Chapter III: Part 3

The process of speciation within insular populations has been discussed by many authors. Hesse, Allee, and Schmidt (1937:517) list the motives for differentiation as, "Special character of insular faunae rests on the conditions common to all islands--isolation, freedom from competition, space restriction, and special insular climates." This combination of characteristics is seldom found elsewhere in nature, and as Murphy (1938:357) points out, an island is the nearest approach to a "man-controlled laboratory." Isolation of small populations is probably the most influential factor in the process of speciation in insular organisms. Lack (1947:134) writes that "in all organisms the isolation of populations is an essential preliminary to the origin of new species." Buxton (1938:265) also stresses this point with regard to the formation of species of insects in Samoa and emphasizes that evolution may occur more quickly in small populations. When mutations appear in such small and isolated populations, they have a greater chance to become fixed than do mutations in less restricted populations in a larger land mass, where such a mutation might be lost by the swamping effects of outbreedings. In addition, Wright (1931 and elsewhere) suggests the possibility of change by accidental elimination and recombination of hereditary characters in micropopulations. This mechanism could well be a factor in Micronesian bird populations, many of which possess no more than a few hundred individuals. Huxley (1938:256) emphasizes that "accidental" mutations may be perpetuated in small, isolated groups. It might be added that such changes might be either advantageous or disadvantageous to the organism concerned. Huxley (1938:263) states also that geographic isolation may promote nonadaptive differentiation, which may be caused by "colonization by a random sample" or by subsequent "preservation of nonadaptive mutations in numerically small isolated groups." Mayr (1942b:237) cites the importance of the "founder" principal for reduced variability in small populations. He points out that if the "founders" of the population carried with them only "a very small proportion of the variability of the parent population," one would expect to see divergence from the ancestral stock.

Freedom from competition, especially interspecific strife, is an important factor in differentiation; this is especially true in the early period of colonization. Lack (1947:113) points to the absence of food competitors, especially in the initial period of colonization, as an important influence in the evolution of Darwin's finches at the Galapagos Islands. Once a population has become established and "adjusted" to a given environment on a small island, intraspecific competition might bring about adaptative selection. Subsequent colonists might be eliminated by the competition brought about by these previously adapted organisms, especially if both organisms were adapted for life in the same ecologic niche. Space restriction may be important in such Micronesian birds as _Rhipidura_ and _Myiagra_, which appear to possess recognizable territories. A new colonist entering the territory of one of these birds might be forced out. This competition might not play such an important part among birds, which live in flocks and do not range in closely guarded territories; birds in this group include some pigeons, starlings, and white-eyes.

Freedom from the pressure of predation probably exerts a direct influence on formation of species. Aside from a few migrant hawks and two kinds of resident owls, most of the avifauna feeds on vegetable and invertebrate foods. The large lizard _Varanus_ may be classed as the only native predator on many of the islands. Man has been responsible for the introduction of rats, house cats, and other mammals, which may be destructive to birds. Thus, before the advent of man the factor of predation may not have been of great consequence. As mentioned previously, nonadaptive modifications may be perpetuated where the "weeding-out" process by predation is not an influence. Flightless rails have apparently developed in the absence of predation.

The absence of the pressure of predation should remove a certain amount of control on the population turn-over. As Hesse, Allee, and Schmidt (1937:521) write, a characteristic of the faunas of oceanic islands is the fact that they are distinguished by the occurrence of "disproportionately developed taxonomic groups in which one or a few basic types have undergone adaptative radiation and come to fill unduly large proportions of the population as compared with conditions that obtain on neighboring continents." Lack (1947:114) writes, "that the absence of predators may well have accelerated the adaptative radiation" in the Galapagos finches. In Micronesia, the starling (_Aplonis opacus_) dominates much of the available habitat on some of the Caroline atolls, and even on "high" islands, where other land birds are present. There appears to be no tendency towards selective adaptations occurring, or towards ecologic isolation.

Available data indicate that the life spans of individual birds in Micronesia may be short. For example, it was obvious on many of the islands visited by the NAMRU2 party that starlings (_Aplonis opacus_) in immature plumage outnumbered starlings in adult plumage, although it is possible that immature plumages are retained longer in these island birds than in others. Similar observations were made by Coultas, who noted the ratio of birds in immature plumage to birds in adult plumage at Kusaie to be 5 to 1. If the life span is shorter in these insular forms as compared with that of the ancestral stocks, the higher annual population turn-over would allow for the speed of genetic changes to be accelerated.

The origin of species by hybridization between different kinds of organisms has been a subject of frequent discussion. Lack (1947:100) concludes that it is improbable that hybridization has played an important part in the origin of new kinds of birds. Nevertheless, the absence of sufficient mates in the confines of a small island probably stimulates the crossbreeding between two species of birds. Fertile offspring of such a cross might conceivably account for some of the populations, the origins of which are puzzles to present day taxonomists. Such Micronesian forms as _Metabolus_ and _Cleptornis_ could conceivably have been derived in such a manner. Yamashina (1948) has described the origin of _Anas oustaleti_ as a result of hybridization between _A. platyrhynchos_ and _A. poecilorhyncha_. It might be difficult to explain every case of the formation of other insular species on the basis of the effects of isolation and paucity alone. However, Mayr (1942b:236) includes the development of questionable and unusual kinds of insular forms in a general statement: "The potentiality for rapid divergent evolution in small populations explains also why we have on islands so many dwarf or giant races, or races with peculiar color characters (albinism, melanism), or with peculiar structure (long bills in birds), or other peculiar characters (loss of male plumage in birds)."

Nutrition may be also a factor influencing speciation in bird life. The types of food plants (coconut, papaya, breadfruit, pandanus, etc.) might be similar on a Micronesian island and on a continental island in the Philippine region; however, the value of these plants as foods might vary and might reflect differences in mineral content of the soils. For example, if the soils on an island lack, or by leaching out have lost, sufficient amounts of potassium and other elements, plants may store foods, not as proteins, but possibly as carbohydrates, simple sugars, or alkaloids. Whether nutritional influences might have a selective effect on the bird populations, has not been ascertained.

In summary, it may be said that genetic change altering the phenotypic expression of avian characteristics is no more apt to happen in insular populations than in continental populations but genetic change may have a greater chance of being perpetuated in small insular populations where isolation, limited competition, freedom from the selective influences of predation, and other factors exert influences.

CONSERVATION OF THE AVIFAUNA OF MICRONESIA

The islands of Micronesia are small and their occupation by man often produces serious effects on the endemic animal life of the islands. The vulnerability of insular bird populations is well attested by the fact that the majority of birds, which have become extinct in the past two hundred years, have been insular forms. Two birds in Micronesia, the Kusaie Rail (_Aphanolimnas_) and the Kusaie Mountain Starling (_Aplonis corvinus_), are known to be either extinct or so rare that they have not been taken since the time of Kittlitz, who visited the island of Kusaie in December, 1827, and January, 1828. Other birds (_Anas oustaleti_, _Caloenas nicobarica_, _Megapodius l. lapérouse_, and _Metabolus rugensis_) have become reduced in numbers and may be threatened with extermination.

Nelson (1921:270-274) has described the following agencies destructive to island life of the Pacific: fire, volcanic eruptions, tidal waves, hurricanes, clearing of the land, introduction of domestic animals and grazing, introduction of wild animals and birds. Mayr (1945c) also presents a discussion of conservation problems in these islands.

Fire is a serious hazard to island life, especially to the land birds. It destroys both food and cover, these two habitat requirements being most essential to the birds. The firing of open lands to improve grazing conditions was a practice which persisted in the Marianas during the time of the Spanish. This practice has declined, but the resultant vegetational changes and erosion have adversely affected the avifauna. Tidal waves and hurricanes (typhoons) are occasionally of such intensity as to flood low coral atolls. Such events are damaging to, or might even exterminate populations of land birds (_Aplonis_, _Acrocephalus_ and others), and prevent colonizations which might otherwise occur. Clearing of the land for agricultural use probably has affected the avifauna, especially on the island of Tinian where much of the island has been placed in cultivation. The occurrence of domestic stock, especially feral hogs and cats, has affected the birds. Hogs, apparently, have been in the islands for a long time. The English privateer, Lord Anson, visited Tinian in October, 1742, and noted a large number of hogs present at that time. At Guam, in 1945, the NAMRU2 party found both hogs and cats moving freely in all parts of the island. Stomachs of cats examined showed that they had been feeding principally on rodents.

Introduction of wild animals and plants have not been so extensive as in the Hawaiians or other islands. There have been at least five importations of land birds to Micronesia as well as several mammals, other vertebrates and invertebrates. The effect of these established colonies on the native bird life has not been studied.

The late world war has brought changes to the population of bird life in Micronesia. The author (1946b) has elsewhere described some of the effects of the bombing, invasion, and occupation of small islands. Some islands, like Peleliu, suffered severely from bombing and invasion operations. Some islands, especially smaller ones like Kwajalein and Ulithi, were partly or almostly entirely cleared of vegetation by occupation forces. Other effects were caused by "recreational" shooting of birds by garrison forces; introductions of pests in materials unloaded; and pest control by clearing, draining, and spraying with DDT and other insecticides to the detriment of inoffensive species.

It is obvious that a well-planned program of conservation should be placed in operation to insure survival of the endemic avifauna of Micronesia.

THE FUTURE OF ORNITHOLOGICAL RESEARCH IN MICRONESIA

Collections of birds have been made at most of the major islands of Micronesia, and it is thought that there are but few if any unnamed birds in the region. The distribution of several species has not been completely investigated, especially those land birds (_Ducula_, _Ptilinopus_, and _Aplonis_) which inhabit coral atolls in the Carolines and Marshalls. The bird life of the northern Marianas is also incompletely known. Continued observations in the Micronesian islands will increase our knowledge of the kinds of migratory shore birds and migratory land birds which reach the island as winter visitors. Further information is needed concerning the breeding activities of sea birds in Micronesia, especially in the Marshalls and Carolines.

The systematic status of most of the birds in Micronesia is already established. It is hoped that the present account advances our knowledge of the methods of colonization. Although these fundamental investigations have been nearly completed in Micronesia the field of avian ecology has been relatively untouched. In the past, expeditions have visited Micronesia with the aim of obtaining within a short time collections of the animal life as large and as representative as possible. Many of the collectors made few or no field notes on the bird life; some, like Finsch, Kubary, Marche, and Coultas, made valuable observations on the habits of the birds. Intensive ecological researches may be accomplished more thoroughly by resident investigators, who can devote full time to such pursuits.

METHODS AND ACKNOWLEDGMENTS

My own opportunity to study the bird life of Micronesia came as a member of the scientific staff of the Laboratory of Mammalogy of United States Naval Medical Research Unit No. 2 (NAMRU2) in the late war. The primary duty of this laboratory was to obtain examples of the vertebrate fauna for examination for ectoparasites by the Laboratory of Acarology and to preserve specimens for identification. As a result sizeable collections of mammals, birds, and other vertebrates were obtained. In addition, ecological data were obtained (as time permitted), especially as an aid in studying the distribution of ectoparasites which affected man. In 1945, I spent eleven months in Micronesia; for most of this time I was stationed at Guam, the headquarters of the Unit, although one month was spent in the Palau Islands, two weeks were spent at Ulithi Atoll, and short stop-overs were made at Eniwetok and Kwajalein atolls. Other members of the laboratory staff visited Rota and Truk islands.

Subsequent to the field studies in the Pacific, I was sent to Washington and spent approximately eight months at the United States National Museum studying the collections of birds and preparing several reports for publication. In this period other material was studied, both in the United States National Museum and at the American Museum of Natural History, New York, and the literature dealing with the birds of Micronesia was explored and a bibliography of Micronesian birds was prepared. At the University of Kansas, I continued the bibliographic work, borrowed and studied some specimens, and completed accounts of the avifauna of Micronesia.

Under the account of each bird, all known references in the literature, which mention the scientific name of the bird and its distribution in Micronesia, are listed. The references are arranged as follows: (1) citation to the original description, and (2) citations to names in literature in the order of their first appearance. When a name is a pure synonym, it may be recognized as such by the fact that the type locality is given immediately following the citation. In compiling these references the writer made use of the invaluable work by Wiglesworth (1891) and of Utinomi's "Bibliographica Micronesia," made available through the translation by Fisher (1947). The arrangement of the families follows that of Peters (1931-1945) and Wetmore (1940).

Specimens examined are designated as to collection in which catalogued by the following abbreviations: USNM, the United States National Museum; AMNH, the American Museum of Natural History; MCZ, the Museum of Comparative Zoölogy; and KMNH, the University of Kansas Museum of Natural History. Average and extreme measurements of specimens are usually listed in tables; unless otherwise indicated, measurements are in millimeters, and are of adult specimens. The wings have been measured by flattening them on a ruler. Weights are in grams. Unless otherwise indicated, descriptions of the birds have been written by the author. Descriptions of shore birds are not given; for these the reader may refer to Mayr (1945a:28-47) where characters useful for identification of the birds in the field also are given. The writer is especially indebted to Dr. Ernst Mayr for making available the descriptions of Micronesian birds made by Miss Cardine Bogert, especially those dealing with color of the irides, feet, and bill. Color terms in quotation marks refer to those in Ridgway (1912).

In dealing with insular forms the criterion of intergradation as indicative of subspecies cannot be applied as it can in kinds of birds on the mainland which have geographically continuous distributions. Instead, degree of difference in combination with geographic position plus other factors such as degree of variation in the geographic races of the same species or a related species on continental areas are used in deciding whether two closely related kinds are subspecies or full species. Many kinds of birds in the islands are modified but little from island to island (examples, _Rhipidura rufifrons_, _Aplonis opacus_, _Ducula oceanica_, and _Myzomela cardinalis_), and can be treated as subspecies. Others show much variability from island to island and it is uncertain whether they should be treated as subspecies or as separate species (examples, _Myiagra oceanica_, _Zosterops cinerea_, _Rukia_, and possibly _Acrocephalus luscinia_). Decisions on generic status are equally difficult to make. In many cases the experience and judgment of the taxonomist may be the only criteria by which he can decide whether a bird is different enough to be considered as a distinct genus. This "human element" has caused some disagreement. Knowing whether the bird is to be considered as a distinct genus or instead merely as a species may not be as important as knowing its correct phylogenetic relationship. The circumstance that variation in these insular birds is in general less predictable than in mainland birds adds, I think, to the pleasure inherent in the classification of the variations.

First, I thank Commodore Thomas N. Rivers (MC) USNR, then commanding officer of NAMRU2, for the opportunity to join the Unit, for his interested cooperation in seeing that the plans for field trips were successful, and for his thoughtfulness in obtaining for me the orders for duty at the United States National Museum subsequent to our field investigations. Greatly appreciated also is the help rendered by my former colleagues of NAMRU2, including Dr. David H. Johnson, Dr. George W. Wharton, Dr. Aaron B. Hardcastle, Mr. Odis A. Muennik, Mr. L. P. McElroy, Mr. Charles O. Davison, Mr. Merle H. Markley, Mr. Walter L. Necker, Dr. Wilbur G. Downs, Dr. Bernard V. Travis, and Mr. E. W. Coleman. Other personnel, then stationed in Micronesia, who contributed data used in this report include: Dr. Joe T. Marshall, Jr., (who generously loaned some of the specimens taken by him in Micronesia), Dr. C. K. Dorsey, Dr. George Hensel, Mr. Tom Murray, Dr. Irwin O. Buss, Mr. James O. Stevenson, Dr. Wilfred D. Crabb, Mr. Herbert Wallace, and Dr. M. Dale Arvey. Authorities of the United States National Museum provided generously for using the collections there, and I am especially grateful to Dr. Alexander Wetmore, Dr. Herbert Friedman, and Mr. Herbert G. Deignan for their cooperation and assistance. Doctor Wetmore kindly made available many of the birds collected at Bikini during the atomic bomb experiments. Dr. Robert Cushman Murphy, Dr. Ernst Mayr, and Dr. Dean Amadon of the American Museum of Natural History made available the collections in their charge. Doctor Murphy allowed me to examine some of the heretofore unstudied collections of sea birds of the Whitney South Sea Expedition. Doctor Mayr generously helped me with taxonomic and evolutionary problems and made available to me some of his own unpublished taxonomic notes, the unpublished field accounts of Mr. William F. Coultas and a partly completed manuscript on the birds of Micronesia by Miss Cardine Bogert. Mr. James L. Peters generously loaned specimens from the Museum of Comparative Zoölogy. The use of unpublished field notes made by Mr. Larry P. Richards at Ponapé and Truk in 1947 and 1948 is also gratefully acknowledged. I am grateful also to my colleagues at the Museum of Natural History of the University of Kansas and would single out for special mention Dr. E. Raymond Hall who gave critical assistance with the manuscript, Drs. Edward H. Taylor and Herbert B. Hungerford who made helpful suggestions, and Mrs. Virginia Cassell Unruh who drew the distributional maps.

ACCOUNTS OF THE KINDS OF BIRDS OF MICRONESIA

=Diomedea nigripes= Audubon

Black-footed Albatross

_Diomedea nigripes_ Audubon, Ornith. Biog., 5, 1839, p. 327. (Type
locality, Pacific Ocean, lat. 30°44´N., long. 146°W.)

_Diomedea fuliginosa_ Oustalet, Le Nat., 1889, p. 261 (Mariannes).

_Diomedea nigripes_ Oustalet, Nouv. Arch. Mus. Hist. Nat. Paris
(3), 8, 1896, p. 51 (Agrigan); Hartert, Novit. Zool., 5, 1898, p.
68 (Marianne); Seale, Occ. Papers Bernice P. Bishop Mus. 1, 1901,
p. 22 (Marianas); Safford, Osprey, 1902, p. 70 (Mariannes);
_idem_, The Plant World, 7, 1904, p. 268 (Guam?); Kuroda, in
Momiyama, Birds Micronesia, 1922, p. 32 (Marriane); Peters,
Check-list Birds World, 1, 1931, p. 43 (Marshalls); Hand-list
Japanese Birds, rev., 1932, p. 188 (Marianas); Hand-list Japanese
Birds, 3rd ed., 1942, p. 210 (Marianas); Mayr, Birds Southwest
Pacific, 1945, p. 5 (Marshalls).

_Geographic range._--North Pacific Ocean. Breeds on islands
northwest of Hawaii. In Micronesia: Mariana Islands--Agrigan.

_Characters._--A large oceanic bird with sooty-brown coloration;
darker on nape, wings and tail; lighter on forehead, sides of head,
and abdomen; area surrounding bill whitish; tail whitish at base;
bill dark reddish-brown; feet black.

_Remarks._--This albatross has been recorded from waters near the Mariana Islands. Quoy and Gaimard (1824:145) observed "albatross" between the Mariana and the Hawaiian Islands. The only actual specimens obtained from the islands were reported on by Oustalet (1896:51). These were eight Black-footed Albatrosses which were taken on the coast of Agrigan by Marche in December, 1888, and January, 1889. Oustalet gives the following measurements: total length, 680-785; wing, 485-525; tail, 180-225; tarsus, 80-90; culmen, 108-125. The specimens are apparently in the Paris Museum.

Peters (1931:43) lists the Marshall Islands as part of the range of _D. nigripes_.

In the period of the late war Gleise (1945:221) observed eight Short-tailed Albatrosses (_D. albatrus_ Pallas) "off Saipan." Specimens of _D. albatrus_ have not been taken in Micronesia. According to Austin (1948b:32) this albatross "is now virtually extinct," and this record may be questioned.

=Puffinus pacificus chlororhynchus= Lesson

Wedge-tailed Shearwater

_Puffinus chlororhynchus_ Lesson, Traité d'Ornith., 8, 1931, p.
613. (Type is from Shark's Bay, West Australia.)

_Puffinus sphenurus_ Schmeltz and Krause, Ethnogr. Abth. Mus.
Godeffroy, 1881, p. 299 (Mortlock).

_Puffinus chlororhynchus_ Wiglesworth, Abhandl. und Ber. Zool.
Mus. Dresden, no. 6, 1890-1891 (1891), p. 80 (Luganor?); Godman,
Monogr. Petrels, pt. 2, 1908, p. 88 (Carolines); Kuroda, in
Momiyama, Birds Micronesia, 1922, p. 33 (Luganor or Ruk?).

_Puffinus pacificus chlororhynchus_ Hand-list Japanese Birds,
rev., 1932, p. 187 (Lukunor or Truk?, Kusaie); Hand-list Japanese
Birds, 3d ed., 1942, p. 209 (Lukunor or Truk?, Kusaie).

_Geographic range._--Breeds at the Seychelles, Australia, Lord
Howe, Norfolk, and other islands in the Australian area. Ranges
throughout most of the warmer parts of the Indian and Pacific
oceans. In Micronesia: Mariana Islands--Guam; Caroline
Islands--Lukunor or Truk?, Kusaie.

_Characters._--A large shearwater with long wedge-shaped tail;
upper parts sooty-brown with crown, neck, and wings darker and
forehead paler; under parts paler than upper parts; bill dark;
feet flesh-colored.

_Remarks._--This shearwater was taken by Kubary either at Lukunor or at Truk in the Caroline Islands. At a later date, apparently between 1922 and 1932, the Japanese recorded the bird at Kusaie. In using this subspecific name, I am following the Hand-list of Japanese Birds (Hachisuka _et al._, 1932:187).

At Guam on August 10, 1931, Coultas obtained a male shearwater, which is tentatively placed in this subspecies. Its measurements are as follows: wing, 290; tail, 128; exposed culmen, 39; tarsus, 47. Coultas (field notes) writes that he was told by natives that petrels nest and roost on the high cliffs behind the city of Agaña on Guam. At sea south of the eastern Caroline islands, Coultas obtained five other birds which appear to be the same as the bird from Guam. All specimens are in the collections of the American Museum of Natural History.

=Puffinus pacificus cuneatus= Salvin

Wedge-tailed Shearwater

_Puffinus cuneatus_ Salvin, Ibis, 1888, p. 353. (Type locality,
Krusenstern Island==Ailuk, Marshall Islands, _fide_ Fisher, Auk,
63, 1946, pp. 587-588.)

_Puffinus cuneatus_ Wiglesworth, Abhandl. und Ber. Zool. Mus.
Dresden, no. 6, 1890-1891 (1891), p. 80 (Krusenstern); Salvin,
Cat. Birds British Mus., 25, 1896, p. 371 (Krusenstern); Godman,
Monogr. Petrels, pt. 2, 1908, p. 76 (Marshalls).

_Puffinus pacificus cuneatus_ Mathews, Birds Australia, 2, 1912,
p. 84 (Marshall Group); Peters, Check-list Birds World, 1, 1931,
pp. 55-56 (Krusenstern); Hand-list Japanese Birds, 3d ed., 1942,
p. 209 (Krusenstern); Fisher, Auk, 63, 1946, pp. 587-588 (Ailuk).

_Thyellodroma cuneata cuneata_ Mathews and Iredale, Ibis, 1915, p.
597 (Krusenstern); Mathews, Syst. Avium Australasianarum, 1, 1927,
p. 113 (Marshall Group).

_Thyellodroma cuneata_ Oberholser, Auk, 34, 1917, p. 474
(Krusenstern).

_Thyellodroma pacificia cuneata_ Mathews, Novit. Zool., 39, 1934,
p. 186 (Caroline Islands).

_Geographic range._--Pescadores east to the Hawaiian Islands and
south to eastern Micronesia. In Micronesia: Marshall
Islands--Ailuk.

_Remarks._--Osbert Salvin received two specimens of this shearwater from H. J. Snow, who got them at the Krusenstern Islands in 1883. In describing them, Salvin (1888:353) comments that the locality is seemingly in the Marshall Islands at approximately 10°17´ N. and 190° W. This locality was confusing to Seebohm (1891:191) who thought it was between the Hawaiians and the Marshalls, while Hartert (1926:352) decided it was really Krusenstern Rocks in the Hawaiian Group. To clear the matter up, Fisher (1946:587-588) writes that Salvin was correct and suggests that the name of the island should be the better established one, Ailuk, rather than the little used one, Krusenstern.

_P. p. cuneatus_ resembles _P. p. chlororhynchus_ but is whiter on the underparts, especially the breast. These two subspecies are inseparable according to the twenty-fourth supplement to the American Ornithologists' Union Check-list of North American Birds (Auk, vol. 66, 1949:281).

=Puffinus tenuirostris= (Temminck)

Short-tailed Shearwater

_Procellaria tenuirostris_ Temminck, Pl. Col., livr. 99, 1835, text
to pl. 587. (Type locality, Seas north of Japan and shores of
Korea.)

_Puffinus tenuirostris tenuirostris_ Bryan, Guam Rec., vol. 13,
no. 2, 1936, p. 15 (Guam).

_Puffinus tenuirostris_ Yamashina, Tori, 10, 1940, p. 677
(Kinajon, Marshall Islands); Hand-list Japanese Birds, 3d ed.,
1942, p. 210 (Kinajon, Marshall Islands).

_Geographic range._--Breeds in Tasmania, southeastern Australia,
islands in Bass Straits, and Bounty Islands. Ranges north to the
Bering Sea. In Micronesia: Mariana Islands--Guam?; Marshall
Islands--Kinajon.

_Character._--A rather large shearwater with short, rounded tail;
upper parts sooty brown; underparts paler and more grayish than
back; throat may be occasionally whitish; bill lead-gray; feet
grayish, browner on outer side.

_Remarks._--On migration this shearwater probably reaches most parts of Micronesia. It has been recently recorded by the Japanese at Kinajon in the Marshall Islands. Bryan (1936:15) includes this species as a "chance arrival" in his list of the birds of Guam.

=Puffinus nativitatis= Streets

Christmas Shearwater

_Puffinus (Nectris) nativitatis_ Streets, Bull. U. S. Nat. Mus., 7,
1877, p. 29. (Type locality, Christmas Island, Pacific Ocean.)

_Puffinus nativitatis_ Salvin, Cat. Birds British Mus., 25, 1896,
p. 389 (Krusenstern); Lister, Proc. Zool. Soc. London, 1891, pp.
295-300 (Krusenstern); Godman, Monogr. Petrels, pt. 3, 1908, p.
153 (Marshalls).

_Geographic range._--Breeds at Wake and Laysan Islands south to
Christmas, Phoenix, Marquesas, Tuamotu, and Austral Islands. In
Micronesia: Marshall Islands--Ailuk.

_Characters._--Upper parts chocolate brown; underparts resemble
upper parts but throat may be slightly grayer; bill and feet
black. _P. nativitatis_ resembles _P. pacificus_ but is similar
with black feet.

_Remarks._--The only specimens of this bird known from Micronesia, are those taken in the spring of 1883 by H. J. Snow at Krusenstern (Ailuk) in the Marshall Islands. For two birds from this island in the collections of the British Museum, Godman (1908:154) gives the following measurements: wing, 9.6 and 10.0; tail, 3.35 and 3.4; culmen, 1.15 and 1.2; tarsus, 1.7 and 1.8; middle toe and claw, 2.0 and 2.1.

=Puffinus lherminieri dichrous= Finsch and Hartlaub

Dusky Shearwater

_Puffinus dichrous_ Finsch and Hartlaub, Fauna Centralpolynesiens,
1867, p. 244. (Type locality, McKean Island, Phoenix Group.)

_Puffinus dichrous_ Hartlaub and Finsch, Proc. Zool. Soc. London,
1872, pp. 90, 108 (Pelew); Finsch, Journ. Mus. Godeffroy, 8, 1875,
pp. 6, 44 (Palau).

_Puffinus opisthomelas_ var. _minor_ Hartlaub, Proc. Zool. Soc.
London, 1867 (1868), p. 832 (Type locality, Pelew); Finsch, Journ.
f. Ornith., 1872, p. 57 (Pelew).

_Puffinus opisthomelas_ Hartlaub and Finsch, Proc. Zool. Soc. London,
1868, pp. 9, 118 (Pelew); Finsch, Journ. f. Ornith., 1870, p. 371
(Pelew).

_Puffinus tenebrosus_ Pelzeln, Ibis, 1873, p. 47, fig. 1 (Type
locality, unknown==Pelew Islands, _ex_ Mathews); Oustalet, Nouv.
Arch. Mus. Hist. Nat. Paris, (3), 8, 1896, p. 55 (Rota); Hartert,
Novit. Zool., 5, 1898, p. 69 (Marianne); Seale, Occ. Papers Bernice
P. Bishop Mus., 1, 1901, p. 23 (Marianas?); Safford, The Plant World,
7, 1904, p. 268 (Guam).

_Puffinus obscurus_ Finsch, Journ. Mus. Godeffroy, 12, 1876, pp.
18, 40 (Ponapé, Palau); _idem_, Proc. Zool. Soc. London, 1877, p.
786 (Palau); _idem_, Proc. Zool. Soc. London, 1877 (1878), p. 782
(Ponapé); _idem_, Journ. f. Ornith., 1880, pp. 295, 309 (Ponapé,
Kuschai); _idem_, Proc. Zool. Soc. London, 1880, p. 577 (Ruk);
_idem_, Ibis, 1881, p. 109 (Kuschai); _idem_, Ibis, 1881, pp. 113,
115 (Ponapé); Schmeltz and Krause, Ethnogr. Abth. Mus. Godeffroy,
1881, p. 353 (Ruk); Salvin, Ibis, 1888, p. 357 (Pelew);
Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891
(1891), p. 79 (Ruk, Ponapé, Pelew); Oustalet, Nouv. Arch. Mus.
Hist. Nat. Paris, (3), 8, 1896, p. 54 (Saypan, Palaos); Salvin,
Cat. Birds British Mus., 25, 1896, p. 382 (Carolines, Pelews);
Hartert, Novit. Zool., 5, 1898, p. 68 (Marianne); Seale, Occ.
Papers Bernice P. Bishop Mus., 1, 1901, p. 23 (Marianas?); Safford,
Osprey, 1902, p. 70 (Marianas); Dubois, Syn. Avium, 2, 1904, p.
1031 (Pelew, Carolines); Godman, Monogr. Petrels, pt. 2, 1908, pp.
126, 127 (Pelew, Ruk, Ponapé).

_Puffinus obscurus obscurus_ Hartert, Novit. Zool., 7, 1900, p. 10
(Ruk); Kuroda, in Momiyama, Birds Micronesia, 1922, p. 32 (Saipan,
Ruk, Ponapé, Pelew).

_Puffinus lherminieri minor_ Mathews, Birds Australia, 2, 1912, p.
70 (Pelew, Carolines).

_Puffinus assimilis minor_ Mathews, Syst. Avium Australasianarum,
1, 1927, p. 111 (Pelew).

_Puffinus lherminieri dichrous_ Murphy, Amer. Mus. Novit., no.
276, 1927, p. 10 (Pelews, Carolines); Peters, Check-list Birds
World, 1, 1931, p. 60 (Pelew); Yamashina, Tori, 7, 1932, p. 408
(Arakabesan); Hand-list Japanese Birds, rev., 1932, p. 188
(Saipan, Truk, Ponapé, Palaus); Hand-list Japanese Birds, 3rd ed.,
1942, p. 209 (Saipan, Truk, Ponapé, Palau); Mayr, Birds Southwest
Pacific, 1945, p. 10 (Carolines, Palaus); Baker, Smithson. Misc.
Coll., vol. 107, no. 15, 1948, p. 37 (Palau).

_Alphapuffinus lherminieri minor_ Mathews, Novit. Zool., 39, 1934,
p. 182 (Pelew Islands).

_Puffinus obscura_ Bryan, Guam Rec., vol. 13, No. 2, 1936, p. 15
(Guam).

_Geographic range._--Known from Phoenix, Nauru, Micronesia, and
south to the Samoan, Society, Tuamotu, and Marquesas islands. In
Micronesia: Mariana Islands--Guam, Rota, Saipan; Palau
Islands--Babelthuap, Koror, Arakabesan; Caroline Islands--Truk,
Ponapé, Kusaie.

_Characters._--A small shearwater with upper parts sooty-black;
under parts white except for sides of breast grayish and under
tail-coverts blackish; bill blackish; feet yellowish, outer toe
black.

_Measurements._--Measurements of 17 adult birds (9 males, 7
females, 1 unsexed) from Micronesia (Palau, Truk, Ponapé, Kusaie)
and 10 adult birds (6 males, 4 females) from the Phoenix Group
(Enderbury, Canton) are listed in table 14.

TABLE 14. MEASUREMENTS OF _Puffinus lherminieri dichrous_

===========+=============+============+==============+==============
LOCALITY | Wing | Tail |Exposed culmen| Tarsus
-----------+-------------+------------+--------------+--------------
Micronesia |203 (197-211)|83.6 (77-89)| 27.9 (26-30) |38.5 (37.5-40)
Phoenix |197 (193-203)|82.2 (79-85)| 26.3 (25-28) |37.2 (36-39)
-----------+-------------+------------+--------------+--------------

_Specimens examined._--Total number, 72 (44 males, 19 females, 9
unsexed), as follows: Palau Islands, AMNH--exact locality not
given, 64 (Oct., Nov., Dec.); Caroline Islands, AMNH--Truk, 4 (June
15, 16)--Ponapé, 3 (undated)--Kusaie, 1 (April 25).

_Nesting._--The Dusky Shearwater in Micronesia nests in holes on
high, and usually isolated, coral cliffs. Owston's collectors,
according to Hartert (1900:10), found a nest with one egg at Truk
on June 16. The nest was in a hole four feet deep in the side of a
cliff. The egg is white and measures 42 × 35. Yamashina (1932a:408)
records the taking of one egg at Arakabesan, Palau Islands, on May
26. Coultas (field notes) gives an interesting account of nesting
activities of this shearwater at the Palau Islands. He found the
bird nesting on small islands of the group from October to
December, 1931; however, he states that the natives told him that
the bird nests throughout the year. Land crabs and shearwaters were
often found together in the same burrow. Apparently the adult birds
did not remain in the burrow with the young during the day. At
Kusaie, Coultas was told by the natives that the adult birds were
caught by tying the mandibles of the young together. When the
parent birds approached and hovered over the young birds expecting
their mouths to open, the natives had the opportunity to strike
them down with clubs. Coultas collected six downy nestlings at
Palau in November and December.

_Remarks._--The first published account of this shearwater in Micronesia was apparently by Kittlitz (1858, pt. 1:358) when he recorded his "Schwärzlicher Sturmvogel" at Kusaie, according to Wiglesworth (1891a:79). Finsch (1875:44 and 1881b:113, 115) studied specimens taken by Tetens, Heinsohn, and Kubary at the Palau Islands and those taken by Kubary at Ponapé. Earlier, Hartlaub (1868:832) used some of these specimens from the Palau Islands to describe his _Puffinus opisthomelas_ var. _minor_, which was destined to be placed in synonymy (Murphy, 1927:10). Oustalet (1896:54, 55) recorded specimens taken by Marche at Saipan in May, 1887, and at Rota in July, 1888. Oustalet referred to them as _P. obscuras_ and _P. tenebrosus_, respectively. T. W. Gulick obtained undated skins at Ponapé. Hartert (1900:10) reported on specimens taken by Owston's collectors at Truk. In 1931, Coultas with the Whitney South Sea Expedition took one shearwater at Kusaie and a series of 64 skins at the Palau Islands. He failed to find birds at Ponapé and wrote that their scarcity there may have been due to persistent hunting of them by the inhabitants of the island. The NAMRU2 party obtained no information concerning the birds at Guam, Rota, or Truk, but at the Palau Islands observed shearwaters at sea approximately 6 miles east of Babelthuap Island on September 2, 1945.

Murphy (1927:6-15) revised the shearwaters of the _Puffinus lherminieri_ group, and recognized several subspecies. _P. l. dichrous_ was assigned a range consisting of Micronesia, the Phoenix Islands, and Nauru Island. The breeding range of _P. l. polynesiae_ was given as the Samoan, Society, Tuamotu and Marquesas islands. Color differences between the two subspecies are very slight, and he separated them on the basis of the length of the exposed culmen as follows: _P. l. dichrous_ 22.6-27 (26) in _P. l. polynesiae_ 25.5-30 (28.9). In other measurements they closely resembled one another. At the time of his study, Murphy did not have the shearwaters from Micronesia collected by Coultas and actually did not have a large series from these islands. On studying this new material, I find the length of the exposed culmen of 17 adult birds from Micronesia (including 12 from the Palaus) to be 26-30 (27.9). In comparison with Murphy's findings, my measurements of Micronesian birds fall almost midway between the measurements which he recorded as characteristic of _P. l. dichrous_ (from the Phoenix Islands) and _P. l. polynesiae_. The intermediate position of the measurements of the Micronesian birds, together with the absence of other distinguishing characters, suggests that these shearwaters belong to only one subspecies which consists of a group of isolated and variable populations. Unless the old specific name, _obscuras_ of Gmelin, is revived, the name for the entire group in Micronesia and Polynesia would be _P. l. dichrous_. I agree with Murphy that the Bonin form, _P. l. bannermani_, is a well-defined subspecies.

=Pterodroma rostrata rostrata= (Peale)

Tahiti Petrel

_Procellaria rostrata_ Peale, U. S. Expl. Exp., 8, 1848, p. 296.
(Type locality, Mountains about 6,000 feet on Tahiti, Society
Islands.)

_Procellaria desolata_ Pucheran, Voy. Pôle Sud, 3, 1853, p. 138
(des îles Carolines); Hartlaub, Journ. f. Ornith., 1854, p. 168
(Carolinen).

_Procellaria (Aestrelata) desolata_ Gray, Cat. Birds Trop. Is.
Pacific Ocean, 1859, p. 55 (Caroline Islands).

_Oestrelata rostrata_ Wiglesworth, Abhandl. und Ber. Zool. Mus.
Dresden, no. 6, 1890-1891 (1891), p. 82 (Caroline Is.); Godman,
Monogr. Petrels, pt. 3, 1908, p. 190 (Caroline Is.).

_Pterodroma rostrata_ Kuroda, in Momiyama, Birds Micronesia, 1922,
p. 33 (Carolines).

_Pterodroma rostrata_ subsp. (?) Hand-list Japanese Birds, rev.,
1932, p. 188 (Carolines); Hand-list Japanese Birds, 3d ed., 1942,
p. 210 (Carolines).

_Geographic range._--Known to breed on the Society and Marquesas
Islands. In Micronesia: Caroline Islands--exact locality unknown.

_Characters._--A large petrel with blackish-brown plumage except
for belly and under tail-coverts white and throat, upper breast
and flanks pale brown; bill black; legs yellowish; feet black.
This oceanic bird differs from other petrels and shearwaters of
Micronesia by the presence of a white abdomen in contrast with
dark plumage on upper parts, throat, and breast.

_Remarks._--A petrel which is referred to this subspecies has been taken once in Micronesia, by Hombron and Jacquinot in the Caroline Islands. It may be pointed out that the subspecies _P. r. becki_ Murphy is known from the sea east of the Bismarck Archipelago and might range into Micronesian waters.

=Pterodroma hypoleuca hypoleuca= Salvin

Stout-billed Gadfly Petrel

_Oestrelata hypoleuca_ Salvin, Ibis, 1888, p. 359. (Type locality,
Krusenstern Island = Ailuk, Marshall Islands, _fide_ Fisher, Auk.,
63, 1946, pp. 587-588).

_Oestrelata hypoleuca_ Salvin, Cat. Birds British Mus., 25, 1896,
p. 409 (Krusenstern); Godman, Monogr. Petrels, pt. 3, 1908, p. 212
(Krusenstern).

_Cookilaria hypoleuca hypoleuca_ Mathews, Syst. Avium
Australasianarum, 1, 1927, p. 122, (Marshall Group).

_Pterodroma leucoptera hypoleuca_ Hand-list Japanese Birds, rev.,
1932, p. 188 (Marshalls); Hand-list Japanese Birds, 3d ed., 1942,
p. 210 (Krusenstern); Fisher, Auk, 63, 1946, pp. 387-388 (Ailuk).

_Pterodroma hypoleuca hypoleuca_ Mayr, Birds Southwest Pacific,
1945, p. 11 (Micronesia).

_Geographic range._--Ranges from the Bonins east to the Hawaiians
and south to Micronesia. In Micronesia: Marshall Islands--Ailuk.

_Characters._--Upper parts grayish except for forehead whitish,
crown and nape sooty-black; underparts whitish except for sides of
breast sooty-black; legs and feet flesh color except for tips of
toes and webs which are black.

_Remarks._--In Micronesia, this petrel is known only from the type locality, Krusenstern or Ailuk, Marshall Islands. Fisher (1946: 587-588) has corrected the confusion regarding the exact position of this type locality.

=Phaëthon aethereus mesonauta= Peters

Red-billed Tropic-bird

_Phaëthon aethereus mesonauta_ Peters, Occ. Papers Boston Soc. Nat.
Hist., 5, 1930, p. 261. (Type locality, Swan Key, Almirante Bay,
Panama.)

_Phaeton aethereus_ Finsch, Ibis, 1880, pp. 329, 333, (Ratak
Chain, Marshalls); _idem_, Journ. f. Ornith., 1880, p. 310
(Kuschai); _idem_, Ibis, 1881, p. 109 (Kuschai); Wiglesworth,
Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p.
73 (Kushai, Marshalls); Ogilvie-Grant, Cat. Birds British Mus. 26,
1898, p. 457 (Kushai, Marshalls); Schnee, Zool. Jahrbücher, 20,
1904, p. 390 (Marschall Inseln); Kuroda, in Momiyama, Birds
Micronesia, 1922, p. 34 (Kusaie, Marshall Islands).

_Phaethon aethereus [?mesonauta]_ Hand-list Japanese Birds, rev.,
1932, p. 187 (Kusaie, Marshalls); Hand-list Japanese Birds, 3d
ed., 1942, p. 208 (Kusaie, Marshall Islands).

_Geographic range._--Tropical parts of Atlantic and eastern Pacific
from Cape Verde Islands west to Panama and Galapagos Islands. In
Micronesia: Caroline Islands--Kusaie; Marshall Islands--Ratak
Chain.

_Characters._--Adult: A large, white sea bird with a long white
tail; dorsal surface marked with blackish, transverse
vermiculations; bill red; tarsus and foot flesh-colored with a
yellowish hue, with plantar surface grayish. Immature: Resembles
adults but dark transverse bars are broader; crown blacker; bill
yellow.

_Remarks._--No specimens have been examined. The Red-billed Tropic-bird is placed in the list of birds known from Micronesia on the basis of two observations by the German ornithologist, Otto Finsch. It has not been reported since his time, and may be considered as an unusual record for the area. I am following the Hand-list of Japanese Birds (Hachisuka _et al._, 1942:208) in assigning the bird to the subspecies, _P. a. mesonauta_.

=Phaëthon rubricauda rothschildi= (Mathews)

Red-tailed Tropic Bird

_Scaeophaethon rubricauda rothschildi_ Mathews, Birds Australia, 4,
1915, p. 303. (Type locality, Laysan and Niihau.)

_Phaeton rubricaudus_ Finsch, Journ. f. Ornith., 1880, p. 296
(Carolines); _idem_, Ibis, 1881, p. 115 (Ponapé).

_Phaeton rubricauda_ Finsch, Proc. Zool. Soc. London, 1880, p. 577
(Ruk); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no. 6,
1890-1891 (1891), p. 73 (Ruk, Ponapé, Marshalls).

_Phaeton rubricauda_ Ogilvie-Grant, Cat. Birds British Mus., 26,
1898, p. 451 (Caroline Islands); Hartert, Novit. Zool., 7, 1900,
p. 11 (Ruk); Hand-list Japanese Birds, rev., 1932, p. 187 (Pagan,
Truk, Ponapé, Marshalls).

_Scaeophaethon rubricauda_ Kuroda, in Momiyama, Birds Micronesia,
1922, p. 34 (Mariannes, Ruk, Ponapé, Marshalls).

_Phaethon rubricauda rothschildi_ Yamashina, Tori, 7, 1932, p. 406
(Pagan); _idem_, Tori, 10, 1940, p. 676 (Maug).

_Phaethon rubricaudus rothschildi_ Hand-list Japanese Birds, 3d
ed., 1942, p. 209 (Maug, Pagan, Truk, Ponapé, Marshalls).

_Geographic range._--Bonin and Hawaiian islands south to
Micronesia. In Micronesia: Mariana Islands--Maug, Pagan; Caroline
Islands--Truk, Ponapé; Marshall Islands--exact locality unknown.

_Characters._--Adult: Long-tailed sea bird white with pinkish tint
except for black lores and eye streak; black shafts on feathers of
secondaries, flanks, and tail coverts; black bases on feathers of
head; central tail feathers elongate with black shafts and bright
red webs; bill orange-red with black nasal streak; tarsus and foot
bluish-yellow, distal part blackish. Immature: Resembles adult but
barred with black above; bill blackish.

_Measurements._--Yamashina (1940:676) lists the measurements for
seven adult birds from Maug in the northern Marianas as wing
304-319 and exposed culmen 55-62.

_Nesting._--Yamashina (1932a:406) reports the taking of one egg at
Pagan in the Marianas on February 15, 1931.

_Remarks._--The Red-tailed Tropic Bird has been recorded from the Mariana, Caroline, and Marshall Islands. On the basis of our present knowledge it appears to be uncommon in most of Micronesia and may be established as a resident bird only in the northern Marianas, as shown by Yamashina (1932a:406 and 1940:676), Coultas obtained an immature male at 3° N and 158° E, which is at a point in the ocean south of the eastern Carolines. Possibly this bird and others obtained in the Carolines are representatives of the subspecies, _P. r. melanorhynchos_ Gmelin, which is known from the Palmerston, Society and Turtle islands.

=Phaëthon lepturus dorotheae= Mathews

White-tailed Tropic Bird

_Phoethon lepturus dorotheae_ Mathews, Austr. Avium. Rec., 2, 1913,
p. 7. (Type locality, Queensland.)

_Phaeton candidus_ Kittlitiz, Denkw. Reise russ. Amer. Micron. und
Kamchat., 1, 1858, p. 382 (Ualan); Hartlaub and Finsch, Proc.
Zool. Soc. London, 1868, pp. 9, 118 (Pelew); Finsch, Journ. f.
Ornith., 1872, p. 57 (Pelew); Hartlaub and Finsch, Proc. Zool.
Soc. London, 1872, pp. 90, 114 (Pelew, Ualan); Finsch, Journ. Mus.
Godeffroy, 1875, pp. 6, 47 (Palau); _idem_, Proc. Zool. Soc.
London, 1877 (1878), p. 782 (Ponapé); _idem_, Journ. f. Ornith.,
1880, pp. 296, 309 (Ponapé, Kuschai); _idem_, Proc. Zool. Soc.
London, 1880, p. 577 (Ruk); Schmeltz and Krause, Ethnogr. Abth.
Mus., Godeffroy, 1881, pp. 281, 299, 330, 353 (Ponapé, Mortlock,
Nukuor, Ruk); Finsch, Mitth. Ornith. Ver. Wien, 1884, p. 52
(Kuschai); Wiglesworth, Abhandl. und Ber. Zool. Mus. Dresden, no.
6, 1890-1891 (1891), p. 73 (Pelew, Ruk, Luganor, Nukuor, Ponapé,
Ualan, Marshalls); Oustalet, Nouv. Arch. Mus. Hist. Nat. Paris,
(3), 8, 1896, p. 62 (Agrigan, Palaos, Ruk, Kushai, Marshalls);
Hartert, Novit. Zool., 5, 1898, p. 68 (Marianne).

_Phaeton flavirostris_ Finsch, Ibis, 1880, pp. 329, 333 (Ratak
Chain); _idem_, Ibis, 1881, pp. 105, 109, 115 (Kuschai, Ponapé).

_Phaethon candidus_ Salvadori, Ornith. Papuasia, 3, 1882, p. 426
(Pelews, Carolines, Marshalls); Seale, Occ. Papers Bernice P.
Bishop Mus., 1, 1901, p. 23 (Agrigan); Safford, Osprey, 1902, p.
70 (Mariannes); Takatsukasa and Kuroda, Tori, 1, 1915, p. 50
(Pelew, Ponapé); Uchida, Annot. Zool. Japon., 9, 1918, pp. 489,
492 (Palau).

_Phaëthon lepturus_ Ogilvie-Grant, Cat. Birds British Mus., 26,
1898, p. 453 (Pelew, Carolines, Marshalls); Hartert, Novit. Zool.,
7, 1900, p. 10 (Ruk); Safford, The Plant World, 7, 1904, p. 268
(near Guam); _idem_, Contr. U. S. Nat. Herb., 9 1905, p. 80
(northern Marianas); Mayr, Birds Southwest Pacific, 1945, p. 17
(Palau); Strophlet, Auk, 63, 1946, p. 535 (Guam); Borror, Auk, 64,
1947, p. 416 (Agrihan); Stott, Auk, 64, 1947, p. 524 (Saipan).

_Phaeton lepturus_ Schnee, Zool. Jahrbücher, 20, 1904, p. 390
(Marschall Inseln).

_Leptophaethon lepturus dorothea_ Mathews, Birds Australia, 4,
1915, p. 309 (Pelew).

_Phaethan lepturus_ Cox, Island of Guam, 1917, p. 22 (northern
Marianas).

_Leptophaethon lepturus lepturus_ Kuroda, in Momiyama, Birds
Micronesia, 1922, p. 33 (Agrigan, Saipan, Pelew, Ruk, Luganor,
Nukuor, Ponapé, Kusaie, Marshalls).

_Phaethon lepturus dorotheae_ Yamashina, Tori, 7, 1932, p. 407
(Ponapé); Hand-list Japanese Birds, rev., 1932, p. 187 (Agrigan,
Pagan, Saipan, Agiguan, Palaus, Truk, Luganor, Nukuor, Ponapé,
Kusaie, Marshalls); Hand-list Japanese Birds, 3d ed., 1942, p. 209
(Agrigan, Pagan, Saipan, Agiguan, Babelthuap, Koror, Urukthapel,
Angaur, Unusuto, Truk, Luganor, Nukuor, Ponapé, Kusaie, Namorik);
Baker, Smithson. Misc. Coll., vol. 107, no. 15, 1948, p. 38 (Guam,
Peleliu, Ulithi, Truk).

_Geographic range._--Islands in the southwestern Pacific area. In
Micronesia: Mariana Islands--Agrigan, Pagan, Saipan, Agiguan, Rota,
Guam; Palau Islands--Babelthuap, Koror, Urukthapel, Peleliu,
Anguar, Unusuto; Caroline Islands Truk, Ulithi, Luganor, Nukuor,
Ponapé, Kusaie; Marshall Islands--Namorik.

_Characters._--Adult: White often with pinkish shade but lores and
eye streak black; feathers of head, flanks and under tail-coverts
with bases black; black on outer and subterminal part of inner
webbing of primaries; black, subterminal coloring on scapulars and
secondaries; black on shafts of elongated tail plumes; bill horn
yellow, dark basally; tarsus dark yellow; feet blackish.

Immature: Resembles adult but upper parts barred with black, bill
black on terminal part.

_Measurements._--Measurements of adult birds from Micronesia are
given in table 15.

_Weights._--The NAMRU2 party recorded weights of five adult males
from Guam as 294 (267-321) grams.

TABLE 15. MEASUREMENTS OF _Phaëthon lepturus_ FROM MICRONESIA

---------------------------+-----+---------+--------+---------+-------
| | | | Exposed |
| No. | Wing | Tail | culmen | Tarsus
---------------------------+-----+---------+--------+---------+-------
Marianas: Asuncion, Guam | 6 | 264 | 107 | 47 | 21
| | 256-287 | 97-117 | 44-50 | 20-21
| | | | |
Palaus: Peleliu | 11 | 257 | 108 | 45 | 21
| | 242-270 | 98-122 | 40-49 | 19-21
| | | | |
Carolines: Ponapé, Kusaie | 11 | 261 | 105 | 47 | 21
| | 252-271 | 97-114 | 44-49 | 21-22
+-----+---------+--------+---------+-------
Total: Micronesia | 28 | 260 | 107 | 46 | 21
| | 242-287 | 97-122 | 40-50 | 19-22
---------------------------+-----+---------+--------+---------+-------

_Specimens examined._--Total number, 37 (22 males, 10 females, 5
unsexed), as follows: Mariana Islands, USNM--Guam, 5 (June 11, July
21); AMNH--Asuncion, 1 (June?); Palau Islands, USNM--Peleliu, 5
(Aug. 29, 31, Sept. 5, 6); AMNH--exact locality not given, 7 (Oct.
13, 26, Nov. 15, 23, Dec. 18); Caroline Islands, AMNH--Ponapé, 9
(Dec. 8, 9, undated)--Kusaie, 10 (March 1-8, April).

_Nesting._--The NAMRU2 party observed nests of the White-tailed
Tropic Bird at Peleliu in August and September, 1945. Several
nests were seen in hollows of the Australian pine (_Casuarina
equisetifolia_) between 20 and 30 feet above the ground. Birds
could be seen in the nest hollows because the plumes of their long
tail usually extended well out of the entrance. One nest was found
in a dead tree in a battle-cleared area; others were observed in
jungle habitat. Coultas observed nesting at Ponapé between
November 1 and December 30, 1930, and found nests in the tops of
trees and in hollow trees; a few were observed in holes in cliffs.
Yamashina (1932a:407) records the taking of one egg at Ponapé on
August 18, 1931. At Guam the NAMRU2 party found birds along the
high cliffs which edge the beach. There was no evidence that they
were nesting from May to July; nevertheless males taken in June
had enlarged gonads. The bird is known to breed at Namorik in the
Marshall Islands, according to the Hand-list of Japanese Birds
(Hachisuka _et al._, 1942:209).

_Food habits._--The NAMRU2 party found small fish in the stomachs
of these birds taken at Peleliu.

_Parasites._--Uchida (1918:489, 492) records the bird lice
(Mallophaga), _Colpocephalum epiphanes_ and _Menopon eulasius_,
from the White-tailed Tropic Bird from Palau.

_Remarks._--Birds taken in Micronesia differ only slightly from those from other areas in Oceania. Within Micronesia (see table 15) the birds from the Palaus have the shortest wing and shortest exposed culmen.

The White-tailed Tropic Bird appears more numerously in western and northern Micronesia than in the Marshall Islands. This distribution may be correlated with a preference for the "high" islands; especially those which have rocky cliffs, including Guam, Rota, Peleliu, Angaur, and Truk. Reports were received in 1945 that the birds were only infrequently seen at Ulithi, a low atoll. Stott (1947:524) observed birds flying into rocky crevices at Saipan on December 18. Gleise (1945:221) also recorded the bird in the vicinity of Saipan. Borror (1947:416) reports seeing birds at Agrigan on July 29, August 5 and 6, 1945. Coultas (field notes) found tropic birds common at Ponapé in November and December, 1930, in forested regions and along the cliffs. He made similar observations at Kusaie and Palau. At Ponapé and Palau, Coultas noted the use of the eggs, young and adults as food by the natives. At Palau the plumes are used in headdresses worn by the natives, the birds being taken with the blowgun.

Murphy (1936:807) states that the principal enemy of the White-tailed Tropic Bird at Bermuda is the introduced rat (_Rattus rattus_). Introduced rats, particularly _Rattus mindanensis_ on Guam, may prey on the nesting birds. Baker (1946c:404) writes that this rat is a good climber and may spend considerable time in trees. The rat was trapped also in rough coral jungle at the edge of the cliffs, where tropic birds, Micronesian Starlings and other species, may have been nesting.

Little has been recorded concerning the post-breeding season wanderings of these tropic birds in Micronesia. They seemingly spend considerable time at sea, but whether they move as far from their breeding areas as do birds in the Atlantic, as reported by Murphy (1936:803), Baker (1947a:253) and others, is not known.

Murphy (1936:796) notes that the northward distribution of the tropic birds in the Atlantic is dependent on the warm currents of water. In the western Atlantic, the poleward-flowing, warm currents of the Gulf Stream allow for the northern extension of the range of these birds to Bermuda. In the eastern Atlantic, cool currents flowing toward the equator restrict the northern range. The same condition prevails in the eastern Pacific where warm current flowing toward the pole enable the birds to range north to the Bonins and other islands.

The three species of tropic birds known from Micronesia overlap very little in their ranges in this area. The White-tailed Tropic Bird has become firmly established in the western part of Micronesia, but there are only a few records from the extreme eastern part. The Red-tailed Tropic Bird appears to be resident only in the northern Marianas although it has been recorded in the Carolines and Marshalls. Interspecific competition may prevent considerable intermingling of breeding populations in Micronesia, or it may be that each species requires different ecologic conditions.

=Sula dactylatra personata= Gould

Masked Booby

_Sula personata_ Gould, Proc. Zool. Soc. London, 1846, p. 21. (Type
locality, North and northeast coasts of Australia = Raine Island.)

_Sula cyanops_ Finsch, Ibis, 1880, p. 219 (Taluit); Wiglesworth,
Abhandl. und Ber. Zool. Mus. Dresden, no. 6, 1890-1891 (1891), p.
72 (Marshalls); Ogilvie-Grant, Cat. Birds British Mus., 26, 1898,
p. 430 (Marshalls).

_Parasula dactylatra personata_ Kuroda, in Momiyana, Birds
Micronesia, 1922, p. 35 (Marshall Islands); Mathews, Syst. Avium
Australasianarum, 1, 1927, p. 232 (Marshall Islands).

_Sula dactylatra personata_ Yamashina, Tori, 7, 1932, p. 407
(Medinilla); Hand-list Japanese Birds, rev., 1932, p. 187
(Medinilla, Marshall Islands); Hand-list Japanese Birds, 3d ed.,
1942, p. 208 (Medinilla, Marshall Islands).

_Geographic range._--Central and western Pacific from the Hawaiian
Islands south to Australia, probably also in the Indian Ocean. In
Micronesia: Mariana Islands--Medinilla; Marshall Islands--Jaluit?

_Characters._--Adult: A large, white sea bird, with brown wings
and tail; face dark blue; bill horn-colored with base
orange-yellow in males and pink or light red in females; feet
olive in males and lead gray in females.

Immature: Resembles adult, but head, wings, tail, chin and throat
dark brown; some white mottling may be present on back and rump;
bill dark; feet lead colored.

_Nesting._--Yamashina (1932a:407) reports the taking of 12 eggs on
February 19, 1931, at Medinilla Island in the Marianas.

_Remarks._--No specimen has been examined by me from the area reported upon. Little is known regarding the distribution of the Masked Booby in Micronesia. It is found on the island groups which surround Micronesia and future field observations probably will add to our knowledge of its occurrence in this area. It is known to be resident only in the northern Marianas.

=Sula sula rubripes= Gould

Red-footed Booby

_Sula rubripes_ Gould, Syn. Birds Australia, pt. 4, 1838, app., p.
7. (Type locality, New South Wales = Raine Island.)

_Pelecanus piscator_ Kittlitz, Obser. Zool., in Lutké, Voy. "Le
Séniavine," 3, 1836, pp. 296, 299 (Lougounor = Lukunor); _idem_,
Denkw. Reise russ. Amer. Micron. und Kamchat., 1, 1858, p. 351
(Lugunor).

_Dysporus piscator_ Hartlaub, Proc. Zool. Soc. London, 1867
(1868), p. 831 (Pelew); Hartlaub and Finsch, Proc. Zool. Soc.
London, 1868, pp. 9, 118 (Pelews); _idem_, Proc. Zool. Soc.
London, 1872, p. 90 (Pelew); Finsch, Journ. Mus. Godeffroy, 8,
1875, pp. 6, 47 (Palau).

_Sula piscatrix_ Wiglesworth, Abhandl. und Ber. Zool. Mus.
Dresden, no. 6, 1890-1891 (1891), p. 72 (Pelew, Luganor);
Oustalet, Nouv. Arch. Mus. Hist. Nat. Paris, (3), 8, 1896, p. 64
(Rota, Palaos, Carolines); Hartert, Novit. Zool., 5, 1898, p. 68
(Marianne); Safford, Osprey, 1902, p. 70 (Rota); _idem_, The Plant
World, 7, 1904, p. 267 (Guam); _idem_, Contr. U. S. Nat. Herb., 9,
1905, p. 80 (Guam); _idem_, Guam, 1912, p. 19 (Guam); Cox, Island
of Guam, 1917, p. 22 (Guam).

_Sula piscator_ Ogilvie-Grant, Cat. Birds British Mus., 26, 1898,
p. 432 (Pelew); Seale, Occ. Papers Bernice P. Bishop Mus., 1, 1901,
p. 24 (Guam).

_Piscatrix sula rubripes_ Kuroda, in Momiyana, Birds Micronesia,
1922, p. 34 (Pelew, Luganor, Rota).

_Sula sula rubripes_ Hand-list Japanese Birds, rev., 1932, p. 185
(Medinilla, Saipan, Rota, Palau, Lukunor, Likieb); Bryan, Guam
Rec., vol. 13, no. 2, 1936, p. 15 (Guam); Yamashina, Tori, 10,
1940, p. 676 (Maug, Bikar); Hand-list Japanese Birds, 3d ed.,
1942, p. 208 (Maug, Medinilla, Saipan, Rota, Palau, Lukunor,
Bikar, Likieb).

_Geographic range._--Indian Ocean east to central Pacific islands.
In Micronesia: Mariana Islands--Maug, Medinilla, Saipan, Rota;
Palau Islands--exact locality unknown; Caroline Islands--Lukunor;
Marshall Islands--Bikar, Likieb, Bikini, Eniwetok.