Searching for the Gulf oil leak's victims
Queen Bess Island off the Louisiana shore is on the front line of the oil threat; but at first sight this precious home to seabirds looks surprisingly untouched.
We approach through waters that appear to be clean and, as we get close, the cries of hundreds of brown pelicans intensify - this is one of their key nesting-grounds.
I've joined a search and rescue mission, and one question leaps immediately to mind: is the problem really that bad?
Images of pelicans struggling through syrupy oil have become the icon of this crisis, and some impacts have clearly been severe. But today the scene is more benign than I had expected.
The island lies in Barataria Bay, one of the areas worst affected, which makes it all the more surprising that the sea is sparkling and the birds are seemingly healthy.
Some of the pelicans are even perching comfortably on the very containment booms that have been laid to keep the slick at bay.Invisible threat
I put this to our guide, Tom MacKenzie, spokesman for the US Fish and Wildlife Service. He has heard the question many times before.
"The oil's there, it's landed, but you can't really see it," he tells me, pointing out a dark stain along the rocks, a residue of the slick's last advance.
A combination of favourable winds, helpful currents and the clean-up operation has meant that no fresh oil has reached these particular waters for five weeks. Other places have been hit instead.
It is a feature of this spill that the slicks are patchy and mobile, and only reach the shores occasionally.
For the pelicans we are watching, the conditions are still threatening.
Tom explains how, if oil coats the rocks, the birds can walk on it, try to clean it off and then ingest it with fatal consequences.
While we are talking, a shout goes up when one of the officials spots a pelican that is unusually dark. It is stained with oil: a victim.
It beats its wings to get airborne, but the oil weighs it down and we watch the pitiful sight of its failed attempt to fly.
End Quote Professor Christopher D'Elia Louisiana State University
Are there small droplets getting in and interfering with the food chain? We just don't know”
The members of the rescue team debate the merits of trying to catch the bird; there's always the risk of causing more harm than good by disturbing other birds and nests.
In the end, a decision is taken to attempt a capture, and two boats manoeuvre close to the pelican. It tries to take off again.
Wildlife official Mike Pixley reaches out with a net but misses. But then, on a second go, he manages to scoop the stricken bird.
It is caged and taken at high speed to a treatment centre. It should survive, along with some 1,282 oiled birds rescued in all so far.
A further 969 have been found dead. These are the official figures up to 20 July.
The numbers may seem surprisingly low, given all the talk of catastrophe. They are certainly small compared to the hundreds of thousands of birds estimated to have died in the Exxon Valdez disaster in 1989.
So how serious is this BP spill?
Experts agree that it's too early to come to a definite conclusion - there's a lot of oil still out at sea. But they are divided on the impact so far.
Professor Paul Kemp of the Audubon Society, a leading conservation charity, believes the region is under threat anyway and that the leak's impact has been exaggerated.
"The brown pelican population has taken a hit but we're not concerned about losing all of them," he says.
"We had maybe 4-5 periods of a day or so in which we got oil in Louisiana. Most of time it's not coming ashore, it's not a continuous thing, and when it did come ashore it came as patches."
Professor Christopher D'Elia of Louisiana State University sounds more alarmed.
"There are lot of unknowns. The geographical extent and the duration of this spill has been so long that it's very hard to say what's going to happen.
"It's so complex with dispersant used, things going on to the oil before it gets there, some good, some not so good.
"Will it get there as large gobs of heavier fractions? Or are there small droplets getting in and interfering with the food chain? We just don't know."
Meanwhile the patient, uncertain work of hunting for the victims continues. I ask Tom Mackenzie how long that mission is likely to go on for.
"Who knows?" he says. "Months; maybe longer."