■^'ol^XXVIIj Henshaw, Miyration of the Pacific Plover. 259 



The motive for the fall migration of the plover, like that of the 

 other waders breeding in the far north, is easily understood. 

 Whatever may have been the case in the distant past, to-day 

 the waders have no alternative. They must migrate from the 

 Arctic in the fall or starve. The only choice offered is as to the 

 selection of winter ciuarters. Thus compelled to migrate, it appears 

 that a certain number of plover and of several other shore-birds find 

 the Hawaiian Islands a winter resort so attractive that to reach them 

 they brave the perils of migration across a wide and stormy ocean. 

 Why then do they not permanently colonize the islands ? If 

 adapted to the bird's needs for nine months of the year, why not 

 for the other three ? 



It cannot be said of the spring migration of these Hawaiian 

 migrants as of the fall, that the birds have no alternative. On the 

 contrary the choice is open, and they would seem to have every 

 incentive to remain, with no very apparent motive to migrate. The 

 chief cause compelling winter visitors to the Tropics to leave and 

 to seek northern regions in which to breed has been supposed to 

 be the overcrowding of the Tropics in spring and the resulting lack 

 of room and of food. No such conditions appear to confront the 

 winter sojourners of Hawaii. During its stay in the islands the 

 plover, as also the turnstone, feed chiefly in the upland pastures 

 and clearings, up to GOOO or 7000 feet, and on newly plowed cane 

 land. Both the sugar planter and the stock raiser have much to 

 thank the plover for, since, while the birds feed on small seeds 

 to some extent, they live chiefly on insects, and according to Perkins, 

 on insects of mucli economic importance, since they depend largely 

 on the caterpillars of two of the most widely spread and destructive 

 of the island 'cut worms.' These insects are most abundant when 

 the grass on the island pastures is green and luxuriant, and this 

 usually is in winter when rains are most copious. That the supply 

 of food in winter and spring is ample is sufficiently attested by the 

 fact that the birds get into such excellent condition. Even if it be 

 assumed that the supply of food in summer is less than in spring, and 

 hence inadequate for the needs of the thousands that winter here, 

 together with their young, still there is enough to sustain very many 

 more than the comparatively small number of non-breeders that 

 summer here. 



