Ways of describing horsemanship

He looked natural on a horse.

That might be one way.  Gets the point across.  But, just in case, let’s try another way:

The boy who rode on slightly before him sat a horse not only as if he’d been born to it which he was but as if were he begot by malice or mischance into some queer land where horses never were he would have found them anyway.  Would have known that there was something missing for the world to be right or he right in it and would have set forth to wander wherever it was needed for as long as it took until he came upon one and he would have known that that was what he sought and it would have been.

(theory: all great writers are comedy writers?  “Cracker Cowboys of Florida” by Frederick Remington, 1895)