A Thrush was part of the key to opening the secret door of the Lonely Mountain. The Moon-letters Elrond read out in Rivendell said 'Stand by the grey stone when the Thrush knocks'.

During the Quest of Erebor, a Thrush overheard Bilbo’s conversation with the dwarves, and learned from this that Smaug the Dragon had an uncovered patch on his left breast. Later it passed this message to Bard the Bowman as Smaug attacked Esgaroth, and Bard slew the Dragon.

There were many birds that knew the language of Elves and Men and Dwarves in Middle-earth. However there used to be an ancient breed of Thrushes that had an alliance with Men and Dwarves in Dale and Erebor.

The men of Esgaroth and Dale could understand the Thrush language, and often used them as messengers.