Terns to Stay Busy for Summer

Junlin “William” Chen East Bay Regional Park District naturalist, Morgan Dill looks through a spotting scope to observe the California least terns near Ballena Bay.

 

On June 18, during a windy and scorching Saturday afternoon, I attended a brief walking tour along Crab Cove that explored the California least terns. Led by East Bay Regional Parks District (EBRPD) naturalist, Morgan Dill, visitors watched the terns dash across the pristine coastline using binoculars provided by the visitors center and learned why Alameda is a desirable habitat for the terns. 

Looking into a spotting scope, one can discern a California least tern by recognizing its distinct physical features. According to Dill, least terns generally feature an elongated body with a white or gray belly, a yellow beak with a black tip, and black primary feathers on their wings. In terms of size, California least terns are the smallest of all terns nesting in Alameda. Nevertheless, it was still challenging for me to distinguish a least tern from other birds since Crab Cove hosts several different types of terns such as, the Forester, Caspian, and Elegant terns. While few least terns were present, I did catch several Forester and Elegant terns in the lenses of my binoculars. 

According to Dill, although the least terns’ migration patterns slightly vary from one another, they migrate seasonally from South America to various locations across the Bay Area. 

Most of them arrive by late April or early May and return south by late July or early August. In other words, we are currently in the midst of the birds’ mating season, as they will reproduce, nest, and forage (look for and gather food) throughout next month. Like most birds, terns feed on small fish that are ubiquitous in the Bay Area, such as king salmon and pipefish. During the tour, I noticed that they, like hungry and determined eagles, dive while utilizing their hook-shaped beaks to pounce on unsuspecting fish swimming near the water’s surface. 

Some least terns establish their colony at Alameda Point after their long journey from the Southern Hemisphere. Dill notes that the Point’s flat, open space with little vegetation provides an auspicious nesting ground for the birds. Little vegetation is beneficial to the tiny birds’ development since it deters larger predators that depend on tree cover. While the birds mainly settle at the base, few occasionally fly into Crab Cove to forage and seek out a potential nesting spot. During the tour, many terns stopped briefly at Ballena Bay, which contains a small stretch of flat land before foraging at Crab Cove.

Unfortunately, despite their efforts to seek shelter, least terns are never truly safe from environmental and ecological factors. According to Dill, the bird was listed as “Endangered” since 1970. The most common threats to least terns are: habitat destruction, housecats, gulls, and hawks. As a result, several local organizations, like the Golden Gate Audubon Society continue to raise public awareness about the bird.

Next time you’re walking along any shoreline in Alameda, remember to gaze out into the sparkling bay. You might witness the incredible sight of a nimble least tern diving rapidly towards the water to catch its fish! 

 

Courtesy U.S. Fish & Wildlife Service A California least tern tends to its nest. The endangered bird has a nesting site at Alameda Point, which is carefully monitored.