The brush-tailed penguins are the Adelie, chinstrap and gentoo, three species named for their long, stiff tail feathers that sweep the ground behind them as they walk. The Adelie penguin pictured stands about 28 inches (70 cm) tall and weighs 8-13 lbs (3.6-6 kg); the gentoo is the largest of the three at up to 35 inches (90 cm).
The Adelie is the classic tuxedo penguin, black and white with a white ring around the eye. The chinstrap has a thin black line under its chin, and the gentoo a white patch over each eye and a bright orange bill.
Gentoos are the fastest swimming birds in the world, reaching 22 mph (36 km/h) underwater.
Brush-tailed penguins live in Antarctica and on the sub-Antarctic islands. Adelies breed only on the Antarctic coast and nearby islands, and with the emperor penguin are the most southerly birds on Earth. Chinstraps and gentoos breed mainly on the Antarctic Peninsula and islands such as South Georgia and the Falklands.
They need ice-free rock to nest on in summer and spend the winter at sea among the pack ice.
All three feed mostly on krill, along with small fish and squid. Adelies in particular depend on Antarctic krill, and their numbers rise and fall with it. They dive to about 160 feet (50 m) on most trips and can go much deeper.
Brush-tailed penguins build nests of small stones, which are so valuable that neighbours constantly steal from one another. Colonies can be enormous: more than a million pairs of chinstraps nest on the volcanic Zavodovski Island.
Both parents take turns incubating two eggs and feeding the chicks, which gather in creches while the adults fish. On snow the penguins often toboggan on their bellies, pushing with their feet.
Pygoscelis contains the Adelie, chinstrap and gentoo penguins. The IUCN lists all three as Least Concern, but their fortunes are diverging as the Antarctic Peninsula warms: Adelie and chinstrap colonies there have shrunk sharply, while gentoos, which tolerate open water, are spreading south.
The loss of sea ice, changes in krill, and growing krill fishing and tourism are the main concerns.
