What is the purpose of a bird's mouth in rafter construction?

The purpose of a bird's mouth in rafter construction is to create a secure fit against the top plate. The bird's mouth cut is a notch made in the rafter that allows it to rest snugly on the top plate of the wall. This connection is vital for the structural integrity of the roof, as it ensures that the weight of the roof is evenly distributed across the walls of the structure. By providing this secure fit, the bird's mouth helps prevent movement or shifting of the rafters, which might occur due to environmental factors like wind or snow load. This connection is essential for maintaining the overall stability and durability of the building.