This work describes the main aspects of bird ecology and conservation in two sections. The first focuses on evolutionary and behavioral aspects related to their origin, feeding, reproduction, habitat and migration. Each topic is illustrated with a variety of well-founded examples from the scientific literature and high-quality colourful images. The second addresses the conservation status of birds, from extinct species to those currently threatened. A thorough analysis is made of the main causes that have led to the disappearance of a variety of them and have caused the reduction of their populations. In addition, research and conservation efforts aimed at reversing the critical state in which many bird species are found today are described.