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The Weeping Rocks of Oregon Mountain

Updated: Feb 22

According to California lepidopterist Ken Davenport, author of Butterflies of the Sierra Nevada, the Western Cloudywing is one of our rarest skippers in North America, and is found only within "a very limited range in California and extreme southwestern Oregon." It occurs on limited sites in six counties in northern California, and in Josephine and Curry counties in Oregon. Oregon Mountain is in the far southwest corner of Josephine County, and that's where we find this scarce little skipper in Oregon.

My search on the history of the name Oregon Mountain came up empty, but I surmised that since it sits right on the Oregon-California border, it may have been a landmark that told travellers they had reached Oregon coming from the south. Even now, the only way to reach Oregon Mountain is via the old Wimer Road, built in 1882 by "enterprising Postmaster" P. T. Wimer. It was the only route from this area to the coast until Highway 199 was built in 1926. The partially improved gravel road still follows the historical route, passing on the southern shoulder of Oregon Mountain.

Close up photo of a Western Cloudywing butterfly, dorsal view
Western Cloudywing (Cecropterus diversus)

My friend Rob Santry, a fine butterfly photographer living in Grants Pass, met me in O'Brien at the country store, where I rescued him from an old-timer who was fully chewing his ear off about a wide range of topics. We agreed to head straight to the stretches of road where we knew rocks and water would attract one of our top target butterflies for the day: the Western Cloudywing.

The Western Cloudywing is very similar to the Northern Cloudywing which also flies at this time of year at Oregon Mountain. The latter species differs in both field marks and behavior from its Western cousin. Western Cloudywings fly in fast circles, and land exclusively on rocks. Northern Cloudywings have a fast, but more varied flight pattern, and they often land on plants. The field mark differences are subtle: on its dorsal (upperside) forewing, the second white bar from the tip of the wing is generally longer and narrower on a Western than on the Northern. Northern Cloudywings are also generally larger and darker, but you can't count on that every time. So the flight pattern is the first thing you see, and after following the dizzying circular flight, you look at the cloudywing that landed on a rock for the field marks.

Close-up photo of a Western Cloudywing butterfly, ventral view
Western Cloudywing (Cecropterus diversus)

The sites that we searched for Western Cloudywings all had streams, seeps, and lots of rocks. Rob had heard from Ken Davenport that formations of weeping rocky walls existed at some of the sites where Western Cloudywings are found in California, though in his aforementioned book, Davenport simply says they are found "in wet forested areas along streams and in small damp forest glades." Some reaches of the streams we visited were dry, but there was always water nearby, sometimes higher up the creek bed. Where Shelly Creek flows under the Wimer Road and directly into California there is a big rock slab that the creek flows over, and lots of fractured rock. The geology of this area is fascinating, with shallow rocky soils, serpentine rock outcrops and groundwater seeping out in many places.

A photo of the Shelly Creek "Slab" on Oregon Mountain
The Shelly Creek "Slab" on Oregon Mountain

All these seeps attract butterflies in general, though on this trip it was a bit early for many species, and the butterfly assemblage was dominated by small, dark brown, fast-flying skippers: Western Cloudywing, Northern Cloudywing, Propertius Duskywing, and Persius Duskywing.

Close up photo of a live Persius Duskywing butterfly
Persius Duskywings were more common on Oregon Mountain than than is typical in the rest of Oregon

The first week of June, according to Rob, is the week when Western Cloudywings usually start flying and he was correct. We found them at each of the sites we visited, though the numbers were limited -- we saw maybe 10 or 12 individuals in a day.

A photo of water seeping from rock formations on Oregon Mountain
Weeping rocks along the Wimer Road

Rob and I talked about having to use the "stakeout" strategy to photograph some butterfly species, and how it could work well with these cloudywings that keep returning to the same perch. I simply watched the cloudywings for a few minutes and noted which rocks were the favored perches. Then, when no cloudywing was perched, I found a comfortable seat about 8 feet away from one of the favored rocks. I sat down, and waited. Sure enough, if I was still enough, a cloudywing would eventually land, and if I moved minimally and slowly, I could take several photos before some other butterfly or insect sent my quarry into its speedy circles.

A close-up photo of a Gray Marble butterfly
Gray Marble (Anthocharis lanceolata)

It turned out that the Western Cloudywing was not the only butterfly on Oregon Mountain for which I needed to use the stakeout strategy. The Gray Marble (Anthocharis lanceolata) is a lovely butterfly in the Pierid family, closely related to the more colorful Julia's Orangetip and Sara's Orangetip. I had found it a very difficult species to photograph well in my previous attempts because they land very infrequently, and if you move towards them at all while they are perched, they zip off up or down the hill and disappear rapidly. Rob and I had seen many whites in flight, and could only guess what species they were because they flew fast, somewhat erratically and without stopping. On the second day, I resolved to see what species they were, so I put away my cameras, and got out my net. I spent about 90 minutes just chasing and netting pierids, and what I found was interesting. About one-fourth of them were Large Marbles (Euchloe ausonoides) and the majority were Gray Marbles.

After watching and chasing the Gray Marbles for a couple of hours I got to where I could often spot the slightly hooked shape of the Gray Marble's forewing in flight. So I found a stretch of road where I could see several flying in one area, and just stood and watched them for several minutes to see when, where and why they perched. It didn't take too long to see that they were only stopping to sip nectar, and only on one species of flower.

Photo of native mustard plant with a butterfly larva.
Native mustard, note larva near the top, probably a Gray Marble or Large Marble larva.

I scouted the roadside to find where these plants were, and planted myself about 8 feet away from the freshest and most robust plant, and sat down. I waited a lot longer than with the cloudywings, because the marbles were ranging over a much larger area, and visiting the flowers only occasionally. However, the strategy paid off, as four times a Gray Marble came to nectar on the plant I had staked out.

A close-up photo of a Two-Banded Checkered-Skipper butterfly
Two-banded Checkered-Skipper (Pyrgus ruralis)

I had also hoped to discover some Spring Whites (Pontia sisymbrii), which fly in southwestern Josephine County from early April to mid-June, among the pierids on Oregon Mountain. There was one slightly larger white that I saw several times, with a more rounded wing-tip than the Gray Marble, but I strongly suspect they were Mustard (Margined) Whites, rather than Spring Whites, which have strong black forewing tip markings. I don't mind planning another spring trip to southwestern Josephine County for 2021 to search again for Spring Whites.

Close up photo of a mating pair of Dotted Blue butterflies
Mating Dotted Blues (Euphilotes enoptes)

At the end of the second day, I headed down to the lower stretch of Wimer Road, to see what was flying there. I found good numbers of Northern Checkerspots (Chlosyne palla), Field Crescents (Phyciodes pulchella), Propertius Duskywings (Erynnis propertius), Greenish Blues (Icaricia saepiolus) and Cedar Hairstreaks (Callophrys gryneus). The full list of sightings and counts for the two days on Oregon Mountain is below.

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