A new study, conducted by the Center for Ecological Research in Hungary in collaboration with the Doñana Biological Station in Spain, the Wildfowl & Wetlands Trust, and Liverpool John Moores University and the University of Lincoln in the UK, has brought attention to the overlooked role of ducks and geese in seed dispersal in UK wetlands. Published in the journal Ecology and Evolution, the research challenges previous assumptions about the limited ability of plant species without fleshy fruits to disperse via animals.
In the UK, Canada Geese are commonly found in urban areas, known for their abundance and their unfortunate habit of fouling parks with their feces. However, this study delves into a more positive aspect of their behavior, highlighting their contribution to seed dispersal—a crucial ecosystem service.
The study compared the plants dispersed by mallards and Canada geese in 18 different wetlands across northwest England, including urban and rural areas. Researchers collected and examined over 500 droppings from the waterside, identifying and germinating more than 900 intact seeds to prove their survival after passing through the birds’ digestive systems.
“Although Darwin recognized the importance of migratory waterbirds in dispersing aquatic plants, this is the first detailed study of seed dispersal by ducks ever to be conducted in the UK, as well as the first European study to compare coexisting ducks and geese,” stated Andy J. Green, co-author of the paper.
The findings revealed that mallards and Canada geese play complementary roles in seed dispersal. Mallards dispersed more aquatic plants, especially those with larger seeds, while Canada geese were more effective at dispersing terrestrial plants.
The study challenges the assumption that only plants with fleshy fruits (approximately 8% of European flowering plants) are dispersed inside birds’ guts. Both ducks and geese were found to be vectors of dispersal for a variety of plant species, contributing to the connectivity between isolated plant populations in different habitats, including urban parks.
Notably, even wind-dispersed trees, such as the Silver Birch, were found in the feces of both birds, suggesting that wildfowl can disperse seeds much farther than wind alone.
The study also emphasized that these birds can continue to move seeds months after they have been produced on the plants, contributing to adjustments in plant distributions under climate change. Additionally, the research raised awareness about the potential spread of alien plant species from urban parks into natural habitats by wildfowl.
“We have been wrong to assume that only the 8% of European flowering plants with a fleshy-fruit are dispersed inside birds’ guts,” said senior author Ádám Lovas-Kiss. “Our study shows that many other plants are dispersed by birds, and that we need to pay much more attention to the role of ducks and geese as vectors of dispersal in urban ecology, as well as in natural ecosystems. Even alien geese can provide an important service by dispersing native plants.”