Monitoring Fender's blue butterflies

The Fender's blue butterfly (Icaricia icarioides fenderi) is an endangered species which is only found in the Willamette Valley, at sites that include its preferred host plant, the threatened Kincaid's lupine (Lupinus oreganus).

Thought to be extinct, the species was rediscovered in 1989 in small remnant populations. Prairie habitat loss, degradation and encroachment by trees, shrubs, and invasive species have led to the species' decline. However, many restoration partners are actively restoring prairies with the aim of to reversing the butterfly's decline and increasing the populations.

The butterflies live a precarious existence - adults begin laying eggs, primarily on Kincaid's lupine, during May, then caterpillars feed on the lupine leaves until the plants senesce in early July. At that point, they move to the base of the plants and enter diapause, continuing their development the following spring. The few larvae that make it through the winter then enter the pupal stage, prior to emerging as adults. In a brief 10-day life, an adult butterfly must find sufficient nectar to survive while searching for mates and potentially migrating to nearby meadows.

The Institute for Applied Ecology is participating in a US Fish and Wildlife Service funded project to monitor Fender's blue butterfly, key bird species, and habitat quality at prairies across the Willamette Valley in order to gauge the success of restoration efforts. Carolyn Menke, IAE's Assistant Director, is coordinating the project, which includes several contractors and IAE staff. Peter Moore, one of IAE's restoration ecologists, has been surveying at Butterfly Meadows, an isolated prairie nestled in forest near Corvallis.

Some of the more populous sites , such as Baskett Slough National Wildlife Refuge, are sampled by counting male butterflies along transects several times during the flying season. At smaller sites such as Butterfly Meadows, butterflies are counted by zig-zagging through suitable habitat, and a peak count is determined. In addition, several butterflies are captured to work out the ratio of Fender's and the more common silvery blue butterfly.

It is hoped that the monitoring of butterfly, bird, and habitat quality over a range of Willamette Valley sites will allow us to track prairie recovery.