A decided wave of rising temperature usually reaches the Delaware Valley from the middle to the last of March, maintaining itself longer than the February rise, and ushering in a well-marked bird wave. It is about this time that the vanguard of the robin migration scatters over the country. The grackles or crow blackbirds, which have been more or less in evidence since their first appearance in February, begin renovating the old nests or laying the foundations of new ones in the tops of tall pines. The shrill call of the flicker sounds through the woods, and before the end of the month one is sure to hear the plaintive song of the field sparrow. This is about the time that the spicebush shows its yellow blossoms through the grays and browns of the spring underwoods, and the skunk cabbage unfolds its fresh, green leafage in rank abundance along the boggy course of woodland rills. A week earlier the streaked yellow and purple of its fleshy spathes shows here and there in the oozy ground by the side of the folded leaf spikes. It is just at this time, too, that one must go to the woods for the first spring wild flowers--bloodroot, hepatica, anemones, and the yellow dog-tooth violet--if one would get the real freshness of spring into his soul. The crows, that all through the winter filed away each evening in straggling lines of flight toward the distant roost, have broken ranks, and go rambling in small groups through the woods and over the fields of green winter wheat. Like the grackles, they have thoughts of courtship and the more earnest business of family cares. The liquid notes of meadow larks sound clear and sweet in the greening fields and pastures, and small flocks of vociferous killdeers scatter in wheeling flight over the newly plowed lands. In tangle covers the rustle of dead leaves here and there tells of the whereabouts of a flock of fox sparrows halting in their northward pilgrimage. The pewee is back, inspecting her last year's house under the span of some old bridge, and the melancholy voice of the dove is borne on the air from the fence rows and cedars along the farther side of fields.