Passive internal transport of aquatic organisms by waterfowl in Doñana, south-west Spain

Aim Waterbirds may play an important role in the main- tenance of aquatic ecosystem biodiversity by transporting plants and invertebrate propagules between different wet- lands. The aim of this study is to provide the first quantitative analysis of the transport of plant and animal propagules by a community of waterbirds. Location Doñana marshes in south-west Spain. Methods We quantified the number of intact seeds and invertebrate eggs in 386 faecal samples from 11 migratory waterfowl species (10 ducks and coot), collected from 3 November to 3 December 1998 (when birds were arriving from further north), and 22–25 February 1999 (when birds were leaving Doñana). Results Intact seeds of at least 7 plant genera, and inverte- brate eggs (ephippia of at least 2 crustacea, statoblasts of at least 2 bryozoans and eggs of Corixidae) occurred in 65.6% of the faecal samples in early winter and 67.8% in late winter. Main conclusions The abundance of different propagule types varied between waterfowl species in a seasonal and species specific manner, probably owing to differences in foraging strategies, bill and gut morphology, and seasonal shifts in propagule availability or distribution. Lamellar den- sity was positively correlated with the abundance of intact propagules. Our results confirm that waterfowl play an important role in the dispersal of organisms in aquatic envir- onments by internal transport. Wherever there is a propagule bank accessible to waterbirds, transport can occur even when propagule production and waterfowl movements do not overlap in time.

Peer reviewed