If the base of a raised earth embankment is below the normal water level of a reservoir, it's a dam. If the base of a raised earth embankment is above the normal water level of a reservoir, it's a Bund.
I saw the Heron yesterday, it took off from a neighbours garden and was mobbed by a flock of seagulls, actual seagulls, not the popular combo. Seagulls have gone up in my estimation.
Visitors to my garden this week: Magpies trying to nest in the Hawthorn, a Heron stealing the goldfish and next door's hens leaving deposits on the rails, rearranging the the borders and gravel. Oh, and a Blue tit did look in the bird box.