While black swifts can be found across B.C., only single-digit nest numbers have been found on Vancouver Island for the federally endangered species in decline – leading experts to urge birders to report nests they find.
Nanaimo wildlife biologists Paul Levesque and Christine Rock have studied black swifts for 20 years and have worked on creating the current best method for finding the nests. The pair presented their research April 17 as part of Nature Nanaimo's speaker series.
While black swifts were once abundant on Vancouver Island, Levesque said the numbers have dropped off considerably.
"There was a 50-per cent decline in the Canadian population between 1973 and 2012, which pushed for the species to be federally endangered, and it's listed on the Species at Risk Act," added Rock. "So it went from never being assessed prior all the way to 'endangered' – which is the highest level of conservation concern – kind of overnight."
While the cause of the decline is unknown, the biologists said it's likely based around food availability.
"Food availability, or accessibility, or declining food quality – those types of things which are likely driving aerial insectivore declines," Rock said.
Most of the black swift population breeds in Canada, accounting for an estimated 79,000 individual birds, most of which are in B.C. Yet until the year 2000 there were only two confirmed nesting sites in the province. The reason is in how the species raises its young, exclusively alongside or behind waterfalls, seeps, wet canyons and sea caves in tiny crevasses in cool, wet, well-shaded environments.
When the pair of biologists began their work, the method for finding the sites involved setting up outside a suspected nesting waterfall at dusk and watching for a parent to fly in. They spent 98 hours in southern B.C. searching for nests at 16 different locations from 2001-15, finding only two nest sites.
"We were trying to do all these evening surveys and not finding nests, and then we were camping and one morning Paul got up super early and went to the waterfall and saw the birds flying out," Rock said. "So we flipped it on its head, instead of the evening surveys we tried these morning surveys. As birders we're more used to getting up early in the morning."
The next season, the pair received funding from Environment and Climate Change Canada to test the method, which led to 14 new breeding sites being identified across 30 potential sites, detecting five times more birds per minute more than the previous method.
"We don't know for sure why this is, whether it's a bird behaviour thing or a limitation of our own eyesight."
Just because they're difficult to spot doesn't mean they're not there. Levesque said one season, in 2022, using an infrared camera, the pair, along with the Canadian Wildlife Service black swift lead Eric Gross, found five nests at a site in an urban park in Vancouver after spotting the adults travelling in and out. Nobody had noticed or reported them before. More nests have been found there since.
"I say every time we find a new nest site we learn a little bit more," Rock said. "It helps us identify some of those biophysical attributes, those features of the site that are important and will ultimately be critical for the species that needs to be protected. It can also help us address those knowledge gaps."
One thing people can do, the pair said, is report nest sightings. People can do this by contacting the Conservation Data Centre at cdcdata@gov.bc.ca or Gross at Eric.Gross@ec.gc.ca. Sightings can also be posted to http://ebird.org, which is monitored by conservationists, but Gross told the News Bulletin that the other two methods are preferable.
"Every year we're hearing about more sights, there's a little bit more communication too with rock climbers, because they sometimes put in their anchors near nests and find their nests that way, so we're trying to get everyone talking and communicating and working together on this…" he said. "If you're interested in doing surveys, it can be worthwhile going out and doing the morning surveys and also looking for nests."
Characteristics of the bird include long black wings with some white edging, short legs, a forked tail, slow wing beats with long glides, flying at 110km/h. The eggs are white, and the nestlings have more of the white edging.
The breeding black swifts are believed to arrive at their nests around mid to late May or early June, based on information from a nest site in Alberta, and incubation is believed to start in mid June. The nestlings fledge around the end of August to the beginning of September, then migrate south for the winter season soon after they leave the nest.
Each pair lays a single egg per season.
"If the population is declining, the recovery is going to be much slower compared to a duck or chicken that lays seven or eight eggs," Levesque explained. "Most of the species that lay single eggs are on watch with the government."
Nature Nanaimo's next monthly meeting features Mike Dedels from the Grassland Conservation Council of B.C. to talk about grasslands conservation. It will take place on May 15 at 7 p.m. at the Beban Park Social Centre.
