I’m jinxed when it comes to sea turtles. Although I rarely venture out to sea, I’ve narrowly missed seeing them on two occasions. The first time was in November 2000, while Jen and I were floating above the Great Barrier Reef in a tourist-laden semi-submersible. The woman behind me couldn’t handle the gentle swell and began to vomit. While I was shuffling along my bench in an attempt to put a few more inches between us, everyone else in the boat, including Jen, suddenly cried out, “TURTLE!” By the time I looked round, it had gone.
A few years later, Jen and I decided to forego a romantic moonlit walk along the beach in Tobago on account of the number of other couples who had beaten us to it. Next morning, over breakfast, everyone else was raving about the enormous sea turtle that had hauled herself on to the beach the previous evening and started to lay eggs in the sand.
Jinxes though they are, I have a soft-spot for sea turtles. They’re one of evolution’s great oddities: a reptile gone back to the sea, but still forced to breath air and return to land to lay her eggs. What sort of crazy ‘intelligent design’ is that? Why not give her gills, and eggs that can survive in the sea? It’s a design that seems to work perfectly well for most fish.
Like all of us, the sea turtle is constrained by her evolutionary past. She might be beautifully adapted for a life in the oceans, but she hasn’t found a way to sever all links with her species’ landlubbing ancestors. When she drags herself on to the beach on her klutzy flippers, she’s as much out of her element as the proverbial vomiting woman in a semi-submersible.
The non-optimal designs of creatures such as the sea turtle provide some of the most compelling evidence we have that species evolved, and weren’t created from scratch by some omnipotent, omniscient creator. Evolution through Natural Selection can produce beautiful adaptations, but it can only work on what’s already there.
Closer to home, another favourite tetrapod with an unusual lifestyle is the avian equivalent of the sea turtle: the swift. This bird spends its entire life in the air. It hunts, eats, copulates, and even sleeps on the wing, but, like the turtle, is forced to return to dry land—usually in the form of a rock face, cave, or building—to lay its eggs. The swift is beautifully adapted for a hectic life hunting insects on the wing, screaming and soaring in our summer skies, making swallows look positively sedate. But, as with the sea turtle, the swift flounders when she returns to terra firma to lay her eggs. Her skylubber legs are situated far back in her body to improve streamlining, and have shrunk to almost nothing to reduce weight. She can still use her rather pathetic feet to lurch around the nest site, or to cling to ledges, but they’re so diminished it was once commonly believed swifts didn’t have any feet at all—hence the bird’s scientific name, Apus, from the Greek for without foot.
Swifts only visit Britain for a few months each year, making their annual return a much anticipated summer event. I always keep my ears open for them from early May, often first hearing them as they screech down the canyon of Market Street in Hebden Bridge, like TIE fighters down a Death Star trench. Then I know it’s time to start making plans to visit Hewenden Viaduct, whose arches are a popular nesting site for swifts.
Unlike turtles and swifts, Hewenden Viaduct was, indeed, intelligently designed—most likely by the Victorian railway engineer Richard Johnson. Just like turtles and swifts, however, the viaduct’s underlying design is based on that of its ancient predecessors. The 17 arches that carried the Great Northern Railway’s Keighley branch line across Manywells Beck to Halifax, Bradford and beyond hark back to Roman aqueducts, which were also designed to maintain level courses across undulating countryside. The viaduct’s railway line is long gone, a victim of the Beeching cuts of the 1960s, but the hard-won flat route has been adapted for a new use as a picturesque cycle- and foot-path.
There’s no sign of swifts as I approach the viaduct. Perhaps, in my keenness, I’ve come too early. Perhaps I should have waited a week or two. I take a couple of photos from afar, then join the course of the former railway track and, passing through a modern gate, walk on to the viaduct.
I follow the curve of the viaduct to its far end, then turn and begin to head back. Still no sign of swifts. Then I hear a distant screech off towards the reservoir to my right. I hurry across to the parapet and gaze over. A trio of swifts weave their way towards me, splitting and re-grouping, then disappear from view as they shoot under the arch beneath my feet. I rush to the other side of the viaduct, but they’re already long gone. Either that, or they landed on the underside of the arch.
Two more swifts appear from nowhere, banking above the viaduct and heading off down towards the reservoir. Then, without warning, there are swifts everywhere. They criss-cross the sky a short distance above me. About 30 of them is my best guess, but it’s impossible to say for sure: they’re so damn fast it’s bewildering. I pull out my camera and start firing.
I’ve yet to take a satisfactory photo of a swift. They’re way too fast and small for the autofocus on my camera. Experience has shown the best technique is to bump up my camera’s ISO setting a bit to give me a bit more depth-of-field, set my aperture to around f/16, over-expose by a stop or so to compensate for the bright-sky background, focus manually, and take dozens and dozens of shots in the vain hope that one or two might actually end up in focus.
As always, I’m far from satisfied with the resulting photos, but they’re better than the ones I took last year—which, in turn, were better than the ones from the year before. Practice makes perfect, and all that. What better excuse could I have to come back soon?
“…wonderful. Science and history and geography and evolution and culture all tangled up in musings while walking about the moors around Hebden Bridge.”—PZ Myers
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