Neville, our house rabbit, says:
"Jealousy. I haz it."
We have a different model of this same cage for him, just a little smaller and closer to ground level so he can come and go easily. Poor little guy. Between the bigger cage and the scent of the rabbit that used to live in it, I am sure he thinks he is going to get replaced at any moment. He'll get over it once I get my birds though. :)