A pueo owlet too young to fly waits for its next feeding in wetlands near Kailua, Oahu. Photo courtesy Javier Cotin

Vehicle collisions are the leading cause of documented deaths for the pueo, or the Hawaiian short-eared owl, according to a statewide study led by researchers at the University of Hawaii at Manoa.

Described as the most extensive mortality assessment to date for the culturally significant raptor native to the Hawaiian Islands, the study reviewed records containing data from 1993 to 2024 from 10 organizations across the state.

Researchers compiled 242 documented pueo deaths and found trauma accounted for 62% of them. Within those cases, two-thirds were linked to vehicle collisions or occurred close to roads.

Wind turbines represented 13% of trauma-related deaths, while other identified causes included emaciation and disease.

“Our findings highlight that many Pueo deaths may be preventable,” said Melissa Price, senior author of the study and an associate professor in the University of Hawaii’s College of Tropical Agriculture and Human Resilience. “Reducing vehicle collisions and increasing awareness about rodenticide use can help all of us support Pueo conservation.”

Price said pueo are especially active in the morning and evening and often hunt along roadsides.

“Pueo are very active in the evening and the morning,” she said. “So as you’re driving along, if you keep a good eye out for wildlife, you can minimize the chance of hitting them with your car.”

While trauma was often the immediate cause of death, researchers said many birds also had underlying health problems, including parasites, emaciation or suspected exposure to rodenticides.

“Wildlife mortality is often complex,” said Thierry Work of the U.S. Geological Survey, a collaborator on the study. “Perhaps owls are more likely to forage along roadsides because that is where prey are easily available, or other underlying conditions increase their risk of collision. Without systematic necropsies and toxicology testing, it can be difficult to untangle these contributing factors.”

U.S. Fish and Wildlife Service biologist Olivia Wang said the study adds to a growing body of research showing that many native bird species in Hawaii are killed by vehicle and infrastructure collisions.

“Understanding the magnitude of impact of these threats helps us identify areas to target management and outreach efforts so we can minimize and mitigate the various threats Pueo face,” Wang said.

Researchers said the number of reported pueo deaths has increased over time, though that could reflect improved reporting, more cars on the road or faster driving speeds. They said a statewide assessment of the pueo population is needed to better understand how mortality is affecting the species over time.

Price said residents can also help protect pueo by keeping cats indoors because pueo nest on the ground.

“Pueo are ground nesting birds, and so those nests are vulnerable to things like cats,” she said. “So, keeping your cats indoors is another way that you can help protect our Pueo.”

The study was conducted by the Department of Natural Resources and Environmental Management in UH Manoa’s College of Tropical Agriculture and Human Resilience.