Seabirds fatten on anchovies near Santa Cruz Wharf, harbor

SANTA CRUZ – Sea animals and all kinds of seabirds, from pelicans and gulls to migrating terns and shearwaters, have flocked to the beach in recent weeks – flying , they dive, fly and dive – feathers fly by feeding as each creature fights for a share of the anchovies swimming below the surface of the sea.

This exhibit is a summer highlight for those who study and admire the motley seabirds, such as long-flying and deep-diving sooty shearwaters, that migrate from east to west along the Santa Cruz coast. .

Josh Adams, a wildlife biologist with the United States Natural Resources Institute, says: “It’s the same every year that we have a lot of smoke in our bay every year. “Some years it might seem like there are a lot of them or they’ve been here a long time or they’re disappearing quickly, but it’s hard to keep numbers because they travel in such large herds.”

Adams said there could be tens of thousands of sooty shearwaters swirling and drifting off the coast of Santa Cruz. Although these birds live in New Zealand, during the summer months they go to California and Monterey Bay to feed and fatten so that they can return home.

“When they arrive in this part of the World, their diet is known to shift from juvenile rockfish and krill early on, to a diet dominated by anchovies in late summer,” said Adams. “The anchovies are the real fuel for their final migration. Their protein needs change in the summer and when they get here, they’re exhausted from New Zealand and Chile and need protein to replace their feathers. they are made of protein.”

Those outside the water who find themselves in the eye of the seabird storm may notice that sooty shearwaters struggle to fly after diving underwater to fill up on anchovies.

“There’s a couple of things going on there,” Adams said. They eat enough food for their body weight that it takes a lot of effort to get out of the water. And they are also in primary molt so they have less wing space. They are cool because they are designed to fly underwater and long distances across the ocean, and melting impairs their ability to get up and fly quickly, especially if they have a full stomach. – anchovies.”

For years, the depth and length of time sooty shearwaters can stay underwater were murky statistics until San Jose State ecology and evolution professor Scott Shaffer and other researchers used storage tags to measure bird behavior in the 2000s when Shaffer was an expert. postdoc researcher at UC Santa Cruz.

“We knew they could dive as close as 60 meters because other researchers had used these capillary depth measurements,” Shaffer said. “Those would tell you the maximum depth they dived. They don’t tell you anything about time or how often they dived. When we put our time-depth records on animals, we were able to find a lot of information about their diving habits. It’s a diving depth of between 30 and 45 feet.”

Shaffer and the researchers used the information they gathered to write a paper on the behavior of the colorful seabird, which he studied in California and New Zealand. He said that the migration process of sooty shearwater between the northern and southern part of the world causes them to find endless summer.

“It’s amazing to see the full range of migration that these birds do and the idea that they have an eternal summer is correct,” Shaffer said. “They can get the best of the world by crossing the equator and coming here.”

Shaffer says that before sooty shearwaters were tagged, they were thought to travel in a circular pattern with the birds often appearing in California, Alaska and Japan before returning to New Zealand, but researchers have found that the pattern they follow it was. like figure eight.

“The popular idea was that they made this big cycle around the Pacific, and we were able to show that that’s not really what’s happening,” said Shaffer. “Birds tend to look at the North Pacific Ocean and as far as we know, they live there.”