Shannon Wilmot

This fall, Ontarians had the rare pleasure of witnessing the largest monarch butterfly migration in 10 years.

Monarchs migrate to Canada from Mexico each spring and return to the sunny south each fall. During the autumn migration, monarchs gather in large groups (numbering from a few hundred to several thousand) along the north shores of Lakes Ontario and Erie before crossing these large bodies of water on their way southward. Between the end of August and early October, enormous groups of the butterflies were spotted at Thickson’s Woods, Whitby (several thousand), on the Leslie Street Spit in Toronto (about 5,000) and in locations along the Niagara peninsula.

Why was this fall’s migration so large? It all started with last spring’s migration, says monarch enthusiast and long – time Ontario Nature member Don Davis, who has been tagging and tracking monarchs since 1968. According to Davis, the butterflies had a highly successful migration from Mexico thanks to exceptionally good weather – neither excessively hot nor unusually cool. The excellent travelling temperatures, coupled with a mild summer and flourishing milkweed plants, on which monarch butterflies feed exclusively, provided the butterflies with ideal conditions for reproduction. Consequently, huge numbers of the insects migrated south in the fall.

The monarch is Canada’s most recognizable butterfly. This brilliant orange and black insect has a wingspan of 93 to 105 millimetres and is found in most parts of Ontario. You can attract them and other colourful butterflies to your backyard by planting milkweed, black-eyed susan and wild bergamot.

For more information about monarch butterflies and their migration, visit the Monarch Watch website at