Gods of the Morning (4 page)

3

So Great a Cloud of Witnesses

Wherefore seeing we also are compassed about with so great a cloud of witnesses . . . let us run with patience the race that is set before us.

Hebrews 12:1

Those few last geese to arrive from the Arctic, straggling down from the great heights at which they travel, often many thousands of feet, are special to me not just because I love to catch their excited voices on the wind and see their silhouetted chevrons against the clouds, but because they are living, crying witnesses to nature's biorhythms present within us all.

We all migrate. We venture out and we return home. We send forth our young. The winged seed spiralling to Earth from a sycamore or an ash; the rowan berries ingested by Scandinavian fieldfares and redwings are cast to the hills; the lonely ‘outcast' badger that dug himself a temporary home among the roots of one of our western red cedars last year; the spiders I witnessed ballooning down the wind on their silk threads; the rooks and jackdaws I was watching this afternoon, surfing the wind over the river fields; the swallows and house martins swooping low into the stables each spring; the salmon surging up the Beauly River to spawn every summer – all of these and myriad more organisms
around my home, around all of us all the time – are responding to the secret codes emitted by the sun and the spinning Earth, received and processed to serve each species' individual ends. ‘So great a cloud of witnesses.'

They're heading out, patiently running the race their needs have set before them. They all need to feed, to breed and to survive, like surfers riding the waves of Fate. I, sitting tapping these words into my laptop, and you, reading them – whoever we are, wherever we may be and whatever our private pretensions – are also part of that same grand opera: the pull of life's imperatives. We migrate, whether a few yards before finding a suitable place to put down roots or circumnavigating the globe, like the Arctic tern, which travels ten thousand miles to the Antarctic and back again every year, patiently making the most of our lot, our personal shout at the survival of ourselves and our species. That's what migration is.

These days we understand it – at least, quite a lot of it. Seasonal bird migration in particular has been well and widely studied. We now know, for instance, that migration can be triggered by temperature, by length of daylight hours, by weather conditions and by diminishing food supplies, but we also know that it is genetically controlled. Glands churn and swell, hormones swirl. The imperative to get up and go when we need to is written into the electrochemical circuitry of human brains as well as bird brains.

In the case of geese, intricate studies have demonstrated that their innate circuitry and navigational skills are added to year on year by experience. Old birds get canny: they
learn to read the wind. They know exactly the right moment to head off, and the youngsters follow. I've always loved the expression ‘wise old bird'. It's never truer than of mature geese, sometimes individual birds that have made their twice-annual trek more than fifty times. A ringed (banded) snow goose hatched in Alaska and wintering in Mexico has been recorded still migrating at twenty-six years old – that's more than 130,000 miles of reading the wind. I ask myself just what huge range of conditions and changes, trials and close-calls lurk behind the twinkle in that wise old bird's eyes.

We also know that different families of birds respond to and navigate by different signals, reflecting each species' needs and capabilities and determining their route and destination. Experiments in planetaria have proved that some
Silviid
warblers, such as the blackcap, are genetically wired to navigate by the stars, requiring them to migrate at night. Artificially exposed to different seasonal constellations, caged birds become restless and flutter to the north or south, according to their migratory instincts. Other species can detect the Earth's magnetic field or memorise significant landmarks, such as coastlines, river valleys and mountain ranges. Yet others follow the sun, demonstrated by German ornithologist Gustav Kramer's 1950s experiments with caged starlings. Most significantly, he proved, with mirrors and artificial cloud effects, that it wasn't direct sun they required, but that sufficient light intensity was all they needed for the correct orientation – an important ability for birds since the sun is so often obscured by clouds.

One of the most remarkable experiments in bird
navigation was conducted by my late great friend Ronald Lockley, a real pioneer of ornithological research and author of the ground-breaking monograph
Shearwater
(1946) – a study of Manx shearwaters nesting on the island of Skokholm off the Pembrokeshire coast of Wales. He took mature birds from their nesting burrows, then shipped them off to Venice and to landlocked Basel in Switzerland, many miles from any normal shearwater habitat or migratory route. They were back in their burrows fourteen days later.

Another bird was flown across the Atlantic to Boston, Massachusetts, some three thousand miles from home; a starting point completely unknown to that shearwater species. It took just twelve days to arrive back on Skokholm. What Lockley's experiments proved conclusively was that shearwaters must use navigational aids other than landmarks. What we now know is that birds often employ a combination of abilities: stellar, solar, geo-magnetic and geographical recognition, to locate themselves and return to precisely the same wood, moor, field, tree or bush, swamp, stream, burrow or cranny they departed from many months before. Our swallows swoop home from Africa to the rafters of their birth through the same door in the same stable at approximately the same moment, year after year. Nowadays we know so much that we take bird migration for granted, but it was not always so.

In the early sixteenth century the Bishop of Uppsala, Olaus Magnus, was convinced that swallows and other similar birds spent the winter months under water or in deep mud. In his
Historia de Gentibus Septentrionalibus
he goes so far as to cite the evidence of fishermen landing a catch of swallows in
their nets. He was sufficiently persuaded by this bizarre explanation for the sudden disappearance of swifts and swallows in the winter that he commissioned a woodcut illustration of the fishermen with their catch, thereby endorsing an entirely bogus scientific claim that would remain substantially unchallenged for the best part of a hundred and fifty years.

There were doubters and fence-sitters, of course, casting around for objectivity, such as Robert Burton, who wrote in his 1621
Anatomy of Melancholy
:

Do they sleep in winter . . . or lye hid in the bottom of lakes and rivers,
spiritum continentes
? so often found by fishermen in Poland and Scandia, two together, mouth to mouth, wing to wing, and when the spring comes they revive again . . . Or do they follow the Sun . . . or lye they in caves, rocks and hollow trees, as most think . . .?

Yet this thesis sat uncomfortably with the drip-drip of evidence coming in from ships returning to British ports from the Mediterranean and Africa with tales of exhausted swallows landing on rigging or on decks.

John Rae, the great English naturalist of the seventeenth century, editing
Willughby's Ornithologica
in 1678, certainly expressed doubt: ‘To us it seems more probable that they fly away into hot countries, viz., Egypt or Aethiopia.' But others would have none of it. Even the great Swedish taxonomist Carl Linné (Linnaeus) was insisting as late as 1768 that Bishop Olaus's confident assertions, with all the authority of the Church, were correct – that they hibernated under water.

By the end of the eighteenth century the ever more divided world of science had split clearly into migrationists and hibernationists. Gilbert White, curate of Selborne, was well aware of the debate. His lengthy correspondence with the Hon. Daines Barrington (hibernationist) and Judge Thomas Pennant (migrationist), both eminent naturalists of their day and Fellows of the Royal Society (and from which correspondence much of the text of his 1789
Natural History and Antiquities of Selborne
was gleaned), reveals strong influences in both directions, but White was canny and stuck to a much more cautious scientific approach: ‘As to swallows being found in a torpid state in the winter in the Isle of Wight or any part of this country, I never heard any such account worth attending to.' But with the scientific objectivity that would make his natural history so famous (never out of print in 225 years), he also hedged his bets.

I myself on the 29th October last (1767) . . . saw four or five swallows hovering around and settling on the roof of the (Oxford) county-hospital. Now is it likely that these poor little birds . . . should, at that late season of the year . . . attempt a journey to Goree or Senegal, almost as far as the Equator? I entirely acquiesce with your opinion – that though most of the swallow kind may migrate, yet that some do stay behind and hide with us during the winter.

Gilbert White's brother was chaplain to the British garrison on Gibraltar. Also a keen naturalist and a reliable observer, John sent his brother reports of swallows crossing
the strait to Africa. This first-hand evidence enabled Gilbert to write back to the devout hibernationist Daines Barrington:

You are, I know, no friend to migration; and the well-attended accounts from the various parts of the country seem to justify you in your opinions, that at least many of the swallow kind do not leave us in winter, but lay themselves up like insects and bats in a torpid state . . . But then we must not, I think, deny migration in general; because migration does subsist in some places, as my brother in Andalusia has informed me. Of the motions of these birds he has ocular demonstration, for many weeks together, both spring and fall: during which periods myriads of the swallow kind traverse the Straits from north to south and from south to north according to the season.

This may well have irritated Barrington, because shortly afterwards he published a damning paper utterly refuting the whole idea of bird migration. Although White was totally convinced that bird migrations were real, he was evidently puzzled by the late movements of some species, often well into November, but his admirable scientific objectivity would never permit him to reject altogether, without positive proof, the hibernation possibility. Right at the end of his life he was still instructing labourers to search for hibernating birds in winter. In April 1793, only three months before his death, he asked a neighbour to assist him in examining the thatch on an empty cottage in Selborne.

*  *  *

Things are very different, these days. We possess an astonishing log of scientific knowledge about migrations of all sorts. Thanks to ringing (banding) and radio tagging, birds are perhaps the most studied, but so are elephants and polar bears, herds of antelope, the great wildebeest migration from the Serengeti across the Mara River, and the carnivores and scavengers that follow them; deer, like the caribou migration of the Alaskan tundra and their attendant wolf packs; whales and seals of many different species migrating to breed or feed; eels and basking sharks and many other migratory fish; reptiles, such as turtles and crocodiles; and, of course, insects in uncountable numbers. Billions of monarch butterflies migrate up to 2800 miles down the North American continent from Alaska to Mexico because they can't withstand the cold winters.

Some of the research aided by modern technology has revealed previously undreamed-of feats of endurance and ability. Imagine their surprise when the pilots of an Air India passenger jet found themselves flying alongside a large skein of bar-headed geese at thirty-two thousand feet, an altitude required every year as the geese cross the highest Himalayan peaks.

Radio transmitters have revolutionised bird research. Very recently, an electronic tracking device weighing less than a paperclip uncovered what is now thought to be one of the world's greatest bird migrations. It revealed that a red-necked phalarope, a tiny wader the size of a wagtail, migrated thousands of miles west across the Atlantic to the Pacific Ocean, a journey never recorded for any other European breeding bird.

Dave Okill, of the Shetland Ringing Group, fitted
individual geo-locators to ten phalaropes nesting on the Shetland island of Fetlar. When a bird returned to Fetlar in the spring, Dave was astonished to discover that it had made an epic 16,000-mile round trip during its annual migration – across the Atlantic, south down the eastern seaboard of the US, across the Caribbean and Mexico, ending up off the coast of Peru, taking the same route back. Prior to this, many experts had assumed that Scottish breeding phalaropes joined the Scandinavian population at their wintering grounds, thought to be in the Arabian Sea.

My conservation colleague Roy Dennis has hugely increased our knowledge of osprey, marsh harrier and golden eagle movements by attaching transmitters to young birds leaving the nest. The British Trust for Ornithology has done the same by attaching solar-powered radio tags to English cuckoos in an attempt to discover the route and precisely where our diminishing British cuckoo population spends the winter. The results have been illuminating and, for us, deeply disappointing. Aigas Field Centre sponsored one bird named Kasper; he made it to the Congo Basin for the winter, but perished on the way back in the spring – just our luck. Of the first five birds tagged in 2011, only two made it back to Britain.

Sophisticated modern radar can also accurately track the movement of small passerine migrants. We now know that most small birds migrate at below five thousand feet, the most popular altitude being two to three thousand feet, whereas flocks of waders choose to travel much higher, at twenty thousand feet. We can also measure speed of flight very accurately. Warblers, finches and other small birds
commonly cover thirty to fifty miles a night with daytime stopovers to rest and feed, whereas swifts, swallows and house and sand martins regularly cover up to two hundred miles a day, preferring to roost at night and fly by day so that they can feed on flying insects as they go.