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What can seabirds tell us about interactions occurring beneath the water’s surface?

Land-based Views Into the Marine Ecosystem

Dan Robinette


PRBO biologists and helpers view seabird colonies near the coast of Point Conception, California. Photo by Jaime Jancke / PRBO.
Seabirds are far-ranging and not bound by geographic landmarks. Many of them are so exclusively tied to the sea that we must travel far offshore to obtain brief glimpses into their complex lives. But those are not the seabirds I see on this brisk spring morning. I am not on an island. I did not travel by ship or by plane to get here. I woke up this morning in my home, got into my truck, and drove for 30 minutes to the Central California coastal habitat that I have been studying for the past 12 years.

From the shore near Point Conception, the birds I see are cormorants, Pigeon Guillemots, Western Gulls, Black Oyster-catchers, and endangered California Least Terns. A Brandt’s Cormorant displays his bright blue throat patch to attract a mate; a raft of guillemots floats effortlessly in the pounding surf; a Western Gull relentlessly harasses a sea otter that just surfaced with a meaty abalone.
Rocks nearshore offer seabirds nest habitat and proximity to food resources in nearshore "hot spots" of marine productivity. Photo by Charlotte Chang.

I see all of this from the shore because these particular seabird species have developed intimate relationships with California’s coastal ecosystems. They roost on the offshore rocks, breed on the coastal cliffs, and forage in the kelp forests. For this reason, even though they are a common feature of the California Current, they’re one that is often overlooked—and a feature that is heavily impacted by the increasing amount of human activity along California’s coast.

As I watch these birds interact with their dynamic ecosystem, I consider two questions. What can these birds tell us about interactions occurring beneath the water’s surface? And how can we protect them against the many ways in which humans are disrupting these interactions?

In work aimed at answering the first question, we have found that coastal seabirds can tell us a lot about how fish larvae are delivered to coastal habitats. For example, the seasonal convergence of two ocean currents in the region between Point Arguello and Point Conception produces interesting patterns of larval distribution. Through studying Pigeon Guillemot diet, we have discovered a localized refuge of relative stability from year to year for sanddabs, bottom-dwelling fish whose populations are much more variable elsewhere.
Brandt's Cormorant colony. Photo by Julie Howar / PRBO.

Recently I have also become involved in a possible answer to the second question. California is close to completing the long overdue process of establishing new marine protected areas (MPAs) under the Marine Life Protection Act. Though MPAs are designed to protect species targeted for human consumption, it is important to recognize the cascading effects this protection will have on ecosystems. As integral components of coastal ecosystems, seabirds can receive both direct and indirect benefits from MPAs. Direct benefits include reduced interactions with humans, such as by-catch (the non-targeted species taken) from fisheries and disturbance to breeding and roosting sites; indirect benefits include reduced competition for food resources.
Brandt's Cormorant. Photo by Tom Grey / www.tgreybirds.com.

The potential benefits of MPAs to seabirds are not always obvious, and many people have asked me how drawing a small box on an ocean map can benefit something as far-ranging as a seabird. I tell them PRBO studies show that California’s coastal seabirds can benefit because they will forage, roost, and breed “in the box.”

It is my ambition to spend the next 12 years (and beyond) determining whether these MPAs can provide the types of protection that California’s coastal seabirds need. As if to encourage me in this, ambition, two Black Oystercatchers call excitedly at the edge of my seabird study area, and a half-dozen California Least Terns swoop by on the ocean breeze.