Flock of Dark-bellied brent geese (Branta bernicla) flying in formation across the setting sun, Wallasea Island RSPB reserve, River Crouch, Essex, UK, March 2011. Photographer quote: 'Every winter thousands of geese arrive from their breeding grounds in northern Russia. Sitting on the sea wall on Walleasea Island as they fly over itís hard to imagine you are so close to London and the Thames Gateway.' Did you know? Britainís estuaries and mudflats are like a massive Mars Bar to thousands of wintering geese and ducks.