Butterflies of the Skyline OSPs

Skyline, Long Ridge, and Windy Hill Open Space Preserves occupy prime habitat in the coastal range of the San Francisco Peninsula. Habitats include dry chaparral, Douglas Fir, open grasslands, and Oak forest. Special butterflies include the scarce Unsilvered Fritillary, "Grinnell's" Pacuvius Duskywing, Coronis Fritillary, Bramble Hairstreak, "Chalcedon" Variable Checkerspot, and Golden Hairstreak.

Getting there

From Highway 280, take Woodside Road (also marked as Highway 84) west to its top at Skyline Boulevard, also known as Highway 35. Turn left (south), and take Skyline Boulevard south for about 7 miles. Shortly after passing a four-way intersection (with Page Mill Road on your left and Alpine Road on your right), continue for almost 1 mile to the entrance to Skyline Open Space Preserve (on your right). The entrance to Long Ridge Open Space Preserve is on your right a further two miles.

Windy Hill OSP is another worthwhile destination, just a few miles south of the intersection of Highway 35 and Highway 84. Two-banded Checkered-Skipper has been found here. All of the OSPs doubtless contain highly worthwhile butterflying and await future exploration.

When to go

The preserves can be visited with some success anytime from April to August.

Other wildlife

Skyline OSP is also a first-rate locality for finding dragonflies and damselflies. Alvaro Jaramillo has worked up a checklist of the Odonates of Skyline OSP, which he's graciously allowed me to post.

Interesting birds in this area include Lazuli Bunting, Ash-throated Flycatcher, Wrentit, Black-throated Gray Warbler, and (rarely) Pileated Woodpecker. Lawrence's Goldfinch is regular some years at Windy Hill OSP. Mountain Lions are up here, but your odds of seeing one are next to nothing.

Exploring the preserves

At Skyline, from the parking lot walk down to Horseshoe Lake and follow a smaller trail along its edge. Dragonflies are plentiful here. At the bridge, cut back to your right. Turn left up the Ridge Trail, which ascends a steep incline to the ridgetop. (Lazuli Buntings frequent this area.) From up top here you can walk a loop to the north to Alpine Pond, then back around the other side of the ridge and back down to the parking lot.

It's possible to walk the Ridge Trail a little more than two miles (each way) south from Skyline to Long Ridge, but if you're lazy like me you'll drive south to Long Ridge. Follow the (only) trail down into the valley, continuing on to Peters Creek Trail. At the second trail junction (just after crossing the creek), follow Long Ridge Trail up to your right. The trail climbs steeply to a small opening in the forest where Unsilvered Fritillaries were found in 2002. (Look for these fritillaries nectaring on thistle, but take care to eliminate Coronis and Pacific Fritillary.) Continue along the trail, eventually switching over to Long Ridge Road, then dropping back down to Peters Creek Trail. Look for Tailed Coppers in open areas as you head back towards the start of your hike.

Species list

Species are followed by their abundance and a range of months. The months are conservatively listed, restricted to confirmed records from this park. If you have any additional records, please .

Swallowtails

Anise Swallowtail (Papilio zelicaon): Common 4-5, 7, 9
Western Tiger Swallowtail (Papilio rutulus): Uncommon 3, 6-7
Pale Swallowtail (Papilio eurymedon): Uncommon 5-7

Whites and Sulphurs

Cabbage White (Pieris rapae): Uncommon 6,10
Margined [Mustard] White (Pieris [napi] marginalis): Common 3, Rare 6
Checkered White (Pontia protodice): Uncommon 7
Large Marble (Euchloe ausonides): Uncommon 3
Sara Orangetip (Anthocharis sara): Common 4-5
Orange Sulphur (Colias eurytheme): Uncommon 10

Coppers, Hairstreaks, and Blues

Tailed Copper (Lycaena arota): Uncommon 6-7
Great Copper (Lycaena xanthoides): Rare 6
Gorgon Copper (Lycaena gorgon): Uncommon 5-6
Golden Hairstreak (Habrodais grunus): Abundant 6-9
California Hairstreak (Satyrium californica): Uncommon 5
Hedgerow Hairstreak (Satyrium saepium ): Uncommon 6
Brown Elfin (Callophrys [Incisalia] augustinus): Uncommon 4-5
Bramble Hairstreak (Callophyrs [dumetorum] perplexa): Uncommon 4-5
Echo [Spring] Azure (Celastrina [ladon] echo): Common 3-6
"Pardalis" Boisduval's Blue (Plebejus icarioides pardalis): Common 5
Acmon Blue (Plebejus acmon): Common 3-4, Abundant 5-9,11
Silvery Blue (Glaucopsyche lygdamus): Uncommon 4

Brushfoots

Coronis Fritillary (Speyeria coronis): Common 5-9
Unsilvered Fritillary (Speyeria adiaste adiaste): Uncommon, 7-8 (Long Ridge only)
Pacific Fritillary (Boloria epithore epithore): Uncommon, 6
Leanira Checkerspot (Thessalia leanira): Uncommon, 5
Northern Checkerspot (Chlosyne palla): Uncommon, 5-6
"Chalcedon" Variable Checkerspot (Euphydryas chaledona): Abundant, 5-7
Field Crescent (Phyciodes pulchella (syn. campestris)): Uncommon, 5
Mylitta Crescent (Phyciodes mylitta): Common, 4-8, 11
Satyr Comma (Polygonia satyrus): Uncommon 5-6, 10
California Tortiseshell (Nymphalis californica): Uncommon, 1, 4
Painted Lady (Vanessa cardui): Common, 5, 9-10
American Lady (Vanessa virginiensis): Uncommon 9
West Coast Lady (Vanessa annabella): Uncommon, 5, 9
Red Admiral (Vanessa atalanta): Uncommon, 5, 10
Common Buckeye (Junonia coenia): Abundant 4-7, 9-11
Lorquin's Admiral (Limenitis lorquini): Abundant 6
California Sister (Adelpha bredowii ): Abundant 5-11
"California" Common Ringlet (Coenonympha tullia california): Abundant 4-9
Common Wood-Nymph (Cercyonis pegala): Common 5-8
Monarch (Danaus plexippus): Uncommon 3,6

Skippers

Propertius Duskywing (Erynnis propertius): Uncommon/Common 3-6
Mournful Duskywing (Erynnis tristis): Uncommon/Common 6-9
"Grinnell's" Pacuvius Duskywing (Erynnis pacuvius pernigra): Rare 6
Two-banded Checkered-Skipper (Pyrgus ruralis): Uncommon 4-5 (Windy Hill only)
Common Checkered-Skipper (Pyrgus communis): Uncommon 1
"Dodge's" Western Branded Skipper (Hesperia [comma] colorado dodgei): Uncommon-Common 7-9
Woodland Skipper (Ochlodes sylvanoides): Abundant 7-10
Rural Skipper (Ochlodes agricola): Common 6-7
Umber Skipper (Poanes melane): Uncommon 6, Common 10