Ornithology, Evolution, and Philosophy 123

Birds of Oceania 149
His second article (1931d) dealt with the isolated Rennell Island, a raised atoll 90
miles southwest of the Solomon Islands. Here “the bird fauna […] has turned out to
be one of the most interesting in the whole South Sea,” because of its extraordinary
endemism:20ofabout33nativespecieswere endemic species or subspecies. He
described no less than three new species (one of them later reduced to subspecies
rank) and 14 new subspecies. As an oceanic island, Rennell has received all of
its fauna by dispersal across water barriers, from the Santa Cruz Islands and the
New Hebrides in the east (30% of the native birds; 56% of the prevailing winds
come from the SE or E), from the Solomon Islands in the north (48% of the native
birds; 16% of the winds come from NW, N or NE), and from New Guinea and
Australia in the west and southwest (5% of the winds come from the W or SW).
The very frequent winds from the east compensate somewhat the greater distance
of the eastern source region. Studies of particularly variable species like, e.g., the
Golden Whistler (Pachycephala pectoralis; 1932c,d) and the Scarlet Robin (Petroica
multicolor; 1934b), led to discussions of the genetic or hormonal control of bird
plumages (1933l).
In monographic studies of particular species and species groups Mayr analyzed
geographical variation on a regional scale, as illustrated by, e.g., the thrushes of the
Turdus javanicus–poliocephalus group (Fig. 4.4). From Solomon Islands and New
Guinea to the west they are high-mountain birds, usually not found below 2,000 m
elevation,butsomeofthepopulationsinsouthernMelanesiaandinPolynesia
occur in the lowlands or even on small coral islands. Subspecies from neighboring
islands are sometimes more distinct (e.g., in the Fiji Islands) than those from
opposite ends of the range. Other examples Mayr discussed include species of fruit
doves, trillers, and fantails.
When the southwestern Pacific Ocean became a Theater of Operations during
World War II, the demand for a field handbook or field guide to the birds of the
islands was great. Ernst Mayr, the expert of this region, produced such a book in
a relatively short time. It appeared in 1945(n) under the title Birds of the Southwest
Pacific. The book covered the birds of Samoa, Fiji, New Caledonia, New Hebrides
(Vanuatu), Banks and Santa Cruz Islands, Solomon, Marshall, Caroline, Mariana
and Palau Islands, 803 forms in total (388 species and 415 subspecies). The layout
is a happy compromise between a strictly systematic and a geographical treatment.
Wide-ranging species like sea birds and shore birds, are presented in the
first chapters. The land and fresh-water birds are grouped systematically in one
section and geographically by seven island groups in Part II of the book. This
organization permitted a separate treatment of all the endemic species of seven
different island groups and yet avoided space-consuming repetition of the more
wide-spread species. Mayr summarized the then available knowledge of these island
birds and emphasized the many gaps particularly regarding life history, again
and again stating “habits unknown” to encourage the observer in the field to gather
more information. Lists of questions relating to the behavior and ecology of birds
are included in the introduction. The book comprises this whole avian fauna in
a manner which satisfied both the amateur observer in the field and the specialist
in the museum. It also contains much unpublished data from personal research.