Red Admiral Butterflies stream through Ontario

Nature Notes for April 27, 2012

Red Admiral butterfly                          ©Bruce Parker

As I write, the temperature is only a couple of degrees above freezing, there is a strong wind and the weather forecast is for a mix of rain and snow. It’s hard to believe that the most recent flurry of excitement among naturalists concerned butterflies.

The first reports were from southwestern Ontario on April 15. Several hawk watches reported massive flights of Red Admiral butterflies. By Monday, April 16, they were in Northumberland. They were being reported in Ottawa by the end of the week. By Saturday, April 21, even the Toronto Star had noticed.

Those who study butterflies were amazed by the sheer numbers. Most were declaring that they had never seen such a flight.

Red Admirals are about two-thirds the size of a Monarch, medium sized by butterfly standards. They are quite easy to identify. The upper side is mostly black, with an orange band in the middle of the fore wing and another orange band on the trailing edge of the hind wing. The tip of the fore wing also has several white spots.

They are one of the butterfly species which overwinter as adults. They don’t usually survive Ontario’s winters. They overwinter in the southern states or Mexico and migrate north when warm weather arrives.

Red Admirals are a Holarctic species, that is, they occur in Europe and northern Asia as well as in the Americas. The occur all across Canada and have been recorded as far north as the Yukon and Northwest Territories.

The adults feed on flower nectar. Last week, there were several reports from around Port Hope of flowering trees or shrubs covered with dozens of butterflies.

In my garden, there were not many flowers in bloom: a few scilla, pulmonaria, the first violets, hyacinths and daffodils. The latter two are probably too large for the butterflies to use. In any case, the Red Admirals I observed in my garden didn’t stay for long. They paused briefly to sip at a flower and then continued flying north.

The caterpillar, or larva, feed on stinging nettles as well as several other species of nettle. I haven’t yet seen much growth of nettles so the female Red Admirals have no place to lay their eggs at present. The Red Admiral caterpillar is usually black with white dashes along its sides and tufts of bristles.

The caterpillar lives in a rolled leaf nest that it makes on the food plant. I wasn’t able to find any indication in my reference books as to whether many birds eat these caterpillars. Many birds find fuzzy caterpillars unappetizing.

Migration is a risky undertaking. This huge flight of Red Admirals came very early, with warmer than average temperatures and brisk south-west winds. Although this flight was mostly of Red Admirals, a few Question Marks and American Ladies, two other migratory butterfly species, could be found in the flight.

Then early this week, the weather changed: cold, rain and snow in areas north of Northumberland. Many of these butterflies will probably die if the cold persists for several days.

A word of caution to readers who check out this butterfly on Google. Only two of the five photos shown are actually of Red Admirals.