Journal of the Holy Hieromartyr Nikon of OptinaMarch 6, 1908:

While there is time I’m hurrying to write down everything I remember. I stopped at the fact that birds and beasts have their own language, their own signs for conversation.

… “One patriarch, a man of holy life, had a deacon who constantly mocked him. The saint endured it all. Once, when the patriarch was sitting at table with many guests who had come and gathered to see him, the deacon, as usual, began to ridicule him in front of everyone. All were amazed at the impertinence of the deacon, and even more so at the patience of the patriarch. Suddenly a raven sat on the windowsill and began to caw. The deacon, laughing, asked, ‘Well, Your Holiness, tell us—what is the raven saying?’ ‘He’s saying that satan is about to snatch your soul from you.’ The saint had barely said this, when the deacon fell dead and turned black.

“You see—that means he understood what the raven was saying, or perhaps that was satan himself cawing in the form of a raven. But the saint understood this clearly; he understood this language….

Holy Elder Barsanuphios of Optina