They're birds from home, the product of a mockingbird and a jabberjay. The jabberyjay is a muttation, a Capitol creation, and one that failed to do what it was supposed to. Despite the Capitol's attempt to destroy them all, they lived on and even bred a new species of bird.

The situation in your world just reminded me of the jabberyjays and mockingjays, living on despite all attempts to wipe them out.