Delta News

How Overflight Reduces the Fall Flight

How Overflight Reduces the Fall Flight

Accompanied by her chosen drake, the hen pintail soars over the prairie pothole region, where 50 to 80 percent of North American ducks are produced. Her mission: To find a shallow, invertebrate-rich wetland to nourish both her and her ducklings. But it’s a dry year, and after an unfruitful search, the pintail continues north where she’ll attempt to nest in the boreal forest or Arctic tundra — and where her odds of achieving a successful nest plummet.

Unfortunately, overflight was a common scenario this spring for pintails, as evidenced by the 2016 Waterfowl Population Status report released by the U.S. Fish and Wildlife Service. The annual spring survey index puts the spring pintail population at 2.62 million, which is down 14 percent from last year and 34 percent below the long-term average. In southern Saskatchewan, pintails were down 60 percent from 2015. Certainly, many of those ducks responded to dry conditions there by flying farther north.

“There was a phenomenal overflight of pintails this year, because they strongly key in on the shallow wetlands that were lacking on the PPR landscape,” said Dr. Frank Rohwer, president and chief scientist of Delta Waterfowl. “They almost certainly will have lower duck production than in recent, wet years.”

However, one might ask, given northern Canada’s unspoiled habitat and lack of wetland drainage, why do nesting ducks fare so poorly in the boreal forest and Arctic tundra?

“We haven’t done enough research in these remote places to be confident in any one answer, but there are a few suspected culprits,” Rohwer explained. “First, colder climates result in shorter nesting seasons, so renesting is much less common — hens get just one chance to succeed. I also suspect northern predator populations have changed over time and could be having a greater impact than some believe. An additional unproven theory suggests northern wetlands aren’t as rich in invertebrates, which makes it harder for hens to consume adequate protein for egg production.”

The effects of overflight vary among duck species. Production decreases for mallards and pintails, but they at least mount a nesting effort. Other species, such as shovelers, largely don’t nest at all when they reach the tundra.

Not all species overfly dry areas. For instance, canvasbacks breed in parkland habitat in the northern half of the PPR. When they find that it’s dry — a rare occurrence, given the parklands’ semi-permanent wetlands — they stay put, but don’t nest.

“Another aspect of overflight is it can decrease breeding duck population estimates,” Rohwer added. “USFWS pilots conducting aerial surveys fly the prairies systematically, because that’s where most of the ducks are. They fly the boreal in much more patchy fashion, so there can be areas where ducks overfly and simply won’t be counted.”

What’s the key takeaway for duck hunters?

“I expect overflight resulted in decreased duck production and a higher ratio of adult birds in the fall flight — which are much tougher to decoy than juveniles,” Rohwer said. “It may be a little bit harder to shoot ducks this season.”