In southeastern Pennsylvania there comes a day in February that brings with it an indefinable sense of joyousness. A southerly wind wanders up the Delaware with a touch of the spring in its air that quickens, for the first time, the slumbering life. It is then that those mysterious forces in the cells of living things begin their subtle work--hidden in the dark, underground storehouses of plants and the sluggish tissues of animals buried in their winter sleep. On such a day the ground hog ventures from his burrow, some restless bee is lured from the hive to wander disconsolate over bare fields, a snake crawls from its hole to bask awhile in the sunshine, and one looks instinctively for the first breaking of the earth that tells of the early crocus and the peeping forth of daffodils. The southerly wind is more apt than not to be a telltale, for with all its springtime softness it is drawing toward some storm center, near or remote, that will inevitably follow with rough weather in its sweep. The country folk rightly call such a day a "weather breeder," and even the ground hog knows its portent in the very sign of his shadow. Come as it will, the day is really a day borrowed in advance from the spring, as though to hearten one through all the dreary days that will follow and, in starting the growing forces of vegetation, to make ready for the season's coming. With this forerunner of the year come the harbingers of the bird migration. With the rise of the temperature to sixty or over, a well-marked bird wave from the south spreads over the Delaware Valley. On this balmy, springlike day we hear for the first time since November the croaking of grackles as a loose flock wings overhead or scatters among the tree tops. A few robins may show themselves, and the mellow piping of bluebirds lends its sweet influence to the charm of such a day. There is a sense of uncertain whereabouts in the bluebird's note, a sort of hazy, in-the-air feeling that suggests sky space. It does not seem to have the tangible element by which we can locate the bird as in the voices of the robin and the song sparrow. It is on such a day as this that song sparrows are first heard--cheery ditties from the weather-beaten fences and the bare, brown tangle of brier patches. The day may close lurid with the frayed streamers of lofty cirrus clouds streaking across the sky--the vaporous overflow of a coming storm--or a week of the same bright weather may continue with the wind all the while blowing softly out of the south, but sooner or later the inevitable winter storm must close this foretaste of the spring.