St. James's Park: Ross'sling Through the Leaves
Bigger a fledgling in large!
Extra: Mandarin duck's pretty plumage
It's the Ross'sling! It had to be the Ross'sling...
I was trying to describe the goose-y shapes with the contrasty sunshine, but only the older young Ross's goose was really playing ball (and shaking its tail feathers); the Ross'sling and its parents were mostly fully in sunshine or wandering closer in the shade (tempted over by someone with seeds).
I preferred some of my Mandarin duck pics, but it had to be the Ross'sling.
Others here (or right from Ross'sling with parents)