Little birds

"My little birds are everywhere."

- Varys

Little birds are the members of a network of spies and informants in the service of Varys, the Master of Whisperers on the small council of the Red Keep. Many of Varys's "little birds" are seemingly innocuous street children, although of course adults are counted amongst their ranks as well.

Varys's network spans not only the length and breadth of Westeros, but also Essos as far east as Vaes Dothrak and possibly even Qarth.

Season 1
Varys informs Catelyn Stark that he has "little birds" all over the continent, even in the North. 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 Cassel were coming to King's Landing.

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

A young boy reaches Ser Jorah Mormont at the market at Vaes Dothrak, gives him a letter of pardon from King Robert Baratheon for his reports on the movements of Viserys and Daenerys Targaryen, and informs him he can go home. The letter clues Ser Jorah that an assassination attempt against Daenerys is imminent.

Season 2
Shortly before the Battle of the Blackwater Varys's little birds bring him tidings from the edge of the Known World: Daenerys Targaryen still lives, and has hatched three dragons.

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

Season 3
Ros continues to act as one of Varys's little birds, informing him of Littlefinger's plan of taking Sansa Stark with him to the Eyrie. Ros's arrangement is eventually discovered by Littlefinger, who then sells Ros to Joffrey for target practice before Varys can protect her.

Season 4
In a meeting of the Small Council, Varys informs Tywin that Daenerys has come to power in Meereen and is growing stronger, with three dragons, two experienced knights at her side, and a powerful army behind her. While Cersei merely brushes these off, a more concerned Tywin decides to deal with her. He enquires of Varys whether his little birds can find their way into Meereen. Varys assures him that they can.

Later, a young boy approaches Ser Barristan Selmy in Meereen and presents him with a letter. Barristan reads the letter and discovers that Ser Jorah Mormont was reporting Daenerys's activities to Varys.

Season 5
Many weeks after losing Tyrion in Volantis, Varys presents himself to the Imp in Meereen. He explains that his little birds sing in the east as well as the west, and he was thus aware that Tyrion had reached the city and become Daenerys's new advisor, exactly as Varys had intended. The Spider then implies that he will put his little birds to use helping Tyrion enforce the Queen's peace in Meereen.

Season 6
While investigating the Sons of the Harpy with Tyrion, Varys determines that the Sons must have a leader and confirms that his little birds are already aflutter.

Varys's little birds eventually enable him to locate Vala, the prostitute who has been helping the Sons of the Harpy prey upon the Unsullied. After dealing with her, Tyrion asks Varys if his little birds can infiltrate Yunkai, Astapor, and Volantis, the three cities now arrayed against Meereen. Varys assures him that they can. Back in King's Landing, Qyburn, the new Master of Whisperers, is busy co-opting Varys's little birds (at least those in the capital) for himself. Like Varys, he is kind to the children, asks after their families and gives them sweets, simply asking for whispers in exchange.

In the books
In the A Song of Ice and Fire novels, at least some of Varys' "little birds" have had their tongues cut out (though Varys himself did not cut them out). After Qyburn's appointment to Varys's position on the Small Council, the failed maester boasts that he has easily taken over Varys's network, since most of the little birds are eager to be rewarded for their information, regardless of who the Master of Whisperers actually is. Nonetheless, Varys himself remains at large.