BANFF – Parks Canada is keeping an eagle eye on an endangered bird species in Banff National Park.
After flying thousands of kilometres from their wintering grounds in South America, a handful of black swifts returned in May to Johnston Canyon – one of only two known places in the park where they rear their chicks in small, mossy nests in cavities high up on the walls of the cliffs.
Only laying one single egg a season, black swifts have a lengthy seven-week rearing period before the chicks fledge in September; however, this year, one of the four chicks born at Johnston Canyon died.
“We've had three successful nests and one nest actually failed,” said Jennifer Reimer, a Parks Canada resource conservation officer who has been leading the black swift monitoring program in Banff National Park since 2015.
“We had an egg and the egg hatched and the chick was there, and then it just didn’t survive. It has happened in Johnston Canyon before, but infrequently, but it’s been several years since that’s happened.”
While the cause of death of this chick is unknown, Reimer said it was unlikely killed by a predator because of the nest’s inaccessible location on ledges or cavities high up on the steep canyon walls.
“It's possible, but unlikely, that a raven could have gotten it,” she said.
Reimer said there is not much evidence in the literature on why chicks die given there are so few predators.
“We can guess or have theories… they are small nests and you're fitting three birds on a small ledge or small cavities, and it's possible that an adult could accidentally push the chick out of the nest,” she said.
“The chick could also have just died in the nest and then they pushed it out.”
In 2019, the black swift was designated as an endangered species under Canada’s Species at Risk Act. It is estimated black swifts have faced a 50 per cent decrease in population since 1973.
Johnston Canyon provides critical nesting habitat for the birds and is one of only two known nesting areas in Banff National Park. The other one is in the backcountry near Egypt Lake.
In 2022, there were four active nests in the canyon, while another female bird returned to the area but didn’t have a mate.
The year before, five active black swift nests were confirmed in Johnston Canyon – the highest number of active nests recorded there since 2004.
In 2020, three nesting pairs were spotted, while only one or two active nests were recorded between 2005 and 2019.
Today, the numbers in Johnston Canyon are still below historical numbers of up to 12 active nests in the 1970s and early 1980s.
Parks Canada uses thermal imaging cameras to locate and monitor nests while time-lapse remote cameras reveal bird activity patterns.
Reimer said two of this year’s chicks have already fledged and left the area, while the third was within days of fledging.
Based on research from tagged black swifts in Colorado, and Parks Canada’s own observations, she said once the chicks fledge they don’t return to the nest.
“So once that chick leaves, the adults don't come back again and everybody starts the migration all the way down to South America,” she said.
This year, the birds arrived between May 30 and June 3.
However, it is not known if they fly individually or as a group on their long migration north each spring.
“We don’t know for sure, but there have been some observations of large flocks of black swifts seen on the coast of B.C. in the spring and the fall,” she said.
“So we suspect that they migrate in larger flocks and then disperse to their individual colonies and populations within B.C. and Alberta.”
While it was initially thought pairs may breed for life, Reimer said there is some evidence from tagged birds in Colorado that some adult females are returning to use the same nest each year, but with different mates.
“The young, once they’ve fledged, we do not know for sure where they go until they’re of breeding age, so the first two or three years of their life, they can be roving around between different colonies or coming back to their natal colonies,” she said.
“There is some evidence that some females come back to their natal colony two to three years later and then there’s evidence of at least one male coming back to a colony that was about 300 kilometres from his natal colony.
“So there’s a little bit more dispersal with the males from what we've seen so far and more fidelity for the females to come back to same the colonies where they hatched from.”
Researchers have also been able to figure out what the day in the life of a black swift looks like.
Reimer said black swifts leave the nesting sites about half an hour before sunrise.
“They tend to interact and socialize with each other before they are more focused on foraging for insects throughout the day,” said Reimer.
“There's a lot of interactions between pairs and other individuals from the nests."
Progressively over the day, the agile birds fly higher and higher in altitude looking for flying insects, and fly at great speeds.
Reimer said black swifts have been found to travel up to 175 kilometres in a day to locate enough food for themselves as well as their growing chicks.
“We know they fly as high as 3,000 metres and then a full moon they fly up to 4,000 metres,” she said, noting one of the theories on why they fly higher during full moons is related to foraging opportunities.
“During one study, there was an eclipse, and birds came at lower elevations quite quickly during the eclipse and then went back up again when the eclipse was over, which is really fascinating.”
The nesting duties are shared by the parents, with both the male and female trading off on shifts during the incubation period.
“Once the egg is laid in late June, at least here in Banff, there's always going to be one adult on the nest incubating that egg, and that incubation is going to take about a month,” said Reimer.
“Both the male and female incubate that egg with the female slightly more than the male, but fairly equal distribution of that incubation duty.”
When the egg hatches, initially the parents are feeding that chick at regular intervals.
As the chick grows and its feathers allow better thermal regulation, Reimer said the chick might be left alone for up to 12 hours by itself over the last three to four weeks before fledging.
“It’s only fed first thing in the morning and then at night. We know that the adults come back to the nest about half an hour before dusk, and then both adults will roost on the nest with the chick,” she said.
"Once the chick starts to get bigger, you'll often see one of the adults clinging to the rock to a little roosting spot beside the nest when there isn't a lot of room.”
Remote camera footage this year showed the birds are quite active at nighttime.
“We used to think that birds would come back to the nest and rest quietly throughout the night, but we’re seeing more evidence that birds come and go,” said Reimer.
“They’re active throughout the night and even before sunrise, those birds might be flying to other nests, visiting their neighbours, interacting before they all collectively leave the colony first thing in the morning.”
Amazingly, Reimer said once the birds get to their wintering grounds in South America they remain in flight for the entire winter.
“So 99 per cent of their time is spent in flight, so that's about eight months of the year that they're not resting on land,” she said.
“Then spring comes around and they make that migration, it’s a non-stop migration all the way back to their breeding grounds, which can take anywhere from two to four weeks depending on where their nesting colony is.”
Due to the sensitive nature of black swift nesting, Parks Canada implements a yearly off-trail closure at Johnston Canyon from May 1 to Nov. 15.
While the official law enforcement numbers aren’t in yet, Reimer said staff have reported that compliance was better this year with construction of an extended railing in the canyon.
“I can say observationally from our staff that compliance is improving for sure,” she said.
