Stealth bombers take a big bite out of bugs

Ducks Unlimited didn't plan for its boardwalk in the John E. Poole wetland to become an aircraft carrier for birds.

But it's become one for the barn swallow – one of the smallest and swiftest insectivores in the region. While most other birds in the wetland are out for a leisurely swim or soar, the barn swallow is doing its best Top Gun impression, making wicked jack-knife turns in mid-air and skimming just over the surface of the water before it comes in for a landing on – or more often underneath – the boardwalk.

Barn swallows often nest on human-made structures with straight ledges and a roof over their heads – structures like the underside of the boardwalk, explains Ducks Unlimited habitat manager Shel Graupe. It wasn't intentional, but by building the boardwalk, his group built a home base for these birds.

Barn swallows are small, swift, bug-eating birds that frequent open fields and wetlands.

"They have kind of an angular shape like a stealth bomber that propels them quickly through the air," letting them chase down flying bugs, Graupe says.

Look for a dark blue back, a deeply-notched tail with streamers on the outer edges, an orange throat and a salmon-pink breast, says local birder Alan Hingston.

"They fly extremely fast," and spend most of their waking hours on the wing "hawking" for bugs, he notes.

Tree swallows often hang out with barn swallows, but have white bellies and lack the long tail streamers of the latter, Hingston says. Bank swallows prefer holes in banks and are brown and white, while cliff swallows prefer bridges. It's tough sometimes to tell them apart since they move so fast, he says.

Barn swallows get their name from their tendency to hang out in old sheds and barns, Hingston notes.

"It's sort of the quintessential bird of summer and rural areas."

These birds will build a nest out of mud about the size of a small cereal bowl and stick it to a wall or a rafter, lining the interior with scavenged feathers, Hingston says. (Some people put pillow stuffing in their bird boxes for this reason.)

Barn swallows are currently winging their way back to St. Albert from their wintering grounds in South America, a trip they make in just three weeks, says Dick Cannings of Bird Studies Canada.

"You can imagine how many bugs they'd have to eat to fuel that," he says.

The barn swallow typically picks off bigger bugs such as flies and beetles out of the air rather than swarms of smaller ones, notes the Cornell Lab of Ornithology. These birds often follow humans, cattle and farm equipment to gobble any bugs they flush out of the grass.

They do all this while on the wing, the Cornell Lab notes. They even drink and bathe in flight, swooping low enough to the water to scoop water into their beaks or to wet their belly feathers.

Climate casualty?

The barn swallow is the most abundant and widely-distributed sparrow in the world, notes the Cornell Lab.

So it may be a surprise to some to learn that it's classified as a threatened species in Canada – threatened being one notch below endangered.

Like most aerial insectivores, barn swallows have plummeted in number in Canada during the last 40 years, Cannings says.

"We're looking at about an 80 per cent decrease sine the 1970s."

No one's exactly sure why, Hingston continues. Some think that modern insecticides have devastated the bugs that these birds need to survive. Others blame modern farms, which lack the old barns and buildings so beloved by these birds.

One leading theory points to climate change as the culprit.

The one thing that ties all these insectivores together is their super-long migration from South America, Cannings says. Research has shown that these birds tend to leave South America and arrive in Canada at roughly the same time each year, with their migration timed to coincide with what used to be the peak of Canada's bug season.

But climate change has shifted the start of bug season back about two weeks in the last few decades, Cannings notes. Since these birds have no way to know this (as they can't tell what the weather is like in Canada before they leave), they haven't changed their arrival times to match. That means there are fewer bugs around to eat when they get to Canada, lowering their reproductive success.

This theory is bolstered by the fact that this decline is geographically specific.

"It's Canadian barn swallows and barn swallows of the northern U.S. that aren't doing so well," Cannings says. "Barn swallows of the southern U.S. are doing fine."

Barn swallows have to guess weather conditions back home when scheduling their migration, Cannings says, and it's easier to do that when you're 500 miles from home than when you're 5,000. That gives southern U.S. birds an advantage – they have a much shorter migration, meaning they're better able to sense an earlier spring and change their departure times accordingly.

Cannings and Hingston say we can help barn swallows by enhancing their habitat by letting them nest in old barns and sheds.

But if the climate change theory is right, there's only one sure-fire way for us to keep these birds landing at the Poole wetland, and that's to reduce our greenhouse gas emissions.