The budgies, Winter (female) and Piper (male) are in their own flight cage. Since Emma has been sitting on her infertile eggs, Silver (male cockatiel) occasionally visits the budgie cage, clinging to the side bars.

My impression originally was that Silver and Winter didn't care for each other. But, lately, it seems as though Piper considers it his "job" to keep Winter away from Silver. It's fun to watch. Piper chats to Silver from the long perch. Winter then comes across on the same perch to join in. Piper chases her away, then goes back to Silver. It happens over and over again for several minutes. Sometimes, Winter ends up upside down on the perch while Piper stands over her and bawls her out. Eventually, Silver gets bored and goes off to do something else.

I wonder whether Piper is beginning to see Winter as his mate and wants to keep her away from Silver. But, he's not particularly aggressive toward Silver.

That might be what he's doing!