why is the 12 days of christmas about birds

The 12 Days of Christmas is a traditional English Christmas carol that is widely known and sung. The lyrics refer to a series of gifts given to the singer by their "true love" over the course of 12 days, culminating in the giving of "true love" on the last day. While the lyrics of the song mention various birds, such as partridges, calling birds, and swans, the song is actually about the celebration of the birth of Jesus Christ and the giving of gifts in his honor.