In fact, these are two distinct species -- similar in shape and size.

In reality these are two distinct species— similar in shape and size, but never appearing at the same time. Over the following centuries, birds were said to morph into humans, plants, and even the timbers of ships. This last transmutation was especially popular with many Christian clergy. If barnacle geese were truly made of wood, they could be deemed vegetarian and enjoyed during meatless fasts.