As Old Rag Master Naturalists (ORMN) was organizing the first butterfly count in 2011, many of us involved had talked about seeing fewer that year. Results from the count seemed to confirm this, but without a baseline of data from previous years, it was still hard to say if populations had diminished in the county. Creating such a baseline was one of the reasons the chapter decided to start an annual count in conjunction with that of the North American Butterfly Association (NABA).
Beyond differences in habitat, butterfly species in Rappahannock do not vary wildly throughout the county and the portion of the total some species have was not at all surprising. Generalists, which use a variety of host plants for their larvae (caterpillars), obviously have a better shot at reproducing and therefore tend to outnumber specialists, which depend on fewer plants.
At 615 (about 25 percent of the total), the eastern tiger swallowtail, a generalist, led in individuals counted. The other most plentiful species included the Eastern Tailed Blue, Cabbage White (an introduced species), spicebush swallowtail, silvery checkerspot and silver-spotted skipper. By contrast, only eight monarchs, a specialist, were counted this year.
Rappahannock resident and ORMN member Robin Williams, who has coordinated the count both years, says there were a few surprises this year, including an “unusual variety” of skippers, some of which she says she hadn’t seen often, such as the zabulon skipper (Poanes zabulon). Measuring in at a whopping 1.5 inches in wingspan, 35 of these little orange-and-brown butterflies were counted this year versus none last year.
The count sites lie within a circle that is 15 miles in diameter, in accordance with NABA protocols. For Rappahannock, the center of that circle is Bruce and Susan Jones’ property at the base of Long Mountain. The count is officially named the “Washington, Virginia, Butterfly Count.”
Butterfly species vary by habitat, and absence is as significant as presence, so the 18 count sites within the circle were picked for their diverse habitat, from wetlands, to meadows, to gardens, to mountain forests. Other than one site in the park (Jordan River Trail) and the few small sites in the town of Washington, including along the nature trail the chapter recently constructed near the new water-treatment plant, most are on private property. Fortunately, property owners have been generous in allowing the chapter access to their land for the count and, in return, they get copies of the results.
As expected, sites that are naturalized with diverse native plants generally had the highest number of individual butterflies and species. Robin noted that such restored habitats – including the Farm at Sunnyside, Waterpenny Farm and the Joneses’ property – are “by far and away the best locations.” Julie Connelly, a count team leader, reported that the butterfly numbers at Sunnyside were “almost too plentiful to count.”
Butterflies were also “flocking to” the large naturalized garden at the property of Bev and Hal Hunter, near Amissville, Robin says, who describes the garden as “extremely rich” in plants that attract butterflies. The unmowed fields at Christina and Don Loock’s farm, in Amissville, also yielded good numbers. The forested areas, such as Jordan River trail, yielded the lowest numbers.
“Planting native species vital to butterfly caterpillars’ survival is a huge help,” Robin says, adding that five years of planting host plants on her own property in Slate Mills is now yielding a wider variety of species each year.
Counting butterflies is hot, sweaty work, but Robin says that the 42 volunteers who formed the nine counting teams (most from the Old Rag chapter’s six-county service area) still enjoyed it this year.
“Enthusiasm was possibly even bigger this year than last,” she says. “Most of us had fun chasing after butterflies through some of Rappahannock’s rich habitat. Many nectar plants were in bloom, including clover, Joe Pye weed, butterfly weed and sunflowers.”
Although count volunteers were relieved to see so many more butterflies during this year’s count, the reasons why the numbers were so much higher are unclear. Small differences in variables such as weather, count hours and sites were not enough to account for the huge difference in this year’s results over last year’s, says Robin.
While big changes in the environment can have devastating effects on some species, most species also have normal population swings triggered by various factors, including weather, availability of food, disease, genetic proclivities and changes in predator populations. Perhaps this year’s early spring, hot summer, and amount and timing of rain helped increase egg production and caterpillar survival.
The data collected during the count goes to NABA as well as to government conservation agencies and other conservation organizations, so researchers can try to determine trends and the factors underlying them. Two years of data is by no means enough to do this, so the chapter is already planning for next year’s count, and the public is always invited to participate.
Butterflies are not only beautiful, but many are important pollinators and all serve as prey for other native species. To sustain species diversity, we need to know all we can about the health of butterfly populations and factors that affect them. For more information on the count, visit oldragmasternaturalists.org and naba.org.