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9/15/2005

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Monarch Migration


Both the birds and the Monarch butterflies were on the move today. Monarchs typically peak around mid-September in Ontario although their concentration fluctuate year-to-year. 2004 was a weak year for monarchs at the spit as numbers were clearly down from the previous fall. Today may have been the peak this year as they were everywhere one looked, all moving southwest along the spit. Numbers really picked up after we closed nets around noon today. The butterflies were migrating between 4-25 feet above the ground and I counted 187 pass me by in a 5-minute span. This movement continued for at least 4 hours thereafter. That means that roughly 9,000 passed through peninsula D between 1230pm and 430pm (bear in mind I was counting from inside the forest and could only clearly see butterflies within a 40m radius and therefore the actual number would have been higher). I had a hunch that they would all concentrate in the trees near the lighthouse at the extreme southwest tip of the peninsula before attempting a potentially perilous crossing of Lake Ontario). The cottonwood woodlot just before the lighthouse was alive with thousands of Monarch Butterflies, quite a spectacle! This event was very difficult to photograph but some attempts are posted here.