Curious George's Home for Pigeons

what happens

George has found himself a new friend in the city, Compass. One of the Doorman's homing pigeons which he keeps on the roof of the apartment building. But the only thing is, Compass has a bad sense of direction. So when the Man says George is not allowed to let pigeons inside the apartment, George decides to build Compass a new home on the balcony outside their apartment, eventually deciding on a tree. But soon George finds out building a tree is not as easy as it seems. Where do trees in nature come from if people don't make them?