Division of Bird Habitat Conservation

Birdscapes: News from International Habitat Conservation Partnerships

Species at Risk

Of Fens and Butterflies
by Laura Ragan, U.S. Fish and Wildlife Service

As I step onto the boardwalk at Sarett Nature Center in southern Michigan, a small, chocolate-brown butterfly bobs lazily through the sedges. The dark color, row of dark eye-spots, and lazy flight readily reveal its identity: a Mitchell's satyr butterfly. The July day is warm and slightly overcast—perfect weather for satyrs but not for people, because the deerflies and mosquitoes are swarming. Gently pushing a dogwood aside and being careful not to graze the poison sumac, I step off the slippery planks onto the only well-traveled path through the fragile fen. I have walked this trail many times over the past month, striving to learn about this rare butterfly and its unique habitat.

During a 2-week flight period, the butterfly mates, lays eggs, and dies. Questions remain about the life stages of Mitchell's satyr, however. Where does it lay its eggs? How do the larvae overwinter? What, if anything, do the adults eat? We do know that it is restricted to a rare wetland type called a fen, an uncommon wetland characterized by calcareous soils and low nutrients and fed by carbonate-rich water from seeps and streams.

Because fens are groundwater fed, they maintain a fairly constant water temperature, warmer in the winter and cooler in the spring and summer. Because of these cooler growing conditions, the vegetation (dwarf birch, tamaracks, and showy lady's slipper) is more reminiscent of my home in northern Minnesota than that of southern Michigan. Fens support many uncommon species and are home to several state and federal rare and imperiled plants and animals, including spotted turtles, massasauga rattlesnakes, Dion skippers, and pitcher plants. Sandhill cranes often feed in these wetlands as well as common yellowthroats and red-winged blackbirds.

Mitchell's satyr butterfly received the protection of the Endangered Species Act in 1991. Historically, the butterfly ranged from Michigan through northern Indiana to northeastern Ohio, and skipping over into New Jersey and perhaps Maryland. By the time it was listed as an endangered species, it had disappeared from nearly half of its historical locations. Presently, the species is found only in southern Michigan and two sites in northern Indiana.

Throughout the satyr's range, wetlands have been drained for agriculture or residential development; invasive weed species, such as glossy buckthorn, reed grass, and purple loosestrife, crowded out native plants; and natural processes of wildfires and hydrologic regimes were altered. By working to overcome these threats and recover this butterfly, we are learning more about the extraordinary ecosystem on which the satyr and many other species depend and are finding new ways to protect the fen's distinctive components.

Freshly emerged from its cocoon, a female settles on a sedge blade beneath a nearby redcedar. I watch quietly for a few minutes. Turning away slowly, I pick up my notebook and empty water bottles, absent-mindedly scratching my arm. . .

A deerfly bite or did I get too close to poison sumac?

. . .and head up the hill to my car, knowing I will be back again tomorrow for another glimpse into the satyr's world.

For more information, contact Mark Hodgkins, U.S. Fish and Wildlife Service, East Lansing Ecological Services Field Office, 2651 Coolidge Road, Suite 101, East Lansing, Michigan 48823, (517) 351-2555, mark_hodgkins@fws.gov.