Read it through once

At these non-human hours they could get quite close to the waterfowl. Herons came, with a great bold noise as of opening doors and shutters, out of the boughs of a plantation which they frequented at the side of the mead; or, if already on the spot, hardily maintained their standing in the water as the pair walked by, watching them by moving their heads round in a slow, horizontal, passionless wheel, like the turn of puppets by clockwork.