How do you explain the term "shooting birds" in the SLR world?

"Bird shooting" means using a telephoto lens for telephoto shooting.

Using a telephoto lens to shoot distant scenery is so called because it requires a high degree of physical stability on the part of the photographer and is similar to shooting with a rifle. Although it is called "bird shooting", the subjects of the photos are not necessarily birds, but can also be wild animals, celestial bodies, people or other things.