Jabberjays are a type of muttation that consist of all male birds that were created in the 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, before they became extinct, 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.
By the 75th Hunger Games, the Capitol had replenished the jabberjay population. In the 4:00-5:00 sectiothehungergames.wikia.com the birds mimicked the screams of the tributes' loved ones, luring in Finnick and Katniss. A transparent barrier kept them inside, forcing them to listen to the torturously realistic shrieks of Annie Cresta, Prim, Gale, Katniss' mother, Madge, 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, from the words said in the final 8 interviews with the remaining tributes' families.
Jabberjays are said to have black feathers and white crest.