What a baffling question! I can think of a couple of possibilities. You are referring to the following sentence:
Increasingly, after my amputation and during the long time when I lay around feeling sorry for myself, I came to feel like the contour bird.
He goes on to say that he wanted to fly around the Sierra foothills backward--another impossibility for all birds, except the hummingbird. Perhaps Stegnor is playing on the "tour" part of the word. The narrator--not interested in his own life anymore--would like to tour about in someone else's life, hence the interest in his grandmother's letters. "Contour" also works in this sense. He would like fly about and fit the contours of the lives of his grandparents:
I'd like to live in their clothes a while, if only so I don't have to live in my own.
So we have several fantasies in this paragraph: the contour bird, which does not exist; birds that fly backwards; living the lives of those dead and gone; and the last and most important, the narrator's wish to touch ground again--impossible because he is a double amputee.
Perhaps he was referring to the contour feathers which are the outermost feathers and provide the color of the bird. They also lay on top of one another like shingles, protecting and insulating the bird from water and the elements.
contour bird - perhaps no particular species, but a bird soaring a fairly constant distance from the terrain below. As noted above, Stegner closes the paragraph: "I want to touch once more the ground I have been maimed away from."
The US Army breaks up terrain flight into nap of the earth (NOE), contour, and low level. NOE is flying as close to the earth?s surface as vegetation or obstacles will permit. Airspeed and altitude are varied in accordance with weather conditions and ambient light. Contour flight is characterized by varying altitude, adhering to the contours of the earth, and a constant airspeed.