In late July, Marlene and I completed our 18th "4th of July" butterfly count season in northern Minnesota. We did reach a milestone this year: our 101st summer count. For 16 straight years we've conducted six counts a summer. As always, we appreciate the small, but dedicated, band of counters who join our efforts to census butterflies.
We were very optimistic as the count season began. Nectar sources were the most abundant in years, possibly a decade or so. Temperatures were not too hot or too cold.
The "stage," so to speak, was set. But where were the butterflies? We tallied only 4,328 individuals - down 22.5 percent from last year's 5,583.
Marlene and I were left shaking our heads as to what went wrong. Was it getting only 24 inches of snow last winter? Or getting no snow in March or April, but eight hours' worth on May 7? Or the deluge of five inches of rain the night of July 3-4? Or continued negative impacts on habitats that butterflies rely on? Or other factors that are just starting to emerge?
'Grading' 2010
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Last year, I unveiled a grading scheme that portrayed 2008 and 2009 count seasons as showing modest, but positive gains over a low point: 2007.
Since we have completed 101 counts, I now present a new grading approach. It is based on a count's rank for total butterflies tallied. Our 2008 Bluestem count had our "lowest" number with only 75 butterflies. I've assigned that count one point.
On the other end, our "highest" count was Central Polk County in 2001 with 3,907 individuals. So I assign that count 101 points.
Where does 2010 stand? In my latest grading method, 2010 garnered a total of 217.5 points divided by six counts yielding a score of 36.25. This score is the lowest or "poorest" for the 17 seasons going back to 1994.
Not surprising, 2001 stands as our "best" year with a score of 92.17. Four of our five highest counts were tallied that year.
Some 2010 tidbits
Nine of the 10 most common butterflies counted in 2010 showed remarkable increases from the two previous years. (See table).
Ten species found in 2009 became "no shows" in 2010. On the other hand, five "no shows" of 2009 showed up on this year's counts. However, that means 2009's total species of 70 dropped by five to 65 for 2010.
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Nine of the 65 species were present on all six summer counts this year: Clouded Sulphur, Summer Azure, Great Spangled Fritillary, Meadow Fritillary, Northern Crescent, Mourning Cloak, Red Admiral, Eyed Brown and Monarch. It was not surprising that six of these nine appeared in the "Top Ten".
On one hand the "Top 10" masks what was going on at the "bottom end." That's because 21, or one-third of the 65 species, had four or fewer individuals each. Even more distressing, of those 21 species, 13 species (20 percent of total) had only a single individual show up to be counted.
Talk about needles in the haystack!
Red Admirals deserve a special note. They have had a tremendous surge this year in the eastern United States. Their presence on all of our counts this year "skewed" our overall total. That's because they accounted for almost 14 percent of all butterflies tallied. Without them a poor year would have been that much poorer.
The total number of species we've registered over the 101 counts remains at 97. No new species were encountered this year. This is not unusual. About 70 percent of all butterfly species found in the entire state of Minnesota have shown up on our counts.
Fading dynasty?
The Northern Crescent, a small orange and black butterfly, has been found on all 101 of our summer counts. It is the only species to do so. With a total of 23,393 individual Northern Crescents tallied for the 18 years, it is the most common species on our counts.
Just last year, I boldly predicted that our 25,000th Northern Crescent would appear on the third count of the 2011 season.
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Comparing Northern Crescent numbers from 2010 to the two previous count seasons, you can see my prediction is in double jeopardy. The 280 Northern Crescents in 2010 were the fewest tallied during the 16 years we've conducted six counts a summer.
Will Northern Crescents have a population rebound? After all, the previous low of 315 in 1998 was followed by 2,628 just two years later in 2000. Only time will tell!
Skippers skip out
Also adding to 2010's poor showing was a serious lack of grass skippers. The six counts produced only a total of 199. On counts in the past, with seemingly little effort on our part, members of the 24 species of grass skippers seemed to abound. There were 875 grass skippers tallied in 2009 so the decline of almost 700 is noticeable.
Purpose of counts
Our six counts, known as "4th of July" butterfly ones, are part of a much larger effort. The North American Butterfly Association (NABA) compiled data collected from over 400 counts conducted each year in the U.S., Canada and Mexico.
All living butterflies found in an established 15-mile diameter circle on a single day are tallied and reported to NABA. Now in their 36th year, these counts are providing important citizen-gathered data for scientific analysis.
These areas are covered by our counts: Nevis, Deep Portage, Central Polk County, Bluestem Prairie, Itasca State Park and Bemidji.
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Monarchs and beyond
Monarchs were the second most-common species found on our counts last month. Plus I've seen a number of adult Monarchs, most-likely migratory generation, for most of this month.
Both happenings come as a surprise given our weekly Monarch monitoring of adults, eggs and caterpillars.
Though 2010 data so far indicate an upswing, the current year is still only a fraction of 2007's activity. In fairness, I should note that 2007 was one of our best monitoring years since we began our weekly summer visits in 1998.
In addition to migratory Monarchs on the wing, there are a number of whites and sulphurs flittering around. The whites are Cabbage Whites and Mustard Whites. The yellow sulphurs are Clouded Sulphurs, and a few Orange Sulphurs are mixed in as well.
Mourning Cloaks should be emerging at any time. They will over-winter in tree bark crevices, woodpiles and unheated structures. Then when warmer days return next spring, they will be among the first butterflies we'll see around here.
