As the temperature begins to warm and the ground begins to thaw, earthworm casts appear, heralding the return of the robins. For this reason, the March full moon is often known as the Full Worm Moon.
Northern Native American tribes knew this moon as the Full Crow Moon when the cawing of crows signaled the end of winter. They also used Full Crust Moon because the snow cover became crusted from thawing by day and freezing at night.
The Dakota Sioux named it Moon When Eyes Are Sore From Bright Snow. The Full Sap Moon, marking the time of tapping maple trees, is a Colonial American variation. To the settlers, it was also known as the Lenten Moon. It was considered to be the last full moon of winter.