some kind of goose?

Went for a walk with my brother along the Thames - first of all at Walton, and then at Shepperton to visit the places we scattered our mother's ashes. Fantasised about buying some of the houses with frontage on the river, and wondered at the houseboats. Saw quite a lot of birds - grebes, coots, mallards, a tree full of green parrots and these two - which look fairly exotic to me but I'm 450 miles away from my bird books, so no idea what they may be.

(Sorry can't get map to show me the whole details, will try to edit it another time.)- map now edited.