In the discussion of the migration of the Arctic tern (p. 31) it was noted that this species makes a very distinct west-to-east movement across northern Canada, continning the flight eastward across the Atlantic Ocean toward the western coast of Europe. It seems likely that there are other species, including the parasitic jaeger (_Stercorarius parasiticus_) that regularly breed in the northern part of the Western Hemisphere but migrate back to the Old World for their winter sojourn. Some others, as the red-legged kittiwake (_Rissa brevirostris_) and Ross's gull (_Rhodostethia rosea_), remain near the Arctic region throughout the year, retreating southward in winter only a few hundred miles. The emperor goose _(Philacte canagica_) in winter is found only a relatively short distance south of its breeding grounds, and eider ducks (Somateria and Arctonetta), although wintering in latitudes well south of the breeding grounds, nevertheless remain farther north than do the majority of other species of ducks (fig. 21). The routes followed by these birds are chiefly coastwise, and in the final analysis may be considered as being tributary either to the Atlantic or to the Pacific coast routes. The passage of gulls, ducks, and other water birds at Point Barrow, Alaska, and at other points on the Arctic coast, has been noted by several observers, and from present knowledge it may be said that the best defined Arctic route in North America is the one that follows around the coast of Alaska. =EVOLUTION OF MIGRATION ROUTES= From the foregoing descriptions of migration routes it will be observed that the general trend of migration in most species of North American birds is northwest and southeast. It is comparatively easy to trace the probable steps in the evolution of the migrations of some species, and some routes have developed so recently that they still plainly show their origin. The tendency is for eastern species to extend their ranges by pushing westward, particularly in the north. For example in the Stikine River Valley of northern British Columbia and southwestern Alaska the eastern nighthawk (_Chordeiles minor minor_), eastern chipping sparrow (_Spizella passerina passerina_), rusty blackbird (_Euphagus carolinus_), eastern yellow warbler (_Dendroica aestiva aestiva_), redstart, and others have established breeding stations at points 20 to 100 miles from the Pacific Ocean. The robin, flicker (Colaptes auratus), slate-colored junco (_Junco hyemalis hyemalis_), blackpoll warbler, myrtle warbler (Dendroica coronata), and ovenbird (_Seiurus aurocapillus_), all common eastern species, also are established as breeding birds in western Alaska, the ovenbird having been detected on the lower Yukon River. These birds, however, do not migrate in fall by any of the Pacific routes, but instead retrace their journey across the mountains and move southward along the broad flyways of the interior.