My first thought was that it may have been a large bug, or that I clipped a small bird. About three minutes later, I looked in the right mirror to see that my brother was still behind on a 1990 R100GS, and noticed what first appeared to be a piece of wet paper bag. To my surprise, it was this small bat, with its body on the backside of the mirror and a wing wrapped around the front.
I continued without stopping for another ten to fifteen miles at the same speed until we reached a gas station at Sedro Woolley. The bat had stayed affixed to the mirror until my bike slowed to about ten miles per hour, then it just dangled by one wing, and clearly its injuries were fatal.
Amazed by this, I had to show my brother and take some photographs. Without removing it, I drove nearly eighty miles to Seattle. The bat stayed on the entire distance and didn't appear to have any external damage afterwards, so my buddy Jeff is now attempting to preserve it for display.
Yes, odd...