Of the 104 native fresh-water birds and land birds which are resident in
Micronesia, only 7 kinds or 6.5 percent remain undifferentiated from
populations elsewhere. These birds are _Phalacrocorax melanoleucus_,
_Pandion haliaetus_, _Demigretta sacra_, _Ixobrychus sinensis_, _Anas
poecilorhyncha_, and possibly _Lonchura punctulata_ (may be an
introduction by man). Another bird, _Gallinula chloropus_, a resident at
Palau, may or may not be distinct from the gallinule of Malaysia, _G. c.
orientalis_. Of the 104 resident birds, 97 kinds or 93.5 percent have
become differentiated and can be separated taxonomically from
populations elsewhere. Of the kinds of birds which are found only in
Micronesia, there are 5 endemic genera (16 percent), 31 endemic species
(32 percent) and 76 endemic subspecies (75 percent). If we consider the
avifauna of Micronesia as a single element, the endemism is high as
compared with that on larger and less isolated islands. For example,
Mayr (1944a:174) found 137 resident birds on Timor including 22 endemic
species (16 percent) and 67 endemic subspecies (47.5 percent).
Stresemann (1939b:313) found 220 species including 84 endemic species
(38.2 percent) on Celebes. Mayr (1944a:174) also writes that on Java, of
337 breeding species, 16 (4.8 percent) are endemic, and on New
Caledonia, of 68 species 19 (27.9 percent) are endemic. Speciation in
Micronesia has not progressed much farther than that at New Caledonia
and not so far as at Celebes, but subspeciation has progressed
considerably more than at the island of Timor. The avifauna of the
Hawaiian Islands, as recorded by Bryan and Greenway (1944), has 73
resident land birds and fresh-water birds, all of which are endemic,
including one family, 23 genera and 36 species. The North American night
heron, _Nycticorax n. hoactli_, may be included in this list as the only
resident which is undifferentiated. The development of full specific
differentiation within the resident avifauna is greater in the more
isolated Hawaiian chain where 49 percent of these birds are regarded as
endemic species, while in Micronesia, which is less remote from other
bodies of land, the specific endemism is only 32 percent.
TABLE 12. ENDEMISM IN FAMILIES OF NATIVE LAND AND FRESH-WATER BIRDS IN
MICRONESIA
==================+===========+=========+=========+============+=========
| | Endemic | Endemic | Endemic | Total
FAMILY | Residents | genera | species | subspecies | endemic
------------------+-----------+---------+---------+------------+---------
Phalacrocoracidae | 1 | 0 | 0 | 0 | 0
Ardeidae | 3 | 0 | 0 | 1 | 1
Anatidae | 2 | 0 | 1 | 0 | 1
Accipitridae | 1 | 0 | 0 | 0 | 0
Megapodidae | 2 | 0 | 1 | 2 | 2
Rallidae | 7 | 1* | 2 | 4 | 6
Columbidae | 13 | 0 | 4 | 11 | 13
Psittacidae | 1 | 0 | 1 | 0 | 1
Strigidae | 2 | 0 | 1 | 1 | 2
Caprimulgidae | 1 | 0 | 0 | 1 | 1
Apodidae | 5 | 0 | 1 | 5 | 5
Alcedinidae | 7 | 0 | 1 | 7 | 7
Campephagidae | 3 | 0 | 0 | 3 | 3
Corvidae | 1 | 0 | 1 | 0 | 1
Sylviidae | 5 | 1 | 2 | 4 | 5
Muscicapidae | 14 | 1 | 6 | 9 | 14
Artamidae | 1 | 0 | 0 | 1 | 1
Sturnidae | 9 | 0 | 3[+] | 7 | 9
Meliphagidae | 7 | 1 | 1 | 6 | 7
Zosteropidae | 14 | 1 | 6 | 10 | 14
Ploceidae | 5 | 0 | 0 | 4 | 4
+-----------+---------+---------+------------+---------
Totals | 104 | 5 | 31 | 76 | 97
------------------+-----------+---------+---------+------------+---------
* _Aphanolimonasa_ is included but may be extinct.
[+] _Aplonis corvinus_ is included but may be extinct.
Table 12 lists the families of land birds and fresh-water birds which
have resident members as part of the avifauna of Micronesia. It can be
observed from the table that only two families are represented by no
endemic kinds, several families are represented by one or two endemic
kinds, and others are represented by as many as 14 endemic kinds.
Endemism has reached its greatest development in the families Rallidae
(6), Columbidae (13), Apodidae (5), Alcedinidae (7), Sylviidae (5),
Muscicapidae (14), Sturnidae (9), Meliphagidae (7), and Zosteropidae
(14). Generic endemism is greatest in the Sylviidae where one endemic
genus occurs among 5 endemic species and subspecies (20 percent), in
Rallidae one in 6 (17 percent), in Meliphagidae one in 7 (14 percent).
Specific endemism is greatest in Psittacidae and Corvidae where the
single representative of each family in Micronesia is considered
specifically distinct (100 percent), in Megapodidae and Strigidae one in
2 (50 percent), in Muscicapidae and Zosteropidae 6 in 14 (43 percent) in
Sylviidae 2 in 5 (40 percent), in Rallidae 2 in 6 (33 percent), in
Sturnidae 3 in 9 (33 percent) in Columbidae 4 in 13 (31 percent).
Subspeciation within species which are endemic in Micronesia has
occurred in 8 families, occurring within two species in each of the
families Columbidae and Zosteropidae and once in each of the families
Megapodidae, Apodidae, Alcedinidae, Sylviidae, Muscicapidae, and
Sturnidae.
In summary, the families of land and fresh-water birds found in
Micronesia which have the greatest number of endemic forms are
Muscicapidae (14), Zosteropidae (14), Columbidae (13), and Sturnidae
(9). Speciation has occurred in the single representative of the
families Psittacidae (_Trichoglossus rubiginosus_) and Corvidae (_Corvus
kubaryi_). Where family representation is large, speciation has occurred
most frequently, as in the Muscicapidae (6 in 14 = 43 percent), in the
Zosteropidae (6 in 14 = 43 percent), and in the Columbidae (4 in 13 = 31
percent). Subspeciation has occurred in 8 families, in two species in
the Columbidae and Zosteropidae and in one species in each of 6 other
families.