Precipitation sets stage for butterfly boom
In late July, Marlene and I completed our 19th season of "4th of July" butterfly counts in north central Minnesota.
We have now attained our 107th count since July, 1993. Over those years we have been joined by a small, but dedicated band of counters who have enabled more of our count circles to be covered.
Last summer's rainfall was the most in 15 years. Last winter's snowfall was also the most in 15 years around here. Both types of precipitation really set the stage for lush butterfly host and nectar plants this year.
However, unlike most of the nation that was sweltering with record highs, summer warmth took its time showing up around here. As a result, the first two counts of this season logged modest butterfly numbers. Then as our count season was nearing its end, the butterfly season really took off.
As a result, we logged a total of 6,313 individual butterflies - up 45.9 percent over 2010's 4,428. Number of species was also slightly higher at 68 versus 65 for last year.
Where does 2011 stand?
By a grading method I used last year, the 2010 count season scored the lowest or "poorest" for the 17 seasons going back to 1994.
During the past winter, I came up with a new scoring method: average number of butterflies per party-hour for a count season. This approach acknowledges that the more teams or "parties" in the field, the more butterflies that will be counted.
So it is an attempt at standardizing count effort such as mpg (miles per gallon) standardizes fuel efficiency comparisons.
Using the party-hours, 2010's counts produced an average of 55.70 butterflies per hour. This was still the lowest average since our first year: 1993.
On the other hand, this year's average 78.82 placed 2011 12th out of 19. Definitely an improvement over 2010. However, this year becomes the fifth straight year of a "valley," of sorts, since the last "peak" of 96.57 butterflies/hour was achieved in 2006.
Why the five-year slide? That's a very good question. Butterflies are sensitive to so many factors that it's hard to pinpoint the "whys." Certainly spraying and excessive mowing take a toll, also adverse weather.
Some 2011 tidbits
Five species were present on all six summer counts this years. However, only Monarch, Northern Crescent and Long Dash Skipper made it on the "Top 10" list; Eastern Tailed-Blue and Mourning Cloak did not. Other members of "Top 10:" Common Wood-Nymph, Clouded Sulphur, White Admiral, Mustard White, Eyed Brown, Gray Comma and Meadow Fritillary.
Those 10 species accounted for almost three-fourths of all individual butterflies we logged.
A Two-Spotted Skipper became our overall 98th different species during our 19 years of counts. It was quite a find. I'd seen it only once before in my life!
Last year, 490 members of the Vanessa/lady family of butterflies produced over 11 percent of all the butterflies on our six counts. However, only five members of that family showed up this year.
The Vanessas (American Lady, Painted Lady, and Red Admiral) mainly appear around here in years when large numbers disperse from the South/Southwest U.S. Whereas 2011 was not one of those years, 2010 was.
Northern Crescents continue to be the only species spotted on all 107 of our summer counts. For 10 of the 19 count seasons, they were the most common butterfly for that count season.
In 1996, they represented 51.8 percent of all butterflies that year. However, in 2011 their share has dipped to the lowest in 19 years: 5.8 percent. Will their numbers rebound now that their host plant asters have had a year of more favorable precipitation? Only time will tell.
The return of summer rains brought an increase in an interesting butterfly activity called "puddling."
Basically limited to adult males, "puddle parties" convene on our damp gravel roads. The males are sipping salts and other nutrients that are thought to aid reproduction.
The puddling Canadian Tiger Swallowtails and White Admirals were definitely noticeable on our Deep Portage count. Again, on the Itasca State Park count puddling Eastern Commas, Green Commas and Gray Commas, to name just the more numerous species, put on quite a show puddling.
A variation of "puddling" is "mineralizing". That can be accomplished when butterflies are on animal scat or sipping human sweat. The latter was the case during our humid Itasca count when a Harvester flew onto my sweaty right hand.
It proved quite a challenge getting a self-portrait of my hand with the butterfly slurping away. (I then transferred "him" to Marlene's hand for some additional pix where I didn't have to be such a contortionist with camera and tripod.)
Purpose of counts
For 17 straight years, we have conducted six "4th of July" butterfly counts. They are part of a much larger effort.
The North American Butterfly Association (NABA) compiles data collected from over 400 counts conducted each year in the U.S., Canada and Mexico.
All living butterflies found in a single day in an established 15-mile diameter circle are tallied and reported to NABA. Now in their 37th year, these counts are providing important citizen-gathered data for scientific analysis.
Currently, our counts cover: Nevis, Deep Portage, Central Polk County, Bluestem Prairie, Itasca State Park and Bemidji.
Monarchs and more
n Monarchs: Last fall, the migratory generation had both good numbers and a long duration. (This was a bit of a surprise given our weekly Monarch monitoring observations had provided no hints that the migratory generation would be that impressive.)
Spring 2011 brought drought to Texas. Then floods, tornados, high winds, hail and other strong weather events hit the Midwest and Minnesota. Therefore, I'm not surprised that the 2011 Monarch season had such a modest start around here on June 1.
By the end of July, the Monarch season went into overdrive. Migratory Monarchs have been sipping Rough Blazing Star nectar for a number of days now.
Our August 16 Monarch monitoring revealed more caterpillars and even two eggs that could help swell migratory ranks in the next two to four weeks. (Will there be any drought relief in Texas by the time the migrants arrive there on their way to Mexico?)
n Viceroys: These Monarch-mimics are having a banner year the past few weeks. Previously I had encountered no more that 29 during an entire butterfly season. In just one day this month there was eight. Many joined the ranks of puddlers.
n White Admirals: Another species that started slow earlier this year, but is having a strong finish with high numbers flying and puddling everywhere it seems.
n Cabbage Whites: For the first August since 2006, the road sides have been a veritable "blizzard of white."
n Milbert's Tortoiseshells and Gray Commas: Both enjoyed abundant puddling earlier this month. These are two species that can and do overwinter.
n Compton Tortoiseshells and Mourning Cloaks: Of late, both species have been "fairly quiet." Are they just biding their time in emerging this fall? They, too, can and do overwinter in unheated structures, woodpiles and crevices of bark.
Even thousands of butterflies later, Marlene and I continue to be enchanted and amazed by the butterflies that flutter around us.
We hope these beautiful insects will continue to enhance and inspire all our lives for many years to come!