A Bestiary reflected the belief that the world itself was the Word of God, and that every living creature had its own special meaning. Some of the information on this page, about the Blackbird, is taken from the Aberdeen Bestiary which was written in the 12th Century.
The Definition and Meaning of the Blackbird as a Religious Christian Symbol - Allegory and Moral
The blackbird represents those who are tempted by carnal pleasures. The blackbird in flight represents the temptation to desire. To reject the desire symbolised by the blackbird, you must discipline yourself and thus rid yourself of pleasures of the mind by inflicting pain on your flesh. A white blackbird represents purity of will.