(CNN) As oil-covered animals come ashore, the broader effect of the California oil spill on wildlife is unknown, experts say.
A brown pelican was the first casualty of the oil spill, wildlife officials said. The bird was euthanized Sunday after it was injured in the spill off the Orange County coast, Michael Ziccardi, director of the Oiled Wildlife Care Network (OWCN), said at a press conference Monday morning.
Officials captured four live birds as of Monday afternoon, Ziccardi said. A coot, ruddy duck and pelican were captured Sunday and a sanderling came in on Monday. Other oiled birds have been spotted in flight, but they've been difficult to catch, he said.
"When we heard of the large size of the slick with the volume that was reported released, we had grave concerns about this impact," Ziccardi said. "In our initial assessment of the area, the number of birds in the general area seems to be lower than we had feared."
With about 126,000 gallons of oil leaked about 5 miles off Huntington Beach, California, experts from wildlife organizations are concerned for animals.
The number killed is unknown. Wildlife experts are collecting animals as they come to shore.
"At this point, we are cautiously optimistic related to the number of animals that might be affected at this point," said Ziccardi, who added that it's too early to tell the impact on wildlife.
Birds are the priority, since they're most likely to come ashore after an oil spill, Ziccardi said.
"Birds have a high body temperature; they use their feathers almost like a dry suit to keep themselves warm in the marine environment," Ziccardi said. "If they get soiled, their first response is to get warm as quickly as possible. That's why they usually come ashore quickly, so that they can try to stay warm."
The organizations rely on offshore cleanup operators who may spot dolphins or other marine life in distress, he said.
The good news for dolphins is that these mammals are "much less susceptible to oil impacts than birds," Ziccardi said.
There isn't enough information to speak to the long-term effects of an oil spill on marine mammals, Ziccardi said. It depends on how much oil the marine life ingest or inhale, he said.
"Just now we are starting to learn some of those long-term effects from the Deepwater Horizon oil spill more than 10 years ago," Ziccardi said.
Oil pollution was found in thousands of fish 10 years after the disaster, according to a study published in 2020. Millions of gallons of oil spewed into the Gulf of Mexico's waters over 87 days in that spill.
OWCN is based out of the University of California at Davis (UC Davis). Its job is to respond to oil spills that affect or could threaten wildlife anywhere in the state, Ziccardi said.
The organization has more than 1,600 responders trained to go to an oil spill. Since 1994, OWCN has responded to more than 75 oil spills and cared for 10,000 animals.
Animals collected from the oily waves have a shot at recovering and returning to the wild, Ziccardi said.
"Oiling is a traumatic experience for these animals, but in our experience, as far as large-scale spills we've responded to, we have more than a 50% to 75% success rate to return animals back into a clean environment," he said.
Field teams are out at the site collecting animals and bringing them to a "field stabilization site" so they can give them basic first aid, Ziccardi said.
"We're giving them warmth, we're giving them fluids, we're giving them a bit of time from the stress of being captured here. Then from this location we have an organized transport up to our Los Angeles Oiled Bird Care and Education Center," he said.
When the animals are at the center, workers photograph each animal and document as much as they can. The animals are then stabilized for 24 to 48 hours, he said.
They're cleaned of the oil before their human helpers give them "time, good nutrition, observe them carefully," Ziccardi said. For birds, this process takes an average of 10 to 14 days, he added.
If you see oiled animals, do not pick them up. It's not safe for the humans or the animals, Ziccardi said.
He encourages people to call the 877-UCD-OWCN hotline to report oiled animals. The organization is not taking volunteers, but instead it's relying on its 1,600 trained responders, he added.