Urban Ducks and Geese Help Spread Plant Seeds Across Cities

A new study has revealed that urban waterfowl, such as mallards and Canada geese, are important seed dispersers for both native and alien plant species in city parks.

The researchers found that these birds can carry seeds of various plants on their feathers or feet, or in their guts, and deposit them in different locations within and across urban green spaces.

This can have significant implications for the biodiversity and ecosystem functioning of urban habitats.

Urban waterfowl as seed dispersers

(Photo : CHRISTOF STACHE/AFP via Getty Images)

The study, published in the journal Biological Conservation, was conducted by a team of researchers from the University of Bristol, the University of Exeter, and the Royal Society for the Protection of Birds (RSPB).

They collected feathers, feet, and feces from mallards and Canada geese in four city parks in Bristol, UK, and examined them for seeds.

They also conducted field experiments to test the viability and germination of seeds after being transported by waterfowl.

The researchers found that waterfowl carried seeds of 97 plant species, including 23 alien species, on their feathers or feet, or in their feces.

Some of these seeds belonged to plants that are typically dispersed by wind or by other birds in their guts, such as dandelions, hawthorns, and blackberries.

The researchers also found that waterfowl can move seeds over distances ranging from a few meters to several kilometers, depending on their movement patterns and behavior.

Moreover, they found that waterfowl can enhance the germination and survival of some seeds, especially those of wetland plants, by exposing them to water and digestive enzymes.

The researchers concluded that urban waterfowl are effective seed dispersers for both native and alien plant species and that they can influence the composition and diversity of urban plant communities.

They also suggested that waterfowl can facilitate the spread of invasive plants, such as Himalayan balsam and Japanese knotweed, which can have negative impacts on native biodiversity and ecosystem services.

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Implications and recommendations

The study highlighted the role of urban waterfowl as seed dispersers in city parks, and the potential consequences for urban ecology and management.

The researchers pointed out that urban waterfowl can increase the connectivity and resilience of urban green spaces, by creating corridors and patches of suitable habitat for plants and other wildlife.

Moreover, urban waterfowl can contribute to the conservation of rare and threatened plant species, by dispersing their seeds to new locations.

However, the researchers also warned that urban waterfowl can pose a threat to native biodiversity and ecosystem functioning, by introducing and spreading alien plant species that can compete with or displace native plants.

They also cautioned that urban waterfowl can cause problems for human health and well-being, by fouling parks with their feces and increasing the risk of disease transmission.

The researchers recommended that urban waterfowl populations should be monitored and managed to balance their positive and negative effects on urban ecosystems.

According to the researchers, urban green spaces should be designed and maintained to enhance their biodiversity and ecosystem services, by providing diverse and native plant species, and by controlling invasive plants.

Moreover, public awareness and education on the ecological role and impact of urban waterfowl and the promotion of responsible feeding and wildlife-watching practices should be considered.

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