Worms are nocturnal, so they prefer to come out at night. If you are a bird, therefore, you have to get up early to catch them. In the proverbial sense, this means “Don’t delay going for your goals; get there before someone else beats you to it.”
The Germans have adopted the English idom: “Der frühe Vogel fängt den Wurm”. However, many Germans are not aware of the fact that this is a literal translation that has only been used since the 80s and has often replaced older synonyms such as “Morgenstund hat Gold im Mund” and “Wer zuerst kommt, mahlt zuerst”.