Unveiling the Amazing Achievements of the Five-Year Butterfly Blitz

Two butterflies sitting on a flower.

It Has Been an Incredible Project

And just like that, five years of the Butterfly Blitz fluttered by. This summer, we hosted our fifth annual CVC Butterfly Blitz. From May 6 to September 16, participants contributed to a butterfly inventory by sharing their observations on iNaturalist.

As we wrap up this year’s project, we’re looking back on the amazing data and experiences gathered over the past five years of the Butterfly Blitz. Here are some things we’ve learned since 2019:

Citizen Scientists Can Have a Huge Impact

When we started the Butterfly Blitz in 2019, we did not have much data on butterflies in the Credit River Watershed. There was a small number of observation records. Over the past five years, our participants added almost 9,000 butterfly records from all over the watershed. Check out our iNatualist project page to view the observations on a map.

Butterfly resting on florets.
Winner of the Best Photo award for 2023. Peck’s skipper by Terence Gui

These observations increased inventory data, providing us with crucial information about butterflies in our area. We’re now able to understand which species are common and which are rare in our area. We’re also able to understand which sites have the most butterfly species and which sites are home to our rarest species. This data informs our work to protect, restore and enhance habitat in the Credit River Watershed.

Some of our Rarest Species Live in Wetlands

Two butterflies sitting on milkweed flowers.
Two mulberry wing butterflies resting on milkweed flowers. Mulberry Wings by danshuurman CC BY-NC-SA 4.0

The group of butterflies that make their homes in wetlands contains some of our rarest species. This includes butterflies like the mulberry wing and bronze copper, which have each been seen only a handful of times in our area. These wetland species may have been more common in the past, before large-scale land conversion removed most wetlands from our area. The rarity of these species highlights the need to identify and protect their remaining habitat.

Southern Butterfly Species are Expanding Into our Area

Caterpillar with prominent markings on a leaf.
Spicebush swallowtail in Mississauga – check out those pretend eyes!

You may have heard predictions that the changing climate will allow some southern species to move north into our area. Though we may think of these changes as something that will happen in the future, we saw evidence in the last five years of the Butterfly Blitz that some species are already making their way north! Species like pipevine swallowtail, giant swallowtail and common sootywing have all become more common in recent years. We also know that they’re not just occasional migrants, but that they’re breeding in our area now too, as their plant hosts are also becoming more common.

Introduced Species Can Spread Quickly

Butterfly perched on a stick.
European common blue

There is a new butterfly in the Credit River Watershed that was not here in 2019 when we started the Butterfly Blitz. The European common blue was first spotted in 2021, at two sites in Mississauga. Since then, it has spread rapidly and is now commonly found throughout most of the watershed. This species feeds on introduced plant species, like birds-foot trefoil, that are common in our natural areas. It will probably continue to become more common, so expect to see more of it in years to come.

In the Spring of 2024, we will announce what is next for the Butterfly Blitz. To stay informed, please visit cvc.ca/butterfly-blitz.

Have questions about butterflies? Want to share your own butterfly photos with us? Connect with us on Facebook, Twitter, Instagram and LinkedIn.

By Laura Timms, Senior Specialist, Natural Heritage Management

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