Ducks in Windsor, Ont., and Essex County will need to start watching their backs. A predator from the Arctic may still be in the neighbourhood.

Karen Hass shot pictures of a falcon at the Vollmer Pond in LaSalle, Ont. in late December. At first, she thought it was a peregrine falcon.

But after a closer look and some help from other birders online, it's been identified as a gyrfalcon, the largest falcon in the world.

"It was so new I thought it was a peregrine falcon," Hass said in an interview with CBC News. "I had no idea it was a gyrfalcon and never expected to see one down here."

Hass has been an amateur bird-watcher for about seven years, but wasn't out hunting for rare birds. She'd gone to the Vollmer Pond to see the the ducks and geese with her boyfriend.

"It's thrilling seeing a new bird, it's hard to describe," she said. "It's exciting, you want to share what you just saw, it brings a smile to your face from ear to ear."

Marion Nash, the director of the Canadian Peregrine Foundation told CBC News in an email that it appears the bird Hass photographed is, indeed, a gyrfalcon, which looks very much like a peregrine.

Gyrfalcons breed in the Arctic and are rarely found in the region. The last gyrfalcon to be positively identified in the Windsor-Essex region was an escaped privately-owned bird.  

Since it's difficult to see any identification bands on the bird Hass photographed, it's difficult to say where it came from, Nash said. 

They're about the same size of a red-tailed hawk, but with a heavier "barrel-chest" with a longer tail than a peregrine falcon, Preney said.

Apart from their scarcity, gyrfalcons are hard to identify, even for experienced birders.

"There are many colour variations from white to jet black in captive [bred]/hybrid birds so it can be hard with just a photo for most people to identify the species," Nash said in an email.

Even in Hass' original Facebook post about the bird, people couldn't agree on the species.

'Incredible find' 

The gyrfalcon is special to bird watchers, explained Tom Preney, a naturalist at the Ojibway Nature Centre in Windsor. Preney is also a bird watcher and in 10 years of birding, he's never seen a gyrfalcon before.

"It's quite uncommon," Preney said. "We only get a handful of gyrfalcon sightings every couple of years in this area. It's quite the incredible find."

Gyrfalcon LaSalle

This bird, identified as a gyrfalcon was seen in LaSalle, Ont. in late December. (Karen Hass/Facebook)

This particular gyrfalcon was only spotted once, on Dec. 27. But Preney said they're known to hunt ducks and other waterfowl, so the best bet on seeing it again would be to spend time near the Detroit River.

"It's something that bird watchers don't get to see very often," Preney said. "I've been birding myself for more than 10 years and I still haven't come across a gyrfalcon."

With open water in ponds and rivers, there is still plenty of time for birders to possibly catch a glimpse of a rare species.

Hass said she hopes the gyrfalcon is still around for others to see.

"I have a feeling it's hanging around woodlots and farm fields, or maybe River Canard, anywhere there's a body of water," she said. "I'm hoping people will keep their eyes out and report it so other people can get the thrill we did."