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Castle Rock National Wildlife Refuge is for the Birds

08/25/2017 11:00AM ● By Jordan Venema

The Bird Isle

September 2017
By Jordan Venema
Photo Courtesy of USFWS

Looking at Castle Rock, a small island about a half-mile off the coast of Crescent City, it’s no wonder how the bit of land got its name. The mound of rock and pinnacle of stone could be interpreted in the shape of a turret rising from a fortress, but more than physically, Castle Rock is also metaphorically similar to some medieval castle, providing a safe place and refuge to the North American common murre.

“It’s actually the biggest murre colony between Alaska and the Faroe Islands,” says Eric Nelson, the manager of Castle Rock National Wildlife Refuge. “It’s a pretty important place in the California system.”

It might surprise the common Californian that the common murre, the northern hemisphere’s equivalent of the penguin, has such a large colony so near the coast.

According to Nelson, the colony population is about a quarter-million birds, even though the island is just 14 acres.

“During certain times of year, the birds are just jammed on there,” he says.

Interestingly, Castle Rock hasn’t always been a designated refuge, and not always for the murre. The island was first designated a refuge in 1980 to protect the then-endangered Aleutian Cackling Goose, “which is no longer endangered,” adds Nelson. “They were taken off the list in 2001, but in 1980 there were probably about only about 1,500 left, and one of the places that they stopped on their way back to the Aleutian Islands where they nest is Castle Rock. As the population has increased, Castle Rock has become less important to the geese, so they now roost in other areas on the mainland.”

Due to the murre colony, Castle Rock remains restricted to the public, since murre do not create traditional nests, but rather keep their eggs lodged against the bare rock. All in all, it makes for a sensitive nesting area.  

“It’s closed for a couple reasons,” Nelson says. “Primarily because the disturbance that would occur with humans going out there would be enormous. One person traipsing about the island at the wrong time can cause the complete collapse of the murre colonies.”

Also, Nelson adds, “the soil is very susceptible to damage, and landing on any kind of island is not typically a very safe thing to do.” 

Which creates a challenge even for those who work at the refuge, who monitor the birds with high-tech equipment. 

“The biggest challenge we face,” continues Nelson, “is how to get meaningful information on the birds and really see what’s going on without a detrimental impact. Sea birds are difficult to study and obviously there are limitations,” he adds, but the effort isn’t without reward.

The refuge conducts some research to care for the birds, which nest roughly between April and October. The equipment and cameras are set up before and taken down after the nesting season.

This surveillance doesn’t just give information about the birds, but also about the local and wider ecosystem. While the refuge surveys murre activity such as nest initiation, the success of laying eggs and hatching, and size of colony, they also pay attention to eating habits, “which is really telling,” adds Nelson. “We can zoom in and see what kind of fish are predominantly being fed to the chicks, such as smelt and rock fish in the north – but in the Bay Area it’s anchovies, and in Oregon it’s different yet.”

Nelson calls the common murre the marine canaries in the proverbial coalmine. “What’s going on above with the sea birds can help tell you what’s going on below the surface,” says Nelson, thanks to the patterns of murre diets depending on the region.

Though the island remains closed off to the public, there are ways for people to enjoy the birds – safely and responsibly from a distance. 

While nobody can prevent kayaks or other boats from coming within 300 feet of the island, Nelson warns, “the seas in that part of California are very fickle.” Plus, he adds, “you can see the island with a good spotting scope on a nice morning with the sun at your back. That way you can get a good look.”


Castle Rock National Wildlife Refuge

www.fws.gov/refuge/castle_rock


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