Weather Watch

From kelp to peregrine falcons, a thriving food chain on the Central Coast

A peregrine falcon eating a mourning dove in Los Osos.
A peregrine falcon eating a mourning dove in Los Osos.

On days with plenty of sunshine and lots of upwelling, California giant kelp can grow up to 24 inches in just one day, ultimately reaching more than 150 feet in length.

At that rate, you could almost see this type of algae grow in front of your eyes.

During the course of the season, especially during large wave events, a lot of this seaweed breaks off from its holdfast and washes up on our beaches. Black kelp flies — scientifically known as Coelopa frigida — lay their eggs in this decomposing kelp. Their larvae quickly hatch and ravenously feed. Needless to say, their population can explode into large, shadowy swarms.

Many bird species take advantage of this flying protein source. Depending upon the weather, cliff swallows arrive in March along the Pecho Coast — which lies between Point San Luis Lighthouse and Point Buchon — after their long northward migration from South and Central America. These fast and agile flyers get right to work building their nest and eating plenty of kelp flies and other bugs.

Unfortunately, their presence doesn’t go unnoticed by the fastest creature in the animal kingdom, the peregrine falcon. These birds of prey can reach speeds of more than 240 mph in their characteristic hunting stoop as they dive toward the unaware swallows and other medium-sized birds. In one swoop, they complete the food web of kelp, fly, swallow and falcon.

Because of their diet, the peregrine falcon is an important indicator species. Its population trends can be instructive about ecosystem health. In other words, they’re like a canary in a mineshaft.

This fact was put into sharp focus back in the ’60s. By 1970 it was estimated there were fewer than 10 nesting pairs left in California; some claim as low as two.

“The cause of this dramatic decline was primarily the same as for the bald eagle — ingesting prey contaminated by DDE, a metabolite of DDT, which prevented normal calcium deposition during eggshell formation, resulting in thin-shelled eggs,” PG&E biologist Sally Krenn told me. “Their eggs became susceptible to breakage during incubation. Thus, the peregrine falcon was one of the first birds to be placed on California’s endangered species list.”

PG&E biologists first sighted a pair of peregrine falcons on Diablo Rock (an offshore pinnacle located in front of Diablo Canyon nuclear power plant’s cooling water outfall) in the early ’90s. PG&E partnered with UC Santa Cruz’s predatory bird research team and sent raptor biologists to the nest to temporarily replace the falcon’s eggs with dummy ones.

I remember back in those days meticulously looking at the long-range models and charts to predict calm enough oceanographic conditions to safely drop the UC Santa Cruz bird team on Diablo Rock from one of our research boats that I piloted.

Once the chicks hatched in a UC Santa Cruz lab, the dummy eggs were replaced with the chicks. PG&E biologists then monitored the chicks to ensure that they fledged successfully. This program was so successful at Diablo Canyon and the other nesting sites in California — including Morro Rock — that the birds were delisted in 1999. There are now more than 300 active breeding sites in California. They reach sexual maturity in one year and mate for life.

On a few mornings before work, I noticed feathers gently floating to the ground from a large Monterey pine in our front yard. Sure enough, perched high up in that tree a peregrine falcon was preparing its breakfast of mourning dove.

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PG&E employees, including those that work at Diablo Canyon nuclear power plant, will donate more than $730,000 to local nonprofit groups and schools in San Luis Obispo and Santa Barbara counties in 2016. Statewide, PG&E employees will donate more than $7.9 million. To learn more, visit

John Lindsey’s column is special to The Tribune. He is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at or follow him on Twitter @PGE_John.