‘Silver’ butterfly counts end; numbers down
In July, my wife Marlene and I completed our 131st summer butterfly count in north central Minnesota. Starting in 1993, those counts have now recorded almost 160,000 living butterflies (actually 159,567). 2015 also marked the 21st consecutive year that we’ve conducted six “4th of July” counts per summer. Over those 23 summers, we certainly appreciate the small, but dedicated band of counters that tromp around with us year in and year out.
Where does 2015 stand? I consider the 15,577 butterflies tallied in 2001 as establishing it as a “gold standard” season. For the past three years, new second-place “silver” seasons were produced each year. However, that “string” ended in 2015. This year’s total of 9,445 butterflies was a 24 percent drop from the 12,428 in 2014. The decrease of 1,121 on the first count at Nevis was largely offset by increases on the next three counts: Bluestem (+259), Deep Portage (+475) and Central Polk County (+214). The decreases on the final two counts at Itasca State Park (-2,411) and Bemidji (-399) largely accounted for the decline of almost 3,000 butterflies in 2015. I feel the timely rains in June, 2014 definitely helped butterflies last year. That favorable situation was largely negated by the ensuing drought that continued through our fairly-cold open winter into the fitful start to spring 2015.
Purpose of counts Our six “4th of July” butterfly counts are part of a North American continental effort to gather valuable data on butterfly population trends. The North American Butterfly Association (NABA) compiles citizen-gathered data collected each year from over 400 counts held in the U.S., Canada and Mexico. A 15-mile diameter circle is established for each count. All living butterflies found in that circle on a single day are reported to NABA. 2015 marks the 41st year that these counts have been held.
Ups and downs in 2015 Since butterflies are insects and insect populations can rise and fall in a short timeframe (i.e. a year versus a decade or more) some ups and downs are to be expected. However, I felt that 10 butterfly species were especially volatile this year compared to 2014 counts. These five species were noticeably up: Clouded Sulphur (+1,133), Compton Tortoiseshell (+842), Common Wood-Nymph (+370), Monarch (+284) and Northern Broken-Dash Skipper (+184). On the other hand, these five species were noticeably down: Northern Crescent (-3,904), Silvery Checkerspot (-888), European Skipper(-244), Long Dash Skipper (-222) and Eyed Brown (-112).
Northern Crescent update Even though Northern Crescents were down 67.3 percent from the 5,789 tallied in 2014, they were still the most common butterfly counted this summer. They remain the only species found on every one of our 131 summer counts. Their total of 39,127 over our 23 years’ of counts mean they still represent one of every four butterflies recorded.
Other 2015 tidbits Sixty-three species were encountered this year. That was down slightly from 67 in 2014. Ten of the 63 were present on all six counts: Mustard White, Clouded Sulphur, Silver-bordered Fritillary, Northern Crescent, White Admiral, Eyed Brown, Monarch, Peck’s Skipper, Tawny-edged Skipper and Long Dash Skipper. These 10 species accounted for almost half (48 percent) of this year’s 9,445 total. Six species were present in 2015, but were “no shows” last year: Black Swallowtail, Harvester, Gray Copper, Appalachian Brown, Dakota Skipper and Dusted Skipper. These really were this year’s “needles in the haystack,” so to speak, since they totaled only 27 individuals. Nine species represented by 25 individuals in 2014 were “no shows” this year. No new species were found this year. Cumulative total remains at 99. However, those 99 species represent almost 70 percent of all species found in Minnesota during the course of an entire year, not the few weeks in mid-summer when our six counts are held.
Monarchs and more In 2012, we had 889 adult Monarchs on our summer counts. That number plunged to 58 in 2013. In 2014, there was a rebound to 250. Happily, that number more than doubled to 534 this summer. However, 320 or 60 percent of that total appeared on our last count held in Bemidji on July 25. A week later on our fall Nevis count, 491 Monarchs were tallied. My enthusiasm was somewhat held in check by the fact that almost all of those Monarchs were found nectaring Rough Blazing Star (Liatris aspera) and rarely anything else. (Most Common Milkweed had finished its blooming season.) Where were these Blazing Star? Primarily, they were in fields and along roadside ditches that hadn’t been mowed or sprayed. We feel Blazing Star provides the “high octane” nectar needed by Monarchs making their migratory journey to Mexico. Though I observed my first Monarch of the year on June 7, it wasn’t until six weeks later that I noticed much adult, egg and caterpillar activity on weekly Monarch monitoring efforts. With the exception of adult Monarchs on the wing, I rated egg and caterpillar activity as still quite sparse this summer. All Monarchs you see now should be heading south to Mexico. Around February, 2016 we should probably know how many Monarchs did overwinter in Mexico. Hopefully it will be above the 50 million reported for the 2014-15 winter. (Remember, in 1996 one billion Monarchs overwintered there!) As I write these lines in mid-August, far fewer butterfly species are on the wing. There is still activity to report: Monarchs, large fritillaries, White Admirals and anglewings are nectaring and puddling. Clouded Sulphurs and Cabbage Whites are, however, the most conspicuous as dozens and even hundreds flit around. So until autumn sets in, enjoy these winged wonders of summer!