At least 2,000 metric tons of fuel spilled into the Kerch Strait when a tanker split open and four freighters sank in a storm on November 11 killing thousands of bids, including many endangered species.
"Birds stained with fuel oil have virtually no chance of survival if no one helps them," Valentin Kozlitin, the chief veterinary doctor at the Moscow zoo, told RIA Novosti following his return from the disaster area.
Earlier reports said some 30,000 birds had died as a result of the oil slick but Kozlitin warned the number of dying birds will increase as their migration routes cross the disaster area.
He said there is still a chance to help the birds arriving at the oil slick site.
"The authorities are taking no steps to rescue the birds and, on the contrary, are restricting and hampering the work of a few volunteers," Kozlitin added.
He said birds are dying of dehydration, hypothermia and starvation.
The Russian Bird Protection Union said earlier birds stained with fuel oil should be washed with cleaning agents and kept warm.
