As the temperature begins to warm and the ground begins to thaw, earthworm casts appear, signaling the return of the robins. The more northern tribes knew this Moon as the Full Crow Moon, when the cawing of crows signaled the end of winter; or the Full Crust Moon, because the snow cover becomes crusted from thawing by day and freezing at night. The Full Sap Moon, marking the time of tapping maple trees, is another variation. To the settlers, it was also known as the Lenten Moon and was considered to be the last full Moon of Winter.
This time of the year, the sunlight is getting stronger, temperatures are slowly rising, and the frozen ground begins to thaw. You can tell the worms have begun to come awake when you find the little curly mounds of dirt on the ground. These mounds, or castings are part of nature's way of preparing the Earth for new growth. Then the flowers and herbs and trees and green grass suddenly burst out and let us know Spring is here.