The California Least Terns are arriving back at Alameda Point’s wildlife refuge to lay their eggs and raise their young. The volunteers, who help maintain the site, and the US Fish & Wildlife Service (USFWS) biologist responsible for the tern colony, have never left. They carry out maintenance tasks during the non-nesting season – September to early April – as well as help monitor bird behavior during the nesting season.
The California Least Terns return to California every April from Central America. The old Navy runway area at Alameda Point is among the limited number of sites where these endangered birds come to nest. Driven to adapt to a loss of undisturbed beach habitat, they began nesting at Alameda Point decades before the Naval Air Station closed in 1997.
While Navy jets would be disturbing for humans to live next to, for the terns the movement of the jets was predictable and easy to avoid. That’s not the case on an increasing number of beach areas where people and pets can easily trample eggs in the sand and frighten the adult birds.
The Alameda Point colony is considered the most successful for this bird. It is believed that the success at Alameda Point has led to new colonies elsewhere in California.
Volunteers are recruited by the Friends of the Alameda Wildlife Refuge, a committee of the Golden Gate Audubon Society. Activity at the Least Tern nesting site started ramping up in January this year as it always does, with guidance from the USFWS biologist. Volunteers perform tasks such as removing weeds, repairing the mesh barrier that keeps chicks from wandering off or getting injured in the chain link fence around the nesting site, and distributing oyster shells to confuse hawks and other flying predators that often circle overhead during the nesting season.
Every year the US Fish & Wildlife Service re-positions all of the numbered cinder blocks that establish a grid pattern for recording bird behavior. The blocks, along with all the other “tern furniture” – wooden A frames and clay tile that chicks shelter under and in, oyster shells, driftwood – are gathered up and set to the side after the nesting season. This allows for easier weed control and for the sand and gravel surface to be graded.
The grid blocks are placed into position using a global positioning system for complete accuracy. When Tern Watch volunteers or the Fish & Wildlife biologist observe activity, they record the data according to a grid letter/number. Without a grid system, it would be difficult to record accurate data for hundreds of eggs and chicks, i.e., did a predator steal an egg last night, or is that the nest that had only one egg?
This year there are two training sessions for the Tern Watch program.
The public is invited to take a bus tour to the site on June 16th. The annual event is hosted jointly by USFWS and the East Bay Regional Park District. The bus tours leave from the Crab Cove Visitors Center in Alameda. Advance registration is required and is handled through the park district. (See comment below.)