A lone visitor

I saw this white Pigeon for the first time although it has been sighted before by others.  A senior birder explained that it is 'a feral species of the original Pied Imperial Pigeon'.  Our senior birder further added that the colour on the tail and the wing patch are faded but otherwise it is the same as the original species.
     The stanford.edu website defines feral birds as "ones that have escaped from domestication and have managed to establish breeding populations in the wild. Feral populations are the results of accidents -- not of releases by people who intended to add new birds to the local fauna."