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Butterflies of The Great Swamp

March brings the Red-Winged Blackbird and the Wood Duck back to the Swamp - but if we are lucky and have a warm April day, we can thrill to the site of the season's first Butterfly. The Great Swamp has a high diversity of butterflies. Over seventy species have been seen in some portion of the Swamp. Most are associated with wet meadow habitats. The number and diversity of butterfly species is a key indicator of the health of both the wet meadow and shrub swamp habitats in the Swamp. Like the "caged canary" of the coal mines, declines in key species of our butterflies can indicate how man-made changes are affecting the health of the Swamp.

Butterflies are Sensitive to Changes

Most Butterflies are resident species. Unlike birds, they are non-migratory. Butterflies live year-round near where the adult butterflies are seen. They have very limited dispersal tendencies and do not move far from where they were hatched. (The migrant "monarch" that travels to Mexico for the winter is a rare exception to this rule.)

Wet Meadows-Shrub Swamp Habitats are Important

Wet meadow habitats and the shrub swamp areas are the most likely places to find butterflies. The most important "habitat" requirement for a butterfly species is the type and variety of food plants available for the larval or caterpillar stage or their life-cycle. There must be sufficient amounts of the "right" food plants at the site. Although some butterflies are generalists and their caterpillars eat many plants, most are "specialists" and eat only one plant family, some favor only one particular species. Most of the "host" plants favored by wetlands butterflies are found in our wet meadows. It is the "specialist" species of butterfly that disappear if the caterpillar host plant disappears or changes. If a meadow is plowed or turned into a lawn, the host plant disappears and so does the butterfly. A meadow abandoned and allowed to grow to shrubs will no longer support the butterflies that formerly fed on the meadow plants. One species of Fritillary feeds only on bird-foot violets low growing wet meadow species. When tall grasses and brush grow up in the meadow, the violets are overshadowed and shaded by the shrubs and soon this butterfly species disappears. Not only does the right plant food need to be available for the caterpillars but other aspects of the "mini environment must be maintained for the butterfly species to survive in this location. For instance, special types of vegetation may be required for protective perches, hibernation spots or basking locations. Adult butterflies are less likely to have exacting requirements for flower nectar and may be able to utilize several different species.

a meadow fritillary, photographed at Sharparoon

More Study Needed

The last butterfly study and census in the Swamp was completed in 1997. More monitoring of the population changes in the swamps butterflies as well as the specific requirements of particular species is needed to determine the best management plans for habitats in the Swamp that attract butterflies.