Birds in Micronesia comprise the most outstanding animal life of the islands, as far as vertebrates are concerned. No fewer than 206 kinds, belonging to 37 families and 91 genera have been found there. Although this number upon first consideration may seem large, actually any large land mass in the same latitude has many more kinds of birds than does Micronesia. In this connection it is pertinent to recall that the islands of Micronesia are oceanic and have apparently been formed independently of any continental land mass. Thus, animal life found on these islands has reached them by overseas migration, either by some passive means or by individual effort. Zoogeographers have had some difficulty in explaining the presence of snails and other nonflying animals on isolated oceanic islands. Crampton, in his studies of the land snails of the genus Partula at Guam and Saipan (1925:10), writes, "Despite the geological difficulties, the biological findings strongly support the view that the dominant process in this part of Oceania has been one of subsidence and of insular dissection." Although there exists today some question as to how certain forms of life have reached these remote dots of land, the ornithologist has not been much in doubt as to the actual means of arrival of birds. With the exception of six kinds of birds which are definitely known to have been introduced by man, the birds have apparently reached these islands by flying there from somewhere else. The ornithologist is, therefore, concerned with learning from where, by what route, when, and why the various species of birds came and how they have become established on these islands of Micronesia. These birds exist in small populations; often less than 100 individuals of one kind may be found on a small island. How have such small numbers had the ability to survive and what environmental adaptations have occurred, are two additional questions which confront the student of Micronesian birds.