Summer really is here. It has spread north so rapidly that June- and July-like temperatures were reported in Hokkaido even before the end of April. The cherry blossom wave rushed northward, too, at such a pace it was as if it were trying to take a running jump at Sakhalin.

For me, though, the true harbingers of summer are always the birds whose songs seem to summon in the warmth and humidity that banish thoughts of winter. Warblers, buntings, chats, thrushes, all of these add their particular, distinctive voices to the chorus that can be heard best in the cool early morning, when sounds seem to be clearer and to carry further.

With the wave of warmth spreading northward, summer birds, too, have put in their appearances early this year. What amazes me, though, is how they seem to know ahead of time. Some of these species pass the winter months in subtropical and tropical regions of Southeast Asia where it is always warm. So how, then, do they know that spring is reaching the north at all, let alone that it is so much earlier this year? It's a mystery to me, but clearly not to them.

If I began by describing to you a bird that has bright-blue eye patches, a tail longer than its body, a black crest and a dazzling, esoteric song, you might think I was referring to some exotic African or South American species. But such a bird -- which goes under two English names -- actually lives here in Japan.

To some, it is the black paradise flycatcher, to others, it's the Japanese paradise flycatcher. Scientists know it as Terpsiphone atrocaudata -- the roots of which are in the ancient Greek word terpein, which means "to delight in," and phone, referring to "sound" or "voice." Thus, this bird's generic name refers to the pleasing songs of some species of paradise flycatcher. The specific name, atrocaudata, is like the English names in being simply descriptive: Atro is derived from the Latin ate, meaning "black," while caudata comes from cauda, meaning "tail."

In Japan, this "black-tailed delighter in song" has, I feel, a more evocative name that conjures up hot summer days and warm summer nights. Here it is known as sankocho, "three-lights bird," referring to the three lights of the moon, the sun, and of the stars. If you once hear this bird sing you will have no doubt about the aptness of this name, because its distinctive song is rendered into Japanese as "tsuki-hi-hoshi, hoi-hoi-hoi" (moon-sun-stars, hoi-hoi-hoi).

This particular beauty is a summer visitor to Japan. The male is a startling creature, distinguished by his blue bill, bright-blue eye patch and black crest -- but most of all by his extremely long tail streamers, which undulate as he flies. The female also has a blue eye patch, but this is less noticeable than that of the male. She has a less prominent crest and lacks the male's elongated central tail feathers. Her wings, back, and tail are chestnut, while those of the male are dark, purplish brown. Both male and female have black on the head, nape, throat and upper breast, but their underparts are snowy white. The body size of the males and females is almost the same, at about 17 cm long, but the male's extended tail feathers take his total length up to 45 cm.

I have found that the black paradise flycatcher, rather like that other stunning summer visitor to Japan's forests, the blue-and-white flycatcher, prefers shady areas near water. These birds can be found most commonly in dark deciduous, mixed, or even coniferous woodland where there are streams.

Once, they were common summer visitors throughout the islands of Kyushu, Shikoku and Honshu to a latitude as far north as Tokyo, becoming scarcer north of that. Like many of Japan's woodland bird species, however, the black paradise flycatcher has declined over the last 50 years and has now become local and scarce except in the south of its summer range.

In these areas, though, the black paradise flycatcher remains a bird to look for. During its migration, it sometimes appears in more open woodlands, and even in suburban parks and gardens. But you will only ever see it in this country during the summer, from May to September. After breeding, when the males lose their long tail feathers, the birds migrate southward to spend the winter in southern China, Indochina, southeast Thailand and the Malay Peninsula.

Now that they have arrived here, however, the flycatchers will be settling down to breed, which they do only during May and June. They build a deep cup-shaped nest in the fork of a branch in a shrub or tree, and there they lay three to five eggs that they incubate for 12-14 days. Two subspecies breed in Japan. One is found in Honshu, Shikoku and Kyushu, as well as on Tsushima and Yakushima, while the other slightly larger and darker southern subspecies lives in the subtropical evergreen forests of the southwest islands, from Amami-oshima south to Yonaguni-jima.

Japanese paradise flycatchers feed on a wide range of adult insects, which they catch in flight. Other flycatchers, such as the Asian brown, sooty and narcissus varieties, usually have a favorite vantage point from where they dash out and snap up insects before returning to the same spot.

Instead, sankocho have a relatively slow, fluttering flight and they move from perch to perch beneath the woodland canopy in search of insects. Species that rely on insects for their food, such as flycatchers, find it impossible to survive in northerly latitudes during the colder parts of the year -- there just isn't enough food for them; but in the subtropics and tropics there is sufficient insect food all year round.

Paradise flycatchers also occur in Africa and Asia, but in the species there, the males are found in two forms -- a dark form and a white one. In the latter, the whole bird is white except for a black hood. These white males look quite ghostly as they are glimpsed flitting through dark tropical forests. Where I have seen them in east Africa, their white plumage seems to act as a focal point for small, mixed-species flocks, which forage together outside the breeding season. Perhaps the long white tail of such a ghostly sprite moving ahead through the forest provides a visual marker for the flock, helping it to remain together. The Japanese paradise flycatcher is unusual among its group in that it has a very restricted range and lacks that white plumage.