The term "yardbirds" refers to a group of people who work in a shipyard or railroad yard. It's often used in a derogatory sense to describe low-level workers. There are several synonyms for "yardbirds" such as grunt, peon, lackey, menial, or flunky, which are often used to describe people who are at the bottom of the hierarchy and perform basic tasks. The use of these words can be seen as derogatory, as it implies that the work they perform is of low importance or value. While these terms may be accurate in describing certain types of workers, it's important to remember that everyone deserves respect and appreciation for their contributions.