Fewer nighthawks grace the aerial diner

When Andrea Sidler was four or five and growing up in Atlin, B.C., her parents directed her gaze to two common nighthawk nestlings on the ground beside the trail to the family home.

When Andrea Sidler was four or five and growing up in Atlin, B.C., her parents directed her gaze to two common nighthawk nestlings on the ground beside the trail to the family home. The little girl was fascinated and her parents took her back to visit the well-camouflaged chicks many times.

Could anyone have guessed then that a future passion for environmental causes, a graduate thesis topic and a career choice had been planted in the little girl’s mind?

“It never really occurred to me that that this was a species I could study,” Sidler says. But after she spent several years at the University of Calgary and at Macquarie University in Australia, she found herself in Katie Aitken’s ornithology class at Yukon College. There she learned that the lovely nighthawk (Chordeiles minor) had been designated as threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2007 and that their numbers had been dropping at least since the early 1970s.

Sidler’s concern and childhood curiosity were rekindled. “We don’t know that much about common nighthawks compared with other birds,” she says. “I think that’s because they’re such a cryptic and crepuscular species.” That is, they are well camouflaged and they feed at dusk and dawn. “Usually we hear them, not see them,” says Sidler.

Many Yukoners have likely been mystified by the nighthawks’ distant “peet peet” call as twilight comes on in summer – or even startled at the booming noise a male nighthawk makes when he pulls out of a dive. The boom is a mechanical sound, as opposed to a call. It is made by flexing wings and letting air rush through feathers, says Sidler.

Despite the name, common nighthawks are ever less common and are definitely not hawks. “They are not related to raptors,” Sidler says. Nighthawks are nightjars, a unique family found around the world, though common nighthawks are the only species of nightjar found in the Yukon. Like flycatchers and swallows, whose populations are also diminishing, they’re aerial insectivores.

As for the ecological role they serve, they behave much like bats – performing impressive aerial dining manoeuvres in the twilight hours and for some species, even in the dark.

A close look at a nighthawk reveals what appears to be a very tiny bill – like something swiped from a songbird. It does not look like a very efficient instrument for chowing down on flying insects. “It’s very deceptive, that little bill,” says Sidler. “When they open them, their mouths take up 15 per cent of the size of their bodies. It’s actually quite huge.”

Though she is working on her master’s degree in biology at the University of Regina right now, Sidler is specializing in the common nighthawks of the Yukon. The working title for her thesis is Common Nighthawks’ Habitat Selection and Activity Patterns in the Northern Boreal Forest.

“Part of what makes them very interesting to study up north is we have all that sunlight in summer,” she says.

In the south, where it gets fully dark at night in summer, nighthawks stop calling when the darkness comes on. So far, limited work has been done on tracking nighthawk activity during the perpetual twilight of a boreal night. The diminishing numbers, however, make a very good case for monitoring the whole summer night through. Is something significant being overlooked in the North?

Canadian Wildlife Service has recording devices that can run all night and be set to automatically switch on and off. Sidler has been given the use of those handy devices for her own research, and may soon be able to determine if common nighthawk night-time activity is drastically different in the North than the south.

“I just started my master’s in January,” says Sidler. “I’ve done just one field season and am still trying to get a feel for what I’ll do next.”

What could be causing the decline in nighthawk numbers? “There are so many things,” says Sidler. “Changes in insect abundance on the way to their wintering grounds, or at the wintering grounds” is one possibility. Nighthawks winter over a vast swath of this hemisphere, right down to Argentina.

Also, common nighthawks prefer nesting in open territory – they lay their eggs (usually two) directly on the ground, on rocky outcrops, on gravel bars and in unused fields. They also appear to prefer open, recently burned-over, areas of the boreal.

Sidler and her field assistants surveyed 15 sites between the Dempster cut-off and Watson Lake and found nighthawks present at 14 of them, across diverse habitat types. “That’s very encouraging, considering this is a threatened species,” she says.

“Fire suppression could be part of the nighthawks’ problem,” she says. Fewer burned areas means fewer open spots for nighthawks to live and hunt in.

Once upon a time, gravel was a common roofing material for buildings along suburban and urban portions of the nighthawk flyways. Nighthawks happily nested on that gravel. Now that our roofing-material preferences have changed, nighthawks have lost their comfortable gravel roosts.

What about predators? Are they a problem?

“Nighthawks are usually quite high up,” says Sidler. They fly quickly and erratically. Catching one on the wing could be more work than it’s worth for a predator. However, those ground-level clutches of eggs are vulnerable to foxes, coyotes, ravens and gulls – among other hungry critters, including that super bane of birds, bird lovers and ecosystems: free-ranging domestic cats, as well as feral felines.

Common nighthawks usually show up in the Yukon in the last two or three days of May or during the first week of June, says Sidler. In mid-August they congregate before leaving on their long trek south. Because of the distance they travel each year, they are among the last birds to arrive in the North in spring and the first to leave at the end of summer.

One of the many facets of research Sidler enjoys is the people she meets and works with. One of these new colleagues is Elly Knight of WildResearch, a British Columbia-based conservation organization that, among other programs, conducts nightjar surveys to monitor long-term population trends.

“This summer WildResearch will expand their nighthawk survey program into the Yukon, as well as into several other provinces, and I’m very excited to be involved with the Yukon expansion,” Sidler says. This expansion should mean more pairs of ears and eyes on nighthawk routes and roosts here.

WildResearch relies on volunteer involvement for data collection and she hopes many of the territory’s bird-loving citizen-scientists will take part in the project and help researchers find out just what the Yukons’ common nighthawk population is up to. If you’d like more information or to participate, contact her at nightjars.yt@WildResearch.ca.

This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at www.yukoncollege.yk.ca/research/publications/your-yukon

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