When SWIFTS return from their unknown winter resort and "tag" each other with merry twittering, our northern Spring is well advanced. They build little baskets on inside of chimneys, usually of abandoned houses but I have known a pair to raise a family while the flue was used. The parents left the chimney soon after a fire was started and returned at intervals, hovered about to test the temperature and either flew off or dropt down. The children took cold or heat without serious discomfort for they became full-feathered Phoenixes.
Wood for home building is grasped from a tree and broken off while the bird is in flight, not picked from the ground.
Like Swallows they gather in hundreds before leaving the northern states and it is remarkable to see thousands swirling into the tree or chimney they have selected for roosting.
They are among the few birds whose winter habitat is unknown. The flocks drift south before Autumn's chill touch, gather on the Gulf coast, then disappear. Elimination points to the central Amazon as their probable destination.
Eastern North America, west to Great Plains.