I worry you didn't actually want an explanation Andy, and apologies if so, but basically the idea is that when a crow is in full flight it can move in a straight line regardless of the terrain on the ground.
"dead to rights" is curious! looking it up made me contemplate the general use of "dead" in phrases like dead broke or dead ringer
I had a brief conversation earlier today about the possible origins of "cotton on (to)"
― rob, Monday, 18 March 2024 23:51 (two months ago) link