In the summer, the coyote brush blooms pale flowers that butterflies feed from. That would be nice to check out.
Cross the southern bridge where fishermen cast their reels and rowboats push through the water, and watch the ducks. And pigeons--lots of them swooping overhead in flocks. Note the marshy flora and consider that Lake Merced is freshwater, fed by an underground spring, and used to be San Francisco’s drinking source until Hetch Hetchy was made (and possibly could be an emergency drinking source for the City). Try walking around the lake, but avoid rush hour.