This happened to me. When I was a teenager growing up in Illinois, my brother, friends and I used to spend our summers doing day-long bike rides. We were pedalling along around DeKalb in the middle of nowhere when my brother flatted and unfortunately we were not smart enough to have carried spare tubes during that ride. We tried to persuade him to stuff grass in his tyres and proceed to the closest bike shop which was about 5 miles away but he refused and instead opted to try and patch the tube on the spot. Just as my brother was applying the glue, a flock of crows decided to swoop down upon us. I figured they might have been attracted to our helmets. One flew away with my lycra helmet cover. As my friends and I were busy swatting at the crows with our pumps, I happened to glance over and notice my brother frantically tearing off clumps of grass and stuffing them into his tyre. We beat a hasty retreat followed by a string of birds.