Jabberjay

Jabberjays are a type of all male bird that were created in Capitol labs to spy on enemies and rebels of the Capitol. Jabberjays had the ability to memorize and repeat entire human conversations, and were used to gather words and information from the rebels. Once the people in the districts realized how their private conversations were being transmitted, they used the jabberjays to feed lies to the Capitol. The Capitol therefore ceased the usage of jabberjays and abandoned them to die off in the wild. Contrary to what the Capitol believed would happen, the male jabberjays bred with female mockingbirds to create a new species, mockingjays, which were able to repeat both human melodies and birdsong. They were considered a slap in the face to the Capitol, because it had failed to foresee that possibility of survival.

Catching Fire
By the 75th Hunger Games, the Capitol had replenished the jabberjay population. In the 4:00 section of the clock-like arena, the birds mimicked the screams of the tributes' loved ones, luring in Finnick Odair and Katniss Everdeen. A transparent barrier kept them inside, forcing them to listen to the torturously realistic shrieks of Annie Cresta, Primrose Everdeen, Gale Hawthorne, Mrs. Everdeen, Rory Hawthorne, Vick Hawthorne, and Posy Hawthorne. After 4:00 had passed, Katniss worried that the Capitol had tortured their loved ones to produce screams for the jabberjays to memorize, but Peeta and Beetee assure Katniss and Finnick that the Capitol had used digital or mechanical means to warp their voices into screams.

Appearance
Jabberjays are said to be visibly similar to their mockingjay descendants, which inherited their black feathers and crest.