Counting Butterflies – Terry Thormin
I had originally planned on posting the second part to “Hunters in the Pond” next, but after having done the first real butterfly count for the Comox Valley four days ago, I thought I should do a quick blog on that. If you have been reading our blogs regularly you will know just how concerned Annie is about butterfly populations on Vancouver Island. Well she is certainly not the only one, and in fact the reason I decided to organize a butterfly count was in the hope that it would provide some data to support our concerns. The problem however is that this should have been started at least ten years ago when butterfly populations were more “normal”.
None-the-less, figuring that any data might be helpful and that we had to start somewhere, I organized a count for July 14th out at Cumberland Marsh, the area where I seem to see the greatest number of butterflies these days. All in all I was quite pleased with the results. The event was run and advertised by the Comox Valley Naturalists Society and a total of 22 people turned out. We split into two parties and spent a total of 3 ½ party hours in the field. The results are as follows:
Western Tiger Swallowtail 16
Pale Swallowtail 3
Anise Swallowtail 1
Cabbage White 5
Margined White 11
Lorquin’s Admiral 11
The total of 6 species and 47 individuals is, I think, quite poor. I am used to doing counts where one dominant species may produce many more individuals than our total and where there are easily twice as many species. Of course biodiversity here on the island is not nearly as great as it is in Edmonton, Alberta where I have taken part in butterfly counts before, but still I had hoped for at least 2 or 3 more species and many more individuals as the habitat was quite diverse with lots of nectaring opportunities. One of the things that might have affected our populations this year is a spring that was cooler, wetter and cloudier than normal and that persisted much longer than normal. Summer weather didn’t really arrive on the island until early July.
There are many factors that can affect butterfly populations, weather, habitat destruction, invasive species, use of herbicides and pesticides and probably a few others that I have missed. As a result it is very hard to determine just why populations are declining. The first thing that has to be determined though is if they are declining, and the best way to do this is through regular butterfly counts. If a count is conducted in a consistent manner in the same area over a number of years it can provide statistics like this.
I suspect that butterfly populations may be declining everywhere in North America, just as bird populations are, but I also suspect that in most areas there is very little data to support this. The North American Butterfly Association organizes annual counts where the data can be submitted online, and this type of count may just work well for your needs. They do counts with a 15 mile diameter, and are conducted on July 4th in the US and July 1st in Canada. They can be contacted at http://www.naba.org . We had tried this type of count here in the past and had very poor participation, so we tried a different approach, picking our own date and making it in a specific locality that was much smaller than the 15 mile circle.
Whichever way you decide to do a count, it can end up being a fun event for individuals and families and, if done consistently from year to year, can provide very useful data. It may also result in people becoming more interested in butterflies, and perhaps open up their eyes to how much butterflies need protection.
Western Tiger Swallowtail
For anyone interested in the Comox Valley Naturalists Society, you can get more information at their website here: http://comoxvalleynaturalist.bc.ca