SANTA CRUZ — Marine life and seabirds of all kinds, from pelicans and gulls to migrating terns and shearwaters, have gathered off the coast in recent weeks — fluttering, screeching, swirling and diving, feathers flying in a feeding frenzy as each creature fights for its share of the anchovies floating beneath the ocean’s surface.

The spectacle is an anticipated event in summer for those who want to observe and admire the flocking seabirds, such as the long-distance, deep-diving Sooty Shearwaters, that migrate en masse from east to west along the Santa Cruz coast.

“It’s remarkable that we have large numbers of sooty doves in our bay every year,” said Josh Adams, a wildlife biologist at the United States Geological Survey’s Western Ecological Research Center. “Some years it may seem like there are more of them, or they’re here longer, or they disappear sooner, but it’s hard to get a handle on the numbers because they travel in such large flocks.”

In addition to sooty shearwaters, Monterey Bay also attracts other shearwater species in smaller numbers, such as the short-tailed shearwater from Australia, the Buller’s shearwater also native to New Zealand, and the short-billed shearwater from Chile.

“It’s similar in size, but it has a slightly different morphology and doesn’t dive as deep as Sooty Lake,” Adams said. “Our summer is kind of a mix season for a lot of species that come to California from the Southern Hemisphere. We also have a handful of dominant native breeding birds that we see in large numbers off Santa Cruz, like western gulls and guillemots and California brown pelicans and some other gull species. We have a really great diversity of seabirds here.”

Now that summer is coming to an end, Adams says most of the migratory sooty divers will soon begin their journey back to New Zealand.

“We’ll see them disappear now and over the next three weeks or so, and then they’ll all be gone,” Adams said. “The anchovy populations will be somewhat depleted by then because there are a lot of animals eating them, but the anchovy aren’t leaving our system.”

Although the flocks of diving seabirds pose a danger to boaters, Santa Cruz Harbormaster Blake Anderson said their attention is mostly focused on the anchovies and they tend to avoid the boats. He said it is the anchovies, not the birds, that are causing a sense of nervousness among boaters, especially those in the harbor.

“The birds themselves don’t come into the harbor, the anchovies do,” Anderson said. “Whenever we see the shearwaters out there, we pretty much know there are big schools of anchovies nearby. So we watch where those anchovies are going, and when they get close to the harbor, we deploy our ventilation system.”

Anderson said some anchovies have entered the port of Santa Cruz and the aeration system has been turned on, but they still hope the fish will stay at sea.

“We’re running our ventilation system and monitoring oxygen levels,” Anderson said. “Everything is stable right now, but if one of these swarms actually gets here, we could be in trouble.”

A year ago, the port was teeming with anchovies, but the ventilation system prevented a mass mortality. The last major baitfish mortality occurred in late summer 2014, leading to massive cleanup operations in the port and a foul fish smell spreading along the affected coast.

Originally published: August 26, 2024 at 5:25 am