Since late last week a flood of pictures of oil-coated Gulf of Mexico birds—and conservationists painstakingly cleaning them—has added new emotional impact to the BP oil spill.

Some experts—citing traditionally low survival rates for rescued birds—are controversially arguing it would be better to immediately and humanely kill the suffering birds.

In a Spiegel Online article last month, German biologist Silvia Gaus argued that workers helping birds caught in the Deepwater Horizon oil spill, should "kill, not clean." Gaus said studies show that more than 99 percent of rehabilitated birds will die anyway as a result of oil exposure, mainly due to kidney and liver damage caused by oil ingestion.

Each oil spill is different, however, and survival rates