After the 1st of April the tide of migration sets in with force, and the earlier waves bring several species of summer birds--those that come to build and breed in our woods--that rarely if ever make their appearance before this time. It is an interesting fact that none of the migrants that make their first appearance in April are ever found in the Delaware Valley during the winter, though several, if not all, of the species that come on the March waves are occasionally met with in the winter months. It appears, further, that the winter quarters of certain birds which are summer residents with us and some that are transient, passing on to more northern breeding grounds, lie not so very far to the south. If the last of March has been marked by warm weather lapping over into the first days of April, then one may expect soon to hear the familiar notes of the chipping sparrow from the swelling branches of garden shrubbery and the trees about the lawn, and a brown thrasher is sure to be heard volubly proclaiming his arrival from some near-by tree top. Among the budding sprigs of thickets the elusive chewink breaks into occasional fragments of song, and from the red-blossomed maples and the jungle of pussy willows and alders that fringe the meadow brook the metallic creaking notes of the red-winged blackbirds sound not unpleasingly. This jargon of the red-wing has a true vernal ring about it, suggesting the fresh green of oozy bogs and the loosening up of sap. From the middle to the last of April there are several big waves of migration that bring many of the summer residents as well as some transient species, forerunning the greater waves that are to follow in May. On certain warm April days the barn and the bank swallows appear, and the chimney swifts are seen scurrying to and fro above the trees and house tops. These are genuine signs of the coming summer, for swallows and swifts feed only on the minute gnats and other ephemera that develop under conditions of warm temperature. Whoever knows of a martin box that year after year is visited by its colony has an unfailing source of delight at this time in watching the lovely birds. The martins are very prompt in their arrival, rarely coming before the 1st of April nor later than the 10th. We are aware for the first time that the house wren has come back by the voluble song that greets us some morning from the branches just beyond our window--a song that only the lover of his own rooftree can fully appreciate, for the wren's chant, more than any other bird song, seems to voice the home instinct in a man. By the last week of April the woods are fast closing up their vistas in a rich profusion of unfolding leafage. The umbrellalike leaves of the May apple are scattered everywhere through the woods and fields, forming conspicuous patches of green. During this last week of the month a few straggling thrushes make their appearance--the hermit thrush with its russet tail, the veery, and the wood thrush.