Mallard sitting on rooftops? Good vantage point when looking for nest sites, or for defending territory from rival drakes.
Colchester has wild Canada Geese, Mute Swans & Mallard, the odd Domestic Goose, and a nice group of Chilean Flamingos.
Not a birdy zoo at all.
Yes, thinking about it some more, its obviously connected with that, they can survey the area from a great height. Always seems a bit odd seeing them like that.
Colchester's lake area and water quality always looks pretty dirty to me, I would think most waterfowl wouldn't survive long there.