Red Admiral butterflies have been spotted throughout southern Ontario. Photo credit: Astronomer Andrew Yee
Noticing butterflies in your neighbourhood already?
You're not alone. Hundreds of thousands of them have made their way north, and hundreds of The Weather Network's viewers have reported spotting them, especially in southern Ontario.
The Red Admiral, a medium-sized velvety black butterfly with orange bands on its wings, has already migrated up from the southern states and Mexico for the milder half of the year.
"This is a population eruption," says Dr. David Gibo, a professor of ecology and evolutionary biology at the University of Toronto. "That's why people have been noticing them so much, especially in the afternoon hours."
And the weather is a big part of the reason why.
"Temperature conditions very much determine how active the butterflies are going to be," Gibo explains. "Most often you see them coming in good numbers in early May. April is also a common time, particularly when you have a warm spring and a mild winter."
Parts of Canada and the U.S. had exactly that. In addition to a string of record-breaking temperatures
in March, the Gulf states also had plenty of rain
this past winter. As a result, there has been plenty of food plant for the butterflies.
Different kinds of butterflies will arrive in the coming weeks
Another factor in the Red Admirals' early arrival? The wind.
"In Ontario, we've had a number of days with south to southwest winds, and that's perfect for them," explains Gibo. "They've gone up, flown along with the winds and rained down in the afternoon."
Gibo adds that winds from the north slows the butterfly migration, but doesn't stop it.
"If you have a cool spring, migration is slow. If you have day after day of winds that are opposing them, it slows them down. But as soon as the winds switch, they carry on."
There are some concerns over what could happen to the insects if there is a cold snap in Canada. The butterflies also feed on nectar, and flowers' blooming time is less related to warm weather than the butterfly migration.
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