By Matt Walker
Editor, Earth News
Unruffled by oil pollution
Petrels avoided any lasting damage caused by the Prestige oil spill.
The spill, one of Europe's largest pollution events, happened in 2002 when the Prestige tanker sank 120 miles off the Spanish coast, releasing more than 24,000t of crude oil into the sea.
Ten of thousands of seabirds died, but new research shows that European storm petrels avoided any impact.
Most adult birds survived by abandoning attempts to breed, ensuring the colony continued unchecked in later years.
Details are published in the journal Marine Pollution Bulletin.
The study shows how some long-lived seabirds are able to mitigate the long term damage caused by pollution events.
Rather than jeopardise their immediate survival by returning to to feed and breed in a polluted area, the most experienced birds stayed away, skipping their reproductive efforts during the years immediately following the Prestige spill.
The discovery was made by an independent team of researchers in Spain, including scientists at the Aranzadi Society of Sciences in Donostia San Sebastian.
European storm petrels are a sea-going species that only return to land to breed.
Usually, breeding birds feed on surface waters close to shore in intertidal zones near to the breeding colony.
These waters were particularly affected by the oil spill: the tanker sank in November 2002 and by December the first oil slicks reached the Bay of Biscay.
Within a year, 21,070t of oil had been collected from the Basque coast and a further 2950t collected off shore.
But a study by the Spanish researchers, led by Jabi Zabala, has found that many storm petrels abandoned their breeding colony rather than be contaminated by the oil.
They examined petrels breeding on a limestone island 800m out in the Aketz Islet in the Gulf of Biscay, as part of a systematic study begun in 1993.
They found that on average adult petrels had a 89% chance of surviving from one year to the next.
In the years immediately after the spill, that fell to just 85%.
"Our results show no clear affect of the spill on adult survival," the researchers write.
During their study, the researchers found more transient birds, and fewer experienced breeders visited the colony after the spill.
The experienced breeders skipped their breeding effort, while inexperienced birds continued to attempt to breed. In doing so, the younger birds suffered food shortages.
But enough birds abandoned their breeding efforts to ensure that the colony as a whole was not significantly impacted by the spill.
Just three years after the Prestige sank, European storm petrels were surviving and breeding as before the disaster.
Over 23,000 oiled birds were collected in Spain, France and Portugal after the spill, with between 115,000 and 230,000 birds thought to have been affected.
But the newly published research helps explain why just 19 oiled European storm petrels were collected.