As crews continue work on double-tracking the rail line over the Batiquitos Lagoon, they are also restoring a critical nesting site for endangered California least terns.
The lagoon site is one of the most successful nesting sites for the migratory ground-nesting birds, said Tim Pesce, the senior environmental planner for the San Diego Association of Governments (SANDAG).
California least terns were listed as endangered in 1970. There were only an estimated 582 nesting pairs by 1974. The Batiquitos Lagoon nesting site was first built in the 1990s.
"Over time, it has started to erode a little bit," Pesce said. "So we are pushing that sand back up against the site to restore it back to its original size and to prevent it from eroding in the future.”
Restoration work began earlier this fall after the nesting season ended in August. SANDAG used sand dredged from the rail line project to restore the site. On Tuesday, crews were adding crushed oyster shells to the sand to help camouflage the eggs.
The least terns lay their eggs in shallow scrapes or depressions on the sand, Pesce said.
“The California least tern eggs are kind of speckled black and white," he said. "They are very similar looking to the crushed oyster shell that we're spreading. So if they're able to nest in an area that's lined with oyster shells, they blend in really, really nicely.”
The oyster shells were sourced from fisheries in Washington state, cleaned and crushed into roughly dime-sized pieces, and spread over the site with shovels.
Crews will soon add 75 roofing tiles to the site to simulate driftwood, which provides shelters for least tern chicks to escape the heat and predators. They will also install mesh fences along the water's edge, acting as baby gates of sorts to keep chicks from falling into the water and drowning.
The restoration work is expected to finish by year’s end, giving the site time to settle before the nesting season begins in April.
