Scientists believe that its feather-eating habit is linked to the process in which it throws waste. The grebe has a unique excretory system. It throws out one or two balls of waste through its mouth every two days. The main food of grebe is fish. So the ball of waste has something hard to digest like fish bones and scales(鱼鳞). And there are parasites(寄生虫). It is important for the grebe to throw these parasites out. If it didn’t, they would make it sick. According to scientists, the feathers add fiber to its waste. It makes it easier to form the ball of waste and to throw it out.

　　Another interesting characteristic is its toes(脚趾). They are united to form a web near the base, while the rest are rounded like an umbrella. The shape of its toes helps it to swim. In fact, the grebes are excellent swimmers and they use their feet only for diving force under water.

　　The grebe makes its nest on floating leaves or plants and lays about two to ten eggs in it. Both the male and female grebe hatch(孵化) the eggs and take care of the young ones. The young grebes have stripes(条纹) on them.

　　There are 18 to 20 species of grebes living around the world, some of which are endangered.

　　71．What do we know about the grebe?

　　Its feathers feel smooth.

　　It has wings about 7 to 10 inches long.

　　It has stripes on the body when it grows up.

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