After Shetland Oil Spill, Bird Lovers Live in Fear : Ecology: Species hit hardest by the Jan. 5 disaster were those that live all year on the archipelago, 100 miles northwest of Scotland.

Hundreds of birds sail off the velvety green coast of Sumburgh Head. A black guillemot, a dumpy little sea bird, dips to the sea to scoop up a silvery sand eel for a nesting chick.

“A feeding frenzy,” Martin Heubeck, a University of Aberdeen researcher who tallies bird populations for the Shetlands, said with satisfaction.

What usually comes naturally in the Shetlands is welcomed with relief this summer.

No one knew what to expect on Jan. 5 when the disabled vessel Braer ran aground in the Bay of Quendale, creating the world’s 12th worst tanker spill.

“When you have 85,000 tons of oil bearing down on you in storm-force winds, you expect the worst,” said Heubeck, who works for an environmental advisory group.

But, he said, “It’s not as bad we feared.”

In the weeks after the disaster, 1,542 dead birds, their feathers clogged with oil, were found on the southern beaches of Mainland Island, the largest in the Shetland archipelago, 100 miles northwest of the Scottish coast.

The true loss of bird life from one of the world’s greatest sea bird colonies “is anybody’s guess,” said Peter Ellis, director of the Royal Society for the Protection of Birds in the Shetlands. He cited experts’ estimates that 5,000 birds had died.

“From a sea bird side of things, it’s been a bloody serious incident,” Heubeck said. Still, he said, thousands of birds are at Sumburgh Head, the south point of Mainland Island, and “the ordinary person who would return here wouldn’t notice the difference. Only the ‘whiz kids’ would.”

The islands are at the southern edge of the Arctic and the northern limit of the temperate zone, and the crossroad of the east-west and north-south migration routes. They are host to 61 species of breeding birds, including 21 species of sea birds.

Most of the birds were away for the winter or blown out to sea by hurricane-force winds when the pollution was at its worst.

The species hit hardest by the oil spill were those that live on Mainland all year, particularly the black guillemot, shag, eider, great northern diver and long-tailed duck, according to the Royal Society for the Protection of Birds.

The populations of black guillemots and shags are down by more than 50% along parts of the southwest coast of Mainland, Heubeck said, basing that figure on initial counts of birds that returned to breed this summer.

“The good news is that the damage seems to have been restricted to certain areas, there’s a lot of food around and the breeding season is going well,” he said.

“I don’t think we have any great worries left,” he concluded.

“It looks good,” agreed Paul Harvey, an area officer for the Royal Society for the Protection of Birds. “We’ve been incredibly lucky.”

Nonetheless, researchers warn that more birds could eventually be killed by toxins lingering in the sea and on land from the 24.6 million gallons of crude that gushed from the vessel.

The small fish that the birds are feasting on may be contaminated.

“The birds could be eating them and storing up trouble for themselves,” Heubeck said.

The number of shags--glossy, dark-green birds with elegantly curved necks--is down more than 50% in southwest Mainland this summer compared with a year ago. After the spill, 855 carcasses were recovered, 70% of them female.

Their population had already fallen 40% in the last five years for unknown reasons, Heubeck said.

An estimated 8,000 pairs breed in the Shetland Islands, 27% of the British population.

“I doubt we will see a rise in their numbers, but they weren’t wiped out,” Heubeck said.

The population of eiders has fallen from 17,000 birds in the mid-1970s to only 7,000 now. Based on initial surveys, Heubeck said, somewhere between 300 and 500 of the large and chunky sea ducks were killed by the spill.

“The eiders are vulnerable now,” Heubeck said.

The number of black guillemots has fallen 50% from a year ago along the southwest coast, according to surveys.

The population of the black sea bird has been rising around the islands, and is estimated at 15,000 breeding adults, a third of the British breeding stock.

About 300 long-tailed ducks and 50 great northern divers, known as the common loon in North America, normally breed in the Bay of Quendale. At least 96 long-tails and 13 great northern divers were killed.

There are reasons to be hopeful. After an oil spill in 1978 at Sullom Voe, an oil terminal on the north of Mainland, the black guillemot population plunged to 200. It’s now up to 1,200, Heubeck said.

The Braer’s oil killed just 15 puffins. The colorful, clown-like birds were at sea when the tanker heaved onto the rocks.

“The only possibility that they will be harmed is by oil in the food chain or in their nesting sites,” Heubeck said.

At least 2,500 pairs nest on Sumburgh Head.

Patricia Monaghan, a University of Glasgow zoologist, said many birds may die in the coming months.

“Surviving birds and birds that return to breed in the spring may be exposed to toxic effects of the oil in water and sediments or in contaminated food,” said Monaghan, who is studying the impact of the oil on wildlife.

The Braer was carrying Norwegian light crude, which disperses rapidly compared to heavy black Alaska crude. Most of the visible signs of the crude oil were washed away by raging waves and weather within days of the wreck.

But the Norwegian oil contains a higher proportion of the more toxic aromatic hydrocarbons, which are retained in the body much longer than the more benign alkene hydrocarbons that predominate in heavy crude.

The aromatic hydrocarbons can cause tissue damage and severe anemia, which limits the capacity of the blood to carry oxygen. Consequently, a bird may be unable to dive for food.

“Exposure to only very small amounts of oil can dramatically affect egg production, hatching success and even parental behavior,” Monaghan said.