The eight-year-old boy can’t reach the first branch of the largest of a pair of Maples in the front yard so he settles for the lowest branch of the smaller tree. He easily pulls himself up into the first crotch and pauses there, planning his route to the top of his favorite aviary. He knows each branch like the back of his hand, every step, every handhold. He starts to climb, one limb at a time.

As the boy ascends, the branches get smaller and more flexible. He can feel himself now swaying gently in the wind. He can almost (but not quite) poke his head out of the leaves at the top of the tree before he’s forced to stop climbing. Here he tucks a leg into the fork between two branches and settles in. First, he senses the breeze gently evaporating the sweat from his climb. Then he…