Ornithology, Evolution, and Philosophy 123

Expeditions to New Guinea and the Solomon Islands 89
succeeded in discovering the home of most of the so-called ‘rare Birds of Paradise.’
But there were about five or six species left which simply could not be rediscovered.
What Lord Rothschild wanted me to do was to go to three particular mountain
ranges in western New Guinea which so far had been insufficiently explored or not
at all.
I would like to tell you all about my trials and tribulations in exploring these
untouched and largely uninhabited mountain ranges all alone, except for some
native assistants from Java, but my time only permits me to tell you that I obtained
a fine collection of birds, mammals, insects, and plants on all three mountain
ranges, but saw no hide nor hair of any of Lord Rothschild’s rare Birds of Paradise.
As far as its principal purpose was concerned, you might say my expedition was
a failure. But wait a minute!
My failure to find these birds in some of the last unexplored mountains of
New Guinea gave Professor Stresemann in Berlin a bright idea. ‘Maybe there is
something fishy about these species; maybe they aren’t even good species,’ he
thought. So he examined them very carefully, and was able to prove eventually that
each of the so-called species, the home of which could not be found, was actually
a hybrid between two other well-known species of Birds of Paradise [Stresemann
1930]. You can imagine how pleased I was to have contributed to the solution of
this great puzzle of New Guinea ornithology, and to know that my expedition had
not been a failure after all” (1981b: 149–150).
Mayr (1945h) estimated that possibly only one out of about 20,000 birds of
paradise is a hybrid each of which is due to an “error” of the birds because of
their breeding habits. Male and female birds of paradise never form a pair bond.
The mature female is attracted to the display ground of the males when she is
ready for mating and leaves the male soon after. In such a system, especially young
inexperienced females may rather easily commit an error and approach the display
ground of males of the “wrong” species, particularly along the geographical and
elevational range border of its own species, where she may have difficulty locating
a partner of the “right” species (Frith and Beehler 1998: 501–502; see also Nicolai
1977: 124).
The main lessons that Mayr learned in the Solomon Islands were (1) that
each island (except those connected with each other during low sea-level stands
of the Pleistocene) had a very distinct fauna and (2) that there was spectacular
geographic variation and geographic speciation not only of the mountain birds (as
in New Guinea) but also in lowland species.
From the mammal collection consisting of several hundred skins three new
taxa were described: (a) a species of mice, Ernst Mayr’s Leptomys (Leptomys ernstmayri),
inhabiting the montane rainforest of the Saruwaget Mountains (Huon
Peninsula), (b) a subspecies of Doria’s Tree-kangaroo (Dendrolagus dorianus
mayri) of the Wondiwoi Mountains (Wandammen Peninsula), and (c) a subspecies
of the Long-fingered Triok (Dactylopsila palpator ernstmayri); Rümmler (1932),
Rothschild and Dollman (1933), Stein (1932); see also Flannery (1995). In addition,
Mayr collected about 4,000 butterflies, 4,000 beetles, 1,000 grasshoppers, a few spiders,
scorpions, crustaceans, snails, worms, lizards, and snakes. A number of