Jabberjays were a type of muttation that consisted of male birds created in the Capitol labs by Dr. Kay to spy on rebels and other enemies of the Capitol. Jabberjays had the ability to memorize and repeat entire human conversations, and were used as spies, to gather words and information from the rebels. While in record mode, they were silent, but in neutral mode, they acted like normal birds. 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.
By default, jabberjays were set on "neutral." This meant that if they heard a human voice, they would repeat it, but would quickly move on to something else, such as another voice or a snatch of birdsong. Before the end of the First Rebellion, the jabberjays were all released into the wild on neutral. In order for them to work for spying, they had to be placed on "record." In this mode, the bird would fall entirely silent and stay at attention until was placed back on "neutral." Once this was done, another command could be executed to get to recite everything that it had recorded. All three commands were accomplished using tones which were inaudible to human beings, but easily registered by the birds. On a good day, a single bird could record for up to an hour.
The Ballad of Songbirds and Snakes
While he was a Peacekeeper in District 12, Coriolanus Snow and other Peacekeepers were assigned the task of catching 50 jabberjays and 50 mockingjays. The jabberjays were relatively easy to catch, and despite being ten years since the remote controls that controlled whether the birds would be on record mode or neutral mode were used, they still worked. Dr. Kay displayed this to Coriolanus by recording their conversation and playing it back. Coriolanus felt comfort in knowing that Dr. Kay had also been a public failure for creating the jabberjays. Dr. Kay also revealed that during the First Rebellion, the Capitol sent the jabberjays back to the laboratory at the dead of night so no one would notice.
Coriolanus used a jabberjay to record Sejanus Plinth admitting his escape plan, and he worried whether Sejanus would notice why the bird was so silent. When the 100 birds were sent to the Capitol, Dr. Gaul had caught the recording, which led to Sejanus' arrest and execution.
By the 75th Hunger Games, the Capitol had replenished the jabberjay population. In the 4:00-5:00 section 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, Katniss' mother, Madge Undersee, and Gale, Rory, Vick, 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 Mellark and Beetee Latier assured Katniss and Finnick that the Capitol had used digital or mechanical means to warp their voices into screams, their voices being taken from the words said in the final 8 interviews with the remaining tributes' families.
Jabberjays are said to have black feathers and white crest. They also have white tips on their wings.