The influence of macrophyte beds on ducks breeding on fishponds of the Dombes region, France

摘要

Densities of duck pairs and females with broods were highest when macrophyte coverage was between 21% and 40% of total pond area amongst a sample of 80 artificially managed fishponds in the Dombes region of eastern France. Nesting success (brood : pair ratio) and numbers of ducklings in 3-week old Pochard Aythya ferina broods were greater on these types of ponds than those with macrophyte cover of < 20%. Epiphytic invertebrate biomass in a sub-sample of 36 ponds was lower when macrophytes covered < 20% of the pond area whereas invertebrate biomass density was lower when macrophyte coverage was > 40% of pond area. Significantly higher invertebrate biomass densities were observed in filamentous algae than in all other submerged macrophyte species inspected in this study.