Brooches were used as practical accessories to help keep cloaks, trousers and other pieces of clothing fastened. The accessories were status symbols with many brooches being made of expensive materials. The more elaborate the deign also indicated the status of the wearer. Zoomorphic brooches were a common theme and birds-in-flight make up a large proportion of the examples found. Celtic brooches usually portrayed animals that held a religious or superstitious meaning.
For more information on ancient Roman animal symbolism, please see our blog post: Animal Symbolism in Roman Art