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

Abstract

European 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.

Waterbird response to variable-timing of drawdown in rice fields after winter-flooding

“…flooding, disking, etc.) also influence waterbird use [ 12 , 43 , 51 , 52 ]. However, the degree to which these practices influence use during drawdown after 3 or more months of flooding is unknown.…”

“…Available food resources can effect waterbirds’ use of a field and many factors affect seed, vegetation, and prey abundance in rice fields such as post-harvest practices, pesticide and nutrient levels leftover from the growing season, water sources, and placement of the field on the landscape [ 51 , 53 , 54 ]. The clustered design of our fields and the random effect of farm in our analysis controlled for differences in food availability due to farm-level differences in the above factors prior to the start of variable drawdown.…”

Artificial Aquatic Ecosystems

“…The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results. Bird habitat Open water salt marsh management and mosquito ditches USA [191] Integrated marsh management USA [192] Rice fields Philippines [193], Brazil [189], China, Japan [194], France [195] [197,198] Wetland/aquatic plant habitat Paddies and ditches China [199,200] USA [191] Hot springs swimming pools and baths Turkey [211] …”

“…Paddies / fields China [194,199], USA [212], Philippines [193], Brazil [189], Japan [194], France [195] …”

Participatory mapping: Exploring landscape values associated with an iconic species

“…A series of global changes have impacted the breeding colony over the last decade including the reduction of salt production (Béchet et al, 2012), changes in ownership of parts of the salt pans (Ernoul & Wardell-Johnson, 2016) and agricultural intensification (Pernollet, Cavallo, Simpson, Gauthier-Clerc, & Guillemain, 2017) exacerbating humanflamingo conflicts. These changes have caused greater variation in annual and seasonal water levels, reducing flamingo breeding conditions some years.…”