No it realy is a young bird, hatched this year. It was together with 2 other young of the same species in a very low nest - about a meter high on display near the entrance. In amother - similar - nest next to this one there was a Steller's sea eagle on show - see this picture http://www.zoochat.com/457/vogelcommando-steller-s-sea-eagle-chick-448509/
So these birds would nest in nests that are low, close to ground? Or these are just additional nests for young eagles, so they can explore, seat, rest in them?
These nest are display-nests in which hand-raised birds are shown to the public. Normaly nest of Sea-eagles are places much higher in trees or against walls. I know however also of ground ( or almost ground ) nesting birds but in these cases one ( or both ) birds were not or almost not able to fly because of amputated or broken wing(s).