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Thursday, July 19, 2001
Cracking the Coleridge conundrum
By MARK BRAZIL
Snorting salt through the nostrils may seem a strange habit, but it must surely be healthy and can even be a crucial adaptation. After all, albatrosses do it and they can live for 50-70 years, an exceptional age among birds.
In "The Rime of the Ancient Mariner," the anthropocentric British poet Samuel Taylor Coleridge wrote in 1798: "Water, water, everywhere/ Nor any drop to drink." With a salt content of around 3.5 percent, seawater is sufficient to dehydrate the average mammal forced to drink it.
Yet what is poison for one species is merely a challenge for another. Our relatively inefficient kidneys need about 1.5 liters of fresh water in order to be able to flush away the salt we would take in from drinking just 1 liter of seawater. Obviously drinking seawater must inevitably lead to physiological disaster. But the same is not true of birds.
A large number of avian species make their living from the sea, many of them spending almost the whole year away from land, feeding and drinking from the sea, and only returning to shore for the breeding season. Given that the salt content of the sea is about three times that of the body fluids of birds, just how do they survive? Well, snorting salt is one very effective way.
Above or in front of the eyes of all birds there is a gland, the nasal or supraorbital gland. In most species it is tiny and apparently functionless. In marine species, however, this gland is enlarged and its special function is to regulate the amount of salt in the blood and extract the excess. The nasal gland is capable of producing a concentrated solution, containing about 5 percent salt, that drains via the nostrils. In some species, it drains continually, dripping like dewdrops from the bill tip. In other species it is expelled explosively with a salty sneeze.
This is not something most mammals can do, but neither do birds have a monopoly. Darwin's "imps of darkness," the Galapagos marine iguanas, share the habit. They are also salt snorters, sneezing salt solution vigorously, visibly and audibly from their nostrils. They use this behavior not merely to rid themselves of excess sea salt but also as a threat or warning signal to other marine iguanas, thus ridding themselves of salt and competition at the same time. According to naturalists in the Galapagos, it is this salt-sneezing habit, coupled with the frequently breezy conditions on the islands, that gives the marine iguana the gray white crust that covers the top of its head.
You won't find seabirds with crusty crowns -- perhaps they bathe more meticulously than the iguanas. Unless you are able to visit their colonies, you won't see seabirds on shore either, though as the typhoon season approaches you may, through binoculars, see various species careering past our coasts.
The many interisland ferries used to be good places to watch seabirds, though the best of them, the Tokyo-Kushiro ferry, no longer operates. The alternative Oarai to Tomakomai route is far less convenient, but still does offer some good seabirding.
In the last decade, however, the increase in whale-watching in Japan, and the resulting increase in whale-watching operations from Okinawa to Hokkaido, has meant many more opportunities for getting offshore. Join a whale-watching trip and you have a double delight: After all, it can take a while before a cetacean surfaces, and while dedicated whale-watchers will only be happy from that moment on, if you take an interest in seabirds you are likely to have something to look at for the whole trip.
Around the southern half of Japan the streaked shearwater is the commonest species to be found. It breeds in very large colonies on many offshore islands and frequently comes close to boats. Only during the middle of winter do their numbers thin, and sometimes disappear. Especially off the Pacific coast of Japan (though also off other coasts), hordes of sooty and short-tailed shearwaters pass on their Pacific-loop migration taking them from breeding grounds around New Zealand and Tasmania up to the Bering Sea, then down the east Pacific before returning for the next breeding season to the Southern Hemisphere.
I have encountered huge flocks of them even off the Okhotsk Coast, along the Shiretoko Peninsula, and in the strait between Wakkanai and Rebun and Rishiri in northern Hokkaido. Find a flock like that and you may find other species accompanying them, perhaps a flesh-footed shearwater or something rarer.
The bane of Coleridge's ancient mariner, the albatross, is here too. In fact three species occur around Japan, and they bring the ultimate thrill to any offshore excursion. On occasions I have even sighted them from headlands. The short-tailed, or Steller's albatross as it used to be known, is the rarest of the three, but its numbers are increasing. More likely to be seen are the Laysan and black-footed albatrosses. These commonly breed on the Hawaiian Islands, although some nest in the Ogasawara Island chain of Japan.
Conditions that are best for whale-watching (a calm glassy sea exposing every rise of dolphin or whale) are worst from a seabird's point of view. The albatrosses and shearwaters don't like to waste energy flapping when they are such accomplished gliders, so in calm conditions flocks are often found lolling on the surface, resting until the breeze is strong enough to allow them to take off.
If a boat gets too close, they will make a strenuous effort to take off, pattering and splashing, running and flapping across the water. At this time of year, when the shearwaters especially are molting their wing feathers, they are less airworthy. Their wings appear ragged and often have gaps, so they quickly give up and settle again on the water.
Such calm conditions make it possible to enjoy close-up views of seabirds on the sea, and perhaps then you may notice the nostrils on the top of the bill -- and perhaps, if exceptionally close, the glistening dewdrop of saltwater running from the nose.
In windy conditions whale-watching becomes harder. Each wave resembles a dolphin's back breaking the surface for the wishful thinker. Then, though, the winds provide the lift the seabirds need, and as they skim and career over the wave tops, supreme among them will be the gracefully gliding albatrosses.