Condors Throw Dead Sea Lion Party at Big Sur

Condors at McWay Falls | Photo: Rebecca Brinegar

The current alarming die-off of sea lions along the California coast may have a short-term silver lining: offering an occasional meal to California's largest bird.

That's what reader Rebecca Brinegar found out on a southward trip along Route 1 this week, when she chose to stop at the McWay Falls area on the beach in Julia Pfeiffer Burns State Park near Big Sur. An unfortunate sea lion had washed up on the beach, which is closed to public access, and that sea lion had attracted a large gathering of federally endangered California condors, who almost literally filled the sky.

"I don't usually stop there, because it's pretty crowded, but I decided to Monday," Brinegar told me. "And when I got to the beach overlook, I saw this huge crowd of condors. I counted 15 or so, but a state park ranger there told me he'd counted 29 that day."

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Brinegar shot a bit of video of soaring condors with her phone which she made available to Redefine. All these birds seen here are condors, which means those little specks might have an eight- or nine-foot wingspan:


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The crowd of condors had attracted a second crowd, of birders and photographers anxious to get good shots of the majestic scavengers.

Condors feeding on dead marine mammals isn't particularly unusual. In 2006, biologists observed the first known instance of condors feeding on a beached whale since the reintroduction program began in the early 1990s, and the birds had been eating sea lions since 1999. The birds have also fed on sea otters and other deceased marine mammals.

Marine mammal carcasses are a mixed blessing for California condors. Unlike carcasses of terrestrial animals, which often contain lead ammunition, marine mammals generally have a low lead contamination rate. That's crucial for condors, for whom lead poisoning is a major threat; a big enough threat that the state is in the process of implementing a ban on lead ammunition.

Marine mammals have even been used rhetorically by opponents of the lead ammunition ban, with lead ammo fans charging that the condors' historic decline resulted from a drop in the availability of whale and seal carcasses.

Left: Two condors fly over the walkway overlooking McWay Falls; Right: A group of condors feed on a sea lion near the falls.
Left: Two condors fly over the walkway overlooking McWay Falls; Right: A group of condors feed on a sea lion near the falls. | Photos: Rebecca Brinegar

Lead isn't the only environmental contaminant out there, though. Some condor watchers express concern that the increase in dying sea lions might expose condors to unsafe levels of other toxic substances such as dichlorodiphenyldichloroethylene or DDE, a breakdown product of the pesticide DDT. DDE, which is very stable, accumulates in fatty tissues of animals that consume it. The chemical interferes with birds' calcium metabolism, which means that birds contaminated with DDE tend to lay eggs with thinner shells. That can mean chicks crushed before they hatch.

Sea lions are fish eaters that are close to the top of the marine food chain. That means that they will accumulate all the DDE that's in their prey's fatty tissues, which that prey accumulated by eating its smaller prey.

Baleen whales such as the gray and humpbacked whales, on the other hand, are much closer to the bottom of the food chain, due to their habit of eating small organisms such as krill, small fish, and -- in the case of gray whales -- seafloor crustaceans. That makes baleen whales' fatty tissue much less likely to contain large amounts of DDE, or for that matter other bioaccumulative poisons.

Short version of the above: Condors can gorge all they want on beached whales, but sea lion carcasses are best treated as a "sometimes food."

So that's one more reason to hope the current die-off of young sea lions doesn't last long.

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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