Battle Prep for Birds

When Marines tore through Hawaiian mudflats in heavily armed half-boat, half-tractor vehicles this month, they were doing much more than preparing for battle. The 26-ton battle machines that they were learning to use, called amphibious assault vehicles (AAVs), helped to create nesting habitat for an endangered wading bird, the Hawaiian Black-necked Stilt.

At Oahu’s Nu’upia Ponds mud flats, non-invasive pickleweed grows like, well, a weed in the salty water, overtaking any possible nesting sites for the stilt. In the 1970s, the U.S. Fish and Wildlife joined forces with the Kaneohe Marine Corps Air Station to break up the thick mat of vegetation with AAVs in annual training exercises at the Wildlife Management Area. The machines act just like garden-variety rototillers (except, you know, they’re outfitted with machine guns and grenade launchers), opening up areas for the thin, pink-legged birds to lay eggs.

Left to its own devices, the invasive pickleweed would cover the entire mudflat, leaving no mud at all for the stilts to nest, says Jane Rubey, Hawaii State Coordinator for the Pacific Joint Venture.

The vehicles create furrows in the mud that are ideal for stilt nesting, the late Diane Drigot, then a natural resources management specialist at the base, explained in 2004. "The tread marks fill in with water in such a way that the stilts' nests are protected by a little moat that increases the hatchling survival rate."

Only 60 stilts remained in the Nu’upia Ponds when the exercises began back in the 1980s, according to the Marines. The stilt was a popular game bird until waterbird hunting was banned in 1939. The violent, unorthodox habitat management has helped boost the nesting population at Nu’upia today to about 80 pairs. The 517-acre mud flats now has one of the largest stilt populations in the state, says Marjorie Ziegler, head of the Conservation Council of Hawaii, an estimated 10 percent of species’ total population.

The program has benefitted other endangered avian species, too, including the Hawaiian Coot, Hawaiian Gallinule, and Koloa Duck, says Lance Bookless, senior natural resources manager at the base. These birds prefer freshwater pockets with dense vegetation cover, and killing off the pickleweed clears the way for native sedges to flourish and provide cover.

The success at Kaneohe Marine Corps Air Station is making conservationists on other islands take notice. Sonny Gamponia, a volunteer at the Kealia Pond National Wildlife Refuge on Oahu, where pickleweed is encroaching on an estimated two-thirds of the mudflat habitat, says there is talk of asking the National Guard to employ similar tactics there.

Who knew amphibious assault vehicles could make such a great conservation tool.