A) Mallard do form strong pair bonds, though the drake loses interest in the duck as soon as she starts incubating. Most pairings only last a season, and it?s unusual for the same two birds to pair again the following year. However, according to the reference work Birds of the Western Palearctic, ?Old mates in resident populations sometimes pair up again in subsequent seasons?, which is what appears to have happened in the case you have observed.
Intriguingly, resident mallard will start to form pairs as soon as the drakes emerge from their eclipse plumage, which takes place in early September. In contrast, pair formation in migratory mallard populations doesn?t take place until the end of the winter. Despite forming monogamous pairs, drakes are promiscuous, often attempting liaisons with additional duck.