Page:Popular Science Monthly Volume 7.djvu/330

316 the Northern Hemisphere though very unequally, avoiding those spots unfavorable to them. In this distribution they seem to have been somewhat influenced by man, though owing him no other favors than the incidental help of railroad-cuttings and sand-pits which have increased the sites suitable for their nests and enabled them to spread inland.



It is one of the earliest birds to arrive in the spring, appearing in Old England during the last week in March, and in New England early in May, many passing on to the shores of the Arctic Ocean, where Richardson, at the mouth of the Mackenzie, and Dall, on the Yukon, found them breeding in immense numbers. In these high latitudes its summer is necessarily a brief one, and September finds them back again picking up their congeners for company on the southward journey.

Where these and other swallows spend the winter was a hotly debated question among ornithologists at the beginning of the present century; some affirming that they migrated with the sun, while others, believing it impossible that such small and delicate birds could endure the great fatigue and temperatures incident to such a