Waterbirds as pathways for the movement of aquatic alien invasive species
Waterbirds are sometimes cited as dispersing aquatic invasive alien species though to-date there has been little evidence based on scientific evaluation to quantify this. In the present study the authors reviewed the available literature and confirmed that only a small number of studies (14 studies) assessed dispersal by waterbirds. The authors describe dispersal as a three stage movement of organisms that comprises the following (1) emigration or uptake; (2) movement and transport; and (3) immigration or introduction. Uptake can take place either by ingestion or adhering to feet or feathers. A number of alien invasive plants have been found in faecal samples of waterbirds including large amounts of reproductive tissue of Azolla filiculoides (EPPO Observation List of Invasive Alien Plants) in Australia. The movement of plant propagules via entanglement in feathers or on feet may facilitate the establishment of new populations especially as many aquatic plants reproduce asexually. Coughlan et al. (2014) showed that Lemna minuta is readily transported between the feathers of waterbirds; with little effect on the viability of propagules.
Sources
Coughlan NE, Kelly TC, Jansen MAK (2014) Mallard duck (Anas platyrhynchos) – mediated dispersal of Lemnaceae: a contributing factor in the spread of invasive Lemna minuta? Plant Biology 17, 108-114.
Reynolds C, Miranda NAF, Cumming GS (2015) The role of waterbirds in the dispersal of aquatic alien and invasive species. Diversity and Distributions DOI:10.1111/ddi.12334