Mute Swans, Britain’s largest bird and one of the heaviest flying birds in the world, waste no time scaring other birds, predators or people away from their nests. This Grey Lag Goose sailed too close for comfort to the swan’s nest. First of all, Mute Swans try the ‘parallel swimming’ approach but it didn’t work with the large and also aggressive Grey Lag. So, then the Swan just swam headlong towards the Goose until it took off and disappeared to the other end of this pool at Wicken Fen. Conditions: Warm and sunny. Temperature: Max 20- Min 9c.