Mayr (1941b:215) writes that the distance from the nearest land mass and the climatic conditions are important factors controlling dispersal. With regard to the degree of remoteness of the islands, table 13 lists the number of resident land and fresh-water birds present in the Palaus and the "high" islands of the Carolines. Also, the approximate distance from the nearest large land mass and the area in square miles are given. There is some correlation between the distance from the nearest land mass and the number of resident land birds and fresh-water birds. For example, Palau, with 32 resident birds, is only 410 miles from the nearest land mass whereas Kusaie, with only 11 resident birds, is 720 miles from the nearest land mass. The comparative size of the land mass must also be taken into account, as shown by the fact that the large island of Ponapé contains more kinds of birds but is more remote from large land masses than either Yap or Truk. TABLE 13. CORRELATION BETWEEN NUMBER OF RESIDENT LAND AND FRESH-WATER BIRDS AND DISTANCE FROM LARGE LAND MASSES OF "HIGH" ISLANDS OF MICRONESIA Column headings: A: No. of Birds B: Approximate distance from nearest land mass (statute miles) C: Area in square miles ========+====+=====+===================================+===== ISLAND | A | B | Nearest land mass | C --------+----+-----+-----------------------------------+----- Palau | 32 | 410 | Approximately equal distance from | 171 | | | Mindanao, Morotai, New Guinea | | | | | Yap | 13 | 580 | New Guinea | 83 | | | | Truk | 17 | 525 | New Ireland | 50 | | | | Ponapé | 20 | 630 | New Ireland | 145 | | | | Kusaie | 11 | 720 | Malaita (Solomons) | 42 --------+----+-----+-----------------------------------+----- Climatic factors are important in the dispersal of bird life; Micronesia, where the climate is tropical to subtropical, is better suited for colonization by birds from the tropics (Melanesia) than by birds from the temperate or cold climates (Palearctica). The climatic factor may be one of the principal reasons why birds from Palearctica make up only a small part of the avifauna of Micronesia. ANALYSIS OF SPECIATION