The right/left wings and feet of a parrot cannot be independently retextured

(This issue first appeared in 17w13a)
The right and left wings and feet of a parrot cannot be independently retextured from one another, making the model parts always look the same, limiting the player's resource pack creativity.

Steps to Reproduce:

1. Download and apply the following resource pack:
   ParrotWingFootTexture.zip
2. Spawn a parrot

Observed Behavior:

Both wings and feet will look the same with the pack.

Expected Result:

Because only one model part's texture was changed for the wing and foot respectively, only one wing and/or foot would be changed.

Screenshots/Videos: