Kermit,
From the far dark recesses of the junk closet that is my memory. Years ago I read somewhere that birds of prey are very territorial. I think it was an article concerning a glider club where a bird was actually attacking aircraft. Seems that the bird involved thought that the gliders were trying to muscle in on his territory. The close passes and circling are part of a display to scare the intruder off. Powered aircraft usually move faster and beetle off so the bird takes this as a victory on his part and goes back to what it was doing. Gliders on the other hand move slower and circle so stronger action is taken. Fabric wings can suffer quite badly at the claws of our feathered friends, less of a problem with tin and plastic kites but still quite a shock to all concerned when one thumps into you at a rate of knots. Don't know if lights etc will keep them off. I know that the bird-scarers on the ground have to change tactics periodically as they get used to the various methods employed.
Regards
WM.
