On the Trail of Two Rare Species

Following SJPT’s 38th Annual Meeting in Friday Harbor last month, 20 SJPT members piled into a minibus and took off in search of Western Bluebirds and Island Marble Butterflies—two native species that have all but disappeared from the islands. Amazingly, the group was treated to rare glimpses of both …

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The group’s first destination was American Camp National Historical Park near the southern tip of San Juan Island. It was here, in 1998, that a small white butterfly with green marbling on the underside of its wings was rediscovered after a 90-year disappearance. Subsequent searching revealed that this species—Euchloe ausonides insulanus, aka the Island Marble butterfly—existed nowhere else except in small patches (or islands!) of wildflower prairie habitat on San Juan Island, centered at American Camp. The Preservation Trust is working with several partners—including the National Park Service (NPS), which owns and manages American Camp—that are actively engaged in trying to expand the population of this rarest of endemic butterflies.

Fewer than 200 individual Island Marble Butterflies are known to exist, so the likelihood that the field-trip group would actually spot one seemed very low. But we got lucky! Tour leader Kathleen Foley (SJPT’s Stewardship Manager) had arranged for the group to meet with NPS biologist Jenny Shrum. Jenny is part of a captive rearing program based at American Camp. Just that morning, two Island Marbles had emerged from the chrysalis stage in the program’s lab. Jenny answered questions from the group while she opened two containers. From each of these, she plucked the newly emerged butterflies and placed them carefully on their favorite plant: field mustard, which was just beginning to open its yellow blossoms in a fenced-off plot.

Here’s a gallery of photos showing what the group saw that day at American Camp (photos by Joe Belcovson):

The next stop on the tour was the County Land Bank’s Frazer Homestead Preserve, not far from American Camp. There, Kathleen Foley has planted several Island Marble butterfly test plots, sowing seeds of field mustard and other nectaring plants that are native to local grasslands. The hope is that some intrepid Island Marble females will lay eggs in these plots, thereby spreading the tiny population beyond American Camp, where a single harsh natural event could potentially wipe out the species.

And Kathleen announced some exciting news: Four tiny eggs had been spotted in one of the Frazer plots that strongly resembled IMB eggs! (The identity of the eggs was later confirmed, although they proved to be infertile. Still, this was a positive sign that at least one adult female had ventured well beyond the American Camp prairie in search of a good home for her offspring.)

Here are some photos taken at the Frazer plots (photos by Joe Belcovson):

The final stop on the tour was designed for bluebird spotting. Kathleen knew that a nesting pair of rare (to the San Juan Islands) Western Bluebirds had taken up residence in a nesting box on a private property protected by an SJPT conservation easement. The female was probably sitting on eggs inside the box. The male was probably out hunting for food. We’d be lucky if either one of them made an appearance. But they both did, and put on quite a show—including a fleeting midair copulatory “kiss.”

It was a day of many rare sightings!

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