and old pastures and along the borders of the streams. The sweet gum or bilsted, with its gray-colored branches winged with corky ridges, its spiny autumn fruit, and its five-starred leaves, fragrant when crushed and turning crimson in the fall, is a characteristic tree of this borderland. Curiously enough, too, it is confined to the lowlands, growing quite abundantly in the moist woods along the Delaware just south of Philadelphia, but unknown in the northern suburbs save as a transplanted tree.
These woodland features give a decided southern tinge to the region, and are especially significant when we come to know that the tulip tree belongs with the magnolias, a typical southern group, and that the persimmon is one of the ebony trees, a family characteristic of the tropics. But it is the presence of a Carolinian element in the fauna, especially the bird fauna, that marks this region as the beginning of the southern realm. At all seasons of the year the clear whistle of the Virginia redbird—the crested cardinal with mask of black—may be heard in the woods of the lower Delaware Valley and along the tributary streams. I have seen its flash of red against the whiteness of midwinter snowdrifts. In the bramble thickets that fringe the streams and on the wooded slopes above, the Carolina wren finds a home the year round, and its clear, ringing song breaks loudly on the frosty stillness of late winter mornings. I know of no more characteristic sounds in these woods in the early springtime than this wren's song and that of the tufted titmouse. It is a noteworthy fact that these three Carolinian birds are resident throughout the year along the northern limit of the fauna. When the spicebush has blossomed, and "all the wood stands in a mist of green," the first bird waves of the spring tide of migration appear. We wake some morning to hear the chipping sparrow striking pebbles together, and catch the plaintive song of the field sparrow in the pastures and the budding copses along the edge of spring woods. Only yesterday these sounds of the spring were but a memory. The thrasher pours out a medley of sweet notes from the high tree top, and later, in the warm days of early May, the reedy, mellow lute of the wood thrush comes from the bosky glade. During the migration the voices of birds sound unceasingly through the woods from dawn to twilight. When the blackberry is white with blossoms and the arrowwood is in bloom, most of the migrants have passed on to their northern breeding grounds, and those that stay with us have built their nests. Among these latter are several Carolinian birds. In the depths of smilax and brier-tangled thickets the skulking chat—the wildest bird of the woodland—utters its weird, delusive cries. The low-pitched, insectlike notes of the blue-winged warbler and the song of the worm-eating warbler that sounds like a chipping sparrow in the
