There may still be some snow on the ground when mourning cloak butterflies begin flying. If it is cold, they will bask on dark surfaces to warm their flight muscles / Spring peepers begin peeping in earnest. Isolated peepers will peep from now until November, but only now is there a deafening chorus / Turkey vultures are arriving from parts south. They ride storm fronts, sometimes gliding four miles high / Mourning doves are cooing away at the crack of dawn

Male winter wrens returning now are extremely vocal. The soon-to-come winter wren nests will be hidden among the roots of overturned trees / Female spotted salamanders hold their fertilized eggs for several days before depositing them in large spherical masses / As soon as snow melts from the bases of trees, hepatica will flower. The delicate pink or lavender flowers look too fragile to withstand harsh April weather / Look for ospreys along big rivers

While the weather may still be conducive to sap flow, by now the sugar content of maple sap is usually below 1 percent. At 1 percent, it takes 86 gallons of sap to produce a gallon of syrup. Time to quit boiling / Barn swallows may be returning, somewhat earlier than was normal 20 years ago / Bears have left their dens but will continue to lose weight until succulent vegetation becomes available. Wetlands are important because they green up early

Moose hair is in raggedy patches, for they are molting their thick winter coats / Porcupines are successful animals, even though each female gives birth to only one offspring per year. The babies are born from April to June, usually in tree cavities or fissures in rock outcrops / Listen for the first evening songs of the hermit thrush / Balsam shootboring sawflies, a bit larger than blackflies, may be abundant in Christmas tree plantations at midday if it is warm