Ornitho-logic

How Pulling Weeds Can Save Australia's Seabirds

A group of determined Australians are on a mission to reclaim a former island paradise for shearwaters and penguins.

A typical day in the field for park ranger Rowena Morris involves wading through a sea of waist-deep weedswithout stepping on any nesting birds. “It’s the best workout,” she says. Not that Morris is doing it to get in shape: She’s fighting to save the seabirds on Australia’s Big Island, where hundreds of burrowing avians are being strangled to death by invasive weeds.

Big Island, located off the coast of Wollongong in New South Wales, has been plagued by an infestation of Kikuyu grass since the ‘70s. The pesky weed was, ironically, introduced to stop soil erosion that was chipping away at seabird nesting habitat. Unlike other weeds, Kikuyu grass is incredibly strong and over time, has created a barrier across the island. The grass, mixed with the equally problematic morning glory weed, has formed a giant twisted booby trap for birds.

Wedge-tailed Shearwaters and Little Penguins are among the species most at risk. Since shearwaters have to return to the same nesting site each year, they stubbornly wriggle past the weeds to enter their burrows. But once they’re in, they often can’t get out again. The invasive plants have also wrecked Little Penguin population numbers. In 1962 there were about 1,000 breeding pairs on the island; as of 2014 their numbers have decreased to just about 200 pairs.

“[Kikuyu] spreads quite fast,” says Morris. “It’s like grass growing on steroids and the roots are about 30 centimeters [almost a foot] deep in some areas.” The thick roots penetrate the birds’ burrows, entangling the nesting avians or trapping them inside, where they die a slow death from dehydration. The more the birds struggle, the more they risk getting stuck or injuring themselves. Chicks also get trapped in the weedy webs, never making it out of their nests to see the light of day.

That’s why Morris, who works for the New South Wales National Parks and Wildlife Service, has banded together with researchers and hordes of local volunteers. In 2014, the impassioned team founded the Big Island project to restore the island to prime avian habitat. Since then, they’ve  been combing the island inch by inch, eradicating the weeds and replacing them with native plant species.

The year the project began two trial sites were established on the island: One covering nearly three acres and another just over one acre. During the summer months, while the birds were in other parts of the world, both sites were doused in aerial herbicides to kill off the Kikuyu grass and morning glory. The herbicides have no impact on the local fauna, but the weeders still take great care in applying them.

So far, the spraying has been a massive success: Nearly 80 percent of the weeds in the trial zones have been killed. “After the helicopters come in and spray, we allow the weeds to mulch down for a year so that they become this dense grayish-brown material on top of the soil,” says Morris. “Then we plant species typical to that area.” 

The native plants are thriving thus far. “All these different colored species are coming up, and the contrast and variety of the site compared to where the Kikuyu grass and morning glory still grow is magnificent,” says Morris. The larger site has been planted with 11 different species, including coastal saltbush, lomandra, white correa, and boobialla; the smaller site will be cultivated this June.

Gardening on a weed-infested, seabird-packed island is anything but easy. Once a month, Morris and the rest of the team, plus about a hundred local volunteers, take turns piling into a motorized boat and then a small inflatable boat to reach the desolate island. After landing, they have to trek over rocky bluffs and gnarled weeds, lugging all their gear to get to the trial sites. They hand-weed any Kikuyu that’s sprouted up, and spray herbicide on potential problem spots.

In addition to weeding, the team is conducting seabird surveys on the island to see whether populations are improving. “I’d love to say the numbers are going up but that sort of research takes a while,” Morris says. “But as we walk around the sites, we can see that the birds are safely in their burrows, which is a really good indication.”

The plan is to eventually use the helicopters to saturate the entire island with herbicide, Morris says. “We are working hard on the trial sites to prove that our strategy is successful so that people can see this project has potential.” By her estimates, it might take 20 years to eradicate the weeds from the whole islandbut she’s sure it can be done.

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