Often when watching a flock of birds flying I wondered if they ever collide. Flocks of small shorebirds, blackbirds etc are like a live swarm that seems to move on its own, like one organism powered by some intelligent or magical force inside (but every individual is on its own - Birds can resolve rapid movements better than humans, for whom flickering at a rate greater than 50 Hz appears as continuous movement. Humans cannot therefore distinguish individual ï¬ashes of a ï¬uorescent light bulb oscillating at 60 Hz, but Budgerigars and chickens have flicker thresholds of more than 100 Hz. A Cooper's Hawk can pursue agile prey through woodland and avoid branches and other objects at high speed; to humans such a chase would appear as a blur. BTW birds can also detect slow moving objects. The movement of the sun and the constellations across the sky is imperceptible to humans, but detected by birds. The ability to detect these movements allows migrating birds to properly orientate themselves). But I never noticed collisions inside the moving flock. Small tern flocks are different. Birds keep greater distance from each other. Maneuvers by individual birds inside the flock can be impressive (e.g. LETE can fly upside down with head in ânormalâ position) but the flock does not make impression of being one entity. But, evidently, one bird can bump into another. Look here (under tail covert feathers got separated from tail feathers allowing a great view): http://www.pbase.com/mbb/image/149582203 Example of LETE flying with body upside down with its head up inside the flock during quick maneuver (note: To obtain steady images while flying or when perched on a swaying branch, birds hold the head as steady as possible with compensating reflexes). http://www.pbase.com/mbb/image/149582204 I wonder if many observations of colliding birds have been recorded when they are flying in formations (did you ever see one?); I couldn't find any photos, and found only a few anecdotal notes. And I am not talking about aggressive encounters or gulls trying to get thrown piece of bread. BTW long time ego I saw two hummers collided when trying to establish who owns the feeder. One lost conscious for a few minutes but was OK later. Mark B Bartosik Houston, Texas http://www.pbase.com/mbb/from_the_field Edit your Freelists account settings for TEXBIRDS at //www.freelists.org/list/texbirds Reposting of traffic from TEXBIRDS is prohibited without seeking permission from the List Owner