text: do flying birds...excrete...during flight or just once they have landed somewhere? obviously one can see the evidence of birds under trees, on cars, on sidewalks, etc.  but, the 'evidence' in these locations would be left while they are landed.  can birds defacate in mid-air or just once they have arrived? birds can while the fly, but the typical excrete right before they take off to literally lighten the load, weight is a very important factor for birds