Why would it be an escape? Any signs of captivity? Smew are an uncommon but annual visitor to the area - there's always several all winter at nearby Barleycroft.
In reply to Richard T:
Whenever I have seen them on the reserve previously they have been in small groups. Though I only visited Swavesey Lake today, this female is on her own so I was speculating to solicit views (thank you for yours).
In reply to Dirk B:
Smew are an annual winter visitor to the lakes & females (redheads) are regularly seen on Swavesey Lake. No reason to assume it's an escape.
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