A couple of really enjoyable family-friendly events are on the schedule this weekend in the East Bay Regional Parks.

The first is that perennial favorite, the Annual Sand Castle and Sand Sculpture Contest on Saturday at Crown Beach in Alameda.

This one's really a kick, whether you enter the free contest or just enjoy the show. Registration is at 9 a.m. at the Crown Beach changing rooms. Registrants are assigned a plot of sand on which to erect either a sculpture or a castle. Your entry must consist of sand only, with the exception of wood, rocks, shells, etc. found on the beach the day of the contest and used as decorations only. No glass or live animals, please.

Competition is by age -- there are categories for youngsters, adults and families. Awards in the form of ribbons and trophies are presented at 1 p.m., but winners mostly just get bragging rights. There's no prize money involved.

Sponsors are the East Bay Regional Park District, Alameda Recreation & Parks, Bay View Women's Club and the Alameda Youth Committee. For more information, visit www.alamedaca.gov. The Crown Beach entrance is at the intersection of Otis and Westline Drives.

The other crowd-pleaser is the 15th Annual Butterfly and Bird Festival at Coyote Hills Regional Park in Fremont. It's from 10 a.m. to 3:30 p.m. Sunday. Butterfly garden tours, family hands-on activities, educational speakers, photo presentations and live music are all on the program, with a focus on increasing the numbers and species of butterflies and birds in Bay Area open space.

You can learn how to create wildlife-friendly habitat in your own backyard. Coyote Hills is located at the end of Patterson Ranch Road off Paseo Padre Parkway in Fremont. There's a $5 parking fee per vehicle; the festival is free.

CHABOT: Campers and noncampers alike are welcome at the free campfire programs at the Anthony Chabot Campground amphitheater.

The show is on from 8 to 9 p.m. every Saturday through Labor Day Weekend. Learn about the regional parks and natural history through games, songs, photos and stories. There's a new topic each week.

Anthony Chabot Campground is accessed via the Marciel Gate to Chabot Regional Park. It's on Redwood Road between Oakland and Castro Valley. For information, call 510-544-3187.

TILDEN: There are several fun programs scheduled in coming days at Tilden Nature Area in Berkeley.

Early risers will enjoy "Birds of Hill and Dale," a trek to the peak and creek from 7 to 10 a.m. Saturday, led by naturalist Anthony Fisher. There's uphill hiking involved; bring a snack.

Then from 1 to 2:30 p.m. Saturday, Anthony will show how to twist cordage from plant stems and make beads from seeds.

Tilden Nature Area will celebrate the Regional Park District's 80th anniversary with a "Passport to History" program from 11 a.m. to 3 p.m. June 14. It's a day of music, games and fun at one of the original regional parks.

There'll be meet and greet sessions with pigs, goats and chickens at the Little Farm, hand-cranked ice cream samples and a Passport to History walk to Jewel Lake.

All the Tilden programs start at the Environmental Education Center at the north end of Central Park Drive. If construction is still under way, turn off Central Park Drive at Lone Oak Road, park at the end and follow the signs on foot to the center. For up-to-date information, call 510-544-2233.

Big Break: Levees and how they are maintained is the topic of a program from 2 to 3 p.m. Saturday at Big Break Regional Shoreline in Oakley. Levees and dredging influence the Big Break environment.

And from 2 to 3 p.m. June 15, there's a Father's Day program about identifying animals by the signs they leave behind: tracks, chewed branches, and bird calls. The group will make some plaster casts of animal tracks. Big Break is located at 69 Big Break Road off Main Street. For more information, call 888-327-2757, ext. 3050.

Black Diamond: Father's Day will be celebrated at Black Diamond Mines Regional Preserve in Antioch with a walk through the Somersville town site and Rose Hill Cemetery to learn about some of the fathers who helped to shape local history. The walk is from 10 a.m. to noon June 15, led by naturalist Ashley Elliott. Meet at the parking lot at the upper end of Somersville Road.

A note on access to Black Diamond Mines. There has been ongoing construction, which has closed Somersville Road between James Donlon Boulevard and a point just north of Buchanan Road. To reach the park from Highway 4, drive south on Contra Loma Boulevard, turn right on James Donlon Boulevard, drive to Somersville Road and turn left into the park. Somersville Road is unpaved between James Donlon and the park gate. For information on Black Diamond programs and up-to-date status on Somersville Road construction, call 888-327-2757, ext. 2750.

SNAKE SENSE: Here's a word about rattlesnakes, since one showed up the other day near a picnic table at Black Diamond Mines, and I've seen them there before.

The variety of rattlesnake found in this region is not aggressive. The snakes would just as soon avoid humans. They like to hide in rock piles or under logs and will generally sound a warning rattle if you get close.

If you stay on the official trails you are less likely to see a rattlesnake. However, if you do encounter one, give it lots of room and let it escape into the brush.

Dogs are a concern. Sometimes dogs will run right up to a snake and start barking. If a dog is bitten by a rattlesnake, the result can be a very expensive veterinary bill at best. So if you see a snake, leash your dog.

If you find a rattlesnake in a picnic area, at a beach, or any other place in the parks where lots of people gather, let the ranger staff know immediately. That's what park visitors did at Black Diamond. A ranger responded, picked up the snake with a long-handled litter grabber and relocated it to a safe place.

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