On my walk this morning at sunrise, I heard the cardinal singing, and then, for the first time this season, I was able to see him up high in the trees.  There is a symphony of birds each morning, that has been going on for a couple weeks–since around Groundhog Day actually.  I read that birds have photoreceptors in the bases of their brains that record the length of the dark period each day. As the darkness shortens, and as days lengthen, birds get spring fever.  Just like us.  So their songs signal that spring is just around the corner.  Or at least that we are halfway there.  Maybe we in Maine should call Groundhog Day, “Bird Song Day” instead.