548 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1910. 



birds were probably about to migrate across the ocean, but it is, of 

 course, impossible to tell whether they were headed directly for 

 America or for America Ada Asia. 



Absence of fog. — The original discovery of the Hawaiian Islands 

 by birds was undoubtedly greatly facilitated by the fact that, 

 although fog is common on the mountains at altitudes of 5,000 feet 

 and upward, it never occurs at sea level; and as its absence favored 

 the original avian discoverers, so it continues to favor annual mi- 

 grants. 



Date of discovery of the islands by American, migrants. — As to 

 the length of time the Pacific golden plover and its fellow migrants 

 have been visiting the Hawaiian Islands, or when they first discov- 

 ered the group, it were idle to speculate. Their arrival probably an- 

 tedated by thousands of years that of the natives, which is supposed 

 to date back only some 20 centuries. Certain of the bird colonists 

 from America, like the owl, night heron, gallinule, and coot, have 

 resided in the islands so short a time that they have changed very 

 little from their American ancestry. Others, like the hawk, stilt, 

 and goose, have changed more, and hence presumably have been 

 residents of Hawaii a longer time. Changes of color, proportion, 

 and size, however, be they great or small, can not be used as time 

 measures, except in the vaguest way, since practically next to noth- 

 ing is known of the length of time they require. We are perhaps 

 justified in concluding that none of the above species have changed 

 sufficiently to call for isolation from their American ancestors for 

 periods to be reckoned by geologic intervals rather than by thousands 

 of years. 



Spring migration, of placet'. — The impulse to migrate in spring 

 is by no means simultaneous among all the plover that winter in 

 the islands or that winter on any one island, nor, apparently, is it 

 the rule for large bodies of plover to migrate together. The plover 

 and turnstones, probably often in mixed companies, begin to leave 

 for the north early in April, and the migration continues till at least 

 the latter part of May (probably even later), being dependent, ap- 

 parently, on the state of preparedness or the inclination of individual 

 birds. 



"When the time to migrate comes, small parties, from a dozen or 

 even less, to flocks of 200 or more, strike boldly out to the north- 

 ward, apparently without hesitancy or doubt of the result. Mr. 

 Haswell, of Papaikou, which is on the coast about 15 miles north 

 of Hilo, soon after daybreak during the early days of April, 1900, 

 saw several flocks rise to a great height and, after widely circling 

 about a few times as if to orient themselves, finally disappear in a 

 northerly direction. 



