Polar bears, grizzly bears make URI scientist’s goose research a challenge

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‘I enjoy going places where there are animals that can eat me’

KINGSTON, R.I. – September 28, 2015 – Scott McWilliams spent two weeks in August at the edge of Hudson Bay in the Canadian Arctic capturing snow geese as part of a long-term population study. But as he did so, he was always looking over his shoulder.

That’s because the University of Rhode Island scientist’s study site on La Perouse Bay abuts the town of Churchill, Manitoba, which calls itself the polar bear capital of the world. And there were plenty of the massive animals – along with a few grizzlies and black bears – wandering the area.

“It was fun to be on the ground with grizzly bears and polar bears,” said McWilliams, URI professor of natural resources science. “I enjoy going places where there are animals that can eat me.”

The focus of his research, however, was on trying to understand how the growing snow goose population is affecting the habitat on its breeding grounds. The birds spend the winter in the south-central United States, where improved management of national wildlife refuges has enabled more and more geese to survive the winter and return to the Arctic to breed.

“Arctic goose populations are primarily limited by what happens on their wintering grounds in the U.S.,” explained McWilliams. “There are always boom and bust years of productivity in the Arctic, but these are long-lived birds that have evolved to use an Arctic ecosystem where breeding success only happens every few years.” But because the birds now find plenty of food to sustain them through the winter, more and more birds are making it back north.

So for the second year in a row, McWilliams joined a team of scientists as part of a 45-year study called the Hudson Bay Project. The researchers used a helicopter and ground teams to herd geese into groups of 500 to 1,000 birds – the birds were molting their feathers and unable to fly – and then into temporary pens where bands were placed around their legs, those already banded were recorded, and the birds were weighed and measured.

“What you immediately notice when you’re doing this is whether it’s been a good year for productivity,” he said. “If it’s a good year, then for every pair of adult geese there are three to six goslings. This year there was maybe only one gosling per pair.

“It turned out that this was a very difficult breeding year for many Hudson Bay goose populations,” McWilliams continued. “The weather was perfect, it was ice free early, the geese arrived and nested, and the goslings hatched. But then there was really cold, wet weather when the goslings were most vulnerable, and lots of them died.”

The poor year for reproduction is not likely to ease the overpopulation of snow geese, however. Goose populations have been increasing for about 25 years, which has resulted in amendments to the Migratory Bird Treaty Act to ease the restrictions on hunting.

“The snow goose harvest has increased to over a million birds, but it hasn’t put a dent in the population,” said McWilliams, who studied Arctic geese for his doctorate in the 1990s. “So there’s a lot of concern about how that’s going to play out.”

It may be that the geese will end up overgrazing their breeding habitat at a large scale and be forced into inferior habitat, which may result in a decline in breeding success and ease the overpopulation. Increasing predation by Arctic foxes, grizzly bears and now polar bears may also be a factor. Or maybe the geese will just keep on increasing in numbers. Only time will tell.

In the meantime, McWilliams and his colleagues – occasionally including URI graduate students – will continue annual monitoring of the snow goose population while also assessing polar bear and caribou numbers and mapping vegetation to see if it recovers. This year for the first time his colleagues even used drones to get aerial views of the breeding grounds, the abundance of predators, and the vegetation.

“These kinds of studies give us good information about longevity, survival rates, harvest patterns, and other important life history and ecological data that will contribute to management decisions in the future,” he concluded.