On March 18, two days after it had run aground, the Malta-registered "M.S. Oliva broke her back in the force of a relentless swell," leaking oil that spread into an 8-mile (13-kilometer) slick, according to the bird-protection group and the Tristan da Cunha government's website. However the slick seemed to have mostly dissipated by March 23.
Some 65,300 tons of unprocessed soybeans also spilled from into the ocean, and the vegetables' impact to the sensitive marine environment are unknown, the government's website said.
Hundreds of oiled birds are washing ashore, and a preliminary estimate suggests up to 20,000 birds may have been affected, according to the government's website.
"The scene at Nightingale is dreadful," Trevor Glass, the conservation officer for the territory, said in a statement.
The "grave environmental disaster" may also reach ecosystems of the nearby Inaccessible and Gough islands, both UN World Heritage sites, according to the government's website.
The Tristan da Cunha Conservation Department deployed several rescue workers (pictured on March 23) to rescue and clean oiled penguins. Already, workers have collected 750 penguins, which will be transported to Tristan de Cunha for rehabilitation.
"We were planning on going anyway, and en route we received word that a cargo freighter had crashed into the island," Evans told National Geographic News.
Evans, who spent a day on the island surveying the disaster, saw "hundreds—that's not an exaggeration—of northern rockhopper penguins covered in black oil. I saw dozens of fur seal pups with oil on their fur. It's really disturbing to see something like that."
The oil spill may endanger not only penguins (oiled birds pictured on March 23), but also millions of nesting seabirds and other wildlife, the bird-protection group's Richard Cuthbert said in a statement.
Cuthbert also warned of a "twin environmental catastrophe" if rats, which may be aboard the wrecked vessel, escape onto Nightingale Island, which is rodent free.
"If rats gain a foothold, their impact would be devastating," Cuthbert said.
The Tristan da Cunha Conservation Department has already placed rodent traps near the wreck, "with the hope these will intercept any rats getting ashore," he said.
By March, northern rockhopper penguins (pictured unaffected by oil in an undated photo) have finished their breeding cycle and annual molting and are heading out to sea, according to the Tristan da Cunha government's website.
But the oiled birds are now fleeing back to shore, because "they're cold," Audubon Alaska's Warnock said.
An oil stain is "a hole in the wet suit—those feathers are interlocked, and the oil interferes with the mechanisms that interlock those feathers. It allows cold water to get to their skin."
The loss of the birds' natural waterproofing also makes them vulnerable to hypothermia, Warnock said.
The roughly 75,300-ton M.S. Oliva (pictured on March 22) struck a rocky outcrop on Nightingale Island while hauling soybeans from Brazil to Singapore, according to the Tristan da Cunha government's website.
Beyond repair, the ship will be allowed to "break up readily and its constituent parts soon be consigned to the surrounding ocean depths," according to the website.
The resulting environmental disaster may also hobble the rock lobster fishery, which supports one of the world's most isolated communities, the Associated Press reported. The nearest city is Cape Town, South Africa, up to a six-day boat ride away, Traveler's Evans noted.
"The consequences of this wreck could be potentially disastrous for wildlife and the fishery-based economy of these remote islands," the bird-protection group's Cuthbert said in a statement.
Oil coats northern rockhopper penguins in the wake of this month's oil spill at Nightingale Island.
The penguins breed in colonies, which can be situated at sea level, on cliff tops, and sometimes inland, according to the International Union for Conservation of Nature.
The birds arrive in the colonies in late winter, lay eggs in September, and wean chicks in December and January. (See more penguin pictures.)
Rockhoppers feed on krill and other crustaceans as well as squid, octopus, and fish.