The Marine Corps is helping wildlife at Nuupia ponds.

Marines this week are conducting their annual effort to clear invasive weeds that threaten an endangered bird species.

Nicknamed "mud ops," the effort began in the early 1970s when the U.S. Fish and Wildlife Service asked the Marine Corps for help using amphibious vehicles to open up mudflats covered with pickleweed. The invasive weed crowds the birds out of their natural habitat in the ponds.

The Marine Corps says the 33rd annual mud operations will take place until Thursday.