Radar Shows Steep Decline in Kauai Seabirds’ Population

Kauai’s Newell’s Shearwater population is in trouble, according to the results of a new study. (A. Raine)

(CN) – Two endangered seabird species on Hawaii’s Kauai have lost more than 75 percent of their respective populations in the past two decades.

Researchers discovered these concerning trends after analyzing radar data that tracked the movements of the Hawaiian petrel and the Newell’s sheerwaters, a pair of seabird species whose status appear to be in jeopardy after a series of threats have disrupted their habitats.

Publishing their findings Thursday in the journal The Condor: Ornithological Applications, the team observed a 78 percent reduction in radar detections for petrels and a 94 percent decrease for shearwaters, the latter of which experienced a similar decline within the recorded movement of fledglings –  young birds that cannot yet fly.

“It is important to publish this information so that everyone can better understand the severity of the declines in these species and the threats they face,” said Pacific Rim Conservation’s Eric VanderWerf, an expert on Hawaiian seabirds. “We need to consider these data in order to make informed decisions about the best conservation measures.”

The steep population declines likely began in the aftermath of Hurricane Iniki in 1992, according to the team. The storm produced permanent ecological changes, including the opening of new routes for invasion by exotic predators and plants, in addition to significant infrastructure changes across the island.

Mobile radar units mounted on trucks help researchers monitor elusive seabirds. (D. Dow)

“These seabirds face a wide range of threats,” said lead author Andre Raine, a researcher at the Kauai Endangered Seabird Recovery Project. “Conservation effort needs to be focused on reducing power line collisions, fall-out related to artificial lights, the control of introduced predators, and the overall protection of their breeding habitats. Many of these efforts are now underway on Kauai, and I am hopeful that these will continue and expand over the next few years.”

While the sheerwaters’ plight is well documented, previous analyses of petrel radar data suggested their population was stable, or even increasing. The team attributes the difference of petrel-related findings to standardizing the data based on sunset times, which ensured that the time periods – and the corresponding bird movement periods – they reviewed were constant throughout the survey period.

“Ultimately, the conservation of the breeding grounds of endangered seabirds on Kauai is actually the conservation of our native forests and watersheds, with far-reaching benefits for other native plants and birds that rely on these habitats, as well as – ultimately – ourselves,” Raine said.

 

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