A Butterfly Invasion

Red Admiral

Sometimes nature puts on a show so spectacular that even those who are only vaguely aware that there is a wonderful, wild world beyond the technology-obsessed, glass and concrete cityscape take notice. This happened last week when millions of migratory butterflies journeyed north from their wintering grounds in the United States and invaded Eastern Canada, descending on city parks, green spaces and backyards to the astonishment of many. I received notice of this mass migration on Monday, April 16th from fellow OFNC member and University of Ottawa biologist Maxim Larrivée, who sent an email out to me and several other butterfly enthusiasts advising that thousands of migrating Red Admirals, American Ladies and Question Marks had been reported that day as far north as Brampton, Ontario. Maxim is a postdoctoral fellow leading the Canadian Butterfly and Global Change research at the Canadian Facility for Ecoinformatics Research and has been working hard with U of O biologist Jeremy Kerr to develop an online database similar to eBird for citizen scientists to report their sightings. This database, appropriately named eButterfly, has only been live for a few weeks now.

Abnormally warm weather in the southern U.S. this past winter created ideal conditions for the butterfly population to increase. That heat also prompted the northern migration, and the strong southern winds on Monday carried hundreds of thousands to butterflies into Canada. Maxim Larrivée states that the butterflies have likely traveled 300 to 400 kilometres per day on these south winds, an impressive feat for such a small animal.

Red Admiral

This migration was so impressive that even the media took notice. I find that the media usually only covers “nature” stories when there is some sort of human-wildlife conflict (with a human-centric view that no wildlife belongs in our cities) or some sort of “cute” (i.e. desirable) animal is rescued from harm or activists are protesting the destruction of green space by developers (usually with the implication that such protestors are “NIMBYs” – “not in my backyard” – and thus have no real concerns). The Toronto Star and the Ottawa Citizen spoke to Jeremy Kerr and Max Larrivée, while CBC spoke with Edward Bruggink, who manages Carleton University’s greenhouses puts on the annual butterfly show there in the fall, so these are people who know what they are talking about!

Red Admiral (fresh individual)

Although Tuesday was much cooler than Monday (when temperatures reached 25°C!), I headed out to Hurdman Park on my lunch hour to see if I could spot some of these butterflies. Hurdman is a great spot in the city to look for migrants, whether they be birds or butterflies. This former landfill site close to downtown appears as a green oasis in the middle of the city, beckoning weary migrants with promises of food and shelter. Sure enough, I hadn’t walked very far when my first Red Admiral buzzed past my head, flying down the feeder path too fast for me to follow. Once I reached the open clearing at the end of the path, I noticed two resting on the ground and stopped to take some pictures.

Another Red Admiral

On my walk I encountered at least 30 Red Admirals, half of which were flying by overhead, and half of which were resting on the ground, perhaps waiting for the temperature to rise. There weren’t any flowers in bloom at Hurdman that I could see, making me wonder whether these butterflies were finding any food. Elsewhere they have been seen nectaring on dandelions and fruit tree blossoms, with as many as 20,000 butterflies covering the flowers on the trees. Hopefully they will find enough nectar sources to survive until other wildflowers begin to bloom!

The wind finally blew in some new bird species as well. During my walk I encountered several Cedar Waxwings, a small group of White-throated Sparrows, my first Northern Flicker at Hurdman, a couple of Golden-crowned Kinglets, and my first Ruby-crowned Kinglets of the year. I caught this tiny kinglet flying toward me while I was pishing:

Ruby-crowned Kinglet

I returned to Hurdman the following day. There seemed to be fewer Red Admirals around, but more Cabbage Whites. I also noticed quite a few hover flies buzzing about:

Hover fly

I was hoping to find some other migratory butterflies, such as the Question Marks and American Ladies that were also being observed amongst the large number of Red Admirals. I had no luck with either of these two species, but did count at least 7 Cabbage Whites, a non-migratory species which is resident in Ontario.

Cabbage White

While Red Admiral invasions of this scale are unusual, their migration is not and usually occurs every year. The first migrants are usually seen in May over most of southern Canada, although they may arrive in Point Pelee as early as mid-April. Its abundance varies each year, with very few butterflies some years and thousands of butterflies in other years. There are very few years when it is completely absent from Canada in the summer. The Red Admirals breed here, and there are two or possibly three generations per year, with fresh specimens seen as late as September. They occasionally overwinter successfully in Canada in mild winters.

Red Admiral on Tree Trunk

The last such butterfly invasion was two years ago. I recall driving south to Point Pelee from Cambridge in May 2010 and seeing perhaps hundreds of Red Admirals flying north along the Lake Erie shoreline during my drive. Last year I only saw one Red Admiral – and that was at Hurdman Park!

Although I saw fewer Red Admirals on this visit, most of the same birds were around on Wednesday. The flock of Cedar Waxwings had seemingly increased to about two dozen birds, many of which were feeding on what remained of the buckthorn berries. The Ruby-crowned Kinglets were gone, but a few Golden-crowned Kinglets still remained. On the river, I saw a mallard drake swimming with a female Hooded Merganser and a pair of Wood Ducks near the shore.

Cedar Waxwing

It was incredible to see so many Red Admirals this past week. The next couple of days are supposed to be cold and wet; I can only hope the butterflies survive until the warmer weather arrives next week.

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