A common image used in antique jewellery is that of a bird. Doves, swallows and owls are probably the ones we see the most.
Doves are linked to the Greek goddess Aphrodite (she is also linked with sparrows and a range of water birds) as well as being associated with a number of religions. In particular, in France in the 18th and 19th centuries, it was considered by Catholics as a symbol of the Holy Spirit. They are called Saint Esprit doves. The Saint Esprit dove was represented in diamonds and in paste, usually in flight with wings wide and hanging downwards. They usually hang from bows. Sometimes they carry an olive branch in their beaks, or gemstones of some sort. Generally, doves symbolise love and peace.
Swallows were also popular in sentimental jewellery, symbolising love, loyalty and joy. They and similar birds also appeared in mid to late Victorian jewellery from the Aesthetic period which was in turn influenced by Japonesque arts. Lightly etched small birds, flowers, bamboo and fans appeared on silver jewellery as seen in the silver locket below.
Another popular bird represented in charms is the kingfisher or, if the charm was made in Australia, the kookaburra. The bird charm below is probably meant to be a kingfisher as it has UK hallmarks. There is probably no symbolism around using the image of these birds as charms other than generally as a lucky charm. Of course, if you search online for the symbolism associated with kingfishers (and many other birds and animals), there will be numerous web pages giving different meanings but it is difficult to find any evidence supporting most of these suggestions.