Mr. Ellis is very old. He has seen many changes in his home town. He knows that things are different now. But he never forgets the old days. He likes to talk about them. He often talks about his favourite birds, the robins (----).  "When I was a boy, these houses were not here. There were wide fields and tall trees. Every spring robins would come. Thousands of them would fly up to the north from the south. They spent the winter in the south. Some would build their nests in the trees near our houses. Then people started to cut down trees, and they built more houses. The robins stopped coming. They couldn't build their nests near our houses because there were no trees." "Now there are too many houses and too many roads. There are no places for the robins. They do come any more ." Then people  _   trees because they wanted to build more houses.
cut down planted bought watered