ZEUS, married to Hera, had a ‘fling’ with Io. For Io’s protection, Zeus turned her into a cow.
But Hera wasn’t fooled; she sent a horsefly to bite Io on the rump, causing her to plunge into the channel that links the Black Sea to the Sea of Marmora.
“Bous” is the Greek for “cow”, “poros” means “crossing-point” and so the famous strait, 32km long, is known as the “Bosphorus”.
Istanbul straddles two continents at the southern end of it. South of the city, ships of all shapes and sizes linger, waiting for pilots to take them through the hordes of smaller craft, criss-crossing the 2km stretch between Europe and Asia. But sailors are not the only travellers to halt here. Birds gather in spring and autumn; storks, eagles, and kites must wait for suitable weather before crossing the channel.
Small songbirds fly directly across the Mediterranean using islands, such as Malta, Sardinia and Sicily, as staging points.
Island-hopping, however, is not an option for their larger cousins, who rely on thermals, rising currents of warm air, to help them travel.
There are no thermals over the sea, so storks, eagles, and kites must go around, rather than across, the Mediterranean. Huge numbers gather at two bottlenecks: Gibraltar, in the west, and the Bosphorus, in the east. In the heat of the day, hot air rises from sun-baked rocks, lifting the soaring birds high into the air. Then, if the wind is blowing in the right direction, they glide to the other side.
On a good spring or autumn day, thousands of white storks, with a few eagles, buzzards and kites, may cross the Bosphorus north of Istanbul. Birdwatchers must study their weather charts; visiting the celebrated vantage point in the Çamlica Hills, last week, I saw only the resident kestrel.
The temperature was 26C, ideal for thermals but a stiff breeze was blowing from the wrong direction. There were consolations; whitethroats and Alpine swifts had arrived, while the resident laughing doves mocked the bird-watching incompetent from Ireland.
Along the Bosphorus itself, it was a different story; another great movement of birds was under way. Mediterranean shearwaters feed in the Black Sea in winter.
Then, flocks of these brown and white seabirds, often hundreds strong, head down the channel to the Sea of Marmora, and on past the Dardanelles to their breeding haunts in the Mediterranean. Graceful flyers, they skim low over the water, wheeling between ships in front of sumptuous villas and sultans’ palaces, and passing under Istanbul’s two huge suspension bridges. Shearwaters nesting in the Aegean fly back and forth to the Black Sea on feeding sorties during the summer.
The waters here teem with fish. On the bridges over the Golden Horn, the long tapering bay off the main Bosphorus channel, hundreds of rod fishermen stand shoulder to shoulder filling every available space, while schools of dolphins gorge themselves in the waters overshadowed by the Topkapi Palace.
Istanbul, a sprawling metropolis, has 15 million inhabitants, yet the water flowing through it is remarkably clean. The level of the Black Sea is 15m above that of the Mediterranean, ensuring a steady flow through the great city. But this is no ordinary current; it’s a two-way one.
The Black Sea is less salty than the Sea of Marmora. The lighter fresh water “floats” on sea water, generating a surface current southwards. But “nature abhors a vacuum” and a solvent vacuum is no exception.
In the 50m depths of the Bosphorus channel, a current of salt-rich water flows in the opposite direction, seeking to spread its load in the fresh, relatively solvent-free, waters of the world’s largest inland sea to the north.
There is a theory that the Black Sea was formed when the Mediterranean, swollen by melt-water at the end of the last ice-age, suddenly burst through a land barrier where the Bosphorus is today.
The waters swept all before them, the new sea being formed in three months. Core-sampling of mud from the Black Sea bottom suggests this happened seven thousand years ago. Is the Biblical story of the flood based on a folk memory of this catastrophe?
The story of Zeus, Hera, and Io may be mythical, but truth is often stranger than mythology.
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