SAN FRANCISCO -- By air, land and sea, rescue workers scoured miles of Bay Area shoreline Friday for birds and other wildlife struggling to survive the region's most damaging environmental disaster in a decade.

The impact of Wednesday's Bay Bridge-ship crash and spill of 58,000 gallons of heavy bunker fuel in the San Francisco Bay has been compounded by the annual fall migration of thousands of birds along the Pacific Flyaway.

"There are a lot of birds here. This is a feeding area," Jay Holcomb, the executive director of the International Bird Rescue Research Center, told the San Francisco Chronicle. "This is where the surf scoter, the western grebe and other birds feed and spend their winters…A lot of these birds just arrived. We think there is going to be a significant impact."

Lt. Rob Roberts, of the California Department of Fish & Game, said oil-soaked birds had been spotted in the Farallon National Wildlife and Wilderness Refuge -- a group of protected islands some 27 miles west of the Golden Gate Bridge.

He added that 73 birds were currently being treated for exposure to the spill while 19 had been found dead.

Concern over the spill's environmental impact led Governor Arnold Schwarzenegger to declare a state of emergency in the San Francisco Bay area, freeing up additional state personnel and equipment to speed up the cleanup process.

Meanwhile, the U.S. Coast Guard's top official in California has acknowledged that the agency did not inform state and city officials when the magnitude of an oil spill in the Bay became apparent.

City officials say they were still being told more than 12 hours after a ship struck the San Francisco-Oakland Bay Bridge Wednesday morning in dense fog that only 140 gallons of oil had spilled into the bay. But Coast Guard officials have said they knew hours earlier that the spill dumped 58,000 gallons.

"That is not acceptable," said Rear Adm. Craig Bone, who didn't explain the delay but insisted the Coast Guard's response to the incident was immediate and aggressive.

The spill, believed to be the biggest in the bay since 1988, has closed several beaches, canceled weekend outdoor events and threatened thousands of birds and marine animals.

Schwarzenegger toured the command center at San Francisco's Fort Mason where state and federal officials are coordinating on cleanup plans.

"How does a ship, with that much space available, how does a ship hit the bridge?" the governor asked as he was shown a map of the bay and where the vessel struck the bridge,

"That's what we're investigating," Coast Guard Capt. William Uberti, captain of the Port of San Francisco, answered. "That shouldn't have happened."

Early Friday, oil skimmers, surveillance flights and shoreline cleanup teams resumed their work mopping up the damage. The California Department of Fish and Game reported 73 live birds had been collected; 17 were found dead.

"The effects of the oil spill could persist for months and possibly years," said Tina Swanson, a fish biologist with the Bay Institute.

Mayor Gavin Newsom said if the city knew earlier about the spill's scope, it would've responded differently. Newsom has threatened legal action against the parties responsible.

Sen. Barbara Boxer also criticized the Coast Guard's response in a letter Thursday to Commandant Adm. Thad W. Allen. She said she was "very troubled by the Coast Guard's delay in delivering accurate information to the public and the city of San Francisco. Many questions remain as to why it took an entire day to determine the gravity of this spill."

Bone said Friday "their concerns were warranted."

A Coast Guard log of Wednesday's events obtained by The Associated Press showed the Coast Guard briefed city officials around 1:25 p.m., but both the ship's crew and some Coast Guard personnel were vastly underestimating the scope of the spill.

About two hours after the 8:30 a.m. incident, engineers aboard the cargo ship estimated about 146 gallons of fuel had leaked.

The Coast Guard began receiving reports from its own personnel that suggested a much bigger spill, including oil washing up on piers miles away, and "oiled birds and wildlife."

Yet at 4:49 p.m., a team of Coast Guard, California Department of Fish and Game and San Francisco police officials estimated "400 gallons in the water total," according to the log.

Uberti disputed that. He said Coast Guard personnel knew the full extent of the spill by around 4 p.m., and Coast Guard and private response firms responded immediately after the incident.

He rejected any suggestion that the crews could have contained the spill more quickly.

Tides on Wednesday and Thursday carried a plume of heavy fuel beneath the Golden Gate Bridge and into the Pacific Ocean. By Thursday afternoon, oil had been sighted as far north as Stinson Beach, about 15 miles north of the city.

"This is a very environmentally sensitive area, so it's of great concern," said Uberti, who canceled the swim portions of two triathlons scheduled for this weekend because of health concerns.

Coast Guard investigators were focused Friday on communications between the ship's crew, watch officer and helmsman and vessel traffic authorities in the moments before the incident.

According to chief investigator G. Ross Wheatley, the pilot and the shipping company could face civil penalties. He said in Coast Guard interviews, the pilot, Capt. John Cota, had answered every question put to him. Wheatley could not answer Friday what route Cota was trying to take.

The ship, called Cosco Busan, had just left the Port of Oakland and was proceeding to sea when it hit the bridge around 8:30 a.m. Wednesday. The accident caused no structural damage to the Bay Bridge, officials said, but the vessel's hull suffered a large gash.

A series of factors appeared to have contributed to the slow assessment of the spill. The ship's crew could not use its normal means of determining how much fuel had escaped because some of the equipment was damaged in the crash. Instead, they were forced to heat the gelatinous remaining fuel and transfer it to a different tank, then measure it, officials said.

Other normal means of measuring the spill, such as visual assessments by boat or plane, were hampered by the fog, said Lt. Rob Roberts, an investigator with the California Department of Fish and Game.

"It was hard to see what was going on down at the waterline," he said.