Hawaii’s Barn Owl
By Arleone Dibben-Young
The Barn Owl (Tyto alba) was introduced to Hawaii in April, June and October 1958 to control rodents. A total of 15 birds were imported from California by the state Department of Agriculture and released at Kukuihaele on Hawaii Island. Over the next five years, an additional 71 owls were introduced on Kauai, Oahu, and Molokai on Molokai Ranch lands. The Barn Owl is often mistaken for the pueo or Hawaiian Short-Eared Owl (Asio flammeus sandwicensis). A few differences are easily perceivable, however: the Barn Owl is golden-buff in color, while the pueo is dark brown and about half the size. Barn Owls are nocturnal while the pueo is largely diurnal and hunts during daylight hours. Both species are ground nesters.
In the early 1990s, Barn Owls in Hawaii were fitted with transmitters to determine their movement patterns and home ranges. It was ascertained that Barn Owls maintain fairly small, short-term home ranges, suggesting that they move into new areas and re-settle due to food availability. During the study, the stomach contents of 28 Barn Owls were analyzed and it was discovered that their diet was mainly insects (64 percent), rodents (18 percent), and grass. It was originally expected that because Barn Owls are very efficient hunters and have the ability to locate prey by sound alone, that the species would reduce rodent populations. However, intensive studies conducted in Hawaii indicate that this species has done no more in controlling rodents than mongooses.
The Barn Owl is the most widespread owl species in the world and occurs on every continent except Antarctica. They are short-lived, with a life expectancy of one to two years, although the oldest known Barn Owl in North America lived to be 11 years, 6 months. Trauma is the most significant cause of mortality (50 percent), followed by infectious disease (25 percent) and starvation (20 percent – mostly young birds most likely displaced by adults with an established territory). Barn owls are not federally threatened or endangered in the U.S., but are protected under the U.S. Migratory Bird Treaty Act and under CITES Appendix II, and in Hawaii by state wildlife laws.