The East Bay Regional Park District is calling for active senior citizen volunteers to help out in a couple of weekday scientific education and research projects coordinated by naturalist Sara Fetterly.

Both are from 1 to 3 p.m. Thursday and on April 24.

On Thursday, the venue is Crab Cove Visitor Center in Alameda. The group will learn about non-native species of marine life in San Francisco Bay, then put on boots and search for some of the invaders in the mud flats.

In April, the group will meet in the lower parking lot at Roberts Regional Recreation Area on Skyline Boulevard in the Oakland hills. In partnership with Save the Redwood League, the group will learn how climate change can affect the redwoods, then help to collect data on ferns and trees in the forest.

If you're interested in joining either or both activities, call 510-544-3187 for details.

Speaking of redwoods: One of the hikes in the Saturday/Sunday Strolls series is scheduled at Redwood Regional Park in Oakland from 10 a.m. to noon Saturday. This one is more than a stroll -- it's a strenuous 5-miler on the Bay Area Ridge Trail from Redwood north to the Huckleberry and Sibley preserves, then back. From Redwood the trail descends to San Leandro Creek, then climbs up to Sibley, retracing the down-and-up on the return.

Meet at Redwood Regional Park's Skyline Gate, which is on Skyline Boulevard a bit south of the intersection with Pinehurst Road. For information, call 510-544-3187.

name that tune: Even if you can't see birds, you can tell what kind they are by the songs you hear them sing. Naturalist Michael Charnofsky will show how during a walk from 9:30 to 11:30 a.m. Sunday at Leona Canyon in Oakland.

It's free and designed for ages 8 and older. Meet Michael at the Canyon Oaks Drive trailhead off Keller Avenue in the Oakland hills. For information, call 510-544-3187. Other "birding by ear" walks are scheduled on April 6 at Briones Regional Park near Orinda and April 13 at Tilden Nature Area in Berkeley -- read more about those later.

egg time: The art and lore of Easter eggs will be the focus of a program from 2 to 4 p.m. Sunday at Tilden Nature Area in Berkeley, hosted by interpretive student aide Morgan Rani Evans. The group will experiment with natural dyes and try out techniques such as porcelain eggs made with black tea.

The program is free, but you must bring your own hard-boiled eggs. Meet at Tilden's Environmental Education Center. To get there, park at the end of Lone Oak Road off Central Park Drive and follow the signs on foot. For details, call 510-544-2233.

While we're at the center, naturalist "Trail" Gail Broesder will lead a couple of programs there on March 30, that highlight Native Californians' skills. From 9 a.m. to noon, Gail will show how Native Americans in California made soap root brushes. Participants will start the process, then take the brush home to finish the job and dry the completed brush.

The brush program is for ages 8 and older. Registration is required and there's a fee of $5 per person ($7 for nondistrict residents). To register, call 888-327-2757. Select option 2 and refer to program number 4963.

And from 1 to 2:30 p.m. March 30, Gail will show how to make a tule reed boat, a miniature version of the watercraft the Ohlone used to navigate San Francisco Bay. The group will test the final result on a nearby pond. The program is free.

wildflower shows: Black Diamond Mines Regional Preserve in Antioch is probably best known for its underground mining museum. But the park has lots of aboveground attractions, too, including great spring wildflower displays.

Naturalist Eddie Willis will lead a hilly 2-mile wildflower hike there from 10 a.m. to noon Sunday. It's free and best for ages 8 and older. Meet at the uppermost parking lot on Somersville Road, 5 miles south of Highway 4. Rain cancels. For information, call 888-327-2757, ext. 2750.

One of the Senior Safari van tours will be at Black Diamond Mines from 10 a.m. to 2 p.m. April 24. It's designed for ages 50 and older. The itinerary will include a tour of the mine, the mining town sites and panoramic views enhanced by wildflower displays.

Registration is required and there's a $30 fee per person ($34 for nondistrict residents). For registration, call 888-327-2757. Select option 2 and refer to program number 5152. For information call 510-544-3249.

LEVEE LEARNING: Ever wonder how Big Break got its name? You can find out during a program from 2 to 3 p.m. Sunday at Big Break Regional Shoreline in Oakley. Big Break's interpretive staff will talk about the levees that keep back the Delta floodwaters.

The park has lots of ongoing programs highlighting the Delta ecosystem, including a walk-on scale model of the waterway itself. Big Break is located at 69 Big Break Road in Oakley. For information, call 888-327-2757, ext. 3050.

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

---