If you think you’re seeing more butterflies this year than last, you’re probably right. In this year’s North American Butterfly Association count, conducted in Rappahannock County by Old Rag Master Naturalists July 27, the total butterflies counted almost doubled last year’s total, and quadrupled 2011’s, according to forms the chapter submitted to NABA.
Overall, 4,798 butterflies were counted this year, with the eastern tiger swallowtail the big winner at 2,375. And more may have been among the 607 individuals identified only as a swallowtail species, since some females eastern tigers take a dark form rather than the more familiar yellow with black stripes, making them hard to distinguish from other dark swallowtails.
Rain in the afternoon also shortened the count on some properties that normally have high counts, said Rappahannock resident Robin Williams, one of the count coordinators, so numbers probably would have been much higher for many species if it had been sunny.
Eastern tigers also posted huge numbers in the Fauquier County count, based at Airlie. Louise Edsall, assistant director and beekeeper at Environmental Studies on the Piedmont, which conducts the count, said that their results were similar to Rappahannock’s.
“Eastern tiger swallowtail numbers were very high (1,500 individuals) as compared to 400 individuals last year,” Edsall said.
Eastern tigers were also prolific all the way down in the southeastern corner of the Tidewater, according to Ruth Burch, a member of the Norfolk-based Butterfly Society of Virginia and a participant in the Dismal Swamp count. She said butterfly observers down there are calling this the “Year of the Tiger.”
The eastern tiger swallowtail was not the only species out in force in Rappahannock this year. Silvery checkerspots, silver-spotted skippers, eastern tailed blues and cabbage whites (an introduced species) were also counted in high numbers. Burch says she’s been seeing silvery checkerspots “out the wazoo,” too, and that species also were plentiful in the Fauquier count (198, up from 82 last year).
Not every butterfly species was a big winner this year in Rappahannock. Some other species, including some hairstreaks and grass skippers, were scarce or absent in Rappahannock and Fauquier. On the other hand, grass skippers were plentiful in the Tidewater, said Burch.
While factors during the counts, such as the weather on the day, may vary somewhat, those interviewed said the weather earlier in the year was likely more important. A damp, cool spring delayed butterfly breeding and gave the plants on which caterpillars feed, known as host plants, a big boost.
Since host plants and climate conditions vary in different regions and at different elevations, some species will be fewer or not present in some areas, or start breeding at different times. Williams, who also participated in the Shenandoah National Park NABA count this year and last, said eastern tigers were scarce there both years, at least where she counted, around Big Meadows and adjacent areas. Weather was likely the factor there, too, since spring was even further behind at that elevation.
- “Bringing Nature Home,” by Doug Tallamy (bringingnaturehome.net)
- “Butterflies of North America” (Kaufman Focus Guides), by Jim P. Brock and Kenn Kaufman
- “Butterflies through Binoculars,” by Jeffrey Glassberg
- “Caterpillars of Eastern North America,” by David L. Wagner
- “Eastern Butterflies” (Peterson Field Guides), by Paul A. Opler and Vichai Malikul
- “Native Plants for Wildlife Habitat and Conservation Landscaping Chesapeake Bay Watershed,” by the U.S. Fish and Wildlife Service (nativeplantcenter.net)
- North American Butterfly Association (naba.org)
- Butterfly Society of Virginia (butterflysocietyofva.org) focuses more on the Tidewater region, but the society’s list of host plants includes many that are native to the Piedmont
- Nighthawk Communications (nighthawkcommunications.net), which has links to other butterfly resources (under “Nature Resources” tab)
As high as the numbers were for individuals in some species in the Rappahannock count, the number of species actually fell this year to 39, compared with 49 last year, said Williams. Butterfly ecology can be pretty complicated once you get down into the weeds, so to speak. The hosts for eastern tiger swallowtails are trees, which are less likely to be affected by one rainy spring. The hosts of other butterfly species, such as grass skippers and some hairstreaks, are herbaceous plants (those that do not have woody stems, like meadow wildflowers), which would likely get a boost from a wet spring. So why did the swallowtails do better than the others?
The life cycle of butterflies, from egg to adult, is short — a few weeks in most species. Rather than produce many broods, each female produces only one, but her children, grandchildren or even great grandchildren may still be around through early fall, depending on the weather. Since the butterfly’s life tends to be short, brief changes in environmental conditions can have a big effect on an individual’s breeding success, and that can multiply across a species.
As several butterfly observers put it, butterfly populations tend to be boom or bust, often with no clear reason why. Burch, echoing some others interviewed, said she thinks the butterfly season is far from over this year, and we’re likely to see even more of some species, especially the eastern tiger swallowtail, in September.
While butterfly species and numbers tend to vary somewhat over different geographic regions and elevations, numbers also vary from property to property for many reasons. Sites in the Rappahannock count are diverse in terms of size and ecosystem makeup (forest, meadow, wetland, farmland).
This year, the Farm at Sunnyside near Washington was hands-down the winner in terms of the number of individual butterflies (1,523) and species (23). Bruce and Susan Jones’ Long Mountain property came in second, at 669 and 19, respectively, and may have done better if not for afternoon rain curtailing the count there, said Williams.
Both properties have three count sites on them, which is partly why they have high numbers, but both also are naturalized to a great extent, another important factor. One of the first participants in the Virginia Working Landscapes program, Sunnyside is also one the program’s first pilot sites for naturalizing projects, including establishing warm-season grass and wildflower meadows, said biologist and Sunnyside conservation manager Sam Quinn. The numbers counted there weren’t a total surprise to him.
“We did indeed notice more butterflies this year, and I’m glad our anecdotal observations have been validated by the ORMN’s,” said Quinn. He said he expected the diversity of species counted, because of the naturalization — more host plants, more diversity in butterfly species. “What I am unsure of is why there are more butterflies,” he said. Admitting he’s not an expert in butterfly ecology, he echoed many of those interviewed in adding, “I can guess that the relatively moist, cool weather this summer may have positively affected the butterflies’ food sources.”
He adds that the bloom of some early-flowering species and later-blooming species have overlapped more this year, which may have provided a more consistent flow of nectar, a food of adult butterflies in many species. That could partly explain the higher numbers of butterflies congregating in one place, Quinn said, whereas in previous years they may have been more spread out in search of scarce food. He added that Sunnyside tailored the seed mixes in their naturalized meadows to stretch out bloom time and also planted several clumps of native flowers near vegetable fields to direct pollinator traffic.
“These areas are now islands of butterfly activity amid seas of fescue desert,” said Quinn.
Bruce Jones, also a VWL member, has worked for years to naturalize his property, including planting warm-season grasses and special butterfly hosts, such as pipevine for pipevine swallowtails. Waterpenny Farm also had high scores in this year’s count, and Beverly Hunter’s Amissville garden, while small, was “fabulous,” said Williams — packed with butterflies of various species.