eub | uncertainty concerning birds

You know all of those birds that sit in the black poplars by the canal? The ones that I figured were maybe green herons or something? I have an suspicion that they could all be DUCKS. The idea of it is unsettling. Here is my data. Shortly after sunset, I went to sit on the bench by the retaining wall for a bit. Some of the birds flying to the trees have the bill shape and wing-gait of mallards, must surely be mallards. The birds perching in the trees look unducklike, have a unducklike stance, holding their body diagonally, whereas ducks hold theirs horizontally. Now, I didn't get an ironclad example of a transition between a ducklike flyer and an unducklike percher, largely because the flyers couldn't seem to find a place to land. The trees were crowded. But they looked like they were trying to find a place. If they had, they would have been perching up in a tree, the prior improbability of which for a duck is a big Bayesian part of the reason I judge (merely by their silhouettes) the perching birds to be herons, or non-duck whatevers. One in a tree was standing like a duck. Maybe the trees are mostly heron-whatevers, with the odd duck?