Gooseberry Mallards?

Heavy rain recently meant that the playing fields over the road from my house got a bit flooded.

Invariably, the local mallards found the pools - two drakes and one duck. Before long, they had waddled over the road and into my garden. They were aiming for the spilt seed under my bird table.

I've noticed quite a lot recently that the mallards are going round in threes - always two drakes and a duck. Is one of the drakes playing "goosberry" - or do both the males end up fertilising the female? I haven't found an aswer to this anywhere.

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