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It’s Least Terns Season at SAN!

Monday, April 25, 2022

April through September is the least tern nesting season at SAN. Since 1970, this endangered migratory sea bird has found a suitable nesting site each year in the sand and gravel located in four oval areas between the runway and airplane taxiway. 

So, why would these birds choose the ground at an airport to lay their eggs?

“The airport provides a consistent nesting habitat where there is an abundant food source nearby in San Diego Bay,” said Robert Patton, San Diego Zoo Biologist, who has been involved with the least tern nesting colonies at SAN since 1983.

San Diego is the center for the least tern breeding habitats and SAN is one of only 15 nesting colony sites in San Diego County. Over the years the number of nesting colony locations along the coast of California has dwindled significantly due to continued urban development. Today, there are approximately 30 nesting colony sites statewide with half being in San Diego, mostly around San Diego and Mission Bays. SAN and the Naval Air Station North Island (NASNI) are the only two sites in North San Diego Bay to have nesting colonies. 

According to Patton, “another significant fact is the airport staff has the timing down and makes a great effort to ensure the ovals are prepared so they offer an ideal nesting site by the beginning of nesting season. The least tern prefers to nest in small, scattered clusters right on sandy beaches and salt flats. The airport staff diligently works to mimic this natural habitat.”

Each year before nesting season, Airport Authority staff conduct weed abatement in the least tern ovals while many of us are sleeping during the airport curfew hours from 11:30 p.m. to 6:30 a.m.

In addition to removing weeds, the Airport Authority team collaborates with biologists from the San Diego Zoo in preparing the ovals. The biologists add sand strips within the four nesting ovals and FMD installs signs to remind airfield drivers to reduce their speed near the nesting ovals and to educate the public parked off North Harbor Drive near the old Coast Guard gate about the endangered bird species. Throughout the season, staff from Ocean Blue maintains a mesh chick barrier around the ovals to keep the chicks from running onto the taxiway or roadways. 

“Minimizing unusual movement and noises around the nesting areas is essential for a successful nesting season,” said Patton. “These birds habituate to routine noises and movements such as an airplane taking off or a truck driving by. Out of the ordinary noises or movement such as a truck stopping or driving by too quickly can disrupt these endangered birds and that could have an impact on its nesting and laying eggs.”

To ensure that ongoing construction work at the airport does not impact the least tern, San Diego Zoo biologists and the Airport Authority’s Environmental team developed an official “least tern protection” virtual training which was presented for the first time this year. More than 30 participants from the New T1 ARRIVE team and other contractors joined the training that covered the location of buffer zones around the nesting areas, speed limits, and other required measures to help reduce light pollution impacts and avoid attracting predators in construction areas near the nesting ovals.

Since 1997, SAN has worked with biologists, including Robert Patton to protect the least tern nesting habitat around the airport facilities and surrounding community. As part of our ongoing efforts, the number of nests at the airport has gradually increased since the 1990s. SAN’s critical nesting site is considered one of the most productive least tern sites in Southern California.