They're pillow boxes with 3/4" circles for the stomach 'feathers', hearts for feet and beaks, ovals for wings and 1.25" circles plus 3/4" circles for eyes.
Here is a close-up of the yellow guy:
As you can see the rhinestones added that little extra. These are perfect for filling with little treats.
For those Munchkin fans, here's the photo I was sent today as I've had to be away from my angel girl today: