San Juan Island National Historical Park Butterfly Survey, 2003

Pyle, Robert

Brief trip report on 9 days of butterfly surveys at San Juan Island National Historical Park in May and June, 2003 and includes list of species observed. The initial visit of four planned occurred May 5 - 8, 2003; full details will be provided with the final report, but here are initial findings. The first full day was devoted to American Camp (AC) and adjacent NRCA (Lighthouse), bluffs, South Beach, Redoubt and grasslands on all sides of it, Jakle's Lagoon and forests/edges on Mount Finlayson. The second full day was spent at English Camp, on the oak meadows, Young Hill, the cultural sites, and the southwest boundary area. The third final full day was spent searching the pinelands/glades east of the AC VC and north of Cattle Point Rd; targeted re-survey of the Redoubt area and South Beach and slopes between; the northeast boundary area of AC; Fourth of July Beach; and Old Town Lagoon. A total of 18 species was recorded and represents ~half of the butterfly species recorded in the San Juan Islands. The three most notable finds were Pyrgus ruralis, the first record of its genus for the San Juan Islands; Glaucopsyche lygdamus, second county record; and Incisalia mossii, first record for the county since 1950. Both elfins and the Tailed Blue are new for San Juan Island. Future visits will reveal additional species and host/nectar associations, and some additional perspectives on management. The majority of the uncommon specialists being spring-flying butterflies, our findings so far should help management prescriptions likely to protect or enhance their occurrence. It is recommended to maintain all crucifers for now, protecting oaks and junipers, and attacking Himalayan blackberry on a stem-by-stem basis rather than a broadcast herbicide or fire approach that could damage Dewberry, violets, fescues, and other valuable neighbors. The second visit (of four planned) occurred June 22-26, 2003. Conditions were much drier than during the May visit, with much of the flora having dessicated. The butterflies were reduced in number and diversity from the spring season. Nonetheless, substantial nectar resources remained or began (especially weedy and native composites, brambles, monocots inc. Allium and Brodeia, and sand verbena). Certain species had appeared or come into full flight, particularly Vanessa and Limenitis (ladies and admirals). Results with the island marble, Euchloe ausonides insulana, were fairly dramatic and surprising, including discovery of a new hostplant that seems to be a native species. Surveys occurred at Eagle Point, upshore from the Park; in the sand verbena dunes and blowouts above South Beach at AC; South Beach; and the grasslands from the Redoubt to the shore and along the shore path westerly, which was rich with nectar (gumweed, spurry) but absent of butterflies. Surveys at English Camp included Young Hill, where an assemblage of swallowtails and Lorquin's admiral engaged in mass interaction (up to eight together) in the summit glades; the gardens and meadows of the cultural site; and re-survey of the oak meadow/grasslands along the SW border of English Camp. More AC surveys centered on the Lighthouse lupine stands, a transect of the length of Mt. Finlayson, Fourth of July Beach and horse camp heath, and Oldtown Lagoon, and the pineries near the American Camp entrance. A total of 15 species were recorded, bringing the total found on the survey to date to 25.