Sep 14 2010 -- Oct 31 2010 Dragonflies on the Oregon Coast: An Annual Event
Sympetrum corruptum by Terry MorseBy Terry Morse
Picture, if you will, thousands of dragonflies moving through your town, all flying the same direction, like a miniature zombie Air Force. It has the earmarks of a great Saturday matinee film or an episode of the Twilight Zone: “Small town on the Oregon coast invaded by winged piranhas that strip the flesh from residents before moving on, leaving nothing but bones in their wake.”
Cannon Beach, on the north Oregon coast, experienced this recently (except for the “stripping the flesh” part), and it set the whole town abuzz). The Cannon Beach Gazette wondered, “Is the Armageddon upon us?”, and one observer commented, “It’s a plague of some sort, symbolizing … well … something.”
Looked at another way, you could say that Cannon Beach was invaded by a swarm of winged gemstones that graced the city with its presence before moving on. For the dragonfly involved, the variegated meadowhawk (Sympetrum corruptum), is one of our most beautiful.
2. The Phenomenon
Directed flights of Sympetrum corruptum occur essentially every year in August and/or September, often more than once per year, but aren’t usually as spectacular as the recent event in Cannon Beach. More commonly, if you are observant, you may see a few fly by each minute, or 30–40, but not the hundreds per minute of a really major flight that everyone notices. Our last flight of this magnitude in Newport was in 1997, but Mike Patterson reported one at Sunset Beach (Clatsop County) in 2007. You may also see butterflies, particularly the California tortoiseshell (Nymphalis californica), accompanying the dragonflies. In Newport in the last few years, the tortoiseshells have actually dominated the flights, far outnumbering the dragonflies.)
3. 2010: A Dragonfly Odyssey
This year, we had a report of a large flight (species unidentified, but likely S. corruptum) in the Florence area, 50 miles south of Newport, on August 24th, but none from Newport. Then there was one on the northwest coast from Tokeland, Washington to Lincoln City, Oregon on September 2nd (report and photos at northcoast diaries). Major flights have also been observed in the Washington Cascade Mountains (August 2nd), the Olympic Mountains in Washington (September 3rd), and San Francisco, California (September 6th).
4) What We Don’t Know
Much about the flights is a mystery. They tend to occur on days with a strong, warm east wind.
Typically, in Newport, I notice occasional variegated meadowhawks beginning in early August. Late in the month, or in September, we’ll get a warm east wind and suddenly there will be many of them in town. Then, on the next east wind, we’ll get a mass flight heading south or southeast (some, presumably blown out over the ocean by the wind, fly due east, back onto land). One of the mysteries surrounding the flights is that variegated meadowhawks don’t seem to breed in large numbers (or perhaps at all) along the coast (with few observers inland, we can’t be sure they don’t breed away from the coast, where it tends to be warmer). So where do they all suddenly come from? We don’t know. There was a huge flight on the north Oregon coast on September 2nd, but none in Newport, so it appears that it was limited to the north coast. The following day, winds in Newport were from the north and the temperature was mild. No mass flight of dragonflies. So where did the north coast fliers go? No one knows. Perhaps inland?
5) What We Surmise
Sympetrum corruptum is present year round in the south and southwest U.S. and in Mexico. The surmise is that they might migrate diffusely north in the summer, where they breed in warm areas away from the coast, then fly or get blown across the Coast Range mountains on the strong east winds in late summer. Reaching the ocean, they head south back to their year round range. Since no one has managed to follow the flights in a systematic way, this is just speculation. If variegated meadowhawks became as popular as monarch butterflies, with people watching for them throughout the west, perhaps we would be able to piece together more of the story.
6) What You Can Do
First, learn to identify variegated meadowhawks (see accompanying photo and this web site). There are many species of small (1.5" long) dragonflies in our area, but none as distinctive as S. corruptum. Females and immature males are yellowish; mature males are red. Both males and females have two diagonal white stripes on each side of the thorax (“chest”), and a yellow dot below each of the stripes. There is a series of pale spots down each side of the abdomen. The eyes are a blend of red and gray, speckled with dark spots called pseudo-pupils. The leading edge of each wing is orange. Perched on bushes in the late afternoon sun, they shimmer like rubies. Because of their mix of colors, they look paler in flight than any of the similar species you might encounter. They also seem to be more skittish: when disturbed, they tend to fly a longer distance before coming to perch than their near relatives.
Once you’ve learned to recognize the species, look for them on the ground or perched on the ends of twigs as you walk about. If you see them mating or laying eggs in your area, make note of it. In late summer, watch for their flights. Pay attention to any dragonflies that seem to be flying all in the same direction, even if it’s only one or two a minute. Minor flights are as much a part of the phenomenon as the spectacular ones we occasionally see. Report your sightings to Terry Morse (firstname.lastname@example.org) or Range Bayer (email@example.com.) Include as much detail as you can about what you saw, especially what direction the dragonflies were flying, how many pass you per minute, and the speed and direction the wind was blowing at the time of the flight.
Above all, keep watching the skies. The truth is out there.
7) Recommended Readings
Dragonflies and Damselflies of the West, by Dennis Paulson. Princeton, NJ: Princeton University
Dragonflies of the World, by Joy Silsby. Washington, DC: Smithsonian Institution Press, 2001.
Contact: Phillip Johnson, CoastWatch Director, (503) 238-4450, or EMAIL