Experiment involving transmiters, birds and music.

I have an experimental project/idea:

I want to attach a tiny radio transmiter to a whole bunch of pigeons. Each with a different musical tone (seven altogether);
Then I wish to set up a wire, very much like an electric tram line, from wall to wall crossing a street. This street as I have observed is their main flying path; this antenna/receiver like wire is then connected to a set of speakers, so that whenever the pigeons fly over the wire one can here the different tones, hopefully generating some kind of melody. The wire functions very like a linear scanner, scanning the transmiters attached to every pigeon.
I would like some tips on what I should buy or assemble. I'm a complete novice in these electronic ramblings, but I would like to see this project through, so any tips would be welcome.

Thanks.

how about a theremin?

Thanks, it's not such a bad idea, but you see I would like that every tone, 'carried' by the pigeon's transmiter could be heard distinctively. Many tones would compose some sort of a melody... a dling dlong kind of melody, quiet different from the theramine.