As part of a biological control program against rat (Rattus spp.) populations in oil palm plantations, Barn Owls (Tyto alba javanica) were translocated from Peninsular Malaysia and released in an oil palm plantation in Lahad Datu, Sabah, Malaysia, on the island of Borneo. We installed 16 nest boxes every 25 ha at the study site and monitored those nest boxes monthly from June 2014 to June 2018 to assess Barn Owl breeding parameters. We collected regurgitated pellets from nest boxes to analyze the prey of the owls. Average nest box occupancy rate throughout the entire study period was 66.7% (±6.1). Nest box occupancy was lower in the first year of the study (average occupancy rate 23% ± 3.6) but increased significantly in the following years. We recorded 84 successful breeding attempts and a total of 555 eggs throughout the study period; 61% of eggs hatched and 60% of eggs produced young that successfully fledged. Clutch size per laying pair ranged from 1 to 9 (average = 5.6) and the brood size at fledging ranged from 1 to 7 (average = 4.0). Diet of the Barn Owls consisted of only small mammals; rodents made up 99% of analyzed pellets, and shrews accounted for 1%. There has been no previous record of Barn Owls naturally occurring in Borneo and this is the first breeding population successfully translocated and established.

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