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.