Snowy owls have descended on the Great Lakes region and northeastern U.S. in huge numbers in recent weeks, to the delight of birdwatchers.
The mass migration we’re seeing this winter is what’s known as an irruption.
"For snowies, that's usually largely influenced by whether or not they had a really good breeding year,” said Rachelle Roake, a conservation scientist at Michigan Audubon.
And snowy owl breeding is influenced by how much food those snowy owls have access to during the breeding season.
“If there are a lot of lemmings and small rodents up in the Arctic where they're breeding, they can have really great nesting success, really produce a lot of young,” Roake said.
Some researchers say this year’s irruption could rival that of 2013-2014, when thousands of snowy owls flew south to nest in the northern United States.
This winter's mass migration of the owls from their Arctic breeding grounds is more than just a treat for bird enthusiasts – it’s also serious business for researchers. As we reported in 2015, researchers with Project SNOWstorm are trapping and fitting some of the visitors with tiny solar-powered transmitters to track them around the globe. The project was founded after the mega irruption of 2013-2014.
Scientists use the tracking data to study the long-misunderstood species whose numbers likely are far fewer than previously thought. Researchers once believed there were about 300,000 snowy owls worldwide.
Now they say it's closer to 30,000 because of new information about where they nest and winter. That doesn't necessarily mean that snowy owls are in decline. But researchers want to know for sure.
They worry the birds' long-term survival could be affected by global warming.