Lesser Scaup - Conservation Status

Conservation Status

Although the Lesser Scaup has the largest population of any species of diving duck in North America, their population has been steadily declining since the mid-1980s, and reached an all-time low in the early 20th century. During breeding bird surveys, Lesser and Greater Scaup are counted together due to the impossibility of identifying the species unequivocally when large numbers of birds are involved. Lesser Scaup are thought to comprise slightly less than nine-tenths of the scaup population of North America. In the 1970s, the Lesser Scaup population was estimated at 6.9 million birds on average; in the 1990s it had declined to about half that number, and by the late 2000s it is estimated at 3 million individuals or less. Due to the wide breeding range and the fact that the rate of decline, though remarkable, is still not threatening in respect to the enormous overall numbers, the Lesser Scaup is classified as a Species of Least Concern by the IUCN. An increase of the decline is liable to result in an uplisting to Near Threatened or even Vulnerable status.

The causes for this stark – though not threatening, as of yet – decline remain unknown. There are indications that the breeding success is decreasing, but why this is so remains puzzling. On one hand, pollution and habitat destruction, especially in the wintering regions, has certainly increased since the early-mid 20th century. On the other hand, the narrow time frame in which Lesser Scaup breed and raise their young may be tied to some specific ecological conditions – such as abundance of key food items – which shifted winterwards due to global warming, without the ducks being able to adapt. In this regard, it is alternatively or additionally possible that Great Scaup, which may be increasing in numbers, is putting the Lesser Scaup under increasingly severe competition.

However, it seems that Greater Scaup eats larger food items on average, and the species are sympatric in part of their range and presumably have been for millennium without any problems due to competition. The experience of the past as well as the reproduction rate – even if this is declining – suggests that hunting has no major impact on Lesser Scaup populations at present either. Also, the breeding habitat is mainly in regions little-used by humans; habitat destruction on the breeding grounds is also not considered to be problematic.