A few months ago I came across an idea that I knew my kids would love.
Make 4 signs, each with a different bird, then hold them up for the kids to know how you want them to sing.
Parrot = talk,
canary = sing,
owl = oooo,
hummingbird = hum.
So I finally got around to making the signs and since I cannot draw, found a great website for bird clipart that is free http://birding.about.com/library/blclip-direct.htm
The best is the canary with a microphone. I tried to get fun ones that really depicted the sounds the kids should be making.