USING BBS AND THE ATLANTIC FLYWAY BREEDING WATERFOWL SURVEY TO ESTIMATE COMPOSITE TRENDS OF WOOD DUCK IN EASTERN NORTH AMERICA
The North American Breeding Bird Survey (BBS) provides extensive information on population change for >420 species of birds. It is a count-based omnibus survey; however, results among species vary widely in precision of estimates, and the population index provided by the analysis is not readily interpretable as a population size. A variety of additional regional surveys have been established in North America to ensure that reliable information exists for species of management interest. Combining information from these regional surveys with BBS data can provide more precise estimates of population change and provide a means of deriving population estimates for the BBS range. We describe a hierarchical modeling approach for combining BBS results with results from the regional Atlantic Flyway Breeding Waterfowl Survey (AFBWS), and scale BBS index to a population estimate. We implement this analysis for Wood Ducks in the Atlantic Flyway. The AFBWS uses 1 km square plots as its sample units, and was initiated in 1989 to provide population estimates for waterfowl in the Northeastern United States. We analyze both surveys using log-linear hierarchical models, controlling for factors influencing detection in both surveys, and adjust combined results to the level of the AFBWS. Both surveys indicate increasing populations, and the AFBWS results are more precise than BBS results for comparable time intervals. Regional abundances vary by physiographic regions, and we use those regions as the geographic scale for adjustment of the BBS. Initial results from the AFBWS indicate that the Wood Duck population in the Northeastern US has increased from approximately 900000 birds in 1993 to 1.2 million in 2013. Scaling the BBS data in the southeastern US and combining it with the AFBWS data, the model indicated that Flyway-wide population estimates were approximately 2 to 5 times greater than the estimate based only on the AFBWS survey area.
Sauer, J. R., USGS Patuxent Wildlife Research Center, USA, email@example.com
Zimmerman, G. S., USFWS - Division of Migratory Bird Management, USA, firstname.lastname@example.org
Location: Emerald Mountain - Bible Point
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