The Avifauna of Micronesia, Its Origin, Evolution, and Distribution

Part 1

UNIVERSITY OF KANSAS PUBLICATIONS

MUSEUM OF NATURAL HISTORY

VOLUME 3 · 1951

EDITORS

E. RAYMOND HALL, Chairman A. BYRON LEONARD EDWARD H. TAYLOR ROBERT W. WILSON

MUSEUM OF NATURAL HISTORY UNIVERSITY OF KANSAS LAWRENCE 1951

MUSEUM OF NATURAL HISTORY UNIVERSITY OF KANSAS LAWRENCE

PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1951

24-1811

CONTENTS

1. The Avifauna of Micronesia, Its Origin, Evolution, and Distribution. By Rollin H. Baker. Pp. 1-359, 16 figures in text. June 12, 1951

2. A Quantitative Study of the Nocturnal Migration of Birds. By George H. Lowery, Jr. Pp. 361-472, 47 figures in text. June 29, 1951

3. Phylogeny of the Waxwings and Allied Birds. By M. Dale Arvey. Pp. 473-530, 49 figures in text, 13 tables. October 10, 1951

4. Birds from the State of Veracruz, Mexico. By George H. Lowery, Jr. and Walter W. Dalquest. Pp. 531-649, 7 figures in text, 2 tables. October 10, 1951

Index, Pp. 651-681.

The Avifauna of Micronesia, Its Origin, Evolution, and Distribution

ROLLIN H. BAKER

University of Kansas Publications Museum of Natural History

Volume 3, No. 1, pp. 1-359, 16 figures in text June 12, 1951

University of Kansas LAWRENCE 1951

The Avifauna of Micronesia, Its Origin, Evolution, and Distribution

ROLLIN H. BAKER

University of Kansas Publications Museum of Natural History

Volume 3, No. 1, pp. 1-359, 16 figures in text June 12, 1951

University of Kansas LAWRENCE 1951

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Edward H. Taylor, Robert W. Wilson

=Volume 3, No. 1, pp. 1-359, 16 figures in text Published June 12, 1951=

Part 2

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1951

22-8131

The Avifauna of Micronesia, Its Origin, Evolution, and Distribution

ROLLIN H. BAKER

CONTENTS

PAGE

INTRODUCTION 5

DESCRIPTION OF MICRONESIA 5 Climate 8 Soils 9 Surface water 9 Vegetation 10

GAZETTEER OF THE ISLANDS OF MICRONESIA 11 Mariana Islands 11 Palau Islands 13 Caroline Islands 14 Marshall Islands 15

ORNITHOLOGICAL EXPLORATION IN MICRONESIA 16

CHECK-LIST OF THE BIRDS OF MICRONESIA 21

DISCUSSION OF THE AVIFAUNA 28 Oceanic Birds 28 Inshore Oceanic Birds 29 Offshore and Pelagic Oceanic Birds 30 Faunal Components 30 Migratory Shore Birds 32 Original Homes of the Shore Birds that Visit Micronesia 32 Routes of Migration 34 Populations of Shore Birds in Micronesia 37 Land and Fresh-Water Birds 42 Polynesian Component 44 Melanesian Component 44 Moluccan and Celebesian Components 45 Philippine Component 45 Palearctic Component 46 Speciation 48 Time of Colonization 50 Factors Causing Dispersal 52 Analysis of Speciation 55

CONSERVATION OF THE AVIFAUNA OF MICRONESIA 58

THE FUTURE OF ORNITHOLOGICAL RESEARCH IN MICRONESIA 60

METHODS AND ACKNOWLEDGMENTS 60

ACCOUNTS OF THE KINDS OF BIRDS IN MICRONESIA 63

SUMMARY AND CONCLUSIONS 340

BIBLIOGRAPHY 343

FIGURES IN TEXT

FIGURE PAGE

1. The islands of Micronesia. 6

2. The Mariana Islands. 12

3. The Palau Islands. 13

4. The Caroline Islands. 15

5. The Marshall Islands. 16

6. Routes of migration used by shore birds in the Pacific. 34

7. Avifaunal regions of the central Pacific. 43

Part 3

8. Faunal areas from which Micronesian birds have been derived. 46

9. Routes of dispersal of rails in the Pacific area. 120

10. Variation in length of culmen of Sterna s. sumatrana. 159

11. Geographic distribution of Thalasseus bergii. 164

12. Geographic distribution of Gygis alba in the Pacific. 177

13. Distribution and dispersal of Ptilinopus porphyraceus. 190

14. Distribution and dispersal of Gallicolumba in the Pacific. 204

15. Distribution and dispersal of Acrocephalus in the Pacific. 260

16. Distribution and dispersal of Myzomela in the Pacific. 316

INTRODUCTION

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.

DESCRIPTION OF MICRONESIA

The vast expanse of the Pacific Ocean is dotted with numerous islands, most of which are concentrated in the central and western part and are known collectively as Oceania. Within Oceania three divisions are popularly recognized: Melanesia, Polynesia, and Micronesia. According to Krieger (1943:6), the Micronesia islands include the Mariana, Palau, Caroline, Marshall, and Gilbert islands; they may take in also the Volcano, Bonin, and Ellice islands (from the standpoint of anthropology). Zoogeographically, according to Wallace (1876), Micronesia is to be included in the Polynesian Subregion of the Australian Region. Mayr (1941a:193), on the basis of the distribution of birds, ranks Micronesia as one of the four subdivisions of the Polynesian Subregion, and includes within Micronesia the Palau, Caroline, Mariana, Marshall, and Gilbert islands. Except in the discussion of distribution, this report does not treat of the avifauna of the Gilbert Islands, which straddle the equator south of the Marshall Islands. This report is concerned only with the birds in the Mariana, Palau, Caroline, and Marshall islands formerly mandated to Japan, and with the birds of the island of Guam, which is a possession of the United States.

The word Micronesia is, of course, derived from the Greek words mikros meaning small and nesos meaning island, and, as shown in figure 1, this term is appropriate, for the islands of this area are small. For the most part they are too small even for inclusion on standard-sized maps of the world. There are thousands of these islands in an area some 2,400 miles long from east to west and some 1,200 miles broad from north to south. All of the islands of Micronesia are oceanic islands; that is to say, they have never been connected to the Asiatic continent or to other land masses by means of land bridges.

Geologists and oceanographers have shown (see descriptions by Hobbs, 1945), that islands of Micronesia are of two general types: arcuate and strewn. The Pacific Ocean is surrounded by rising mountain ranges which are arranged in elongated, near-circular arcs, which form an extended series of scallops. In the western Pacific these sweeping arcs extend into the ocean, where the mountain ranges project upward from the bottom of the sea with only the crests showing above the waves to point out, in dotted outline, the position of the mountains. The easternmost of these arcs is marked by the islands of the Aleutians, Kuriles, Japan, Izo, Bonins, Volcanoes, Marianas, Yap, Palaus, and others continuing southward into Melanesia. These are characterized by igneous rocks of andesitic nature.

To the eastward of the arcuate islands in Micronesia, are numerous and irregularly distributed islands, making up all of the central and eastern Carolines and the Marshalls, which are known as strewn islands. Strewn islands mark the places of former volcanoes or volcanic peaks. If these volcanic peaks have been completely drowned and are now marked by a series of low islands edged by a protecting reef formed by coral growth enclosing a lagoon and with all exposures consisting of coral rock, the island is known as a coral atoll (example, Ulithi Atoll). Some of the coral exposures lack lagoons; they are known merely as coral islands (example, East Fayu). Some atolls become elevated by geologic activity and the lagoons may dry out or drain. The accumulation of guano of oceanic birds and the residue of fish and other organisms in the area of the lagoon remains as a rich phosphate deposit; these raised atolls have been called phosphate islands (example, Fais). Other strewn islands consist of igneous rocks which are exposed above the surface of the ocean. These are known as "high" or volcanic islands and may occur as a single mountain rising out of the ocean (example, Kusaie), or be partly drowned and surrounded by a coral reef (example, Truk). The igneous rocks found on these strewn islands are basaltic in nature.

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