Water Whistles usually make a lovely bird sound if you put a little water in. The sound can vary depending on your breath strength, and beautifully imitate a bird. No batteries. Powered by your blow.
I had a small blue one from China when I was younger, we bought two. One was a dude and the other was a girl. I dropped one of them so it smashed and stuff, can't remember which one though. The other one's like lost somewhere. I should get some new ones next time I go to China xD