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Patuxent Science Meeting 2006 Poster Abstract

Population trends of sea ducks from the Christmas Bird Count and

North American Breeding Bird Survey

Niven, DK, Sauer JR, Butcher G

Due to the difficulty of conducting range-wide surveys of either breeding or wintering populations,

few data are available to assess the population trends of sea ducks with confidence. We

analyze sea duck data from the Audubon Christmas Bird Count using hierarchical modeling

methods that control for varying effort among circles and over time. These procedures allow us

to assess early-winter relative density patterns among states and Bird Conservation Regions

(BCRs) while also assessing trends in these regions and across the species North American

range. Over the interval 1966 - 2003, continent-wide declines were observed in 1 of 11 species.

Where sufficient data exist, we compare CBC results to estimates of population change derived

from the USGS Breeding Bird Survey. The CBC does not effectively sample offshore

populations of sea ducks; however, the CBC data can be used to assist in development of

species-specific surveys, and CBC data can be used in combination with additional offshore

Friday, September 22, 2006



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