Little birds

Little birds are spies and agents in the service of Varys, master of whispers on the small council. It is these "little birds" that provide Varys with his seemingly inexhaustible supplies of information.

Season 1
Varys tells Catelyn Stark that he has "little birds" all over the continent, even in the North, and they whisper to him interesting stories all the time. He is already aware of the Valyrian steel dagger that was used in the attempt on Bran's life, and knew that Catelyn and Ser Rodrik Stark were coming.

Whilst walking in the Red Keep's gardens, Littlefinger identifies several of Varys's "little birds" to Eddard Stark, most notably several children.

One of Varys's "little birds" even works in Vaes Dothrak. A young boy, this agent gives Ser Jorah Mormont a letter of pardon from King Robert Baratheon for his part in reporting on the movements of Daenerys Targaryen and he tells him he can go home. Ser Jorah is tempted, but relents and decides to remain true to Daenerys, helping thwart an assassination attempt on her.

Season 2
Varys, aware that Petyr Baelsh has mistreated Ros since she came into his service, offers Ros a chance to work for him as a spy.