For a naturalist, traveling the length and breadth of Japan is an endless magical mystery tour. Living in any one part of the country one can easily forget the phenomenal diversity in this immensely varied archipelago.

Autumn in Hokkaido soon sees an end to the year's butterflies, with a final flurry of dragonflies presaging the downturn of the year, while at the opposite end of the country both humidity and temperature remain high and insect-friendly. Whereas the forests of the north are closing down with astonishing rapidity, turning colorful then leafless, those of the south-west, seeming oblivious to passing time, remain a luxuriant, if somewhat leathery, green. Where the northern island turns subarctic with the rapidly approaching winter, the southwestern islands, the Nansei Shoto, barely change. While almost all small birds flee the north, in the south the more amenable climate allows a higher proportion of them to remain resident.

Mountain hiking in Hokkaido in autumn is like watching the proverbial rats leaving a sinking ship. One sees a ragged stream of common buzzards (nosuri) gliding southwestwards in ones and twos, skimming ridges and peaks, flying over the narrow Tsugaru Strait on their way to the outstretched capes of northern Aomori. Crossing the straight they move on steadily, outstretched wings carrying them southwards through Honshu, as far as Kyushu and occasionally even Okinawa, ahead of falling temperatures and declining food supplies in the north.

The gray-faced buzzard (sashiba), a slightly smaller bird of prey, breeds in Honshu as far north as southern Tohoku. It is of a more delicate disposition, fleeing southwards as winter approaches despite the relative mildness of Honshu. Beginning its journey farther south than the common buzzard, it also travels and winters farther south. It passes through the southwest islands and over Taiwan in large numbers each autumn and spring.

In the wake of the departing summer birds come the waterfowl, wetland birds escaping before their habitat farther north succumbs to the icy fingers of winter. Hordes of geese, clamoring groups of swans and wing-whirring clouds of duck all retreat to Japan for the winter months. Were they to stay farther north, they would quickly run out of food, and finally out of access to water as their wetlands freeze over.

Rather like the changeover of shifts at a factory, the wintering waterfowl arrive as the summering forest birds and raptors retreat southwards. The more widely traveled of them, the flycatchers, the warblers and most of the gray-faced buzzards, pass right on through the southwest islands. Yet all the time, a handful of resident species lives year round in those very islands. They are representatives of another realm; where most of Japan lies in the Palearctic, there in the extreme southwest Japan has a finger in the Oriental region.

Red is the color of autumn in the deciduous forests of Japan's temperate region. In Hokkaido the reds have already blazed and waned to gold and brown and on the higher ground no leaves are left. In the evergreen forests in the far southwest, however, red is not an autumn color; it is the color of fresh spring growth. The subtropical laurels and leathery leafed evergreens flush red with new growth in the spring.

The best known of the southwest islands are Okinawa and Amami-Oshima. There, butterflies, beetles and birds draw naturalists from across the country in search of the endemic species, restricted to these twin foci of biodiversity. Less well known is the cluster of islands even farther south -- the Yaeyama Islands. That coral-reef-fringed archipelago within an archipelago, consisting of Ishigaki, Iriomote, Hatoma, Taketomi, Kohama, Kuro and Yonaguni islands, lies closer to Taiwan than to mainland Japan. Not only are those islands physically closer, but from a natural history perspective too they are closer to the countries of the Oriental region. The plants, insects and birds (there are virtually no native mammals) more closely resemble those of Taiwan than they do those of any part of mainland Japan.

Wandering among the evergreen broad-leaved forests of the Yaeyama Islands one can close one's eyes and focus on sounds that are familiar. The incessant wheesping of the brown-eared bulbul is there, as is the musical tittering of the Japanese white-eye, and the scolding of the great tit (though it looks a very different bird from that in mainland Japan).

But having registered those and a few other familiar sounds, if one listens more closely one can hear other "instruments" playing in the forest chorus, sounds unheard farther north.

One that only creeps into the consciousness slowly is a soft, gentle cooing. It seems to emanate from the forest as a whole rather than from any particular point in it. "Hooo-hooo" it goes, repeating itself several times, falling silent, then repeating it all over again. Tracking down this sound is only for the deeply determined, although lucky wanderers may stumble across the source.

Emerald dove

It comes from a bird that loves dense cover, that relishes shade and which lives its life in the Yaeyama Islands -- the emerald dove (kin-bato). For this bird of subtropical warmth, rare northerly wanderings have taken it to Miyako and as far north as Okinawa, but not beyond. The forests of mainland Japan are entirely unknown to it.

Secretively, the emerald dove wanders the forest floor of the Yaeyamas, its mournful cooing a clue to its unobtrusive presence. The emerald green of its wings and mantle merge so well with the forest foliage that it is hard to see. But catch one in a burst of sunlight, see one as it crosses a shaft of light on the forest floor and suddenly it seems richly colored and gemlike. Brightest of all is the silver blaze on the "shoulder" of the closed wing. It seems metallic and has a sheen like sprayed silver. When it flies it whirrs from the forest floor, dropping again quickly into shadowy undergrowth.

The emerald dove, a bird of the tropics, reaches its northernmost limit as a resident of Japan on Ishigaki Island. Elsewhere it may be encountered as far south as coastal New South Wales in Australia and as far west as the Himalayan foothills of northern India. Characteristic of the Asian tropics, it is a reminder that there is so much more to wild Japan than at first meets the eye.