Follow the flight of the blackpoll warbler

Diversity is a mark of richness and environmental health - and birds are its flag-bearers.

Bird variation set both Charles Darwin and Alfred Russel Wallace on the path to discovering natural selection and its role in evolution. Wallace observed it on the Molucca Islands, Darwin on the Galapagos. Diversity is a mark of richness and environmental health and birds are its flag-bearers. Their disappearance, like the collapse of the canary in the mine, is our warning signal.

Yesterday, wondering where blue tits and great tits have gone this summer (am I providing the wrong kind of peanuts?), I found the Shakespearean phrase “nature’s riches” used for a site explaining the rich geological pickings of the Arctic, now being unlocked by global warming. It could equally refer to the tropical forests being destroyed to make monocultures such as palm oil. Maybe only migrating birds know (though it must be a special kind of “knowing”) the true force of the paradox that areas of greatest biodiversity are also areas of greatest conflict – and how fast biodiversity is being lost in our time.

This is true above all between Arctic and tropic. These words first occur in the late 14th century. In Greek, arktikos means “belonging to bears”. Not polar bears: people knew the night sky and the constellation of the Great Bear. Tropic, from the Latin tropicus and the Greek trope, meaning “turn”, refers to the daytime sky where the sun, after reaching its northernmost or southernmost point, stands still (solstitium) and turns back.

If all birds stayed in the tropics, many would die out through competition for food and nesting sites, so species evolved to migrate. As resources regenerate each spring in the north, millions of birds trade tropic for Arctic: less competition for insects, longer daylight hours to find them. When Arctic food dwindles in autumn, they return to the replenished tropics.

These journeys are risky but better than the alternative. Blackpoll warblers winter in Venezuela, then fly north in spring over the Gulf of Mexico up to Alaska, where they build little cup nests in fir trees. They take a different route back: they fly south-east over the Great Lakes and from the New England coast some follow the shoreline down to Florida, some island-hop to South America, but most fly east to pick up winds hurling them over the Caribbean non-stop, day and night, for 88 hours to Venezuela. Four days over the Atlantic in peak hurricane season, facing spiralling winds, clouds, rain. Many crash exhausted in the sea. Yet it’s worth the risk because this route is 1,500 miles shorter and survivors establish a winter feeding territory earlier.

Nature is prodigal, said Darwin. So much waste. “The face of nature may be compared to a yielding surface, with 10,000 sharp wedges packed closely together and driven inwards by incessant blows, sometimes one wedge being struck, and then another with greater force.”

His understanding of the conflict driving nature’s apparent harmony was triggered by reading “An Essay on the Principle of Population” by Robert Malthus. This led him to the concept of natural selection and also to ideas about the evolution of instincts and human psychology.He was young: after South America, his mind was racing. “The principle of population is strife”; “All forms compete against others”; “You can understand the true conditions of life only if you use your imagination to hold on to a sense of the ruthlessness of the natural forces that could waste the bright surface.”

This side of his work inspired Freud’s insight into psychic conflict and the origins of human aggression. “The human mind is shaped by its animal past,” said Darwin. Nature’s ruthlessness is ours, too: our bodies, our psyches.

Unlike a blackpoll warbler, we can’t fly away when resources are gone. In our time, it seems, Arctic and tropic will change their meanings again. But biodiversity may no longer be part of the equation.

Good migrations: macaws fly over a river in Peru. Photograph: Frans Lanting / Gallery Stock

Ruth is a British poet and author with close connections to conservation, wildlife, Greece and music. She has published a novel, eight works of non-fiction and eight poetry collections, most recently The Mara Crossing, which mixes poems and prose to explore migration. She is a Fellow of the Royal Society of Literature and a Council Member for the Zoological Society of London.  See her website for more.

This article first appeared in the 08 July 2013 issue of the New Statesman, The world takes sides

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As the falcon flew towards us, its face looked alarmingly like Hannibal Lecter’s muzzle

In your faces, twitchers!

The BBC2 programme Springwatch may have made the RSPB’s reserve at Minsmere in Suffolk the Mecca of popular birdwatching, but Cley on the north Norfolk coast is still its Alexandria, a haven for wanderers of all species and a repository of ancient and arcane knowledge. I learned what little I know about birding there in the early 1970s, sitting at the feet of the bird artist Richard Richardson as he gave his sea-wall seminars on the intricacies of behaviour and identification. Richard could put a name to any bird, but he never believed that this process rigidly defined it.

The reserve at Cley has been gentrified recently, with smart boardwalks and a solar-powered visitors’ centre, but something of its old, feral spirit remains. On a trip early this winter, we were greeted by birders with the news: “Saker! Middle hide.” Sakers are big, largely Middle Eastern falcons, favourites with rich desert falconers. No convincingly wild individual has ever been seen in Norfolk, so it was likely that this bird had escaped from captivity, which reduced its cred a mite.

The middle hide proved to be full of earnest and recondite debate. The consensus now was that the bird was not a saker but a tundra peregrine – the form known as calidus that breeds inside the Arctic Circle from Lapland eastwards. We had missed the first act of the drama, in which the bird had ambushed a marsh harrier twice its size and forced it to abandon its prey. It was now earthbound, mantled over its dinner on the far side of a lagoon. It was bigger than a standard peregrine, and in the low sun its back looked almost charcoal, flaring into unusually high white cheeks behind its moustachial stripes.

Then it took off. It swung in a low arc around the perimeter of the lagoon and straight towards our hide. It flew so fast that I couldn’t keep it focused in my binoculars, and for a moment its face looked alarmingly like Hannibal Lecter’s muzzle. At the last minute, when it seemed as if it would crash through the window, it did a roll-turn and showed off the full detail of its tessellated under-plumage. In your faces, twitchers!

It was a thrilling display, but that didn’t entirely quieten the identity anxieties in the hide. One or two dissenters wondered if it might be a hybrid bird, or just a large but eccentrically marked common peregrine. The majority stuck with the tundra option. This form migrates in the autumn to sub-equatorial Africa, and days of north-easterlies may have blown it off-course, along with other bizarre vagrants: an albatross had passed offshore the day before.

Calidus means “spirited” in Latin. The Arctic firebird treated us to ten minutes of pure mischief. It winnowed low over flocks of lapwing, scythed through the screaming gulls, not seeming to be seriously hunting, but taunting a blizzard of panicky birds skywards. At one point, it hovered above a hapless tufted duck that dived repeatedly, only to resurface with the quivering scimitar still above it. Then it took another strafing run at the hide.

Does it matter whether the peregrine was a rare variety, or just an odd individual? Naturalists often categorise themselves as either “lumpers”, happy with the great unlabelled commonwealth of life, or “splitters”, rejoicing in the minutiae of diversity. I swing from one to the other, but, in the end, I can’t see them as contradictory positions.

The bird from the tundra was a hot-tempered peregrine to the core. But its strange facial markings – however much their interpretation panders to the vanity of human watchers – are the outward signs of a unique and self-perpetuating strain, adapted to extreme conditions and yet making a 6,000-mile migration that might take in a visit to a Norfolk village. Lives intersect, hybridise, diverge, in the counterpoint between what Coleridge called “uniformity” and “omniformity”.

Next week: Felicity Cloake on food

This article first appeared in the 01 December 2016 issue of the New Statesman, Age of outrage