Bats About Our Town


Woodard Bay Natural Resources Conservation Area

Washington State’s largest known bat colony is tucked away under an abandoned railroad trestle in North Olympia. Here female Yuma and Little Brown Bats cluster together in the trestle above the waters of Puget Sound.

Abandoned Railway Trestle Provides Bat Habitat

(Click on the image to see a larger image)

Photo © Greg Falxa

Where once the Weyerhauser Corporation moved logs, using a train to bring them to Henderson Inlet and tugboats to escort the logs north to Everett, mother bats give birth to bat pups, seals hauled out on log booms give birth to seal pups, and Great Blue Herons in the nearby forest rookery hatch their eggs on ungainly nests, huge platforms of sticks.

Weyerhauser abandoned the site in 1984; by 1988 the area became the Woodard Bay Natural Resources Conservation Area. This wildlife refuge of approximately 680 acres sits in a rural portion of Thurston County, about a 15-minute drive to the northeast of Olympia. Here, along the western shore of Henderson Inlet, two bays connect to the inlet, creating a V-shaped intersection as if a hand were making a sidewise victory sign. The southernmost, Woodard Bay, has given its name to the area. The northernmost, Chapman Bay, is where the bats have their maternity roost.

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Woodard Bay NRCA contains a wide range of habitats, from tidelands that are mudflats at low tide to second growth forest to freshwater wetlands and streams. Here, so close to urban centers, nature abounds—approximately 175 species of birds have been inventoried, for example.

For the 3,000+ members of the bat colony, the railway trestle provides a safe, warm place to raise their young. The mother bats prefer the section of the trestle where large steel plates underlying the tracks still remain. The steel captures and radiates heat, helping bats already massed together for warmth gather even more warmth in the cool spring and early summer. Any time the bats get too warm, they simply spread out a bit.

These bats don’t find the insects they need over mudflats or over salt water. Woodard Bay’s forested areas can give tiny, relatively solitary California Bats the insect food they like among the trees. The area doesn’t provide food for the Yuma and Little Brown Bats, who seek the insects hatching from large bodies of fresh water. Rather, these bats make a nightly commute to find food elsewhere. Their favorite spot is Capitol Lake in the center of downtown Olympia, a 16-20 mile round trip distance from the trestle. See A Night at Capitol Lake to learn more. The mother bats’ commute is the longest known summer feeding distance traveled in North America for these two species.

This video shows Yuma and Little Brown Bats flying out from the left side of the Woodard Bay railroad trestle.  The sound track contains

  1. Voices of people standing off camera to the right
  2. Bat echolocation calls as heard through a bat detector, which translates the very high frequency calls into sounds within human hearing range. For more information on calls see Bat Sounds.

Bats Emerging at Dusk

As the pups mature and learn to fly, they and their mothers disperse.  In the fall the bats head for hibernation sites in cooler areas whose location in unknown.  After the long winter’s torpor, the pregnant female bats return to the trestle while most of the male bats scatter into higher altitude, cooler forest areas.

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Regular Bat Counts

Two biologists, Lori Salzer and Mary Linders, visit Woodard Bay once a week while the bats are in residence. They count the bats as they emerge. This diagram shows the bat census in a typical year:

(Click on the image to see a larger image)

For most of the summer, approximately two thirds of these bats are Yuma Bat females, and one third are Little Brown Bat females. At the peak population, the count also includes male and female pups who are just learning to fly.

U/W Class Visits Woodard Bay

University of Washington biology professor Karen Petersen includes a field trip to Woodard Bay in her Vertebrate Zoology course during the spring and summer classes. To share the experience of one class, go to Biology 452.

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To Visit Woodard Bay



  1. Park by the trail and visit on foot only—no vehicles, bicycles, or horses.
  2. Groups of 10 or less. For a larger group, get prior permission from DNR manager Roberta (“Birdie”) Davenport at 360-577-2025 or send her an email.
  3. No pets. Dogs can mark an area and scare off wildlife. In the winter, some rare water birds resting on the water, then startled into flight, lose needed calories and may actually die from the intrusion.
  4. No camping, campfires, guns, hunting, shellfish collecting, plant collecting.

Viewing Bats

Plan your arrival time at the parking lot according to these facts: Bats emerge from under the trestle about 15 minutes after sundown, so check the sunset information for the day of your visit. The hike into the area covers three quarters of a mile on a gravel road that exits the parking lot. The road is wheelchair accessible with a little help. Remember to bring warm clothes and a flashlight.

The Hiking Trails

By the parking lot, a foot traffic only gravel road called Whitham Road goes three quarters of a mile through the forest to a rustic, small open area with picnic tables and interpretive signs. You will pass rest rooms on the way.

A short distance from the parking lot you can also enjoy a one mile loop trail that begins and ends on Whitham Road.

Warning: Car Prowls

Car prowls are frequent at the parking lot. Don’t leave valuables in your car.

To Get There

From Lacey: Go north on Sleater-Kinney Road, which curves left to become 56th Avenue. Turn right on Shincke Road, which curves left to join Woodard Bay Road. Cross the bridge across the upper end of the bay and turn right into a small parking area just after you cross the bridge.

From Olympia: Go north on East Bay Drive, which becomes Boston Harbor Road. Turn right on Woodard Bay Road to the small parking area just before the bridge.

From I-5: Follow I-5 at the northern end of Olympia, take Exit 109 (Martin Way Exit). Go 0.2 mi towards Sleater-Kinney Road. Turn right onto Sleater-Kinney Rd NE. Go ~ 4.4 mi., then continue going straight onto 56th Ave NE for 0.4 mi. At a "T" turn right onto Shincke Rd NE going 0.5 mi. Then turn right to STAY on Shincke Rd NE for another 0.5 mi., it will curve left to become Woodard Bay Rd NE which then curves right. Cross the bridge to park near the gate into the Woodard Bay Natural Area.

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