Ontario researchers say a booming snow goose population is affecting the habitat and behaviour of arctic-breeding snowbirds, leaving them vulnerable to predation.
Scott Flemming, a doctoral research candidate at Trent University, says the shorebirds he’s studied in Nunavut have been unable to adapt to the changing conditions over the course of a decade.
His research was recently published in the Journal of Applied Ecology and funded partially by Environment and Climate Change Canada.
Flemming says the snow goose population is about 15 million, which is an exponential increase over the last six decades likely due to more corn, wheat and soy available when they overwinter in the southern United States.
He says that has led to a significant decrease in shorebird population over that time frame and he sought to understand the underlying mechanism.
Flemming says goose grazing and foraging lowers the height of grasses and sedges that shorebirds use to hide on islands where the geese nest.
The shorebirds, such as the white-rumped sandpiper and the black-bellied plover, continued to nest at the same site, despite the habitat getting worse over time, Flemming said.
“The geese are limiting the availability of habitat and shorebirds aren’t responding as quickly to that change,” he said.
The researchers found that the grasses and sedges the shorebirds use for cover are longer farther away from a goose colony, thereby offering more concealment.
The data shows shorebird density increases the farther they are from goose-nesting sites, suggesting geese are playing an important role in their population demise, Flemming said.
The team looked at three study areas in Nunavut: two within the East Bay Migratory Bird Sanctuary on Southampton Island and one on the uninhabited Coats Island.
“The geese are having a significant impact on the habitat and it’s affecting shorebirds,” Flemming said.
“We are now looking into the idea that shorebirds who have sites with less concealment may be suffering higher predation rates.”