Anyone know anything about the sociology and natural history of Mallard
ducks?

We have an intriguing situation in our garden. The same family of
mallard take up residence in our garden every year (have done for about
the last five years). They consist of a pair and a younger drake. They
always arrive, from who knows where, in the third week in March and
always leave, for who knows where, in the third week of June. In the
meantime they waddle happily around the garden, completely unafraid of
us and roost under various hedges. Occasionally they nibble at the wild
bird seed we put down; on hot days they dabble in our pond and on one
occasion we had to check the young drake into our local vet. (He had
dislocated his hip in a clumsy landing, it was ok after a week of
anti-inflamatory injections, physiotherapy and feeding and was returned
to its parents(?) fit and well - the vet did it all for free - because
it was a wild animal). We have never seen any signs that these mallard
are actually breeding here - although a fair amount of ducky eroticism
seems to go on - not all of it straight.

Any body got any ideas where these mallard might get to between June and
the following March. Are mallard migratory?

rjbl