several hundred thousand in the case of king, macaroni and chinstrap penguins. In some species, such as emperor penguins, young penguins assemble in large groups called crèches
Penguins form monogamous pairs for a breeding season, though the rate the same pair recouples varies drastically. Most penguins lay two eggs in a clutch, although the two largest species, the emperor and the king penguins, lay only one. With the exception of the emperor penguin, where the male does it all, all penguins share the incubation duties. These incubation shifts can last days and even weeks as one member of the pair feeds at sea. Penguins generally only lay one brood; the exception is the little penguin, which can raise two or three broods in a season.
Penguin eggs are smaller than any other bird species when compared proportionally to the weight of the parent birds; at 52 g (2 oz), the little penguin egg is 4.7% of its mothers’ weight, and the 450 g (1 lb) emperor penguin egg is 2.3%. The relatively thick shell forms between 10 and 16% of the weight of a penguin egg, presumably to minimize the risk of breakage in an adverse nesting environment.
Penguins seem to have no special fear of humans, and have approached groups of explorers without hesitation. This is probably because penguins have no land predators in Antarctica or the nearby offshore islands. Instead, adult penguins are at risk at sea from predators such as sharks, the orca, and the leopard seal.
The Antarctic Peninsula, where half of the world’s emperor penguins and 70% of the Adelie penguins can be found, is heating up faster than the global average and melting the sea ice that the penguins depend on for places to breed and access to food. A 2008 WWF study estimated that 50% of the emperor penguins and 75% of the Adelie penguins will likely decline or disappear if global average temperatures rise above pre-industrial levels by just 2 degrees centigrade—a scenario that could be reached in less than 40 years.
Sources, Wikipedia, World Wildlife Fund.