Agricultural lands can provide suitable habitat for birds under some conditions. 25In particular, waterfowl sometimes rely on ricefields as nocturnal foraging habitat during 26 winter if post-harvest practices make food accessible. To assess whether the winter flooding 27 of ricefields could be a major driver of duck regional abundance in Europe, we relied on a 28 combination of spatial and temporal analyses. In the former, five of the most important 29western European rice growing regions in Spain, Italy and France were compared in terms of 30 habitat composition over the 2002-2012 period. The relative importance of natural wetlands 31 and ricefields (either dry or flooded) in determining the abundance of wintering ducks was 32 then established. In the second approach, the trends in duck numbers before and after 33 implementation of winter-flooding Agri-Environment Schemes (AES) were compared in two 34 of the study regions. Both approaches highlighted the role of winter ricefield flooding in 35 explaining wintering duck numbers and complementing the natural wetlands; flooding 36 harvested ricefields improves habitat attractiveness by enhancing food resource accessibility. 37In Europe, the proportion of ricefields flooded during winter varies considerably between 38 countries (0.17 to 62%), owing to differences in policy initiatives such as Agri-Environment 39Schemes. Promoting such schemes more widely across the European rice production area 40 could make a big difference in terms of waterfowl habitat quality at the scale of their 41 wintering range. 42

Winter-flooding of ricefields provides foraging habitat to waterfowl, which in return may bring agronomic benefits to farmers. Our study experimentally tested the effect of mallards (Anas platyrhynchos) on the standing stalks and weed seed bank in the Camargue (France), both of which present major challenges for farmers. Three duck densities were tested: (D1) 5 ducks ha -1 (historical nocturnal density), (D2) 23 ducks ha -1 (present nocturnal density), and (D3) 300 ducks ha -1 (Asian rice-duck farming density). The ducks reduced the stalks significantly: -27 % (D1), -52 % (D2), and -91 % (D3). Conversely, they decreased the number of seeds by only 3 % (D3) and the seed mass by about 21 % (D1 and D3), which was not significant. Besides they had no effect on seed species richness. This study clearly demonstrates that the winter-flooding effect on straw decomposition can be enhanced by waterfowl foraging, hence showing an agronomic benefit from ducks to farmers. However, there was no clear effect in terms of seed bank reduction.