Hungry Hen by Richard Waring, illustrated by Caroline Jayne Church

From chapters.ca:
There once was a very hungry little hen, and she ate and ate, and grew and grew, and the more she ate, the more she grew. Up on the hill lives a cunning fox. He watches the hen every day and thinks, "If I wait just one more day, the hen will be even bigger."
Then one day he can't wait any longer...