theory: for those who wonder why birds dont escape
 

"Speed kills: ineffective avian escape responses", a piece of FAA funded research published by the Royal Society concludes that birds assess only the distance, but neither speed nor frontal area of an aircraft on collision course. Birds seem to initiate evasive maneuvers at a fixed threshold of the bird-to-aircraft distance. This strategy is potentially good enough to evade natural enemies, birds of prey, however it seems ineffective for avoiding oncoming objects faster than 65 knots.

Speed kills: ineffective avian escape responses to oncoming vehicles | Proceedings of the Royal Society of London B: Biological Sciences

interesting non-essential knowledge for checkers to ask about :E

Theory only

Does not read across to the aircraft flocking bird hazard during takeoff.