阅读理解. Along the river banks of the

Along the river banks of the Amazon and the Orinoco there lives a bird that swims before
it can fly, flies like a fat chicken,eats green leaves, has the stomach of a cow and has claws
on its wings when young.They build their homes about 4.6 m above the river, an important
feature (特征) for the safety of the young.It is called the hoatzin.
In appearance, the birds of both sexes look very much alike with brown on the back
and cream and red on the underside.The head is small, with a large set of feathers on the
top,bright red eyes, and blue skin.Its nearest relatives are the common birds, cuckoos.Its
most striking feature, though, is only found in the young.
Baby hoatzins have a claw on the leading edge of each wing and another at the end of
each wing tip.Using these four claws,together with the beak(喙),they can climb about in the
bushes, looking very much like primitive birds must have done.The hoatzins, however, live
in the modern world.
During the drier months between December and March hoatzins fly about the forest in
groups of 20 to 30 birds, but in April,when the rainy season begins, they collect together in
smaller living units of two to seven birds for producing purposes.
When danger comes in the form of a snake or a monkey, the young hoatzins-maybe
three in one family-jump over the side and into the river.They swim about under the water
until it is safe to return and then, using their claws, lift themselves up through the branches
and get back home.When they have learned to fly they lose their claws and escape enemies
not by swimming but by flying off, in a slow and heavy way, to a neighbouring tree.