_Change of Nesting Habits._--The nesting habits of some birds have been revolutionized by the coming of civilization to the American wilderness. The Swallow family provides three notable examples of this. The Cliff Swallow and Barn Swallow that formerly built their nests on exposed cliffs now seek the shelter of barns and other outbuildings for this purpose. The open nest of the Barn Swallow is usually found on the joists of hay barns and large stables and not infrequently on similar supports of wide verandas. The Cliff Swallow builds its gourd-shaped {136} mud nest under the eaves and hence is widely known as the Eaves Swallow. No rest of any kind in the form of a projecting beam is needed, as the bird skilfully fastens the mud to the vertical side of the barn close up under the overhanging roof. In such a situation it is usually safe from all beating rains. The Cliff Swallow has exhibited wisdom to no mean extent in exchanging the more or less exposed rocky ledge for the safety of sheltering eaves. Swallows show a decided tendency to gather in colonies in the breeding season. Under the eaves of a warehouse on the cost of Maine I once counted exactly one hundred nests of these birds, all of which appeared to be inhabited. Examination of another building less than seventy feet away added thirty-seven occupied nests to the list. The nesting site of the Purple Martin has likewise been changed in a most radical fashion. Originally these birds built their nests of leaves, feathers, and grass, in hollow trees. Here no doubt they were often disturbed by weasels, squirrels, snakes, and {137} other consumers of birds and their eggs. Some of the southern Indians hung gourds up on poles and the Martins learned to build their nests in them. This custom is still in vogue in the South, and thousands of Martin houses throughout the country are erected every year for the accommodation of these interesting birds. By their cheerful twitterings and their vigilance in driving from the neighbourhood every Hawk and Crow that ventures near, they not only repay the slight effort made in their behalf, but endear themselves to the thrifty chicken-raising farm-wives of the country. If gourds or boxes cannot be found Martins will sometimes build about the eaves of buildings or similar places. They have learned that it is wise to nest near human habitations. At Plant City, Florida, one may find their nests in the large electric arc-lights swinging in the streets, and at Clearwater, Florida, and in Bismarck, North Dakota, colonies nest under the projecting roofs of store buildings.