260 Henshaw, Migration of the Pacific Plover. [_^J|y 



From the standpoint of the food supply it is even more difficult 

 to explain why the tatler and the curlew leave the islands in spring, 

 since these birds feed almost wholly along shore where there can be 

 no appreciable difference in the quantity of food summer and 

 winter. 



The question why the island plover migrate is all the more diffi- 

 cult to answer when we remember that the islands have been per- 

 manently colonized by certain other American birds, such as the 

 Hawaiian Stilt among the Limicolas, the Night Heron of the Hero- 

 diones, the Hawaiian Mud Hen and Gallinule of the Paludicolae, 

 the Hawaiian Goose, the Short-eared Owl, and the island Buteo. 

 These birds came to the islands as waifs, as did the plover. Finding 

 room, shelter, and food abundant, they wisely elected to roam no 

 more, but to become permanent residents, and to forswear for all 

 time the perilous and unnecessary habit of migration. Since they 

 successfully resisted the impulse to return to their former summer 

 homes to nest, then why not the other species ? As stated above 

 the failure of the plover and turnstone to become permanent colon- 

 ists is not because they are crowded out by other species. In fall 

 the migrants from Alaska find the inviting island pastures unoccu- 

 pied, and as they find them in fall, so they leave them in spring. 



I can suggest no very convincing answer to the question, but I 

 may note the significant fact that the present suitability of the 

 islands as a breeding ground for the plover and turnstones is very 

 recent as compared with the birds' acquaintance with them. The 

 cleared strip around each island now planted chiefly to cane, which 

 may be roughly stated to be three miles wide, and the extensive 

 clearings above this strip which serve for pasture for cattle, are less 

 than a hundred years old, most of them less than 50. Prior to 

 their discovery by Europeans all the islands were heavily forested, 

 nearly or cjuite to the shore. Possibly then the plover and other 

 migrants have been slower to realize the situation than the other 

 species, and do not even yet appreciate the advantages offered by 

 continuous island life. 



It may be said too that the spring migration of the plover and 

 turnstone is so intimately interwoven with the function of repro- 

 duction, that we are quite safe in assuming that, were it not for the 

 desire to nest, the birds would never migrate. Those in fact which 



