Ashy storm-petrels breed at Santa Catalina Island

Ashy storm-petrel
An ashy storm-petrel sits on an egg at Ship Rock on Santa Catalina Island.
(Darrell Whitworth)

Tyler Dvorak was lying in slippery guano and smiling as his flashlight shined on a telltale shape in a crevice near the top of Ship Rock, which rises sheer and stark from the sea about a mile off the coast of Santa Catalina Island.

It was an ashy storm-petrel sitting on an egg.

The finding confirmed that the 30-foot-high rock is a breeding site for the rare nocturnal seabird, which in turn accounted for Dvorak’s upbeat mood while lying in guano earlier this month.

“Now that we that know they are there, we can focus our attention on monitoring this tiny population to learn more about the species,” said Dvorak, a wildlife technician at the Catalina Island Conservancy, which manages 88% of the island.

Breeding was first suspected on Catalina in 1903, based on murky descriptions of ashy storm-petrel eggs collected by pioneer naturalists. Subsequent surveys failed to turn up solid evidence of nesting anywhere on the island.

However, biologists in the early 1990s did discover up a few tantalizing clues near the top of Ship Rock, including crevices suitable for nesting and wisps of the bird’s distinctive and powerful musky odor.

On a mission to resolve the issue, a research team led by Harry Carter and Darrell Whitworth, both biologists with the California Institute of Environmental Studies, and Dvorak set out in a inflatable boat on July 2.

Whitworth and Dvorak scaled the granite stack and methodically scanned its cracks and crevices with flashlights.

“We found six nests -- four of them with an adult and an egg or a chick,” Carter said.

The researchers now believe that there are perhaps 50 nests on the entire island, about 22 miles off the coast of Southern California.

The discovery of a breeding population on Catalina is a boon for researchers. Most other known nesting colonies of the creature listed as a California Bird Species of Special Concern are on remote islets between the Farallon Islands off San Francisco and the Coronado Islands off Tijuana, Mexico.

“There are only about 10,000 ashy storm-petrels in the world -- and they’re hard to detect,” Carter said. “Now we have a location where trends can be well monitored and studied.”

The ashy storm-petrel’s low population numbers and restricted range make it especially susceptible to chemical pollutants, oil spills and predation from ravens, rats and feral cats.

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