Although the lesser scaup is the most abundant diving duck in North America, its population has been in decline since 1985. The exact cause of this is unclear, but it is likely to be due to a number of threats, including habitat degradation and poisoning (4).
In Florida, for example, much lesser scaup habitat has been lost or degraded as a result of drainage, dredging, filling, and extensive modification of water levels by canal construction. Wetlands used by this species along Lake Erie and the Detroit River have also suffered from siltation, landfill, exotic plant introductions, and water level controls, while new logging practices in Canadian boreal forests may threaten the lesser scaup’s breeding habitat. In addition, the declining number of lesser scaups on the Illinois River, is possibly the result of the loss of prey due to sedimentation and altered water levels, as well as pollution (3).
Other threats to the lesser scaup include DDT, lead poisoning, and drought in prairie parklands, which may affect the ability of migrating females to store enough nutrients for successful breeding (3) (6). The lesser scaup is also a popular game species in the north-central U.S. (3).