To aim at solving problems such that since crows have a high learning capacity, conventional goods for avoiding the crows by simply irritating their eyesight and hearing sense show low effects in preventing the crows from flying in, because the crows sense the presence or absence of its warning property in a few days and accustomed to it on recognizing that there is no danger.

This bird damage-preventing tool is provided by pasting a film having black color as a ground with a red frame on a one side of an acrylic mirror, installing a seasonably adjusted angle on 2 pieces of the acrylic mirrors, irritating the eyesight, hearing sense and taste of the crows having a keen wariness by contacting sounds, complex fluctuation of sun light and mutually rotational reflection caused by natural wind, further their synergistic effects and special liquid for supplementing the dead angle of the acrylic mirrors to prevent the crows from flying in for feeding and scattering garbages.