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Wednesday, Feb. 15, 2006
IN THE DIPPER'S DOMAIN
Underwater walker beggars belief
By MARK BRAZIL
The winter's snow gathers first as a dusting on the riverside vegetation. The wiry dwarf bamboo bows slowly under the accumulating blanket; shrubs and bushes disappear beneath duvet-like domes of crisp whiteness. The surrounding Hokkaido forest becomes hushed; the trees white-coated, their branches laden and bowed almost to breaking point. Ice skirts the water's edge, then creeps out from still backwaters until it threatens to choke off the stream. Snow slanting into the fast-flowing current is washed away in the chill water, but it builds up and up on every exposed pebble, rock and boulder until rounded, curving whiteness is draped over the stream sides like a warming comforter pulled across a sleeping child's shoulders.
The muffling snow lends serenity to the scene, though the air is filled with the rushing and trickling sounds of the dark flowing water, the chink and crackle of ice and the dripping of icicles melting in the sunshine.
In such beautiful but harsh conditions, I never cease to wonder how anything living can survive long winters here.
Then a hard "djit-djit" call sounds out and a dark shape flashes past, low and fast, its wings whirring as it disappears upstream through the falling snow so quickly that it is hard to track. Seconds later, a second image of blackness whisks past, at times following the course of the stream, at others cutting corners to keep a straight course. Then it too is gone.
Pause awhile, and watch carefully from the water's edge; look for any protruding midstream boulder with a disturbed snow cap, or one that shows a small avian deposit. Then patience is rewarded with the sighting of a rather strange-seeming bird on a distant rock. At first glance it looks wrong for its riverine habitat, having neither webbed feet nor a streamlined appearance. In fact, this portly creature appears more like a dark and overgrown wren than the highly adapted aquatic bird that it is.
This is a dipper, a Brown dipper to be precise, which is one of the most specialized of all river birds. Though its plain dark-brown plumage is unrelieved by color, it has a perkily cocked tail, and everything about this bird's apparently agitated, hurried and restless behavior is fascinating. A pugnacious character, proud of its waterfront property, the dipper will see off any intruder, for here, "property," to a dipper, definitely means "private property."
Appearing like a black arrow streaking across the blurred whiteness, the dipper whisks to a halt, a stocky bird standing splayfooted, bobbing and curtsying on a boulder in midstream. It flicks and turns, bobs and peers, its strong legs flexing and bending like an athlete doing push-ups. Then, with what appears to be suicidal abandon, it jumps into the water and is gone.
As it disappears beneath the surface, it is hard not to glance immediately downstream in expectation of its battered body being cast up to the surface, bloodied and lifeless. But nothing appears; there is no trace of feather or wing; it is as if the dipper has quite literally been swallowed by the stream. Casting wildly around downstream for this missing riverine sprite is pointless; instead, a look at a rock a little further upstream rewards with the near-miraculous sight of the dipper there, bobbing restlessly once more and with a droplet of water on its mantle the only evidence of its recent immersion.
Suddenly a fleck of white appears, like a minute curtain drawn across its bright and beady eyes, then it is gone. A few seconds later, the white flicker passes across its eyes again before it takes off and this time plunges from mid-flight into the water -- not with the graceful swan-dive of a kingfisher, but with a solid plop, more like a thrown stone.
The doughty dipper defies the strength of the stream; it even seems to revel in it. Dropping to the bottom, it faces upstream, grasps the stream bed litter of stones and gravel with its strong toes and flexed legs, and works its way up against the current, literally walking underwater. The flow streaming over its head, short neck and broad back force it downward, while its stout legs keep it in place as it pokes and probes between and beneath the rocks in search of invertebrates, particularly the larvae of stoneflies and caddisflies.
After each foraging bout, it releases its grip, points its beak and head toward the surface, bobs up and flies out of the water -- often from exactly where it submerged, or further upstream.
Apparently oblivious to the relentless battering of the white water over the rocks, or the chuckling, gurgling flow around protruding boulders, this is a bird that even seems to like waterfalls and is quite willing to fly through their cascades.
The lightning-bolt blue-and-orange Common kingfisher is a master angler, imbued with endless patience, but capable of plunging in an instant from its hidden perch to catch a small fish idling in clear water. But they shun white water, as the disturbance in that highly oxygenated habitat makes it hard for them to spot fish. Similarly, as winter strikes their favorite streams, and veils of surface ice seal away their food, they are forced to seek out ice-free waters in the lowlands or in warmer regions.
But sharing habitat with our portly dipper, and as at home in fast-flowing streams and rivers, is another fisher, and the punk of this riverine domain -- the enormous Crested kingfisher.
This pied bird with finely barred plumage has a monstrous beak and an enormous head crowned with a crest that it agitates upward. Announcing its presence with a loud chattering "chet-chet" call, it is hard to miss as it perches pallid and top-heavy in a riverside tree or hovers animatedly over midstream before plunging heavily beneath the water to return with a struggling fish.
Bobbing and blinking
Whereas kingfishers are brightly colored or boldly patterned and demonstrative, dippers are drab, but hardy and hardly gentle. In winter, they engage in protective battles along their narrow territorial strips, involving dashing flights and much bobbing and blinking.
Most unusually of all, while the remainder of our resident birds merely do the best they can to endure winter, the dipper, truly in its element, sings. As if vying with the rushing stream, daring it to flow faster, splash higher and swirl more wildly, the dipper pours out a powerful song that is audible even over the roaring of the river.
Long before winter loosens its grip, the dipper senses the turning of the seasons and in song and flight marks out the borders of its riverfront property eager to draw in a mate.
Visit a mountain stream this month, and you may be lucky and hear them braving the elements and staking their claims.
Mark Brazil is professor of biodiversity and conservation at Rakuno Gakuen University. He welcomes contact by e-mail at firstname.lastname@example.org