In the age old Heritage site of Qutub Minar, In New Delhi, lies a well. Inside the well many pigeons have nested and they live there peacefully. They fly through the bars which are made so that no person can enter.
The rock pigeon is the world’s oldest domesticated bird. Mesopotamiancuneiform tablets mention the domestication of pigeons more than 5,000 years ago, as do Egyptian hieroglyphics.-WikiPedia
Pigeons have made contributions of considerable importance to humanity, especially in times of war. In war the homing ability of pigeons has been put to use by making them messengers.
Many domestic birds have escaped or been released over the years, and have given rise to the feral pigeon. These show a variety of plumages, although some look very like the pure rock pigeons. The scarcity of the pure wild species is partly due to interbreeding with feral birds.-WikiPedia
Many birds have double eyelids, one upper and the other lower unlike we humans. Some of them also have a transparent or translucent third eyelid called Nictitating Membrane which they use for cleaning their eyes and its protection.