Birdsall's first book was published when she was 54. The Penderwicks: A Summer Tale of Four Sisters, Two Rabbits, and a Very Interesting Boy introduced the Penderwick sisters and won the 2005 National Book Award.
Birdsall's first published work, "The Penderwicks: A Summer Tale of Four Sisters, Two Rabbits, and a Very Interesting Boy", was released when she was 54 years old. This book won the 2005 National Book Award.