L. Bush, trust your memory, you are correct. Referring to and paraphrasing an Outdoor Life article from Oct. 2013, "The Science Behind Waterfowl Eyesight" - ducks do have poor night vision, yet they have 2-3 times greater daytime distance vision compared to humans Their eye muscles control both their cornea and lenses, resulting in probably both central-tunnel, and peripheral vision. Research shows ducks have highly developed daylight color receptor cones in their retinas, where they can see reds,greens,yellows and blues very vibrantly, plus an extra set of retinal cones which allows them to be receptive to ultraviolent radiation (sunlight) and unique retinal blood structures providing them with an increased sensitivity reaction to unnatural motion,(i.e. why ducks flare with motion while hunting) They can see a lot further than they can hear.
Common sense: No other reason for the colorful plumage, iridescence, mating behaviors and tribalism we see with waterfowl. For the most part, they like to decoy/mate with their own kind. Their instincts draw them to what they can see.
Ken Zaborski