Hundreds of thousands of feet of barriers have been installed in the marshlands of the Mississippi Delta to protect the most sensitive wildlife refuges that lie in the path of a massive oil slick coming from a sunken BP rig in the Gulf of Mexico. About 34,000 birds, including some rare species, are nesting in the ecologically fragile area. Scientists say generations of some species could be wiped out if the oil reaches the wetlands. Duration: 01:57