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Declines of Greater and Lesser Scaup Populations: Issues, Hypotheses, and Research Directions

Summary Of Issues


4. What information is needed to manage greater and lesser scaup separately?

Separation of the 2 species in surveys and other data sets is important for addressing the decline in scaup populations and would allow setting separate NAWMP population goals and deriving management strategies. We reviewed the various data sets and considered the information required to facilitate separate management.

Examination of Issues

Waterfowl Breeding Population and Habitat Survey.--Additional analysis of BGS data can lead to improvements in survey design. Analyses should examine social groupings, distribution and timing of the survey, and consider restratification of the survey for scaup. Biologists noted that increasing numbers of ring-necked ducks (Aythya collaris) seemingly correspond with declining numbers of scaup in some areas. This relationship should be examined to see if improved ability of aerial survey crews to separate scaup and ring-necked ducks contributed to an apparent change in numbers. Analyses also should compare breeding population estimates of scaup to species with a similar breeding range (e.g., wigeon, bufflehead [Bucephala albeola], goldeneye [Bucephala clangula, B. islandica]). Detailed reports of pilot-biologists, containing information on ice-out dates and habitat and survey conditions, should be reviewed because they may contain information on accuracy of annual scaup population estimates.

The BGS, which is timed for mallards, provides only a rough index of scaup population numbers. A new June survey that could provide a better scaup population estimate should be evaluated. This would require recensusing some May survey routes at a time appropriate for scaup.

Separation of Species during Waterfowl Surveys.--The most important need was a practical way to separate the 2 species during BGS. Separation of the species cannot be made effectively from aircraft because they tend not to fly for fixed-wing aircraft and dive or hide when low-flying helicopters approach. The only method to assess species composition in the surveyed areas is a ground survey from Hudson Bay to the west coast of Alaska. We recommend first conducting a pilot ground study to sample an area thought to contain mostly greater scaup and several areas containing a mix of the 2 species. We did not evaluate logistics or discuss survey design. Sampling would require accounting for the patchy distribution of the 2 species among habitats. Some information probably could be gathered on national wildlife refuges in Alaska. The ground survey would require a coordinator to plan the study and work with the aboriginal groups and others to arrange access.

It would be valuable to review recent and historical reports (e.g., general bird and wildlife surveys, impact statements, etc., many of which are unpublished) for areas within the scaup breeding range, particularly the boreal forest. These may contain information on distribution of each species.

Also needed is review of waterfowl migration and winter survey data, including individual state migration surveys, Great Lakes surveys (e.g., Long Point, ON), midwinter surveys, and other surveys. Two new surveys that may be useful are a coordinated Great Lakes survey and improved Gulf Coast surveys, specifically in Louisiana and Florida. Many scaup use these areas during fall and winter. J. Goldsberry suggested that greater and lesser scaup could be separately counted from survey aircraft in fall and winter based upon wing stripe pattern when ducks are flushed. New or expanded surveys could be further justified based on other species that are either poorly surveyed or which may have declining populations, such as scoters, oldsquaw, and mergansers (Merganser spp.). These surveys should be coordinated with Sea Duck Joint Venture efforts.

The Parts Collection Survey data, and possibly state or refuge bag check data, should be reviewed in more detail in terms of distribution, age, and sex. Additional sampling of hunters in the Parts Collection Survey specifically to obtain scaup (which are often shot late in the hunting season) would bias species composition data obtained and thus is not recommended. However, additional bag checks or special wing surveys in selected areas may provide information on species composition, age, and sex.

Banding/Marking.--Potential banding areas could be identified using GPS locations from the BGS to locate concentrated breeding areas. It would be difficult to band large numbers of breeding ducks or broods. Molting birds can be banded, but their breeding area is unknown. A program should be designed to band scaup in all representative parts of the range to allow for differences in migration/winter areas and population parameters. It is a low priority to band in migration/winter areas, unless annual survival estimates are needed for these areas. It may be useful to collect new banding data and compare with older data from certain areas.

It is important to tie major breeding and molting areas for each species with migration, wintering, and harvest areas. Satellite transmitters attached to scaup on winter or breeding areas would provide information more quickly than a banding program, but sample size and costs would be concerns. Scaup marked with satellite transmitters during winter could provide data on multiple counting or undercounting of scaup during the BGS.

Investigators should assess condition of individual birds when marking because this can have an important influence on survival (Pace and Afton 1999). Banding may be the only way to obtain information necessary for developing a population model for scaup. There should be a cost/benefit analysis of banding versus marking birds with satellite transmitters to determine which method provides the most useful information for management, given limited research dollars.

NAWMP Goal.--In 1986, NAWMP established a goal of 6.3 million breeding scaup (both species combined) by the year 2000 (U.S. Fish and Wildlife Service 1986); this was based on the estimated average number of scaup present during 1970-79 (6,305,195). The number of breeding scaup has not met this goal since 1984. Rather than consider the appropriateness of the current NAWMP population goal for the combined scaup population, we believe we should move quickly towards new and separate goals for each species. We recommend that the NAWMP goal be reviewed and separate goals for each species be determined by 2005.

Separate Management.--The information described above is needed to effectively manage these species separately. It would be difficult to manage harvest of the 2 species separately even if population monitoring data are available, although this could be attempted where the species are geographically separated during a portion of the hunting season.

Recommendations

We recognize that the activities listed below may run concurrently, with topics from 1-5 not given in priority order. Within each list, a high priority item is identified that should begin soon.

1. Review of available data (complete a, b, & c by 1999)

a. BGS data: scaup and associated species (High priority)

b. Harvest information (Medium priority)

c. Winter survey data (Low priority)

d. Compilation of all relevant scaup data (Low priority)

2. Separation of species in BGS (initiate 2000, complete 2005)

3. Examination and improvement of survey precision (initiate 2000, complete 2005)

a. BGS (i.e. timing, restratification) (High priority)

b. Harvest surveys (measure of recruitment) (Medium priority)

c. Migration/winter (Low priority)

4. Banding/Marking

a. Link breeding/migration/winter areas (High priority) (initiate by 1999)

b. Survival/recovery estimates - modeling data (Medium priority)

5. NAWMP Goal - Review and determine separate goal for each species (2005)


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