SAN DIEGO – A decades-long conservation effort to preserve an endangered bird species is underway this spring at the San Diego International Airport.

From April to September, it’s nesting season at the airport for the California least tern, a species of small migratory seabird classified by the National Audobon Society as a member of the Gulls and Terns family. They’ve been roosting and nesting in the southeastern portion of the airport since 1970, one of only a few select nesting sites — and among the most productive — in greater San Diego County.

Their preservation is part of the San Diego County Regional Airport Authority’s Biodiversity Plan, a roadmap laid out by airport leaders to balance its operations with the management of plants and wildlife.

“We’ve been doing pretty much everything we can along with the U.S. Fish and Wildlife Service, the Zoological Society and (San Diego Zoo biologist) Robert Patton to protect these birds,” Cara Nager, the airport authority’s environmental affairs manager, said in an April phone interview.

The nesting season typically begins April 1, but most birds are not seen at the airport until about mid-April, Nager said. Each year, Patton visits the airport’s nesting site to monitor it along with others in the county, including North Island Naval Air Station in Coronado, the Tijuana River mouth and Misson Bay.

At the airport, four nesting ovals are carefully maintained to have the feel of the birds’ natural habitat.

That effort includes clearing out weeds prior to the nesting season and targeted training for airport staff and tenants. Training also was conducted for contractors involved in the new Terminal 1 expansion and some elements of that project are not slated to begin until after the nesting season ends in September.

To create optimal conditions, there’s a focus on keeping lights away from their nesting area at night as well as limiting the height of construction equipment and the speeds on nearby roads.

From the time their eggs are laid, it takes about 21 days for them to hatch — and then the fun part begins.

“When they first hatch, they’re already ready to run but they’re not ready to fly,” said Mayra Garcia, an airport environmental affairs specialist. “It takes a while to teach them to fly and go out to the bay.”

Garcia added, “It’s a process but right now, it’s encouraging there’s already 12 of them in the daytime.”

The least tern population has been hampered due to the effect of humans on the environment, according to the Audobon Society. In the airport’s Climate Resilience Plan, officials also note how the effects of climate change such as extreme heat and flooding potentially could impact the birds.

Their population has seen fluctuations at the airport in recent years, too, most likely attributed to “disturbances from construction activity and predators,” the Biodiversity Plan shows. Last year, 11 nests were tallied, a sizable decrease from the 157 recorded in 2005. There were between 19 and 38 nests recorded annually between 2015 and 2018.

But officials are committed to the long haul, defining success in upward trends of the number of birds and nests seen on airport property, Nager said.

“The ultimate success would be to get them off the Endangered Species List,” she said, adding there are short-term successes in seeing the birds utilizing the nesting sites as intended.

For those living in the area or visiting the airport, officials recommend a few strategies to assist in their efforts. Among them, they encourage visitors not to touch or disturb the birds and to avoid littering because it attracts other larger birds and potential predators.