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Canada's 2012 butterfly migration largest on record

Lyndsay Morrison, staff writer

May 16, 2012 — A mild winter, a warm spring and southerly winds helped make this year's butterfly migration in Canada the largest on record.

Thousands of butterflies arrived in March and early April
Thousands of butterflies arrived in March and early April

They came early, and they came in droves. 

And now, Canada's 2012 Red Admiral butterfly migration is being called the largest on record. 

Catching the attention of many Canadians, an estimated 300 million butterflies showed up in eastern half of the country this spring, from Ontario to New Brunswick. That's more than 10 times what would be seen in a typical year. 

Dr. David Gibo is a professor of ecology and evolutionary biology at the University of Toronto. He called the migration a "population eruption," and said the weather is a big reason why it happened. 

"Temperature conditions very much determine how active the butterflies are going to be," Gibo explains. "When you have a warm spring and a mild winter, you see them coming in good numbers."

Warm temperatures and southerly winds helped the migration
Warm temperatures and southerly winds helped the migration

The Red Admiral, a medium-sized velvety black butterfly with orange bands on its wings, migrates up from the southern states and Mexico. This year, they arrived earlier than usual, thanks to those warm temperatures and in part because of strong winds.  

"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." 

In some cases in April, the butterflies flew so north so early, that they arrived in communities still covered with snow. 

A second wave of butterflies arrived in May, adding to the already staggering numbers. 

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