Palearctic Component

Fig. 8. Faunal areas from which the resident land birds and fresh-water birds of Micronesia have been derived. (1) Palearctica; (2) Philippines; (3) Moluccas and Celebes (Malaysia); (4) Melanesia (New Guinea and northern Melanesia); (5) Polynesia.

Birds of Micronesia which have been derived directly from Palearctica are Gallinula chloropus guami, Otus podarginus, Asio flammeus, Acrocephalus luscinia and Anas oustaleti. Apparently Gallinula, Asio, and Acrocephalus arrived in Micronesia by way of the chain of islands from Japan southward to the Bonins, Volcanoes, and Marianas. Otus reached Palau from Asia, possibly by way of the Philippines. The smallness of the representation of this component may result partly from lesser ability of the northern birds to adapt themselves to, and to establish themselves on, the semi-tropical and tropical islands of Micronesia as compared with birds from Melanesia where the climate and ecologic conditions resemble more closely those found in Micronesia. Evidence supporting this possibility is the large number of Palearctic residents in the Bonin and Volcano islands as compared with fewer in the Marianas; the Bonins and Volcanoes are less tropical and more temperate in climate.

Table 11 lists the birds concerned, by faunal areas from which the birds have been derived and shows the number of kinds of birds which are present as a result of these colonizations. There is some overlap in the numbers since some endemics may be found in more than one area in Micronesia. [Figure 8] shows the faunal areas from which the endemic land and fresh-water birds of Micronesia have been derived. Melanesia (Papua) supplied 52 percent of this population. Birds reaching Micronesia by way of the Moluccas and Celebes include 21 percent of the total population. The Philippines have supplied 10 percent; Polynesia, 9 percent; and Palearctica, 8 percent. This population of endemic land birds and fresh-water birds has seemingly evolved from 46 colonizations, of which 27 have been derived from Melanesia, 6 from the Philippines, 5 from the Moluccan and Celebean areas, 5 from Palearctica, and 3 from Polynesia.

The Palaus have received a large part of their avifauna from the west (Moluccas, Philippines, Palearctica). Their Melanesian component is mostly the result of secondary colonization from the Carolines. The Carolines have received a greater share of their land birds and fresh-water birds from Melanesia and a smaller share from Polynesia. The Marshalls are definitely associated with the Polynesian element. The Marianas exhibit a considerable amount of secondary colonization from other Micronesian islands, as well as some unique components from the Philippines, Melanesia, and Palearctica. Thus, the number of endemics in Micronesia provides little information concerning the actual number of successful colonizations by birds from other areas. Many of the endemics probably have resulted in this way: Individuals of an endemic subspecies flew to another island and there underwent further differentiation, producing another endemic subspecies. Such secondary colonization probably is going on now.

This analysis of the avifauna shows that Micronesia, with the exception of the Marshall Islands (and the Gilbert Islands), has but little affinity to Polynesia. It has greater affinity, from the zoogeographical standpoint, with the Papuan Region (Melanesia).

Table 11. Avifaunal Components Which Make Up the Endemic Resident Land and Fresh-water Bird Population of Micronesia

Faunal Component	Palau	Western and central Carolines	Eastern Carolines	Marianas	Marshalls
Polynesian	2	3	5	0	3
Melanesian	11	14	16	12	0
Moluccan-Celebean	6	3	4	7	0
Philippine	6	2	2	4	1
Palearctic	2	1	2	5	0
Totals	27	23	29	28	4