Invasive Rats Decimated in Lehua Island , Native Seabird Recovery Plans Underway — Hawaii

Lehua Island in the state of Hawaii has successfully been rid of invasive rats, according to officials, and discussions of seabird recovery plans are currently underway.

Invasive Rats vs. Native Seabird Species

On Lehua Island, a tiny crescent-shaped volcanic cone located west of Kaua'i, Hawaii, scientists are rebuilding a seabird haven. Hundreds of thousands of noisy seabirds, including albatrosses, terns, and petrels, populated the island's steep headlands before European explorers arrived there in the 1800s. Their guano seeped down bluffs to enrich fish-rich waters. Native Hawaiians paddled their canoes to the rough island to fish and collect shellfish.

However, with the introduction of invasive species like rats and rabbits that decimated native vegetation and seabird eggs and chicks, as well as plants that colonized disturbed ground, the ecosystem started to break down. Seabird populations fell precipitously, and some species left Lehua.

But over the last 20 years, the Division of Forestry and Wildlife in Hawaii has organized a concerted effort to hunt down the rabbits and rats through aerial poisoning, hunting, and research.

The effort, which was carried out with assistance from the US Coast Guard, the National Tropical Botanical Garden, and the California-based nonprofit Island Conservation, is already paying off. The state sanctuary, which is empty and mostly off-limits to tourists, is home to more 'ā, or red-footed boobies, and other species that managed to survive the invaders.

According to Sheri Mann, the forester in charge of the restoration work for the Hawai'i Division of Forestry and Wildlife, Lehua is now rat-free, making it an essential refuge for seabirds.

Seabird Haven

The island protects seabird habitat even as sea levels rise thanks to its steep, rocky coastline, which rises to a height of a 60-story building.

Mann and her coworkers are now faced with an entirely new problem: how to reintroduce the seabirds that have long since left Lehua Island, such as the ʻuaʻu or Hawaiian petrel, 'ewa'ewa or sooty tern, and hinaokū or blue-gray noddy. Thankfully, the scientists have a cunning scheme to draw them in.

The restoration crew is using a solar-powered sound system that plays bird calls from the island's steep slopes, along with wooden seabird decoys enclosed in a mirror-and-mirror enclosure. The objective of the sights and sounds is to deceive passing birds into believing that the island is a bustling breeding colony. According to Hakai Magazine, scientists have successfully tricked birds in other locations using artificial social signals, including O'ahu, Hawaii, where the results are encouraging.

Mann claims that they are also broadcasting the calls of birds that Mann's team is uncertain have ever visited the area. For example, the 'akē'akē or band-rumped storm petrel, a critically endangered bird, has been detected by the island's listening devices, but scientists are unsure if the species has ever lived on Lehua. The rat-free island might be a boon to the petrel's overall survival if they can lure it in.

Along with their deceitful plan, Mann and her coworkers are also restoring the native vegetation on Lehua, which is essential for seabird recovery because it provides a habitat for nesting and rearing. The work is challenging and expensive. To remove weeds, botany crews fly or sail to the island's rugged shores. Another strategy entails having the crews pack native seeds into soluble clay balls and slingshot or throw them onto bird-friendly bluffs because some areas are so steep, Smithsonian Magazine reports.