Sleuthing for scaup

Researchers may be closing in on identifying the reason for the decline in lesser scaup populations, says DUC director of conservation science David Howerter.

This news comes after almost 30 years of study by lead conservation biologists from across North America.

In a recent article published in the Journal of Wildlife Management, authors reveal a decrease in lesser scaup harvest hasn’t resulted in a corresponding increase in the population. They drew this conclusion by analyzing data collected over a 60-year period (1951-2001).

Read the full research article.

When considered along with previous findings, the data show that while some of the usual suspects (death and hunting) are indeed affecting lesser scaup populations, these factors alone don’t explain the continuous population decline.

“There’s no signal that survival rates have changed through the period the population has been declining,” says Howerter.

And so, what has caused the number of lesser scaup to drop from 6.3 million to 3.5 million in less than four decades?

“There are signs that reproduction has been lower,” says Howerter.

The majority of lesser scaup migrate to Canada’s boreal forest in the spring, where they nest. “And so, whatever caused that population to decline likely occurred there,” he adds.

These findings reinforce the importance of safeguarding habitat in the boreal. “We need to ensure that habitat is in good shape so the population can stabilize or grow back,” says Howerter.

Scientific evidence shows mean temperatures in the boreal forest are warming, as a result of climate change. This may be influencing the reproductive success of lesser scaup, which breed in late May and June.

“While historically the peak abundance of foods in the boreal forest and the lesser scaup breeding season would have occurred at the same time, we now believe there could be an increasing mismatch,” explains Howerter.

If found to be true, this would be especially problematic for lesser scaup. Unlike some other duck species, such as mallards, scaup appear unable to adapt by moving up their breeding season. “Lesser scaup breed at similar times, year after year,” says Howerter. Research on the impact a warming northern climate may be having on lesser scaup breeding behaviour is ongoing.

Right now, one thing is certain: safeguarding boreal breeding grounds is essential not just for lesser scaup, but other waterfowl species too. During the breeding season, the boreal forest hosts, on average, 15 million North American ducks.