As part of a project to introduce avian predators for biological pest control, we used hard and soft release methods to introduce Barn Owls (Tyto alba) in the urban area of Universiti Sains Malaysia in Penang, Malaysia. We tested five methods: (1) hard release of non-acclimated adults, (2) hard release of non-acclimated juveniles, (3) soft release of hand-reared fledglings, (4) soft release of acclimated juveniles, and (5) soft release of acclimated adults. We employed radio-tracking to analyze the success of all methods, and the movement and survival of some of the released birds. We analyzed regurgitated pellets to study the diet of the successfully introduced owls. All hard-released non-acclimated adults and non-acclimated juveniles left the study area within a few days after their release. Soft release of hand-reared fledglings was also unsuccessful, as we could only detect the radio-tracked owls for ≤10 d after their release. Of the nine acclimated juveniles that were soft released, one stayed within the study area for 25 d but eventually dispersed. The soft release using acclimated adults was the most successful release method, as 60% (3 of 5 birds) of the released owls were tracked for >30 d and became established as resident birds in the study area. We observed these adults roosting and hunting prey within the study area. Analysis of regurgitated pellets showed the resident Barn Owls preyed primarily on small mammals. Our results suggest that the most suitable method to introduce and establish Barn Owl populations in an urban area was by using soft release of acclimated adults.
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Vol. 54 • No. 3