The bird that wasn’t there

Soon after the Bay thrush was discovered in 1774, it was lost. But we can no longer blame ignorance for mass extinction.

By John Burnside

Watercolour painting by Georg Forster of Turdus ulietensis from Raiatea, 1774. Photo by The Natural History Museum / Alamy Stock Photo

In June 1774, on the Polynesian island of Raiatea, a young naturalist named Georg Forster made a tentative, rather naive watercolour of a bird that, until that moment, had never been seen by any European. At the time, the 19-year-old Forster was working as an assistant to his father, Johann Reinhold Forster, a noted ornithologist and, as of 1772, official scientist to James Cook’s second voyage in the South Pacific; his job was to sketch, make basic field notes and preserve specimens of any interesting, or possibly new species that he encountered on the three-year expedition. This youthful artist was no Audubon, but some of the paintings he made are quite touching: there is real charm in his portrayal of the Cape Verde Islands grey-headed kingfisher, while his vibrant image of the red-billed Tahiti rail is particularly poignant, when we consider that this flamboyant, brightly coloured species would soon be classed as extinct.

That Forster’s one-off sketch was so rudimentary is doubly poignant, however, as yet another sorry episode in the history of European exploration unfolded. Though he was far from categorical in calling the bird “thrush-like”, or even a distinct new species, it was soon officially recorded, in John Latham’s General Synopsis of Birds, as “the Bay thrush”, while the Linnaean classification, Turdus ulietensis was established by Johann Friedrich Gmelin in his Systema Naturae of 1789. This happened rather frequently during those early years of taxonomy: field notes were often sketchy, official experts habitually based their classifications on perceived, and sometimes fanciful, similarities to the flora and fauna they already knew, and collectors raced to acquire rare or new specimens of exotic life-forms from faraway places.

All over the world, as ships driven by scurvy, venereal disease and colonial arrogance scoured what they thought of as terrae incognitae in a spirit of supposed scientific investigation, vast quantities of bird and animal skins, bones, herbarium specimens and blown eggs were sent home, often with misleading records that contained very little about the curated animal’s habitat and behaviour. At the same time, European ships introduced a variety of predatory or disease-bearing species to the lands they had supposedly discovered, from mosquitoes and beetles, through pigs and ships’ moggies to black and brown rats. The aforementioned Tahiti rail, for example, is presumed to have succumbed, in shortish order, to relentless predation by invasive species, all introduced by vessels much like the one on which Forster travelled.

As for the Bay thrush, it is possible that Georg, and perhaps his father, were not just the first Europeans to see a living specimen, they were also the last. Nobody can say for sure when it happened, but it is commonly accepted that the bird (whatever it actually was) became extinct before 1850, when the American naturalist Andrew Garrett surveyed Raiatea’s bird populations.

We will never know why it was lost; but it seems reasonable to hypothesise that, as with so many other creatures in the South Pacific and elsewhere, introduced predators played some part in its demise. Which is a tragedy (as every single species loss is a tragedy), not only because we have forever lost a unique “thrush-like” creature, with its soft, fluting voice, but also because we eradicated it before we ever knew what it was. Ornithologists continue to debate this mystery today: was the Bay thrush really a thrush, or a type of starling? Or does the shape of the bill suggest a Honeyeater? We cannot know.

We could argue, of course, that, sad as this story may be, it is little more than a curiosity in the annals of natural history, but that would be a mistake. From the decidedly colourful Mauritian broad-billed parrot, lost to deforestation and introduced predators around 400 years ago, to the lovely, pink-eyed Australian peep-warbler – the Lord Howe gerygone – last seen in the 1920s, human intervention has always dramatically impacted the world’s bird species and the bird population as a whole. It has been (conservatively) estimated that, since the 1500s, we have lost around 500 species (that we were aware of), but that loss has been compounded by the eradication of around a quarter of the world’s entire bird population.

That depletion was caused by habitat destruction, pollution, the promiscuous introduction of invasive species, and the contamination of waterways, wetlands and oceans. Yet, where earlier losses might be explained by an ignorance of the law of unintended consequences, advances in our understanding, both of ecosystems and of human psychology, have robbed us of that excuse. Unlike the pirates, whalers and colonists of bygone years, we have the means to be informed on the impact of industry, mass travel and agriculture in our own time. These range from the frightening spread of microplastics through the entire biosphere to the proliferation of faux-green energy projects everywhere and the steady contamination of aquatic ecosystems by heavy and “rare Earth” metals such as lanthanides, which researchers have measured at worrying levels in the bodies of some birds such as sandwich terns, as well as in freshwater bioma and macroalgae. As one recent study puts it: “There is an urgent need for additional knowledge on the behaviour of lanthanides in the aquatic environment.” One might reasonably go further and demand a moratorium.

All of which suggests that the real lesson of the Bay thrush is a little more complicated than it first appears. Yes, it is tragic to drive a unique species into extinction before we have even decided what to call it (or before we have found it at all: another group of researchers recently estimated that “the fraction of undiscovered extinct species over all extinctions [has] ranged from 15 per cent to 59 per cent, depending on the group and the region”).

What is even more troubling, however, is that, armed with our knowledge of the law of unintended (negative) consequences, we are doing so little to examine the impact of industrialisation on the world’s biosystems. The logic seems to be that, rather than assessing the potential for harm before bringing dangerous processes and materials into play, we should simply push onwards, and hope for the best – which suggests that, as fully industrialised consumers, we don’t much care about birds, or wetlands, or forests (or, indeed, our own well-being). Or maybe we do care; we just don’t care enough.

Clearly, our ancestors drove many birds to extinction from a mix of ignorance and, in some cases, arrogance but, as BirdLife’s latest State of the World’s Birds report points out: “[in 2022] nearly half of all bird species are in decline, with more than one in eight at risk of extinction. The pressures causing these declines are well understood, and the vast majority are driven by human actions.” It would seem, then, that the lesson of the Bay thrush is that, even as we blunder on (in Rachel Carson’s words) towards “a sterile world ungraced by the curving wing of a bird in flight”, we are systematically depriving ourselves of what is most precious in this life, even before we ever see that it is there.

John Burnside won the David Cohen Prize for Literature 2023. His poetry collection “Ruin, Blossom” will be published in spring 2024 by Jonathan Cape

[See also: The secrets of frost]