Distribution and Dynamics of Waterbird Habitat During Spring in Southern Oregon—Northeastern California

ABSTRACT. The southern Oregon—northeastern California and extreme northwestern Nevada (hereafter “SONEC”) region provides critical spring migration habitat for waterfowl and other waterbirds in the Pacific Flyway. Information on the dynamics and distribution of waterbird habitats in SONEC during spring is needed to guide conservation efforts in the region. We grouped 1992 National Land Cover Data classes into 5 potential waterbird habitat types and used Landsat 5 Thematic Mapper and Landsat 7 Enhanced Thematic Mapper Plus satellite imagery to map flooding of these habitat types in SONEC during February–May, 2002 and 2003. SONEC included 13,727 km2 of potential waterbird habitat comprised of grasslands (37.1%), pasture/hay (24.6%), marsh (15.9%), open wetland (11.8%), and croplands (10.6%). On average, 11.9% of this potential habitat was flooded during spring; but the percentage, area, and composition varied within and among years and subregions. Total flooding increased from 693 km2 in February to 2099 km2 in April during 2002 and from 1630 km2 in February to 2125 km2 in May during 2003. Open wetland comprised 58%–74%, marsh 8%–18%, pasture/hay 4%–11%, grassland 4%–17%, and cropland 3%–8% of the flooded habitat in SONEC. Satellite imagery and land-use data provided useful estimates of waterbird habitat availability in SONEC during spring, but other methods should be tested to more accurately measure flooding of densely vegetated habitats such as marsh. With < 12% of the potential habitat flooded on average during spring, conservation programs have ample opportunity to improve the SONEC landscape for migrating waterbirds.

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