A old video of ours showing the body language to look for when potentially introducing a new caique to an established parrot/flock. These two are safely separated by an acrylic carrier in the video.
This body language is a dead giveaway that one or both caiques are stressed/angry/highly aggressive – ruffled feathers, pulled back wings/shoulders, fanned tail feathers, growling, etc.
This is Marley and Pogo – two of our male caiques that will likely never get along – and if they were allowed access to one another, one or both would likely be seriously injured – or potentially even killed.
Have a caique acting like this when it is near another parrot? Separate them immediately, and do not permit them access to each other.