Seasonal changes in the chaparral will be on view during a 2-mile hike from 1 to 3 p.m. Sunday at Black Diamond Mines Regional Preserve in Antioch, led by naturalist Ashley Elliott.

Visitors will learn how chaparral vegetation anticipates the coming winter rains. The hike is on rough, sandy trails, and is designed for ages 7 and older. It's free of charge. Meet at the trailhead at the end of Somersville Road, 5 miles south of Highway 4. For information, call 888-327-2757, ext. 2750.

FRIENDLY HIKERS: The Wednesday Walkers are an informal, friendly group of hikers coordinated by naturalist Christina Garcia who explore a different regional park on an almost weekly basis. On Wednesday, they will check out Morgan Territory Regional Preserve, east of Mount Diablo, on a strenuous, 4.5-mile trek. Wear sturdy shoes, bring snacks and water and dress for the weather.

Meet at 9:30 a.m. at the park entrance on Morgan Territory Road, 9.4 miles south of Marsh Creek Road in Clayton. For more information on the Morgan Territory hike, or to obtain a hike schedule, call 888-327-2757, ext. 3282, or visit the hiking page on the park district website at www.ebparks.org.

DEL VALLE: Looking ahead, your 3- to 6-year-old children will enjoy a program planned from 10 to 11:30 a.m. Dec. 12 at Del Valle Regional Park, south of Livermore. The kids, accompanied by a parent, will learn to make musical instruments out of recycled materials. This is part of an Outdoor Discoveries series led by naturalists Katie Colbert and Cat Taylor. Registration is required, and there's a fee of $6 ($8 for nondistrict residents). For registration and information, call 888-327-2757. Select option 2 and refer to program number 4070.

LAS TRAMPAS: Katie also coordinates Women on Common Ground, a series of hikes in various parks for women who enjoy the outdoors but have concerns for personal safety. The next hike is from 10 a.m. to 2:30 p.m. Sunday at Las Trampas Regional Wilderness in San Ramon. It's a six miler, some of it steep. The hike is free, but registration is required. Call 888-327-2757, select option 2, and refer to program number 4108. Directions to the meeting place will be sent when you register for the program.

REDWOOD: If you're up for a twilight hike, there's a sunset-to-full-moon walk from 3:30 to 5:30 p.m. Sunday at Redwood Regional Park in Oakland, led by naturalist Sharol Nelson-Embry.

Meet Sharol at the Trudeau Staging Area at 11500 Skyline Blvd., just south of the intersection with Joaquin Miller Road, for a moderate, 3.75-mile hike into the woods, culminating with a view of the setting sun and rising moon. Rain cancels. This is part of the Healthy Parks, Healthy People program, designed to encourage regular use of the regional parks to improve personal health and fitness. For more information on Sharol's hike, call 510-544-3187.

Contact Ned MacKay at nedmackay@comcast.net.

Tilden: There's always something interesting going on at the Environmental Education Center in Berkeley's Tilden Nature Area, and now is no exception.

From 2 to 3 p.m. Saturday, it's reptile rendezvous time, hosted by interpretive student aide Tricia Radis and Cera, the center's box turtle resident. Learn about Cera's habitat and diet.

And from 2 to 4 p.m. Saturday, there's a program titled "Fire: Friend or Foe?" It's an interactive lesson on fire ecology and history in California, led by Tilden's supervising naturalist, Dave Zuckermann, and Sasha Berleman, a UC Berkeley fire science researcher. They will discuss fire's role in our natural environment.

California Indians made shelters, basketry and even boats out of tule reeds. At the center, from 9:30 a.m. to 1:30 p.m. Nov. 23, naturalist "Trail" Gail Broesder will help participants make Ohlone-inspired berry baskets out of the versatile plant material. Registration is required, and there's a fee of $10 ($12 for nondistrict residents). To register, call 888-327-2757. Select option 2 and refer to program 4090.

To reach the center, park at the end of Lone Oak Road off Tilden's Central Park Drive and follow the directional signs on a short walk. For information, call 510-544-2233.

Ned MacKay writes a regular column about East Bay Regional Park District sites and activities. Email him at nedmackay@comcast.net.

Contact Ned MacKay at nedmackay@comcast.net.