by Kimberly N. Chase
- USA -
Once one of the world’s most notorious prisons, Alcatraz is now home to a new type of visitor – nesting seabirds.
On a bright May morning this year, the sun cast bold shadows on the run-down beige buildings that tower over the dock area and make up the prison complex. A cement path leads up above the shoreline, where small waves lap softly against a steep incline covered with vegetation.
But something was amiss this year. Normally a time of bustling activity, the nesting season was marked by scores of Brandt’s Cormorants turning up dead or emaciated on the northern California coast between Monterey and Marin. The dark-feathered, light-eyed seabirds showed up in lower numbers and the stone cliffs where they usually nest were completely empty - the slightly darker circles on the rock the only indications of last year’s nests.
“I’ve been a maintenance worker on Alcatraz almost 14 years and this is the first time that the cormorants have not shown up,” says Ray Katsanes, who pulls up in a small vehicle to the walkway that overlooks what is normally a bustling nesting scene. “It’s kind of a sad thing, it’s like an indicator of the bay, I guess.”
In a normal year, Brandt’s Cormorants produce a first set of eggs by late April, only re-laying later if the first clutch fails to incubate, according to Conservation Science biologist Sarah Acosta at the Point Reyes Bird Observatory (PRBO). Two years ago there were about 1,700 pairs nesting on the same rocky overhang, and last year there were about 1,500. This year there were zero.
Acosta watches through her binoculars as a group of cormorants fly by to perch on a nearby rock jutting out of the water - there are still significant numbers in the area regardless of the die-off, just no nesting. When there is such a big change for one species, biologists wonder what has been disrupted in the larger ecological picture, and many suspected declining fish populations.
“They need to have the proper food source to have enough energy to initiate nesting,” Acosta explains. This year the birds were found to be starving rather than diseased, and responded well to feeding.
“For the most part they don’t have any physical problems, no broken bones – they’re just skinny,” says Michelle Bellizzi, Rehabilitation Manager at the International Bird Rescue Research Center in Fairfield, Calif., where she cares for the birds.
The picture has become clearer in the months since the breeding season, with researchers from the Cordell Bank National Marine Sanctuary, the Gulf of the Farallones National Marine Sanctuary and PRBO looking into the causes for the birds’ decline on Alcatraz and other nearby nesting sites. The scientists say they saw plenty of krill but fewer anchovies than usual, both in the ocean and San Francisco Bay.
“They eat a lot of anchovies, but that’s not the only thing, so you would think they could potentially switch to another species. But for some reason that didn’t happen or maybe it wasn’t good enough,” suggests Acosta. She says anchovies are an easy catch because they swim in schools and the birds can capture more than one at a time. Cormorants also feed on flatfish, but they have to dive to the bottom to get them and may have had trouble with the transition, Acosta explains. She thinks the birds may come back if ocean conditions improve or their prey source returns.
Though the cause for the fish decline is unclear, it may have been caused by a decrease in the normally strong spring and summer upwelling in the Pacific, which provides a steady stream of nutrients that ascend the food chain. The cause of these changes in the ocean currents is infinitely more complicated.
“Climate change could always be a factor in it, but it’s something where we need a more long-term data set to see that,” Acosta says.
But even without the Brandt’s Cormorants, Alcatraz’s breeding season continued as usual for other species, including Pelagic Cormorants, Snowy Egrets, Pigeon Guillemots, and Western Gulls. In addition to seabirds, White-crowned Sparrows, House Finches, Song Sparrows and Anna’s Hummingbirds can be spotted on the island. The site’s total of more than 1,000 pairs of Western Gulls along with about 20 pairs of California Gulls, take over what’s called the parade ground - a low, flat area that’s off-limits to tourists during the nesting months of February through September.
Official agencies now clear the path for seabirds, but the island has a checkered past as a nesting habitat.
Until it was discovered in 1775 by Lieutenant Juan Manuel de Ayala, seabirds ruled Alcatraz. Ayala named it Isla de los Alcatraces, or The Island of the Pelicans, though there is doubt as to whether pelicans ever lived there. The US government bought Alcatraz in 1849, later using it as a military prison. But Alcatraz earned its infamous reputation as a federal prison from 1934 to 1963. The island became a point of focus for the Native American rights movement in the 1960s when activists occupied Alcatraz from 1969-1971. The island was then designated as part of the Golden Gate National Recreation Area in 1972.
Some say Alcatraz would never have been a haven for the diversity of species that frequents its shores today were it not for human impact. The windswept land was actually less hospitable to birds before the military shipped in soil to improve on what was only a meager layer of grass. After the prison was closed in 1963, there were more trees and shrubs than before, planted by prison staff and their families.
Located in a highly trafficked part of the San Francisco Bay about 1.5 miles from the mainland, the site is vulnerable to disturbances from boaters and airplanes, along with crowds of visitors and the occasional tourist trying to scare a bird meandering on the walkway. Some birds build nests in the gardens, which are hard to navigate for maintenance workers.
There are plenty of natural surfaces, but many birds are drawn to the ruins of the former prison, crawling into old pipes or nestling into the hollows of cracked concrete to hatch their young. While the island’s gulls are practically fearless, some species, like the Snowy Egret and the Black-crested Heron are more sensitive to humans and keep their distance.
Researchers from PRBO Conservation Science are working with the National Park Service and the Golden Gate Parks Conservancy to understand the extent of human impact on the birds so that they can balance the site’s cultural and ecological roles.
“We want to do long-term monitoring because we want to be able to detect if these species are declining. If so, we will work to try to stop it, beginning with increasing education and outreach,” says Lara Rachowicz, Alcatraz Biologist for the Golden Gate National Recreation Area.
With as many as 5,500 tourists visiting the island each day during the busy season (March-October) and a total of 1.4 million each year, biologists and the park service have limited construction projects near the nesting areas and carved out sections of land where the species can nest between February and September.
“They’re a real priority to us,” says Rachowicz, “because there aren’t a lot of nesting areas open to them in this urban area.”
About the Author
Kimberly N. Chase is a freelance journalist specializing in environmental features for print and television. She graduated in 2005 from Stanford's MA program in journalism and worked as a crime reporter in California before spending two years in Mexico City. She is now enjoying working on some of the same issues stateside.