With southerly breezes to push them along, insectivorous songbirds are beginning to arrive throughout the lower Susquehanna valley. By the first week of March, Tree Swallows started their push up the river corridor, relying upon the late-winter hatches of stoneflies and other cold-hardy flying insects for sustenance. As temperatures warmed during mid-month, greater numbers of these colorful cavity nesters ventured out across upland areas in search of suitable breeding sites in grasslands and pastures near water. Upon finding a good home in a dead tree or nest box, they’ll defend it vigorously to discourage encroachment.
