In birding, a Big Year is when a person starts on January 1st and spends the year listing as many birds as they can for one year. While there is no prize invovled it is very competitive for the participants, who become obsessed with having as big a list as possible. While this can involve many people, this book concentrates on the activities of 3 people to tell the story. This was made into a movie, which I have not seen.
