Callippe Silverspot Habitat Enhancement Planning-Solano Land Trust
Project description and listed species affected
The Tri-City and County area of Solano County, located between the cities of Fairfield, Benicia and Vallejo, contains some of the best known habitat for the Callippe silverspot butterfly in Solano County. This butterfly was recognized as an endangered species in 1997 by the U.S. Fish & Wildlife Service. Entomologist Richard Arnold has observed these federally-listed endangered butterflies on the Solano Land Trust’s 3,930-acre King, Vallejo Swett and Eastern Swett Ranches (in the area known as Sky Valley-Cordelia Hills) over the past few years.
A native viola (Viola pedunculata) is the sole larval food plant for the Callippe silverspot. Recent resource mapping undertaken for the Sky Valley-Cordelia Hills Resource Management Plan being developed by SLT has outlined relatively large areas where the violet is present, but not all populations of this species are in optimum condition. In some areas, viola appears to be excessively impacted by cattle grazing during the wet months. In addition, competition from exotic weed infestations, mainly yellow-star thistle and artichoke thistle may be displacing viola in some areas. Observations of viola populations on adjacent parcels suggest that altered grazing regimes could benefit viola populations on the King-Swett ranches.
In addition to the larval food plant, Callippe silverspot is dependent on flowering plants in the grasslands, nearby oak woodlands, or riparian areas from which the adults obtain nectar. California buckeye, a primary adult nectar source, is found in parts of the three ranches, but at relatively low densities. Other possible native nectar sources are uncommon due to the long history of habitat alteration and grazing in the area. Although Callippe silverspot has been observed flying about a mile in search of nectar sources, increasing the density of native nectar sources near existing viola populations would improve habitat quality for the butterfly.
The proposed project would help SLT improve its management of the endangered Callippe silverspot’s habitat on the King-Swett ranches and would provide critical information needed to help improve habitat quality throughout the Sky Valley-Cordelia Hills area.
Project Goals
The overall goal of this project is to improve the management of Callippe silverspot habitat at King-Swett ranches. This proposal addresses the initiation of a grazing study and a restoration plan that would serve as a basis for adaptive management.
Objectives
1. Design an empirical study to evaluate the impact of altered grazing practices on populations of the Callippe silverspot larval food plant (viola) on the King-Swett ranches.
2. Develop a plan to increase populations of native nectar sources (buckeye and other native species) used by adult Callippe silverspot butterflies.
Scope
Viola Enhancement Study
Task 1
The Solano Land Trust will work with a qualified botanical consultant to review appropriate Resource Management Plan data to familiarize the consultant with the property and the known viola locations. SLT and these consultants will scout the properties for suitable locations for the empirical study and perform a detailed baseline analysis of viola density in areas selected. The density of competing weeds and physical characteristics of slope, aspect and soil type which may interact with viola occurrence will be evaluated. This task will be completed in the Spring of 2007.
Task 2
The consultants will design a study to evaluate the impacts of alternative grazing regimes on viola population density. The study will test whether alterations in grazing timing and/or stocking rates can improve viola population density. If feasible, the effects of the alternative grazing regime(s) on exotic weeds (yellow star thistle, artichoke thistle) will also be addressed. The plan will include methodology for assessing grazing impacts and vegetation responses. R. Arnold will review and comment on these plans, as needed. This plan will be completed by August of 2007.
Additional funding will be required to implement the study. SLT will base its requests for implementation funding on the study design.
Nectar Source Enhancement Plan
Task 3
SLT and the botanical consultants will investigate existing buckeye populations in the area and determine factors such as slope, aspect and soil for these populations and their use by Callippe silverspot. Consultants will then investigate locations on King-Swett that have potential for reintroduction/restoration of these species using RMP data and current observations. The consultants will prepare a plan capable of being implemented by volunteers for buckeye restoration for these areas of King-Swett. This task can be completed in 2006.
Task 4
Using available published and unpublished data, the botanical consultants will research other possible adult nectar sources that may have been present at one time in this region. R. Arnold will be consulted regarding the possible use of these plants by the butterfly. These plants may require reintroduction. If found, locations for possible reintroduction would be suggested. This task can be completed in 2006.
Partnerships
Solano Land Trust will use this proposed habitat enhancement research to implement several cooperative projects. Once research is complete and an adaptive management plan for this species written, these results will be used on other parts of the ranches for implementation by PG&E and others interested in Callippe silverspot habitat enhancements.
This proposed plan will identify areas of the King-Swett ranches for reintroduction of Buckeye and other adult nectar source plants. SLT will work with our existing volunteer base to implement planting plans in a future phase. These volunteers may include the NorCal Soarers, a model glider club, SLEWs who have provided restoration programs at other SLT properties and groups of adult volunteers that have provided labor for other SLT mitigation areas on King Ranch. Solano Land Trust will also work with the grazing lessee to review and implement the plan.
