Trauma from vehicle collisions caused the majority of documented deaths for the Pueo (Hawaiian short-eared owl), according to a statewide study led by researchers at the University of Hawaiʻi at Mānoa. The findings represent the most extensive mortality assessment to date for this culturally significant raptor, which is native to the Hawaiian Islands.
The study was conducted by the Department of Natural Resources and Environmental Management (NREM) in the College of Tropical Agriculture and Human Resilience (CTAHR). Researchers analyzed 32 years of records (1993–2024) from 10 organizations across the islands.
Researchers compiled 242 documented Pueo mortalities and found that trauma accounted for 62% of deaths. Within those cases, two-thirds were linked to vehicle collisions or occurred in close proximity to roadways. 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, an NREM professor and senior author of the study. "Reducing vehicle collisions and increasing awareness about rodenticide use can help all of us support Pueo conservation. This work is dedicated to University of Hawai'i alumnus Stephanie Bell, whose work on this project for her undergraduate senior thesis made this statewide assessment possible."
Complex factors in wildlife deaths
While trauma was often the immediate cause of death, researchers noted that many birds suffered from underlying health issues, 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 noted, "This study adds to a growing body of research that indicates many native bird species in Hawaiʻi 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."
The study provides the first statewide synthesis of Pueo mortality, identifying critical areas for future research and conservation action. While the number of reported mortalities has increased over time, researchers suggested this could reflect improved reporting efforts, more cars on the road or faster driving speeds. A statewide assessment of Pueo population size is a critical next step to understand how this level of mortality might affect the population over time.
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