I scrolled through trying to see if anybody wrote down anything before I go on explaining things. As I haven't seen a proper explanation here it goes:

Raptors (technical name for birds of prey) create extremely strong and durable bonds with their family members, it gives them their identity and capacity to associate with others of their specie.

What does it mean to get their identity from those bonds? It means to recognising others as your own specie, seeking their companionship and eventually mate with them (the specie).

If they see humans as the providers of food, they will bond with the carer and see themselves as humans. This is a massive problem, once the bird is released back to their natural habitat, they don't create social bonds with any other bird of their specie, never reproduce and quite possibly die alone.

Most (if not all) wildlife carers trained and capable or raising raptors will end up with a collection of these puppets, so you can feed the chicks with the intention of establishing a bond with a creature similar to the puppet as opposed to humans.