Waterbird Use of Harvested Rice Fields in the Sacramento Valley
The impetus for this study was the legal restriction on burning rice straw after harvest as a means of disposal. Several agricultural treatments of rice straw were proposed as alternate methods of disposal, mainly through enhanced decomposition. Harvested rice fields are critical wintering habitat for migratory birds in the Sacramento Valley, so an assessment was needed of the potential effects on migratory birds by changes in agricultural field treatments. This project was designed to representatively sample the dynamics of agricultural treatments and wintering waterbird use and to project habitat preferences of waterbirds on effects of long-term changes in rice agriculture. Because winter flooding of harvested rice fields is one of the alternative straw treatments, the incumbent also assessed quality of water drained from fields in spring as it might affect salmon and other biota of receiving waters. This project has resulted in the first catalogue of waterbirds that use harvested rice fields, made the first density estimates of such bird use, related bird use to field treatments in a statistically defensible way, is the only source of quantitative information on current agricultural treatments of harvested rice fields, and has generated the only information on water quality of flooded harvested fields. Our work also estimated the potential food available to wildlife after rice harvest with stripper headers, new harvest technology likely to increase in use in the Valley. This project also complements various research programs at the University of California which are examining the agronomic aspects of the alternate straw treatments. Our information is being used by agricultural programs of Ducks Unlimited, the Fish and Wildlife Service, the University of California, and the Nature Conservancy. Field work for this study concludes this year.
