The penguin set

Penguins hug eggs.

Penguin parents keep their eggs warm.

Penguins warm their eggs.

An emperor penguin father holds the egg on his feet. A warm fold of skin covers it. His mate passed him the egg before leaving to feed at sea.

An emperor penguin father holds the egg on his feet under a warm fold of skin. The mother passes the egg to him after laying, then leaves to feed at sea. He keeps the egg above the ice while the chick develops through many weeks of Antarctic winter.

An emperor penguin father supports the egg on his feet beneath a fold of abdominal skin. After laying, the female transfers it to him and leaves to feed at sea. His body warmth supports the developing chick through winter incubation, while the egg remains above the ice. This arrangement belongs to emperors; many other penguins incubate eggs in nests.²²

Some penguins get in a big hug.

Some penguins stand close to keep warm.

Some penguins stand close to keep warm.

Male emperor penguins huddle while they warm their eggs in winter. Nearby bodies give shelter and warmth. The huddle helps the fathers save energy.

Male emperor penguins huddle while they care for eggs in winter. Nearby bodies shelter each bird and create a warmer local environment. This helps the males save energy during their long fast. A huddle is a changing group, not a fixed circle with a planned turn for each bird in the middle.

Male emperor penguins huddle during winter incubation, creating a warmer local environment and reducing the costs of exposure. Neighboring bodies shelter each bird while the group changes shape. These huddles are dynamic gatherings, not permanent circles in which every male receives a scheduled turn in the middle. Measurements of warmth and movement reveal a more irregular form of collective shelter.²⁵

Penguin mom and dad fed it.

Penguin parents feed their chicks. The food comes from the sea.

Penguins feed their chicks.

Penguin parents feed their chicks with food caught at sea. An emperor mother returns around the time of hatching, sometimes before and sometimes after.

Penguin parents feed their chicks with food brought back from the sea. An emperor penguin mother returns around the time of hatching. She may arrive before the egg opens or after the chick emerges. Her return allows the parents to exchange care and the father to leave for food.

Penguin parents feed their chicks with food brought from the sea. In emperors, the female returns around the time of hatching, allowing an exchange of care and the male's departure to feed. Her arrival can precede hatching or follow it. The seasonal relationship is dependable, but a perfectly synchronized reunion would misrepresent the variation between families and colonies.²⁸

A penguin can zip on its wings.

Penguins flap their wings to swim. Swish, swish!

Penguins flap their wings to swim. They cannot fly.

Penguins use their wings to swim, not to fly in the sky. Strong muscles move the flat flippers through water.

Penguins flap their wings to swim. The flattened wings are called flippers because of their shape and swimming job. Strong muscles move them through the water. Penguins cannot use these wings to fly in the sky, although a swimming bird can leap out of the sea.

Penguins flap their wings to swim, driving flattened flippers through water with strong wing and breast muscles. Those flippers remain wings, even though living penguins cannot use them for powered flight through the air. The phrase 'flying underwater' describes the resemblance between their strokes and aerial wingbeats; it does not erase the difference between the two environments.¹

Penguins dip in to get fed.

Penguins dive to find food. Down into the sea they go!

Penguins dive to get food. They dive down into the water.

Penguins dive to find food. They breathe air at the surface and hold their breath below it.

Penguins dive to find food and must return to the surface for air. A breath before the dive supplies only part of an emperor penguin's available oxygen. Emperor penguins also carry oxygen in their blood and muscles. These stores support activity while the bird is underwater.

Penguins dive to find food, but they breathe air at the surface and hold their breath underwater. The oxygen available during a dive must come from stores already carried inside the body. An emperor's deep dive belongs to that species and its circumstances; it cannot stand in for the usual feeding trip of every penguin.⁷

A penguin is black on top.

A grown penguin has a dark back and a light front.

Adult penguins have dark backs and light fronts.

Adult penguins usually have dark backs and light fronts. This pattern is called countershading. It may help a swimming bird blend in.

Adult penguins usually have a dark back and a light front. This pattern is called countershading. A dark back may help a swimmer blend with darker water seen from above. A light underside may help against brighter water seen from below. These possible benefits depend on lighting and viewing direction.

Adult penguins usually have dark backs and light fronts. Many are black and white, while little penguins can have blue-toned backs. This countershading may help a swimming penguin blend against darker water viewed from above and brighter water viewed from below. The visible pattern is well established; camouflage is a proposed benefit that depends on lighting and viewing direction.²¹