by Simon Barnes
The common tern is a mere long-distance migrant. The Arctic tern might as well be called the Antarctic tern, or perhaps the bipolar tern. Arctic terns don’t just drop down to Africa for the winter: they travel all the way down for the rich pickings of the Antarctic summer, and then come back again. They nest in the north, all around the pole. North Scotland is included here, and they have bred as far south as Brittany and Massachusetts. When breeding is done they set off on the travelling life again, along coastal migration routes that follow the shape of the continents; some will cross the Atlantic at the shortest possible (how do they know?) bit. They don’t make straight-as-the-crow flies journeys: bugger crows; these are Arctic terns and they take rambling meandering routes that pick up all kinds of food sources and even food bonanzas on the way. It’s been estimated that they cover 70,900 km or 44,300 miles in a single year.
Mad for daylight, these terns must be. I’m from southern England, so I’m always staggered by the length of the day during the summer in northern Scotland. If you go there to look for wildlife you can spend a decent period of time without seeing darkness at all: night is really a brief twilight they call the Summer Dim. This small and marvellously athletic bird spends most of its life in the daylight.
Distance means less to a bird than it does to any other creature. Some mammals, such as whales and wildebeest, migrate, and so do some insects, like monarchs and painted ladies. Some species of bats do it as well, but most species prefer to hibernate, a more economical strategy for dodging the winter. Some even do both. But birds are the best when it comes to the great survival art of being somewhere else.I
Certainly, a migration is full of dangers, but then so is staying in the same place. The pole-to-pole strategy is the ultimate form of the game. Hardly anything can survive in the polar winters, but if all birds were residents, the annual bonanzas produced by the warm weather would go untapped. Migration is not just about avoiding harm: it’s also about taking advantage of things that are only available to the highly mobile.
A tawny owl, as discussed a couple of chapters ago, will spend most of its adult life in the same chunk of woodland, learning every inch of it, knowing every hunting perch and everything that can be caught from it. As you can find your way across your own house in the dark when you take a midnight pee, so a tawny knows its wood, processing meagre scraps of shadowy information in a meaningful way. It will use its wings for silent descent onto unsuspecting prey. But other birds have their being in a much wider world and use their powers of flight to conquer distance. It’s only in the last generation that humans have been able to think of the world in the same way.
* * *
I. The common poorwill, a nightjar relative that lives in the United States, does actually hibernate. A number of species – some swifts, nightjars and hummingbirds – go in for torpor, a short-term drop-out when conditions are against them. These include the swifts that come to Britain for the summer.
The Quaker worm
The Gospel according to Matthew begins with a genealogy: “Abraham begat Isaac; and Isaac begat Jacob; and Jacob begat Judah and his brethren; and Judah begat Pharez and Zerah of Tamar; and Pharez begat Hezron and Hezron begat Ran…” We are all tied to the past by the genes we carry in every cell of our bodies – and we humans have as our ancestor the same creature that begat xenoturbellids.
Xenoturbellid means strange flatworm: same prefix as xenophobia, which means fear of strangers. Here’s a small and apparently pointless little phylum of apparently pointless little creatures. Oh – and by the way, they’re related to you. Not just in the sense that everything in the Animal Kingdom has some kind of relationship to everything else in the Animal Kingdom. These weird little lumps of nothing very much are really quite close to us on the evolutionary bush. The branches keep on forking: but the common ancestor shared by humans – by all vertebrates – and the xenoturbellids was on the same stem for far longer than you’d believe possible to look at them. The fork where we parted company is not as far behind us as we’d think.
If you ever ask a Quaker what Quakers do and what Quakers believe, you will generally get told all the things they don’t do and don’t believe in. Xenoturbellids are in much the same position. They have no brain, no through gut, no excretory system and no sex organs in any coherent form. They really are not anything much, but they are part of our comparatively recent history just the same. What have they got, then? They are wormy things about 4 cm, 1.6 inches, long and they have flagellate cells – cells with little whips on, a reasonably familiar concept by now. They can be found in waters off Scotland, Iceland and Sweden. They were discovered in 1915 by Sixten Bock, a name I shall surely use for the villain if I ever write a thriller. They were not fully described until 1949, when Eimar Westfald did the job. There are two species described so far in the entire phylum: they are called Xenoturbella bocki and X. westfaldi, as is only right and proper.
Their relatively close relationship with ourselves was put forward by Max Telford of Cambridge University, who said: “We have been able to show that amongst all the invertebrates that exist, Xenoturbellida is one of our closest relatives. It’s fascinating to think that whatever long-dead animals this simple worm evolved from, so did we.” Relatedness happens. It’s the way life works.
Think what that means for a moment. The ancestor shared by xenoturbellids and humans was presumably no more complicated than the Quaker worm itself. In other words, it was an insignificant blob of nothing much. Perhaps, like the Quaker worm, it had no brain and no bottom. The ecology of planet earth would hardly have been changed forever if the xenoturbellids had gone extinct and left no further ancestors. So: what if the same fate had overtaken the xenoturbellids’ ancestor? The one they share with us? Say that a worm’s ancestor didn’t actually become an ancestor: well, that would hardly constitute a great event in this history of life on earth, not like the KT extinction that finished off the dinosaurs. If some great scientific intelligence had been tracing the planet’s history, this small extinction would have been a footnoteI at very best.
And yet without that common ancestor, fish wouldn’t swim, bats wouldn’t fly and dinosaurs would never have ruled the earth, Arctic terns wouldn’t be migrating from pole to pole, humans would never have walked the savannah, Joyce would not have written Ulysses, Darwin would not have written the Origin, I wouldn’t have written this book and you wouldn’t be reading it. We’re here because of a worm’s ancestor.
* * *
I. Not the most important part of a book, no matter how much the author may love them.
Swift scramming frenzy
Birds are about flight, and that makes swifts the ultimate birds. Nothing flies like a swift. There are species of swifts (and swiftlets and needletails) in every continent bar Antarctica, but let’s concentrate on the one best known in Europe, the one we call simply swift, or European swift when we need to stress the differences.
Their lunatic limber scramming frenzy
And their whirling blades
Sparkle out into blue –
Words of Ted Hughes. The pub opposite a former house of mine has a seat in the car park that was used once every year. That was when I and my older son sat there in late July to watch the swifts screaming up and down the street. They filled the air with low-level hooligan runs, racing each other for the sheer fun of it, like kids on motorbikes, for these were non-breeders with a belly full of food and nothing to do but raise a little hell. How long do you think they spend in flight?
It’s an answer that can compel the most bird-indifferent person in the world into brief wonder. Most swifts won’t perchI at all between fledging and breeding – and that can be four years. A flight four years long: that puts the economy-class flight to Sydney into perspective. I’ve said that distance doesn’t mean much to a bird: it means almost nothing at all to a swift. It’s been estimated that swifts cover 500 miles, 800 km, in a day. If the weather is bad in England, they can always drop over to, say, the Bay of
Biscay, to load up on the aerial plankton that fuels their endless flights. They roost on the wing, circling for hours at high attitude in the thin, gelid air.
Their biennial migration to Africa is almost the least of their journeys. For them flight is not one big heroic effort: it’s a constant way of being: volo ergo sum. Their lifetime distance has been estimated at 1.28 million miles, more than 2 million km. And in straight-and-level flight, they are fast: young swifts flying competitively have been clocked at close to 70 mph, more than 110 kph. I have tracked swifts at 60 mph, 96 kph, from a vehicle. They are so deeply committed to the air that their scientific name, Apus apus, means no-foot no-foot: it was believed until comparatively recently that they didn’t haven’t any feet at all. Their feet are pretty tiny: just a few claws. They often nest in roof spaces (holes in trees being hard to find in cities) and I have seen them belly-shuffling across a roof to creep in under the pantiles. It is an abiding myth that they can’t take off from a flat surface: it’s possible but tricky. Adults can do it, but young birds, particularly those just fledged, will sometimes belly-out and strand themselves on the ground, and appreciate a helping hand to toss them back into the air. Taking off isn’t the most important skill for a swift: once they’re up, they tend to stay up.
As said earlier, they’re not related to swallows and martins; though their swirling flight and swept-back wings are not dissimilar. Both feed on aerial plankton. But the swift’s wings are much stiffer and they flicker rather than beat: a very distinctive difference once you’ve picked it up. Their wings seem to fluoresce at the leading edge in bright weather: as if their vibrant passage were too much for the air to deal with. They seem to be all black, with the under-chin pale patch occasionally visible. And that shape, that scythe shape, there’s nothing like that: “As if the bow had flown off with the arrow,” as Edward Thomas wrote.
They have rather replaced the swallow and the cuckoo as the bringers of spring in Europe, says Mark Cocker in his magisterial Birds Britannica. Cuckoos have declined drastically, and swallows are seldom seen over cities. Swifts are more aerial even than swallows, and fly higher, and up there they find the aerial plankton that’s out of the swallows’ easy reach. “They’re back – which means the globe’s still working,” as Ted Hughes wrote in the poem quoted earlier.
I have also seen their arrival in Africa. They like to surf in on the weather fronts: I remember hearing the quintessential sound of England in July, the screaming of swifts, out in the Luangwa Valley at the end of October. The ferocious flashbulb light faded as if someone had wound down the dimmer-switch; in minutes the sky turned the colour of ink and rumbled interrogatively, and in came the swifts, maybe a thousand feet up, looking as if they were towing the rains behind them. They bring the sun to England, they bring the rains to parched Africa, and they do so without bothering to touch the ground. Flight isn’t what they do: it’s what they are. And perhaps that makes them the bird of birds: never mind Apus apus: they are avis avium.
* * *
I. And anyway it’s not really perching as a sparrow understands the term – just clinging onto a vertical surface or going bellydown on a horizontal one.
Gutless, brainless
Acoelomorpha means no body cavity. If you wanted to name this wormy thing after something it hasn’t got, you are rather spoiled for choice. This is the super-Quaker worm. It also has no gut, no circulatory system, no respiratory system, no excretory system, no brain, no gonads and no duct associated with female reproduction. It doesn’t even have any ganglia, any nerve centres. It does have a network of nerves beneath the outer covering. It also has a statocyst, which assists balance and movement. It has ocelli, which means it can tell light from dark. Some species are free-swimming, moving about with plankton; while others crawl on algae or exist between sand grains. They are all under 2 mm, 0.079 inches in length.
They are perhaps the ultimate meaningless piece of animal life, so far as a human is concerned. We can’t even decide how to categorise them: it’s only since 2004 that they have been considered a separate phylum, though that status is disputed. They are a classic demonstration of the fact that the world was not set up for human convenience or to aid human understanding. Acoelomorphs are there to baffle humans with their remoteness, with the impossibility of getting any kind of intuitive grasp of the nature of their existence.
We’re going to get on to some super-sexy inverts very soon now, but as every married person knows, life is not just about the sexy bits. It’s about life in its entirety: including the bits you don’t think about much and those things you really can’t be bothered with and those things whose existence you’re not even aware of. But out there, far below the threshold of human awareness, the cavity-less worms are living their brainless and utterly meaningful lives, and they’ve never given a thought to anything as small as humanity in the brief gutless breathless expanse of their lives.
Jewels that breathe
Pineapple rock, lemon platt, butterscotch. So begins the eighth chapter of Ulysses. This chapter is much concerned with sweetness and sweet things, so I’m going to follow the same model. Here we go:
Green hermit, green violetear, Tyrian metaltail, greenish puffleg, bronzey Inca, booted racket-tail, rufous-tailed hummingbird, steely-vented hummingbird. That’s my hummingbird list from three days in the Andes, not far from Medellín, the birds identified not by me but by the miraculous Diego Calderon-Franco.
We barely scratched the surface. There are more than 180 species of hummingbird in Colombia, and the sweet menu is unrelentingly gorgeous: fiery topaz, blue-fronted lancebill, purple-crowned fairy, amethyst-throated sun-angel, spangled coquette, black-tailed trainbearer… so many of them named for precious jewels, they catch the light as aerial brilliants, so much lovelier than the ones we cut and polish and trade and wear. I’m reminded once again of the Underlanders in The Silver Chair: “ ‘Yes,’ said Golg. ‘I have heard of those little scratches in the crust that you Topdwellers call mines. But that’s where you get dead gold, dead silver, dead gems. Down in Bism we have them alive and growing. There I’ll pick you bunches of rubies that you can eat and squeeze you a cup full of diamond-juice. You won’t care much about fingering the cold, dead treasures of your shallow mines after you have tasted the live ones of Bism.’ ” Hummingbirds are jewels from the land of Bism brought to the surface to delight us Topdwellers: jewels that live, jewels that breathe, jewels that hang in the air as if air were something you could perch on.
I’ve never got the hang of hummingbirds as members of a species – and there are around 350 of them altogether. Perhaps I need to spend more time birding in the tropical bits of the Americas. The trouble is that every time I see one, I’m bowled over at a far higher taxonomic level. The family Trochilidae has me so mesmerised I find it almost impossible to start looking for the diagnostic features that will allow me to separate hummingbirds into a sicklebills and thornbills and sapphires. Diego did all that stuff for me when we did our mountain birding.
When it comes to hummingbirds, I’m like a non-birder listening to a spring morning’s birdsong: it doesn’t matter what kind of birds they are, does it? They’re all wonderful. And I, who firmly believe that the key to still greater wonders lies in looking harder and learning more, find myself hypnotised by the whiz and buzz, the flash and vanish of hummingbirds. This is doubly the case at sundown, when I am, say, at ReguaI in Brazil, a rainforest project I visited in my capacity as council member of the World Land Trust. The extravagantly plumaged swallow-tailed hummingbird used to visit us every night: as I took my first drink of the day he took his last, visiting the artificial nectar feeders while I had a beer. Hummingbirds are the perfect accompaniment to beer: they come to you, flaunt themselves, and leave: you don’t have to be quiet or discreet; you don’t even need binoculars.
Hummingbirds have invented an entirely new way of being a bird. There’s nothing quite like them. First, in terms of manoeuvrability, in terms of agility, they are the supr
eme aeronauts among the supremely aeronautical birds. They can hover so immaculately that their bodies look as if they have been pinned to the air like butterflies onto a board – except that they have no wings, for they are invisible apart from a blurring of the air. They can fly backwards as easily as they can fly forwards: unlike with the bateleur, this is no illusion but the real thing. They look more like insects than birds, and some aren’t much bigger than a large insect: so much so that you almost feel you could swat them without remorse. The bee hummingbird is only 5 cm, a couple of inches, long.
They have chosen to live in an insect-like manner, using nectar as the energy source for a lifestyle that requires constant refuelling. And at night, they shut down: an energy-saving technique that’s not far off hibernation. Their metabolism slows right down, their body temperature drops, and they lapse into a state of torpor until the sun warms them up and the process can start again.
As we have seen already, flight is extremely demanding of all birds. But hummingbirds have taken the concept of flight to extremes. They have the most energy-expensive lifestyle of all the birds on the planet. In the entire Animal Kingdom, only a few insects have a higher metabolic rate. Hummingbirds are only ever a few hours away from starvation: life is lived as a perpetual crisis. Nectar, then, is the centre of their lives: but nectar on its own is not enough. They must supplement this with protein from soft-bodied insects and spiders. They move and forage in short, sharp bursts: only about 15 per cent of any one day is spent in flight; any more would be impossible. The rest they spend perched, resting up, digesting.