I've seen a bird today that couldn't move at all; it had a broken wing because it ran into a wall… It wouldn't eat at all either even if it tried to.. I wasn't sure but I was thinking if this bird had avian influenza?
well, birds can have a lot of symptoms that can mean a lot of thinks. With the bird you saw, it is probably normal. Accidents do happen with birds, we normally dont see them. Sounds to me like its in a lot of pain, and cant fly for food, which explains the energy issues, and pain can stop you from moving also. It may have hurts organs or other bones inside its body. You can tell when a bird is sick, discharge coming from the nostrils, dull feathers, dull eyes, no energy, sleeping a lot, and you can even tell by the state of their droppings !! haha. but i doubt it has influenza