This is not a nature book. A nature book is written from above, by someone who has the animal in hand — banded, weighed, filed under a Latin name and a list of behaviors, settled. I am not above this animal. I am across the street from it, and it knows where I park.

What follows is closer to testimony. It is one man's attempt to take the measure of a neighbor who took mine years ago, in an afternoon I cannot remember, and has been quietly updating the file ever since. I went looking for the science because I wanted, badly, to find the bird smaller than it looks from my driveway — to come back with a number that put it in its place. I did not find that number. Every door I opened had a larger room behind it.