Northern Prairie Wildlife Research Center
Analyses of hunter-obtained wings suggest female survival rates have declined compared to males (A. D. Afton, United States Geological Survey, and M. G. Anderson, Ducks Unlimited Canada, unpublished data). The role of hunting in adult female survival is uncertain, but it may have increased in relative importance because harvest of adult scaup (including females) has remained stable in the Mississippi Flyway, where most scaup are shot, despite population declines and a lower immature:adult ratio in the harvest (G. T. Allen, D. F. Caithamer, and M. Otto, unpublished report, United States Fish and Wildlife Service 1999; A. D. Afton, United States Geological Survey, and M. G. Anderson, Ducks Unlimited Canada, unpublished data). Average harvest rate indices of scaup are low (2.9% of combined scaup population during 1961-96) and were least during 1986-93, a period when scaup populations were declining (A. D. Afton, United States Geological Survey, and M. G. Anderson, Ducks Unlimited Canada, unpublished data).
Banding and mark-resighting (including radiotelemetry) studies are critically needed to more accurately estimate annual survival and harvest rates, assess population trends, determine harvest policies, and model population dynamics. Moreover, banding and marking studies would provide important information to address philopatry; affiliation among breeding, migration, and wintering areas (see below); and the role of contaminants and harvest in the current population decline. We advocate implementing a banding program that targets breeding birds (particularly females) and bands greater and lesser scaup in all representative parts of their range to allow for differences in migration and wintering areas and population parameters. Banding in migration and wintering areas is a low priority unless there is a need to obtain annual survival estimates from such data. The relatively low densities of breeding scaup and their broad range will make logistics of such a banding program challenging; consequently, it will require commitments from federal wildlife agencies and Flyway Councils and pilot studies to assess logistics and cost-effectiveness.
Mark-resighting and radiotelemetry studies provide complementary approaches to banding programs. Such studies often provide information more quickly and on other aspects, such as natural causes of mortality. Scaup marked with satellite transmitters on the wintering grounds could provide information on frequency of multiple counting or undercounting of scaup during breeding ground surveys, as well as determine affiliations among breeding, migration, and wintering areas.