Theory:

"The Legend of Northland" is a poem written by Phoebe Cary. It is a ballad that narrates a legend from the Northland where greed and selfishness in a human were adequately punished.

The speaker begins her narrative by claiming that the story she is about to narrate is famous in the Northland, where the nights are considerably longer and colder during the winters. To keep the kids warm and engaged, the adults tell them the story. The speaker observes that the story is unlikely to be true but believes that it has got a good lesson to impart. Having said this, she begins with her narrative.

Once upon a time, when Saint Peter was travelling across the world preaching and teaching, he came across a cottage where a woman was baking cakes. Since the saint was too weak and hungry and felt faint due to the fasting he had observed, he requested the woman to give him a cake. Though she had a pile of freshly baked cakes, she couldn't choose one from them because they seemed too large to be given away. Hence, she decided to bake a smaller one. She took a small piece of dough, but she decided it was too large to be given away as it rose in the oven. She tried twice more with less dough each time, but she couldn't make a cake small enough. As a result, she refused to hand over anything to the famished Saint Peter. Eventually, her actions provoked the saint, and he turned her into a woodpecker as she was too selfish and undeserving of having the comforts of a human.

The speaker concludes the narrative by saying that the bird with a black body and scarlet head can be still seen in the wood where she keeps "boring" for food.