There are many types of bare-skinned tetrapods with feet, and many reasons why they might be hairless. This key will assume there is no genetic disposition. Altristic animals, amphibians, and hairless mammals are included in this key. Several types of birds hatch without feathers, but they all have one thing in common-- a beak.
- It has a beak. (Baby passerines - Order Passeriformes)
- It has no beak. (amphibians and mammals)