Hawky

Hawky was Sokka's pet messenger hawk. Although Sokka referred to him as a lazy bird, there was no evidence of that being so, since he delivered all messages requested from him in a decent radius without any training. Hawky had something of a short-lived rivalry with Momo, as the two frequently got into fights. Though a new addition to the group, he seemed quite loyal to Sokka and apparently understood his speech.

History
Sokka bought Hawky in the Fire Fountain City with the money Toph had obtained through her scams. He had hoped to send messages to his Gran Gran, as well as other far-off friends and relatives. However, the bird refused, indicating this by shaking his head at the suggestion of flying to the South Pole.

When Katara and Toph weren't talking to each other after a spat about Toph's scams and Katara's motherly nature, Sokka came up with an idea to smooth things again between the two girls and test out his new messenger hawk. He used Hawky to send an apology letter "from Toph" to Katara, however, she immediately realized it was fake, due to the fact that Toph couldn't write. Aang suggested to use the messenger bird again, this time sending a letter to Toph saying it was "from Katara", but Sokka immediately rejected the idea, saying that they would "run into a similar problem."

After Team Avatar left Fire Fountain City and Toph and Katara made amends, Toph asked Katara for help with sending a letter to her parents; Katara wrote down what Toph dictated and the girls sent Hawky on his way, apparently without Sokka's consent as he inquired where Hawky was as the bird left for Gaoling.

Hawky never returned to the group after delivering Toph's letter, and it is assumed that he found a new home at the Beifong Estate.

Trivia

 * Hawky and Momo's enmity may be a holdover of Zuko's hawk in the unaired pilot.
 * It is unclear how Hawky found Toph's parents. Homing pigeons, which messenger hawks were based on, could only return to a location they have memorized and consider "home".