Sam Robbins in his 1991 Wisconsin Birdlife wrote that ruddy ducks are “Uncommon summer resident south, east, and west.” In 1973, DNR waterfowl biologists estimated the annual breeding population at 400, and within two years their summer numbers rose to 3,200. DNR biologist Jim March was quoted in the mid-1970s saying that “Horicon Marsh attracts the largest summer population each year with smaller numbers scattered over other prairie marshes between Goose Pond and Green Bay.” Ruddys are present at Goose Pond in spring migration, and while the average number of ruddys is typically more modest, on April 24, 2011 Paul Jakoubek reported 200 ruddys just on our humble prairie pothole. (On October 30, 2000, Tom Schultz reported 27,000 ruddy ducks at Lake Maria in Green Lake County!)
Ruddy ducks are a prairie pothole nesting species with 86 percent of the breeding population concentrated in the prairie pothole region of south-central Canada and north-central United States. They are a diving duck that feeds on aquatic invertebrates, especially midge larvae. They feed most actively at night, so you’ll often see ruddy ducks sleeping during the day, head tucked under a wing and tail cocked up.
These diving ducks lay big, white, pebbly-textured eggs—the largest of all duck eggs (2.5 inches long and 1.8 inches wide) relative to body size. Energetically expensive to produce, the eggs hatch into well-developed ducklings that require only a short period of care.
The females have to be in excellent condition to lay eight eggs, an average clutch size laid in nests built over water in bulrush or cattails. This is one reason that they are the last duck to nest in Wisconsin. It is not unusual to see small ruddy ducklings in September. We remember one year seeing very small ruddy ducklings on October first!