Large-billed Crows Corvus macrorhynchos are often inhabit close to human. They cause problems such as invation to livestock barns, agricultural damage and scattering garbage at trash repositories. To know the appropriate mesh size of nets to prevent invation of crows, we investigated the minimum size of mesh that crows could pass by individual testing. Although the minimum mesh size of net was 13 cm in the spontaneous entering experiment, all four tested individuals passed to 10 cm mesh net, three of four passed 9 cm mesh net and one passed 8 cm mesh net in one of two trials in the compulsory passage experiment. No individuals passed 7 cm mesh net. These suggest that 7 cm mesh nets can prevent passage of Large-billed Crows, and 8 cm mesh nets are practical as protection nets for livestock barns, orchards and trash repositories as they can prevent crows' invation mostly. The commercial welded wire mesh was not passed by all tested individuals at 10 cm pitch because the line is solid, but 7.5 cm pitch was recommended to ensure the prevention.

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