Fender's Blue
This blue is endemic to Oregon's Willamette Valley.
Geography
Range Map
Fender's blue butterfly (Icaricia icarioides fenderi) is found only in the Willamette Valley in Oregon. Its range has been drastically reduced to a few populations.
Fender's blue is one subspecies in the Boisduval's blue complex and it is mostly isolated from all other subspecies.
Study Area
Our study uses sites in Lane County near Eugene, Oregon. These sites are managed annually for this species, and surveys focus on only this species.
This data comes from a team of many individuals, organizations and agencies working to protect this species. The data collection is coordinated and archived by the Institute of Applied Ecology .
Natural History
Habitat
Fender's blue requires lupine and nectar plants in unshaded prairie. Some of their current sites are remnant patches, and some have been heavily restored through planting and management.
Fender's blue habitat is threatened by habitat loss and fragmentation, invasion by non-native species, loss of larval host plants, and encroachment of trees and shrubs due to elimination of natural disturbance regimes.
Fender's blue butterfly and habitat
Population Dynamics
Fender's blue has varied in abundance throughout the years, but according to a 2016 study, the overall population has increased to 29,000 individuals. These increases have led to the downlisting of the species. Four of the butterfly's known populations have had more than 200 butterflies for ten years in a row, marking a significant step forward in the species' recovery.
Fender's blue are fairly sedentary, but are known to colonize nearby sites. Fender's blue exists in metapopulation networks, some with more isolated sites than others.
Life Cycle
Conservation
Listing Status
Fender's blue butterflies were thought to be extinct from about 1940 until the late 1980s, when a few populations were discovered on prairie remnants in the Willamette Valley, leading to a range-wide search for populations. The species was listed as endangered under the federal Endangered Species Act in 2000, it was downlisted to threatened in 2021 .
Recovery Efforts
Conservation Success
In 2021, Fender's blue butterfly was downlisted from endangered to threatened reflecting the positive effect of 30 years of management, research, and restoration efforts.
The dedication and partnerships of many organizations and the communities of the Willamette Valley have been instrumental in recovering this species. Fender's blue populations can now be found in many suburban and rural communities across Western Oregon.
Habitat Restoration
Planting native plants (as pictured) including Kincaid's lupine, the host species, has been an important part of restoring habitat. Efforts began in the mid 1990s and continue to expand to new locations today.
Prairie Management
Tree removal has also been important for bringing back flourishing lupine patches and creating areas to connect butterfly populations. Without management prairies in the Pacific Northwest become forests of Douglas firs, or covered in invasive blackberries (Rubus armeniacus).
Ongoing Efforts
Invasive plant control is now the major focus to maintain and improve Fender's blue habitat. Grasses like tall oatgrass can choke out lupine, and invasive forbs can take away soil nutrients from the plants.
Annual mowing, herbicide applications, and prescribed fires are all used to maintain and create high quality prairie for this butterfly.
Population Trends
We found that most of the Fender's blue butterfly sites with sufficient data are increasing in abundance (activity index). Most sites have advanced their phenology, but some have delayed.
Example of Fender's blue Population Trends: more butterflies earlier each year.
Overall we saw no association between phenology and abundance for Fender's blue. Differences in current management practices, and land management history appears to be more important in explaining the abundance trend of Fender's blue, see also Bonoan et al. (2020) .
