Is Caging Bird Cruel?

Have you ever seen a bird in cage? Surely, most of you have ever seen it. But, have you ever thought that there was something strange with that? Yes I have. Somehow, I feel compassion for the bird. The bird is caged and can't fly as it should be.  

Recently, I've read a book titled "Etika Lingkungan Hidup" (or Environmental Ethics). One of the chapter on the book discuss about nature rights. Basically, the nature rights are similar to human rights. Two basic human rights are right to life and liberty. It means nobody can try to end your life. Liberty right means you have freedom of opinion, speech, and expression. In more details, the writer divides freedom rights into two types, physically and mentally. Physically freedom is ability to do something using the body. Meanwhile, mentally freedom is the ability to use mind to do something.  Therefore, human freedom shouldn't be restricted, either physically or mentally.

As well as animals, they have rights too. They have also freedom rights either physically or mentally. Written in the book, any physical restriction, whether it is confinement, disturbance to habitat, physical torture, is a violation of animal rights. Thus, a bird in cage include in that form I guess.

So what do you think about it? What's your opinion? My opinion is only viewed in one side, namely animal rights. If you disagree with my opinion, of course you can share it. Maybe you will think that caging birds isn't form of right violence as long as you take good care of the bird. My opinion is only based on one reference. So, if you have a lot of references, you can share your opinion to enrich our mind.