long distance microphone
I had great success with a shotgun microphone which I constructed from an old (VERY OLD) magazine article. Fortunately, I have the original article scanned and stored. (Who says it's BAD to hoard stuff!!!)
When I built mine, I metricated all the dimensions and reduced the pipe diameter a bit. The original used an electret mic insert, but I upgraded it to a "real" mic insert which I salveged from a mic with a damaged body.
I built a small but high quality mic amp, powered from a 9V battery which was built into the microhone assembly.
I have used mine for many years (I am a pert-time wildlife film-maker) with great success. I is a bit unwieldy, but when mounted on a tripod alongside the camera, the results are impressive.
I would imagine that plastic tubing (high density) would work just as well as the aluminium tubes I used in the original.
Enjoy.