Read the given passage and answer the question:

The song of birds is one of the wettest sounds in nature. Sometimes when we are out in the country and hear birds singing, it seems to us they are calling back and forth, that they ar telling one another womething. The fact is that birds do communicate with one another, just as many other animals do. Of course, at times’ the sound birds make are more expressions of joy, just as we may makecries of ‘oh! and ‘ah!, But for the most part, the sounds that birds make are attempts at communication. A mother hen makes sounds that worn her children of danger and cause them to crouch down merciless. Then wild birds migrate at night, they cry out. These cries may keep the birds togther and help lost ones return to the flock. But the language of birds is different from the language we use. We use words to express ideas and these words have to be learned. Birds don’t learn their language. It is an inborn instinct for them. In one experiment, for example, chicks we kept away, from cocks and heans so they could not bear the sounds they made.