Three mass kills of ʻUaʻu kani birds discovered on Kauaʻi amid fledgling season

At least three mass kills of native ʻuaʻu kani, also known as wedge-tailed shearwater, have been recorded on the Garden Isle, said Dr. Andre Raine, science director at the Archipelago Research and Conservation in Kalaheo.

In the past two weeks, a minimum of 180 birds have been discovered. In all three cases, the majority of the kills were due to feral cats and dogs, according to the conservation group.

“This is one of the worst kills I’ve recorded on Kauaʻi,” Raine said.

The wedge-tailed shearwater is a non-listed seabird, meaning the population is not in a critical phase compared to the Newell’s shearwater, which is currently in the fledgling season. This is when young birds leave the nest to learn to fly and forage, although they are still dependent on their parents for care. 

Among seabirds in the Hawaiian Islands, the wedge-tailed shearwater is one of the most numerous. It also has a wider global distribution than many other seabird species.

On Monday, 125 dead birds — 106 adults and 19 chicks — were found at a ʻuaʻu kani colony at Ninini Point in Līhuʻe.

The findings of the kill are particularly concerning, since these birds have life history traits similar to those of endangered seabirds — for example, producing only one egg

On average, these bird species do not begin breeding early. After leaving the nest, a chick will not return to breed for another 4 to 5 years. They lay only one egg per breeding season, and if that egg is lost to predators such as rats or cats, they do not lay a replacement. This results in slow population growth.

“Therefore, this is alarming,” said Dilek Sahin, project coordinator at the Kauaʻi Endangered Seabird Recovery Project.

This project is part of the Pacific Cooperative Studies Unit at the University of Hawaiʻi at Mānoa and is conducted in collaboration with the state Division of Forestry and Wildlife.

“The number of wedge-tailed shearwater birds is high, but if we keep seeing this every season, we will see a collapse in breeding and a low count in population,” Sahin said.

At Ninini Point, one dead bird was found with its egg still inside its body, indicating it was killed at the beginning of the breeding season. In addition, two chicks were found freshly killed the previous night.

“These were not isolated events,” Raine said. “Unfortunately, these kinds of reports happen on an almost annual basis and at seabird colonies all over the island.”

Raine and his team were able to examine only a quarter of the colony, making it highly likely that many deceased birds went unnoticed.

“When the adults are killed, their chicks then also slowly starve to death,” Raine said. “It now seems like the cats are also picking off any chick they can pull out of the burrows as well.”

At the site, the team discovered that the cat’s feces contained feathers.

Outdoor cats kill large numbers of Hawaiian birds each year on Kauaʻi and spread diseases such as toxoplasmosis, which also impacts humans. 

About two weeks ago, a separate incident was recorded at Mahaʻulepu Heritage Trail, along Kauaʻi’s southern coast, where at least 16 dead birds were discovered. Another 39 killed birds were discovered along the road past Spouting Horn, also on the island’s south shore.

“What is extremely frustrating is that this is an almost annual event on Kauaʻi,” Raine said of the mass killings.

While reviewing his reports, he noted that there have been “annual kills of ʻuaʻu kani at Spouting Horn for the last three years straight and kills at Mahaʻulepu Heritage Trail going back as far as 2013.”

This year, he began his report in Haʻena and continued to Kapaʻa, noting that more than nine shearwaters were killed by an off-leash dog.

Last weekend, the shearwater fledgling season began in the state of Hawaiʻi, marking a crucial time for the A’o bird or Newell’s Shearwater.

During these months, the young nocturnal birds leave their mountain burrows for the first time, journeying to the sea and guided by the stars or moonlight.

“When we think about protecting them, we need to consider the situation holistically,” Raine said, “Because the ‘Ua’u kani are also attracted to lights.”

“We also really need to increase the effort in cat control,” Sahin said. “And that’s not an easy task, so we really need public support to control and reduce the cat population, because seabirds are all across the island.”

She recommends controlling the cat population by not feeding feral cats and by reporting individuals who persist in doing so.

“We need to be focused on tackling all of these issues; it’s our collective responsibility as a community,” Raine said.

The Archipelago Research and Conservation reported the incidents to the U.S. Fish and Wildlife Service and the Department of Land and Natural Resources, providing detailed information about the birds’ location and conditions.

“The plight of the ʻuaʻu kani on Kauaʻi exemplifies the impact that cats and dogs have on Hawaiian wildlife,” Raine added. “If we don’t start taking this issue seriously, they will eventually disappear from our coastlines.”

Join Dr. Raine and his team from Archipelago Research and Conservation as they discuss the mass killing of wedge-tailed shearwater birds at the ʻuaʻu kani colony at Ninini Point in Līhuʻe.