We did have a pigeon whack the top of the screen on our Plus 4 (not on a motorway, though). If we had been a few feet further on then

would have ended up wearing it as a hat!
A pigeon! Ha that's not even trying. I had a wingtip brush with an eagle whilst on a motorcycle outfit in the Northern Territory but a friend definitely takes the prize for the largest bird: he bowled over an emu on an outback road. Incredibly it was only a glancing hit and he managed to keep his bike under control. The emu went rolling along the road, got up, shook itself and ran off.
PS. I forgot the fact that I had to stop, on the same trip, to clean the engine fins of the slightly cooked remains of several budgerigars after a flock foolishly swerved the wrong way.