Why are birds fast when they fly?

Birds are not inherently fast when they fly. Some bird species, such as swifts and falcons, are capable of reaching high speeds during flight, but many other species fly at relatively slow speeds. The speed of a bird in flight depends on several factors, including its size, wingspan, and wing shape, as well as its flight style and the purpose of its flight. For example, some birds, such as hummingbirds, hover in place while flapping their wings rapidly, while others, such as eagles, soar at slower speeds on long, broad wings.