Seed density and waterfowl use of rice fields in Camargue, France

Abstract

ABSTRACTEuropean rice fields provide potential nocturnal foraging habitat to waterfowl during winter. Agricultural practices may influence seed density and accessibility, thereby influencing the extent to which ducks use this managed habitat. To assess the potential influence of post‐harvest stubble‐management practices (i.e., flooding, burning, chopping, disking, plowing, and their combinations) on waste rice and weeds, and to evaluate the link of the latter 2 with nocturnal duck abundance, we conducted an experiment in rice fields of the Camargue, France. We assessed the density of available seeds 3 times across the winter, from harvest in late October to departure of the wintering ducks in early February, over 2 winters (2012–2013, 2013–2014). We monitored nocturnal duck use of the fields during the second year. Initial post‐harvest rice and weed seed densities were positively correlated and highly variable. Mean seed density was not dependent on straw management procedure (i.e., burning, chopping, disking). Average rice density decreased by 89% and weed seed density by 69% between harvest and late winter. Seed depletion rate was dependent on initial seed density, and was greatest in plowed fields for rice. Winter flooding did not significantly affect seed depletion rate but was the main determinant of nocturnal duck use of the fields. Duck numbers were lower in burned fields than in chopped or disked fields. One hectare of rice field could support an average of 43 mallard (Anas platyrhynchos)‐sized ducks/day for the entire wintering season (i.e., 5,202 duck‐energy days/ha) given initial post‐harvest seed densities. Harvested rice fields have a great potential as nocturnal foraging habitat for wintering ducks in the Camargue. Plowing should be avoided and flooding promoted to better allow ducks to use these fields. © 2016 The Wildlife Society.