Bird Brains
Bottom line is that nobody is certain whether this works or not.
Greg
Ref comments by NickAir, kevinh, and Jimboscr: I?m no ornitho-expert but have also done a lot of thermalling with various kinds of birds. I once was joined in a thermal 7000 feet above a lake by an Osprey carrying a fish that was at least equal to its own weight. Observed that said large fish was purposefully carried in the streamlined orientation.
I?ve noticed that predatory birds especially are the ones that will deliberately close on an aircraft (very slow ones?gliders), but in doing so will never allow the plane to be higher than they are. As long as the bird has the altitude advantage, the aircraft is perceived as not being a threat. Not sure if this signifies either a bit more intelligence than other types of birds, or is the instinctive reaction of a predator, or perhaps both.
In any case, regardless of aircraft type, figure that the birds know very well when they are not alone in their piece of sky, because they are either predator or they are prey. All birds are extremely aware of what?s going on around them. That?s how they live. Collisions occur simply because birds are not instinctively wired to deal with the airplane?s closing speed.
Personally, I doubt if a whistle would help any. When one bird is hunting another, the predator doesn?t scream its intentions, it attacks quietly. Where sound comes into play is when a bird is defending its territory, a totally different scenario. What significance would a bird assign to an airplane whistle, if it did hear it at all? Who knows how to think like a bird?