Assertion: penguin's bird | /r/HasProperty | only
Facets:
Source sentences:
text: The largest penguin, they are the only bird that breeds in the depths of the Antarctic winter, and they can dive deeper (500 m) and survive longer without eating (4 months) than any other bird.
text: Some emperor penguins are the only birds that never set foot on land.
text: They are the only birds that can lay their eggs on ice.
text: While penguins are the only birds that have true flippers, other pelagic (open-sea) birds that spend a good deal of time swimming also have some flipper-like characteristics to their wings.
text: In fact, penguins are the only birds that are unable to fold their wings.
text: Penguins are the only birds that have a naturally upright posture.
text: The penguin is the only bird that can swim, but not fly.
text: It is also the only bird that walks upright.
text: They are the only birds that can lay their eggs on ice.