Bird Chirp noise coming from serpentine belt side of car below 1000 rpm.

The belt may need a tension adjustment, the belt may need replaced, or possibly a belt-driven accessory is starting to fail. Have a shop check it out for you.

Also a cam shaft position sensor will make the bird chirping sound as well....Had one to do it and sometimes it sounded like it was the front of the motor sometimes the rear and sometimes sounded like it was coming from under the intake,come to find out after further diagnostic testing it was the Cam Shaft Position sensor who was the dirty bird.