Though the surfers, skaters and beachgoers might not notice the butterflies fluttering by, conservationists are celebrating the return of the endangered El Segundo blue to its native habitat along Santa Monica Bay.

The insects, with a wingspan of about an inch, are thriving in plain sight at beaches in Redondo Beach and Torrance after scientists nurtured their dwindling population in three fenced-in nature reserves for years. It had been decades since the critters had been seen in their native habitat.

But thanks to an effort to restore native vegetation to the area, buckwheat, source of the butterflies' preferred nectar, now blankets bluffs that had been overgrown with invasive nonnative ice plant.

Still, scientists were surprised the El Segundo blues, thought to be too lazy to travel long distances, returned home without the help of human hands.

They have been on the nation's endangered species list since 1976.

"No one figured that they would just do it on their own," said Ann Dalkey, co-chairwoman of the Beach Bluffs Restoration Project. "You can see them like crazy. They're everywhere."