Big Bear and Bird Trails are in the Anthony Chabot Regional Park, and I accessed them via the Big Bear Staging Area on Redwood Road.
Big Bear is a .38 mile loop with a gentle climb. It's got some nice canopy and a wide trail. It's not much for exercising, but you can use it more as a place to wander and contemplate.
Bird Trail is a pretty but narrow trail, with wild raspberry bushes and poison oak reaching out to grab you as you hike through. However, if you're careful, this short little trail (.34 miles) has some nice little bridges and meanders along a stream.
Have fun and be safe!
Trail Map (Redwood Regional Park)
Trail Map (Anthony Cabot Regional Park)