What draws these small geese to stop at a bay in northeastern New Brunswick?

It's likely that most New Brunswickers have never heard of the Atlantic brant, a small goose that seems to have been dipped halfway into black ink. But there was a time when there were so many they would block the sun as they migrated north. 

"Many locals are not old enough to remember when there were lots of brants," said Melanie-Louise Leblanc, a researcher at the University of British Columbia who grew up in Campbellton in northern New Brunswick.

"But their parents remembered, and many have mentioned that they've heard stories of black clouds of brants passing through the Maritimes." 

Today, about 1,000 Atlantic brant pass through New Brunswick, and new research shows how the species depends on a small wetland on the province's eastern coast. 

According to Leblanc's 2018 research, recently published in the Canadian Field-Naturalist Journal, Tabusintac Bay in the notheastern part of the province has been critical to the Atlantic brant's survival.

"This is one of the very few areas where there are large numbers of brant," said Leblanc. "They come there because of the eelgrass." 

Unlike other species, such as the Canada goose, which forages on land, the Atlantic brant relies on marine plant life, specifically eelgrass, as the main food source for the tiny geese that typically weigh around 1.2 to 1.7 kilograms.

Leblanc describes eelgrass as "underwater meadows" of yellow grass and says between the 1930s and 40s, a wasting disease caused by a slime mould all but wiped out that critical food source along the eastern seaboard. When the grass disappeared, the Atlantic brant population was devastated. 

"[There was] a 90 per cent decline in the brant population when the eelgrass declined," Leblanc said. "That's how ... dependent this bird is on this plant." 

And when the eelgrass eventually recovered, the little goose did not. In fact, the migration route of the entire species was fractured.

The Atlantic brant breeds in the Canadian Arctic and northern Greenland. Before the harsh winter months, the bird flies south to spend the season on the Atlantic coastline between Massachusetts and North Carolina.

Prior to the 1930s, the species would fly to the Maritimes, making stops along the coast to feed and rest on its way down south and on the way back to the Arctic in the spring. 

When the eelgrass died off, Leblanc said, it forced most of the Atlantic brant population to fly directly overland to James Bay, north of Ontario and Quebec, where there are areas rich in eelgrass. But that's a 1,500-kilometre journey without food. 

"It's very taxing for a bird, because resting during migration is important, having food is important, so it's just very impressive," said LeBlanc.