In this series, we’re exploring the interactions and impacts of beavers on other wildlife species. Do beavers help or hinder water voles? How do invertebrates react to a species they haven’t seen for 400 years? Explore the science as we dive into each topic.
The Eurasian beaver, Europe’s largest rodent, is an iconic species renowned for its engineering skills and ability to modify its surroundings, creating complex wetland habitats.
It has been well documented that beaver-modified landscapes have a positive impact on the diversity, density and abundance of bird species, particularly through the new wetland habitats they create and how they alter the structure of the riparian zone(the areas and banks next to rivers). Parts of eastern Germany have seen the return of cranes to beaver wetlands, black storks are increasing and nesting in Belgium and duck numbers have increased significantly in Finland (Muller-Schwarze, 2011).
Meanwhile in Cornwall, Woodland Valley Farm has seen its 11th new bird species record since beavers arrived.
Woodland Valley Farm is home to the Cornwall Beaver Project, a small and secluded 5-acre study site managed in collaboration with Cornwall Wildlife Trust and the University of Exeter. Two adult beavers were released into the enclosure in June 2017, since then the project team has investigated their impact on hydrology with a particular interest in the risk of flooding for the downstream village of Ladock, a location prone to floods. Since their introduction, water now takes over an hour to travel through the site compared to just 15 minutes prior to the beavers’ arrival.
Different bird species, from firecrest and willow tits (the UK’s most threatened resident bird which nests in standing deadwood) to water rail and cormorants have been recorded on site, and on May 4th Woodland Valley Farm announced the arrival of garganey ducks.
“It’s completely wonderful to see new species on the farm, particularly when they’re species that we know need wetlands,” said Chris Jones, a founder of Beaver Trust and owner of Woodland Valley Farm.
Where do garganeys and beavers meet?
Garganeys, Spatula querquedula, are Britain’s only species of summer migratory duck, flying over from central Africa in spring and returning in autumn. There are only an estimated 105 pairs in the UK, found mostly in central and southern England. They prefer shallow wetlands, with flooded meadows and ditches that make them difficult to spot. Their ideal site is a wet grassland or marsh which is crisscrossed with a network of vegetated ditches – this is where beaver canals may offer an ideal landscape.
Beaver canals are forage trails built through active digging or repeated trail use that fills with water (Wilsson, 1971; Muller-Schwarze 2011). These canals create access corridors, which are often exploited as habitats by many other species like amphibians or aquatic invertebrates.
Garganeys are dabbling ducks, which means they don’t dive but feed along the surface of the water. This can involve skimming along the surface or sweeping from side to side to cover more surface area. During the breeding season, they eat mainly aquatic invertebrates, and dabbling is an efficient way to feed on the small aquatic insects that stay on the surface. They’ll also feed on molluscs, worms, insect larvae and crustaceans.
Fortunately for garganeys, beaver wetlands have high invertebrate biodiversity, largely due to the habitat heterogeneity they create (Bush and Wissinger, 2016). An important driver of this is the diversely vegetated edges of beaver ponds, particularly as newly dug channels mature (Hood and Larson, 2014), and the increased insect biomass seen (McDowell and Naiman, 1986). As well as this, beaver dams raise water levels and slow the flow of water, expanding food opportunities for ducks as the slower flow further encourages a diversity of plants and invertebrates.
These changes that have been brought about by beaver activity don’t just benefit ducks: “One of the birds that people get really excited about are willow tits as they’re the fastest declining woodland bird species of bird in the country. What the beavers tend to do is to change the composition of the woodland so it suits willow tits, so that’s incredibly important.”
“I would say the big one for me is the green sandpiper – I’d never heard of them before and they actually require inland freshwater pools for half the year, so that correlates very closely with what beavers are creating.“
How do beaver ponds support duck breeding?
Beaver ponds are also structurally diverse, which is often cited as a reason why they’re popular with many bird species. Their activities enhance the foraging, nesting and breeding opportunities for a diverse range of birds from woodpeckers and willow tits to kestrels and owls.
Garganeys like areas that are rich in water and riparian vegetation so they can hide their nests in patches of grass or sedge along the shores. The nest is built amongst thick vegetation close to the water, where they’ll lay 7-9 eggs. There is widespread recognition that beaver dams play a vital role in maintaining and diversifying stream and riparian habitats (Pollock et al. 1994, Gurnell 1998, Collen and Gibson 2000, Burchsted and Daniels 2014) which could be one of the reasons the garganey ducks were attracted to it.
Beaver ponds are great for waterfowl to rear their young as they create safe places to nest and refuge sites from predators. Nummi and Hahtola (2008) found that teal breeding in beaver ponds increased compared to non-beaver ponds, taking the brood densities from 0.6 per km of shoreline to 0.1 respectively. The mortality rate of their ducklings decreased by up to three times.
In summary
While there are no research papers on the specific interactions between garganey ducks and beavers, there is a wealth of information that points to why the pair that flew into the beaver pond in Cornwall were drawn to that thriving wetland spot, and why we might look forward to more species’ return as the beavers maintain such a buzzing habitat.
“These are species which really are under threat in lots of ways in lots of places and doing what the beavers are doing is exactly what’s needed,” says Chris.
“Returning beavers to appropriate rivers will undoubtedly improve the chances for a very wide range of species.
