Tar sands could threaten millions of migratory birds.

• Author: Block, Ben
• Position: EYE ON EARTH

In April 2008, an anonymous tip alerted Canadian officials to the fact that 500 ducks had mistaken a tar sands company's polluted reservoir in Alberta as a safe place to land. Hundreds of decomposed ducks have since risen to the surface, leading Syncrude Canada to clarify that its toxic tailings pond in fact killed an estimated 1,606 birds.

The losses have become symbolic of the problems associated with the development of tar sands--strips of sand or clay mixed with bitumen, a dense form of...