many features — such as feathers, wishbones, egg brooding, and perhaps even flight — that are seen only in birds among living animals first evolved in the dinosaurian ancestors of birds (Figures 4 and 5). Other features, such as rapid growth, a keeled sternum, pygostyle, and beak, are absent in the earliest birds and evolved,…

About 50% of all bird species migrate. 2 main patterns – long lived, soaring types e.g. Geese, who go in groups (better aerodynamics), and who learn routes from elders. Else flapping songbird types, who go alone, with no prior knowledge of route. Enormous physiological changes, weight can almost double, reproductive organs atrophy, flight feathers may…