The Audubon survey [of the Louisiana shore] found oil in many places.
"In some cases it was buried beneath the sand and oozed upward in response to pressure or changing temperatures," the report said. "Tarballs peppered high-tide lines on some beaches."
The report said tarry material also sits on tidal flats and sends "a steady stream of oily materials to shore."
Audubon: Birds look OK after spill, threats remain, AP, October 13, 2010: