Managing for a Rare Butterfly at Frye Mountain WMA

By Natural Resources Manager Jack Chappen

The early hairstreak (Erora laeta) is a rare butterfly species that utilizes mature hardwood forests from the northern Canadian maritime provinces down to the southern end of the Appalachian Mountains. Their primary food source consists of the nuts produced by American beech trees and beaked hazelnut shrubs. In Maine, the butterfly is considered a Species of Special Concern and has been listed as a Priority 2 Species of Greatest Conservation Need since 2015. The cause of this concern is the decreasing numbers of the butterfly in areas where populations are known to exist. The primary reason for this decline is believed to be because of an introduced disease that kills American beech trees before they are old enough to produce nuts. The resulting lack of food and habitat is likely the reason for the butterfly’s decline in Maine.

As caterpillars, the hairstreak feed on the husks and nuts of beech and beaked hazel. Once butterflies, they feed on nectar from nearby flowers and are primarily found in the upper canopy of forests, thus making detection and monitoring efforts hard. Mature forests adjacent to gravel roads are especially preferred, as the hairstreak is known to use them as sources of water in the Canadian and New England range of its distribution during the summer months.

Frye Mountain WMA presents a unique opportunity to manage habitat for the early hairstreak butterfly because the area features hardwood dominant forest types with a heavy American beech component. Sunnyside Cemetery Road (pictured below) is a small gravel road that bisects this mature hardwood forest and provides great potential habitat for the butterfly. A timber operation to manage for mast-producing tree species for wildlife will also include a 400 ft. buffer along the gravel road which will be specifically managed for mast producing beech to provide food and habitat for the caterpillar and butterfly by combating the beech bark disease.

Beech bark disease causes cankers to develop on the bark of American beech trees once their diameters reach about 5 inches. The disease eventually kills them by exposing the sapwood to pests and rot. This is almost always long before they are old enough to produce nuts. 

However, a small percentage of beech trees are resistant to the disease, allowing them to reach full maturity and nut production. The timber harvest at Frye will focus on removing diseased individuals to allow nut-producing resistant beech space to grow and reproduce, allowing the spread of their genetic resistance. Ideally, this type of forest management will improve the habitat for the rare early hairstreak butterfly and help prevent their population from declining even further in Maine.