Birds of a Feather Flock Together (for better and for worse)
You’re not imagining it. There are more geese than there used to be. Way more.
Lesser snow goose populations have ballooned by 700%, from as few as 2-3 million in the 1970s to about 16 million today.
Geese are herbivores, and in the past, they got their sustenance from marsh grasses, but they’re grazers that can thrive on a diet of corn, rice, and wheat – all of which are widely available to geese improved agricultural practices in the southern United States. Farms sprawl across the continent, and over the past sixty years, the abundance of food they provide has caused a population explosion.
According to Trent graduate student Scott Flemming, the implications of this population boom are far-reaching – and they’re felt beyond from the local parks where most of us encounter geese. Millions of lesser snow geese and Ross’ geese congregate in Nunavut each summer, but they don’t fan out evenly across the North. In areas of high concentration, like Southampton Island – an island in Hudson Bay that’s larger than Switzerland -- they’re altering both the physical landscape and the food chain.
Geese can alter tundra ecosystems, impacting other species that live there
“At low levels geese can have a positive effect on some Arctic vegetation because grazing promotes re-growth and goose feces introduce more nutrients,” says Mr. Flemming, a Ph.D. candidate in Trent’s Environmental and Life Sciences graduate program. “But intensive and long-term grazing and grubbing can have serious negative impacts. “
One impact is the exposure of shorebird nests to predators like the arctic fox. To protect themselves – and their eggs – shorebirds such as dunlins and red phalaropes rely on tall grasses to hide their nests. Lower visibility equals higher probability of survival -- foxes can’t eat what they can’t see.
In the January 2019 edition of the Journal of Applied Ecology, Mr. Flemming, Dr. Erica Nol, Lisa Kennedy and Dr. Paul Smith published Hyperabundant herbivores limit habitat availability and influence nest site selection of Arctic‐breeding birds, which documents exactly how much geese are impacting Southampton Island’s shorebird habitat and nest site selection.
Cataloguing how geese change shorebird habitat
Walking as much as 25 km a day over tundra to conduct habitat surveys, Mr. Flemming worked under the supervision of Dr. Nol and Dr. Smith, the latter of Environment and Climate Change Canada. The team visited shorebird nests after chicks had hatched, cataloguing the types and height of surrounding grasses, and counting goose fecal pellets in the square metre surrounding the nest. They estimated how exposed each nest was, both in the immediate surrounding area, and from each cardinal point in a 75m2 area around the nest.
Their results indicate that the density of shorebird nests can be far lower around goose colonies than unaffected sites, where there grasses are less disturbed. The few shorebird nests near the goose colony were much more visible and could be suffering higher nest predation rates as a result.
Mr. Flemming is hopeful that his research can advance our knowledge of goose-shorebird interactions in both theoretical and practical terms.
“Having one supervisor at Trent and one at Environment and Climate Change Canada has really helped me tailor my research so that it can be applied to support management while also advancing our understanding of Arctic ecology and bird nest site selection.”
Posted on February 19, 2019