As we know, all birds have wings. An animal has to have wings in order to be classified as a bird. And we know that birds probably evolved wings at some point in the past in order to enable them to fly. And most birds today still use their wings to fly, but not all birds. Some present-day birds are flightless. So why do flightless birds still have wings? Well, their wings have evolved to be useful for purposes other than flight. So what would birds use their wings for other than for flying?
Well, some flightless birds have wings that have evolved to be useful for swimming. These birds spend most of their lives near the sea and most of their foods in the water, not in the air. So having wings that help them catch food in the water was better in terms of survival than having wings that would help them catch food in the air. So over time their wings evolved to enable them to move more efficiently through water. Take penguins for example, over time their wings have become very flat and very thin and very wide, perfect for propelling them forward through the water when they're foraging for food.
Other flightless birds have wings that have evolved to help them keep their balance. Since these birds can't fly, when approached by a predator, they run as fast as they can and turn sharply this way and that, and that makes it more difficult for the predator to catch them. But it also increases their chances of falling down. And if they fall down, they may become an easy meal for the predator. So over time some birds have come to use their wings to help them keep their balance. Ostriches are a good example. Ostriches are big, heavy flightless birds. When they're trying to escape from a predator, they spread their wings out away from their body and having their wings spread out like this helps to steady them, so there's less risk of falling.
Summarize the professor’s lecture about flightless birds. Be sure to include her examples of penguins and ostriches.