Page:The Migration of Birds - Thomas A Coward - 1912.pdf/100

80 of the great curve (No. 1) through Mexico and Texas, and a short flight across the Gulf (No. 2) would be gradually lengthened, until the present spring route, then also the autumn route (No. 3), was attained. As Canada opened out, the routes in spring and autumn diverged; in autumn the fruits of Labrador were an attraction, but the Chinook winds made the country east of the Rockies more suitable for spring migration; the fall route tended eastward (No. 4), the spring route remained unchanged. When the fall route had worked east-ward to the Gulf of St Lawrence (No. 5), shortening took place in the some way from the great westward curve, culminating in an ocean flight, short at first (No. 6) and later extended, the total distance shortened, until the present route was attained (No. 7).

This reasoning, sound enough, helps to a more difficult problem—how the Pacific golden plover, Charadrius fulvus, found its way to the Hawaiian Islands, where numbers of the birds winter annually. Roughly the islands are 2000 miles from California, 2400 from Alaska, whence the birds fly, and 3700 miles from Japan. Mr Cooke scouts the idea that, any bird flies aimlessly out to sea to find a new winter home, and the chance colonisation by a storm-swept party is as improbable; if this did occur it is hardly likely that they would at once