EAGLES SOAR
Sightings of the majestic birds on the rise as World Wildlife Day arrives
Sightings of bald eagles in Calgary have been soaring in recent weeks, with some birdwatchers spotting as many as 20 in a single day along the Bow River near the Inglewood Bird Sanctuary.
Bald eagle numbers “have increased over time,” says Phil Cram, who co-ordinates Calgary's Christmas Bird Count, a bird census done each December by volunteer observers.
That number has generally been on the rise since the count began in 1952, Cram says, noting, “This year's number, 39, was a bounce back from a slight decline over the previous few years.”
Nature Calgary volunteer Howard Heffler says there may be more overwintering bald eagles in Calgary “because there is more open water and hence more overwintering waterfowl, their principal food source.” Finding a weak or dead duck to eat can be the difference between an eagle living long enough to grow its signature white-feathered cap or dying before its first birthday.
Pandemic travel restrictions have led to this being a perfect time for anyone to give birding a try in their own communities. COVID -19 may have put a spike through safari travel dreams, but Calgary serves up plenty of fauna drama, especially suitable when marking World Wildlife Day March 3. Celebrating the 1973 United Nations General Assembly's signature on the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES) to protect threatened species, the day commemorates conservation of the world's vulnerable creatures.
Most people have seen a bald eagle even if it's only on the U.S. official seal, but few realize bald eagles made the U.S. Endangered Species List in 1973 because of illegal hunting, habitat destruction and DDT contamination. Fortunately, bald eagle populations have recovered and while some live year-round in Calgary, many more arrive each winter as northern rivers and lakes freeze.
These snowbirds sport white heads, but only upon maturity. Juveniles are dark brown or mottled in colour, causing them to be mistaken for golden eagles.
However, if you're strolling along the Bow River and see a very large, dark-coloured raptor chances are you're watching a young bald eagle. Golden eagles, sometimes called “lions of the sky” are also dark coloured, but unlikely to be found in cities.
In winter, bald eagles are attracted to Calgary because the Bow River doesn't freeze over and there's less chance of starving. Researchers at the U.S. Fish and Wildlife Service have discovered as many as 50 per cent of bald eagle fledglings won't survive their first winter.
Colin Weir — founder of Coaldale's Alberta Birds of Prey Foundation, the province's first privately licensed raptor rescue and conservation organization — explains the challenges young birds face: “One of the big problems for the immature birds is having to move into a totally new area and experiencing different climatic conditions.
“They might be coming from an area in northern Alberta where fish is plentiful and there's big lakes and they're moving into southern Alberta with frozen rivers and lakes, where hunting opportunities are few,” he says. “That's when they start scavenging for road-killed animals on side of the road.”
This can lead to catastrophic collisions between eagles and cars. Weir has rescued many injured birds, including a golden eagle that arrived in the back seat of a minivan. It survived, but due to its injuries couldn't go back to the wild. It became an ambassador greeting summer visitors at the foundation, but fortunately, each year many injured eagles are rehabilitated back to optimum health and released.
Wandering Calgary pathways, it's possible to see evidence of eagle hunts — skeletons and feathers littering the ice shelf, or hundreds of bird tracks concentrated in one place, hinting at a battle between predators over a carcass.
The Cornell Lab of Ornithology online database of bird sightings — ebird.org — confirms that there may indeed be more birds in the sky, not just more eyes looking. This winter and last, there were several days where bird watchers recorded over a dozen bald eagles near Inglewood Bird Sanctuary, although Calgarian Andrew Hart's January 28, 2012 exceptional tally of 51 bald eagles on a day in Carburn Park hasn't been matched.
Weir has also noticed more eagles this year and suggested, “I think the reason there's so many eagles so highly visible this winter is there was obviously a really good hatch (last summer), but they are increasing in numbers and expanding their range.
“We've started to get calls of nesting eagles around Drumheller and High River where previously you'd just hear about them farther west on mountain rivers and lakes,” Weir says. “… Places where there's open water on the rivers, it's like going to a buffet restaurant for them.”
It's not just bald eagles coming to Calgary and area. An hour's drive west of the city, golden eagles already have started migrating north along mountain ridges. Golden eagles can snatch prey as large as young bighorn sheep, but shy away from humans.
In March 1992, professional field ornithologist and former paleontologist and geologist Peter Sherrington spotted a golden eagle while doing a bird survey in Kananaskis Country. Then another and another flew overhead.
Curious to know more, he returned two days later, counting 247 golden eagles in an afternoon. Although the flyway had been known to First Nations, he'd discovered a migratory route undescribed by modern scientists. He founded the citizen-science project Rocky Mountain Eagle Research Foundation. It continues to monitor raptor migration each spring and fall.
Since that first sighting, volunteers have counted 101,656 golden eagles and bird-lovers can be found in any weather, looking at the sky over K-country's Hay Meadows, Mt. Lorette Site.
This year's count started March 1 and anyone interested in the migration is invited to stop by to watch eagles or talk to the eagle-spotters. Although birds are hard to observe without binoculars, it's still possible to see how eagles use mountain thermals to make flying easier.
“It's the only large population of golden eagles with a defined migratory pathway,” count co-ordinator Rosemary Power says.
To increase chances of seeing eagles Power recommends timing your visit for a day “that suggests there will be some warming temperatures.”
“You don't want a day with wind warnings,” she says. “A high overcast sky is ideal because they're easier to spot.”
And then there are days that serve up dramatic sightings.
“If we have a series of bad days, birds aren't moving,” says Power. “When it improves, they're all on their way. Last year we saw 170 golden eagles on a good day. Eight or 10 years ago, we would have seen 300. I've seen over 500 on a day, but that's rare.”
It's possible the drop in eagle numbers is due to cyclical fluctuations in snowshoe hare populations — a staple in golden eagle diets — or climate change, both of which can alter routes, but researchers don't know for sure.
“It's part of the reason we keep counting,” says Power.
Places where there's open water on the rivers, it's like going to a buffet restaurant for them.
COLIN WEIR, founder, Alberta Birds of Prey Foundation, with a rescued golden eagle