If it's a simple sound.....use a loop cassette and a tape player. You can or should be able to get both for under $5.00. RS will have the loop cassette for around 3 or 4 dollars and if you don't have a cassette player you will be able to get one at any thrift store...probably around 1 buck.
Push the play button down and plug it up to your motion detector. When someone walks in front of the detector....Your Crow will crow.
If your cassette player has a mic jack, you can record the sound straight from your PC. If not you can hold the recorder up to the speakers.
Simple, cheap, easy and will work....what more could you ask for