Population Energetics of Northern Pintails
Wintering in the Sacramento Valley, California
Study Area
Miller (1986b) and Heitmeyer et al. (1989) described the Sacramento Valley. During the dry winter of 1980-81, rainfall was 54% of the long-term average (
= 34.5 cm for Aug-Feb; National Oceanic and Atmospheric Administration 1980-82),
and available waterfowl habitat was primarily limited to public areas and privately
managed duck-hunting areas (duck clubs). In contrast, habitat was abundant during
the wet winter of 1981-82 when rainfall was nearly 150% of average (Miller 1986b).
We defined wetlands as managed seasonal and permanent marshes on national wildlife refuges (NWR), state wildlife areas (SWA), and duck clubs (32,000 ha; Heitmeyer et al. 1989). We also included 125 ha of rice grown on 3 NWRs as wetlands (rice marsh), because these fields were left unharvested and available for foraging ducks during August and September (Miller 1987). In contrast, we defined rice fields as harvested commercial fields on private lands, which totaled 208,000 ha in 1980-81 and 223,000 ha in 1981-82 (Larson and Hettinger 1985). These fields could be dry (burned or unburned stubble), puddled by rain, intentionally flooded, and hunted or not.
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