The plight of the pelican is the poignant symbol of this disaster

You mess at your peril with people's cherished symbols, and James Harris, the Louisiana wildlife biologist, made the point to me as we looked at the brown pelicans, emblems of his state.

Bedraggled wasn't the word for them. It needed a stronger word. Enslimed came to mind. The birds, acrobatic fish hunters in their normal existence, were covered from their stubby tails to the tips of their improbably long bills in thick goo – a goo which actually had an oil industry name: "Louisiana sweet crude".

It was the oil gushing from the blowout beneath BP's collapsed Deepwater Horizon rig 40 miles out in the Gulf of Mexico, which, after six weeks of accumulating in the ocean at a rate of 19,000 barrels a day, last week finally began to do serious wildlife damage as it flopped ashore on the Louisiana coast, with brown pelicans the principal victims.

There were 19 of them in front of us, clustered in a wooden pen at a rescue facility set up on the banks of the Mississippi, near the end of the long delta where the great river reaches the sea. Some of them were shivering uncontrollably. One was frantically preening itself, pulling at all the feathers it could reach with its bill, trying vainly to be rid of this evil mess which would certainly doom it, had it not been brought here. The rest of them huddled together, silent, stupefied.

"It really upsets me to see them like this," said Mr Harris, 49, a leading expert on brown pelicans – he's been working with them for 20 years. "To me it's a very important species. I'm very attached to the brown pelican. This is a very charismatic bird; it's big, it's nice to look at."

"People are drawn to pelicans," I said. "They look amusing. Usually."

With the fishing halted, the beaches threatened and wildlife already soiled, it is certainly true that the feeling in America against the British oil giant over its gushing well, now the country's biggest pollution disaster, is extraordinarily strong.

There is, for example, an entrenched unwillingness to give BP the benefit of the doubt, over anything – the company's claims to have partially capped the well at the weekend were met with widespread scepticism. As was said of the MPs' expenses scandal in Britain, there is no arguing with a spasm of public anger – an anger consciously echoed by President Obama, who said last week that he was "furious".

As a senior official of the US Fish and Wildlife Service, James Harris was too diplomatic to say if he thought the anger was justified, but, as a Louisiana native – from Pearl River, north of New Orleans, he pointed out forcefully why it was there, and how the first images of the oiled pelicans had intensified it.

"I think it's possible that they might come to symbolise the whole disaster," he said. "For the people of Louisiana, the brown pelican is just as much a symbol of the state as the American eagle is for the nation as a whole, and to see the state emblem being threatened again and despoiled – people are very upset and angry about that."

When he said threatened again he was speaking quite literally, as Pelecanus occidentalis is a bird that has come back from the brink. It was wiped out in Louisiana by pesticide poisoning in the 1950s and 1960s, and was placed on the US endangered species list, but the state was so anxious to have its emblem back that birds were brought from Florida and a breeding population was re-established. It was taken off the endangered species list only last year.

"We spent all that time bringing them back, and now we have this," Mr Harris said. "They delisted it largely because the Louisiana population was doing so well, but the longer it goes on, the more it has the potential to impact [on] a very significant proportion of the Gulf population."

Not knowing how long it would go on, in fact, was behind a lot of people's upset, he said. "A lot of it, the fear, the anger, is the unknown. This is not a one-time event, it hits a certain place and you deal with it. This is just continuing. We're not sure where it's going to go, what it's going to impact. There's that fear of the unknown."

He was echoed in this by the man running the rescue facility, America's leading expert at saving oiled birds, Jay Holcomb of the California-based International Bird Rescue Research Centre, who in 1989 spent six months saving birds in what was previously America's biggest oil disaster, the spill in Alaska from the tanker Exxon Valdez.

"The difference with the Valdez spill and this one is that the oil from Valdez hit the shores quicker but there was an end to it," he said. "Here, there's not. We've seen some big oil spills, but usually they have a beginning and an end. Look at this one though: there's no end to it in sight. That's why it's worse."

Mr Holcomb's organisation is running the centre jointly with the other major US body which cares for oiled birds, Tri-State Bird Rescue and Research, which is based in Delaware. Both organisations were hired by BP right at the outset of the spill, and both quite independently praised BP for acting promptly, which meant they had a chance to set up the centre properly before any oiled birds came in.

It is situated in a warehouse next to Fort Jackson, an old fort in Buras, an isolated community on the Mississippi Delta about 65 miles south-west of New Orleans. So far it has handled 157 oiled birds, but 66 of those have been in the last two days alone as the real oiling has suddenly begun. Most have been brown pelicans, but there have also been laughing gulls, gannets, royal and sandwich terns and various other sea birds and waders.

The pelicans are the most difficult to clean as they are so big. They are firstly "marinaded" in warmed vegetable oil, which loosens the crude oil sticking to their feathers, and then they are washed in washing-up liquid – a process which takes about 45 minutes for each bird. "It's a real ordeal for them," said Rebecca Dunne, the Tri-State co-ordinator. "That's 45 minutes of each of these guys thinking 'I'm going to be eaten'. Wild animals are not normally handled and they think, 'Something is attacking me'. It's not just panic; there is a huge release of stress hormones. If we handled them too long, they could die."

Yet it was hugely satisfying at the weekend to watch the Louisiana sweet crude come off the Louisiana state birds, and to see the real plumage reappear from under the goo, especially the pure-white crown of the adults, which had been invisible with the oiling.

The birds will stay in the centre for about seven days and then they will be released – but on the Atlantic coast of Florida, rather than in the Gulf of Mexico, where they might get oiled again, as there is no knowing when the gusher will be fully capped.

"That's the thing," said Jay Holcomb. "The technology was here to drill this well, but it's not here to stop it. That's the biggest wake-up call. Don't you agree?"

The flow of events

20 April 2010 Explosion and fire on Transocean Ltd's drilling rig Deepwater Horizon licensed to BP kills 11.

22 April Deepwater Horizon sinks and a five-mile-long oil slick is seen.

29 April US President Barack Obama pledges to contain the spreading spill. Louisiana declares a state of emergency.

30 April BP CEO Tony Hayward says the company takes full responsibility for the spill and will pay all costs.

2 May Obama visits the Gulf Coast. BP starts to drill a relief well.

6 May Oil washes ashore on the Chandeleur Islands off Louisiana.

7 May BP tries to lower a containment dome over the leak, but it is rendered useless by frozen hydrocarbons.

16 May BP succeeds in inserting a tube into the leaking riser pile of the well.

19 May The first heavy oil reaches Louisiana's fragile marshlands.

26 May BP begins a "top kill" manoeuvre, involving pumping heavy fluids and other material into the well shaft.

28 May The top kill is added to a "junk shot" – a push to clog the broken pipe.

29 May BP declares the top kill attempt a failure.

30 May White House energy adviser Carol Browner describes the leak as "the worst eco-disaster ever".

1 June US Attorney General Eric Holder says the Justice Department has launched an investigation into the affair.

2 June BP uses robot submarines to cut off the leaking riser pipe, then lowers a containment cap over the wellhead.

6 June Hayward claims the cap is now catching 10,000 barrels of oil a day.