Naval Air Station-Alameda gained notoriety as a refuge for the endangered California Least Tern when the base closed in 1997. Over 500 acres were dedicated to protecting the terns’ adopted nesting site next to a runway formerly used by jet aircraft.
This unlikely bird habitat for the Least Terns some 400 miles north of their historic breeding grounds along the southern California coast offered the birds something they had lost, which drove them to the brink of extinction – nesting sites free of human disturbance near a source of small fish to feed their chicks.
Surprisingly, two other tern species have recently begun nesting in the vicinity. Elegant and Caspian Terns seem to be thriving there, while the endangered Least Terns are struggling.
The least tern nesting season ended in mid-August much as it usually does – a lonely and dangerous place for young terns. There were three of four pairs of adults flying back and forth with food for their young chicks. These late nesters are often the ones whose eggs or chicks were attacked by avian predators and have re-nested. Their vulnerability is only compounded as the weeks wear on because the rest of the adults and their flight-ready young have left, leaving the remaining families without the strength of numbers to mob a predator.
Volunteers arrived at the nesting site on September 9th to begin gathering up the oyster shells, wooden A-frame shelters, and clay tiles randomly arrayed about the site that serve as camouflage and chick shelters from predators.
They also carefully gathered up over 300 numbered nest markers that were placed near the nests by the US Fish & Wildlife biologist. A tern nest consists of a small depression in the gravel – no twigs. The four-inch white nest marker rings are set upright in a plaster base and each have a number. This allows Fish & Wildlife to monitor breeding success and record predator activity such as taking of eggs. Between now and next April when the terns return, the site’s substrate of gravel will be groomed and weeds removed.
On September 16th, volunteers returned to continue gathering oyster shells and taking care of another task: Removing a pernicious weed call stinkwort. It is virtually impossible to eradicate stinkwort with herbicides and must be removed by hand. Pulling the tough sticky weed out by its roots is usually not successful, and volunteers were limited to chopping the weed off at its base. If not removed by fall, the weed would begin releasing seeds that find their way through the gravel and into small crevices in the old pavement underneath. The weed is so prolific that it can quickly inundate an area.
It is undesirable to have any weeds in the nesting site or in the immediate vicinity of the nesting site. The historic nesting habitat of the terns is on beaches. The presence of vegetation in close proximity to the nesting area signals possible hiding places for predators and may cause the terns to look elsewhere for safe nesting.
On both days, volunteers included members of the Key Club at Encinal High School in Alameda, a student organization that encourages volunteerism.
Monthly work parties organized by the Friends of the Alameda Wildlife Refuge will continue through March of next year. The terns arrive in April. To get involved, contact FAWR.