Looking into research on Lesser Scaup, I came across numerous articles about diet, lipid stores, and reproductive output. All highly cited, and most published within the last twenty years. As it turns out, Scaup remain a bit of a mystery, despite all of this research.
Lesser Scaup flock. Photo by Arlene Koziol
A diving duck that breeds in the prairie pothole region of North America, Lesser Scaup have plenty of habitat and are North America’s most abundant diving duck. Despite recovering waterfowl populations since the 1980’s and 90’s (due to drought in the pothole region), the Lesser Scaup has failed to recover, and in fact, since 1966 has experienced a 59% population decline overall.
The Prairie Pothole Region of the United States and Canada is where over half of North America's waterfowl nest. This area is referred to as the "Duck Factory." Photo Credit: Krista Lundgren/USFWS
This population decline explains the flurry of research into Scaup. In 1998, researchers met for a workshop at the Northern Prairie Wildlife Research Center to try and figure out what was happening with the Scaup decline, setting off rounds of publications, hypotheses, breeding ground surveys, and migration tracking. What hasn’t been able to be pinned down, exactly, is a single reason for Scaup decline.
Guesses abound, and include interesting theories like selenium reaching high levels in tissue on Scaup wintering on the Great Lakes where the invasive zebra mussels comprise a large part of the Scaup diet, and zebra mussels are high in selenium. Yet, on Canadian breeding grounds, selenium levels were found to be normal, and those birds that had high selenium on the Great Lakes had even higher reproductive output.
Great Lakes is host to the exotic, invasive and incredibly problematic zebra mussel. Photo taken by D. Jude, Univ. of Michigan, courtesy of NOAA Great Lakes Environmental Research Laboratory FCC
One of the more persuasive theories is that their breeding grounds are literally being sucked away. As the climate warms, permafrost melts, and what had been productive pothole wetlands have now leached into the ground. In Alaska, almost a quarter of wetlands have disappeared in the last 70 years.
Along their migration route, Lesser Scaup also encounter fewer wetlands throughout the Midwest, with a high percentage of wetlands drained throughout Wisconsin, Illinois, Iowa, and Minnesota. Wetland drainage, and decreased high quality food availability, may explain why researchers found female Scaup with much lower fat reserves than birds from 1980.
Among some of our later spring waterfowl migrants in Wisconsin, Lesser Scaup will refuel on wetlands like those that occur at Faville Grove Sanctuary. The birds feast on species like pondweed, which is abundant around Faville Marsh. Sedges, water milfoil, water docks, and rice cutgrass are some of the other favorites of Scaup, and all occur in abundance at Faville Grove, making the Kettle Pond and Springer’s Pond good spots to see these birds.
Flock of Lesser Scaup. Photo by Arlene Koziol
If you visit, you might park in the pull-off on Hillview Lane and scope Springer’s Pond to the south. Scaup generally flock in tight groups, but it can be difficult to tell between the Lesser and Greater Scaup. The most prominent aspect to look for is a peak at the back of the head on the Lesser Scaup; the Greater Scaup is more rounded. Moreover, the Lesser neck appears longer, and has white barring that extends along its sides, whereas the Greater Scaup has barring on its back, but a plain white on its sides.
Written by Drew Harry, Faville Grove Sanctuary land steward
Cover photo by Mick Thompson
