Abstracts

Presented by Joseph R. Marty - Email: jmarty@wlf.la.gov

Forage biomass estimates at regional and other large spatial scales are fundamental to estimating habitat carrying capacity for migrating and wintering waterfowl. Hundreds of wetland bird species use rice fields in the Gulf Coast Prairie region of Louisiana and Texas. Rice and associated natural seeds in these fields are valuable sources of energy for these birds during migration and winter, providing as much as 42% of the estimated habitat carrying capacity for wintering waterfowl in this region. We conducted a four-year study of the spatial and temporal dynamics of seed abundance and use of fields by wetland birds. We modeled variation in rice and natural seed abundance among production and idled rice fields in southwestern Louisiana, southeastern Texas, and the Texas Mid-coast in August and November 20102014 relative to environmental variables and field-use classification. Rice biomass was greatest in November in fields with an unharvested second crop of rice (i.e., ratoon; 837.7 kg[dry]/ha; CV = 16.7%) and least in fields where no ratoon was grown (119.3 kg/ha; CV = 18.5%). Natural seed biomass was greatest in idled rice fields in October (477.3 kg/ha; CV = 24.8%) where soils and vegetation were disked and in idled fields with standing native vegetation in November (304.8 kg/ha; CV = 17.1%). Wetland bird species richness and abundance were greatest in shallowly flooded (115 cm) ricelands with sparse vertical vegetation (120 cm). Duck abundance was greatest in shallowintermediately (130 cm) flooded ricelands with short vegetation (115 cm). We encourage the production of ratoon rice crops and moist-soil plant communities in idled rice fields, and subsequent shallow flooding during autumnwinter which would significantly enhance food resources for waterfowl and other waterbirds in this continentally important landscape for North American avifauna.