Led perception

   During my daily excursions to Golden Gate Park, I see many animals, chief among them Canada geese. There are lots of them in and around the walking path surrounding Stow Lake, and although they can be aggressive at times, I enjoy seeing them very much. I feel that since it is their home and I am just a visitor, they're entitled to act pretty much as they please, anyway.
   At times, during my three or four mile walk, I choose a slightly different route, and on occasion veer from the pedestrian path to the car path. I usually find it more tranquil there, and it offers me a different view and experience of the area.
   When I take this other route, I usually step over a curb at the southwestern part of the lake, and as I continue walking, the road begins to slope downward.
   Some time ago, for perhaps a week or so consecutively, I followed this slope, and would see from a distance the object shown in the picture below. It became visible as I turned a corner around some heavy bushes, and although I saw it at closer range at least four or five times, on each occasion I always perceived it first as a Canada goose.
   It seems like my knowledge of it being something else was not sufficient to alter my vision and presuppositions of how I chose to see it.
   It makes me wonder how my vision, ocular and as a world view, can be fooled by a prior ideas that I have about things.

Is the proof in the pudding?