A small seabird whose population has been declining for several years has been denied protection under the nation's landmark wildlife protection law. On Monday, the U.S. Fish and Wildlife Service said it would not list the ashy storm-petrel under the Endangered Species Act.

In its decision, the agency said that the ashy storm-petrel's decline in numbers -- a 76 percent drop over three decades in the northern part of its range -- is merely a normal fluctuation in population. That "normal fluctuation" has prompted the International Union for Conservation of Nature to list the bird as globally endangered, which the state of California lists it as a "species of concern."

With at most 10,000 individuals left, the ashy storm petrel (Oceanodroma homochroa) occupies a very restricted range, with the vast majority of its population living on and near the Channel Islands off Southern California and the much smaller Farallon Islands west of San Francisco.

Ashy storm-petrels make their living by skimming the surface of the ocean, feeding on krill, squid and small fish brought to the surface during upwellings. (The adeptness with which the birds move around just above the surface has lent them the common name "water walkers.") They nest on rocky cliffs on just 17 islands off the coast of California and Northern Baja, with about half the breeding population nesting on Santa Barbara, San Miguel, Santa Cruz and Anacapa islands. Mated pairs may stick together through many breeding seasons.

This choice of lifestyle makes the ashy storm petrel vulnerable to a number of threats, especially including upwelling failures, which are expected to become more common as the global climate warms. Nests are particularly vulnerable to introduced predators such as rats, foxes, and cats.

Ashy storm-petrels also suffer from oil spills and collisions with lighted structures ranging from ships to oil platforms.

Nonetheless, USFWS responded to a 2007 petition by the Center for Biological Diversity demanding the agency protect the storm-petrel by denying it protection. That 2009 decision came despite recommendations that the bird be listed from USFWS's own scientists. In 2011 CBD sued to force USFWS to reconsider its decision, as a result of which the agency agreed to review its 2009 decision this year. Monday's ruling was the result.

"Numerous studies have raised red flags that these rare and beautiful seabirds are suffering declines and current management efforts just aren't enough," said CBD biologist Shaye Wolf in a press release.. "I'm so disappointed that the Service didn't give the ashy storm-petrel the much-needed safety net of the Endangered Species Act to make sure we don't lose this unique California seabird forever."