皓宇同学的课程学习报告

按课堂老师纠正后的发音和理解整理，适合课后跟读和听力复习。

Listen to part of a lecture in a biology class.

Birds spend a lot of time in the air, and one problem they have to deal with in flight is strong wind. Windy weather conditions and strong air currents can make it difficult for birds to stay up in the air or to fly straight. So birds change the way they fly when they encounter the wind. This temporary change in the way they fly allows them to avoid getting knocked off course or knocked out of the air by strong winds.

Some birds cope with windy conditions by changing the position of their wings. This is common with soaring birds, birds that fly by stretching out their wings and gliding through the air. Heavy winds can make it difficult for these birds to fly straight and maintain the smoothness of flight, so they change their wing position to cope with that. Eagles, for example, normally fly through the air with their wings outstretched in a gliding motion. But when it's windy and the air is rough and bumpy, they fold their wings in and press them tightly against their bodies. That way they have a smoother, streamlined shape and can't get knocked off course by the wind. They hold this position for just about half a second and then spread their wings out again to continue soaring, changing their wing position again when necessary to stay on course.

Hovering birds move differently. When flying, they often just need to stay in one place in the air. But strong wind can cause them to lose their place or even fall out of the air. So hovering birds cope by changing the way they move and using another body part in addition to their wings to help them stay in the air. For example, hummingbirds need to hover in the air and stay in front of the flower from which they're drinking nectar. If the wind gets strong and they start to lose their position, they begin moving their tail back and forth to stabilize themselves.