The impact of an introduced avian predator, the Barn Owl Tyto alba, on Hawaiian seabirds

The Barn Owl Tyto alba was introduced to the Hawaiian Islands in the late 1950s as a biological control for rats Rattus spp. and has since become common throughout the main Hawaiian Islands. Herein, we address the impact on Hawaiian seabirds by summarizing the number of seabird depredations recorded in the database of the Kaua'i Endangered Seabird Recovery Project. Data were collected on Kaua'i and the neighboring islets of Lehua and Moku'ae'ae between January 2011 and October 2018 as part of ongoing seabird survey work; 379 Barn Owl depredations were recorded of eight seabird species, the most common of which were Wedge-tailed Shearwater Ardenna pacifica, Black Noddy Anous minutus, and Bulwer's Petrel Bulweria bulwerii. Included were 21 depredations on federally listed Newell's Shearwater Puffinus newelli and Hawaiian Petrel Pterodroma sandwichensis. Most depredations were on adult birds. The effectiveness of Barn Owl control was also evident, with depredations on Lehua Islet decreasing significantly after dedicated control operations were initiated. Barn Owl control should be considered as an integral part of all Hawaiian seabird management programs.