The zoological collection of Chicago’s Field Museum contains an astonishing array of birds which provide an insight into the causes of biodiversity loss
An extract from Extinction: Our Fragile Relationship with Life on Earth by Marc Schlossman and Nathan Williams
Fourteen years ago, my nine-year-old twin sons, Ben and Theo, and I were given a tour of the zoological collections at the Field Museum in Chicago by John Bates, associate curator of the bird collection at that time. At one point in the tour, he opened a drawer that contained an astonishing set of bird specimens, some of which were extinct species. We picked them up, held them and read the handwritten labels. It was a rare opportunity to see species such as the ivory-billed woodpecker and the passenger pigeon up close, without a glass case between us and them. My overpowering thought at that moment was that these animals are gone. Forever. The last chance to see them is here, right now, in our hands.
John generously gave me access to the bird collection in 2008 and I began making photographs of endangered and extinct species in the botanical and zoological collections. I started the project because I felt that the key causes of biodiversity loss weren’t receiving enough public exposure and debate. Over ten years, I photographed 82 species whose stories collectively illustrate these driving factors: climate change, disease, habitat loss, invasive species, overexploitation, pollution and the wildlife trade ~ Marc Schlossman
Bird life
While describing a new species of Deinonychus, a theropod dinosaur, during the late 1960s, the eminent paleontologist John Ostrom noticed certain anatomical similarities between his specimen and modern birds. This led him to resurrect the now widely accepted hypothesis that birds are the descendants of dinosaurs, nearly a century after it was first proposed by Thomas Henry Huxley, nicknamed ‘Darwin’s Bulldog’ due to his vehement support for the theory of evolution by natural selection. Consequently, the Cretaceous-Tertiary mass extinction event didn’t wipe out the dinosaurs – their descendants, birds, are alive and well with nearly 10,000 living species.
The oldest known bird in the fossil record, Archaeopteryx, was discovered by quarrymen near Bavaria in the mid-19th century. This strange creature of the Jurassic period has a number of attributes more typically thought of as reptilian than avian, such as teeth, a bony tail and clawed fingers. However, it’s the presence of feathers that identifies it as a primitive form of bird. Originally believed to have evolved for the purpose of temperature regulation, feathers are outstanding, lightweight aerofoils, facilitating the avian conquest of the skies. Indeed, while Archaeopteryx was unlikely to have been a strong flyer, some modern birds are astonishing aeronauts. One of the most impressive is the Arctic tern (Sterna paradisaea), a species that undertakes an annual migration from its Arctic breeding grounds to the Antarctic, where it overwinters. The circuitous route taken to fly between the two poles adds to the total distance travelled substantially, such that during its lifetime, an Arctic tern may cover the equivalent of three round trips to the moon.
At the opposite end of the spectrum, numerous species have independently evolved an entirely ground-dwelling lifestyle. This is very commonly observed among species confined to islands, where, without the risk of mortality from terrestrial predators, they could abandon their powers of flight. The dodo (Raphus cucullatus), a giant, flightless member of the pigeon family endemic to the remote Indian Ocean island of Mauritius, was one such example. Evidently, it was the inaccessibility of its insular home that provided sanctuary from all natural enemies until European sailors first discovered the island during the 16th century. The helpless dodo provided a readily accessible source of fresh meat for the human seafarers, who slaughtered them in their droves until the last of them were killed in around 1681.
The dodo’s name is now synonymous with extinction, such was the speed of its extermination, and its fate actually reflects a broader pattern observed among avian extinctions – strikingly, 92 per cent of recorded avian extinctions since 1500 were species indigenous to islands. In general, the avian communities of islands are particularly vulnerable to foreign species, against which they lack any protective behaviours. For instance, the native avifaunas of New Zealand, Australia and Hawaii have all been decimated by alien species, including rats and the domestic cat. In another notable case, several species were swiftly extirpated from the island of Guam following the introduction of the brown tree snake (Boiga irregularis), a highly efficient nocturnal predator accidentally introduced by the US military at the end of the Second World War.
Island endemics are disproportionately susceptible, but around 14 per cent of contemporary birds are also considered at risk of extinction, including many species found on the mainland. In addition to invasive species, a myriad of anthropogenic stressors are threatening bird populations across the world, with habitat loss being the most dominant reason for decline. However, as outlined in 1962 by Rachel Carson in her book Silent Spring, environmental pollution due to the overuse of certain agricultural chemicals is also particularly harmful for birds. For example, DDT, a now widely banned insecticide, causes eggshell thinning and reproductive failure. Furthermore, climate change is likely to present yet another major challenge in the future. Birds usually time their breeding events so that their eggs will hatch at a period of peak resource availability in the spring. However, warmer average annual temperatures are causing a number of annual environmental changes to occur earlier, such as the time at which leaves first appear on trees in spring. This, in turn, is causing key prey, such as caterpillars, to emerge earlier, increasing the risk of starvation. Proportionately fewer birds are threatened with extinction than most other well-surveyed taxa, but they haven’t escaped the impact of human activity. With a continuation of ‘business-as-usual’, we’re likely to see their situation worsen over the coming decades.
Lost sparrows
Ammodramus maritimus nigrescens
Conservation status: Extinct
Cape Sable seaside sparrow
Ammodramus maritimus mirabilis
Conservation status: Endangered
Declared extinct in 1990, the dusky seaside sparrow was non-migratory and lived only in the marshes of the St Johns River and Merritt Island on Florida’s mid-Atlantic coast. A 70 per cent decline in its population was recorded between 1942 and 1953, following the use of the insecticide DDT to control mosquitoes on Merritt Island. Later, marshes along the St Johns River were drained to aid highway construction, putting yet more pressure on the population. By 1980, six remaining individuals, all males, had been captured to establish a captive-breeding programme that was eventually unsuccessful because no females were ever found. They lived out their lives in a Walt Disney World nature reserve called Discovery Island.
The Cape Sable seaside sparrow is one of eight remaining subspecies of seaside sparrow. It’s native to the prairies of the Everglades on Florida’s peninsula. Efforts to ensure the birds have the right amount of water have resulted in the Everglades Restoration Transition Plan, which aims to improve conditions for the sparrow and ultimately save it from extinction.
Flightless parrot
Strigops habroptilus
Conservation status: Critically Endangered
The kakapo is an extremely unusual species of green-feathered parrot found only in New Zealand. It’s the only flightless parrot in the world; it’s the world’s heaviest parrot (weighing up to 3.6 kilograms); and it’s one of the longest-living birds, with reports of some reaching 90 years of age. Before human colonisation of New Zealand, kakapo inhabited the entire country, but their numbers began to dwindle with the arrival of the Maori people, who hunted birds and also introduced rats to New Zealand for the first time. When European settlers arrived in the early 1800s, they too introduced land mammals, including stoats and ferrets, and cats. The Kakapo’s natural defence mechanism is to freeze when threatened, usually a strategy to avoid aerial predators but not a successful tactic against the new terrestrial predators.
The European settlers also began clearing forest. Kakapo reached their lowest number in 1995, with only 51 known individuals remaining. Thanks to a successful relocation and recovery programme supported by the New Zealand government, in 1987, the surviving population was evacuated to offshore island sanctuaries from which predators such as rats and stoats had been eradicated. By 1995, with the situation still critical, the Kakapo Recovery Plan was initiated and resulted in a 68 per cent increase in the bird’s numbers over a period of eight years.
As of 2021, 204 kakapo remain and with the attention and care of devoted rangers and researchers, that number is expected to rise.
Last passengers
Ectopistes migratorius
Conservation status: Extinct
On 14 September 1914, the last passenger pigeon, named Martha, died in a cage at the Cincinnati Zoo. It’s one of the few species for which we know the exact date of extinction and one of the first whose extinction is credited to human behaviour. When Europeans settled in North America during the late 1500s, the population of passenger pigeons was as high as six billion in its forest habitat in eastern areas, representing up to 40 per cent of the total bird population on the continent. Just a few decades of reckless overhunting and deforestation in the late 1800s brought the world’s largest-ever bird population to zero. During the 1800s, flocks were so dense that the birds could simply be batted out of the air with clubs as they flew over ridges; one shotgun blast could bring down as many as 50 birds. The naturalist John James Audubon observed one flock for three days and estimated that the birds were flying past at a rate of 300 million per hour. Professional hunters tracked the nomadic flocks and met the demand for meat and feathers by suffocating birds nesting in trees with sulphurous fires, knocking nests and squabs (young pigeons) from trees, baiting and intoxicating them with alcohol-soaked grain to make them easier to catch and by using live decoys with their eyes sewn shut. By 1880, overkill had made commercial hunting unprofitable. In April 1896, hunters found the last remnant flock of 250,000 and, in one day, killed all but 5,000 birds (some accounts claim that all were killed). Commercial hunting aside, the passenger pigeon probably wouldn’t have survived the progressive loss of the vast expanses of eastern woodland habitat it needed to survive. Captive-breeding efforts failed and Martha is stored in the National Museum of Natural History at the Smithsonian Institution in Washington, DC.
A success story
Falco peregrinus
Conservation status:
Least concern
The peregrine falcon is the world’s fastest animal, able to dive at speeds of more than 320 km/h. It’s the largest falcon in North America and its adaptability and vast breeding range make it the most widespread raptor in the world, occurring on all continents except Antarctica. The peregrine falcon is classified as least concern by the IUCN. However, it was nearly brought to extinction between the 1940s and ’70s, primarily through exposure to DDT and other pesticides. In use as a pesticide since 1939, DDT is stored in fatty tissues and isn’t metabolised easily. It caused thinning of peregrine eggshells and a resulting crash in hatching rates. Largely due to the 1962 publication of the book Silent Spring by author and conservationist Rachel Carson, DDT was banned in the USA in 1972. Captive-breeding programmes became very successful after the ban was introduced and the peregrine was removed from the US federal endangered species list in 1999 – the North American peregrine population increased by a staggering 2,600 per cent over 40 years. As a cliff dweller that adapts easily to urban environments, peregrines live successfully side by side with humans, nesting on balconies and ledges, and hunting pigeons and other birds.
Blackbirds in decline
Euphagus carolinus
Conservation status: Vulnerable
Euphagus carolinus is a species of blackbird distinguished by the reddish-brown tips of its feathers. It ranges widely across the boreal zone of North America, from New England, through Canada to Alaska – the northernmost breeding range of all North American blackbirds – and it winters in the southeastern and midwestern USA. It’s estimated that numbers of rusty blackbirds have declined by around 85–99 per cent since 1966 – one of the steepest declines of any North American species – and it isn’t clear why. The destruction of wetland and woodland habitats may play a part, depriving the species of its preferred breeding sites, or climate change may have altered the chemical composition of these areas as they’ve become progressively drier.
Extinct woodpecker
Campephilus principalis
Conservation status: Extinct
Thought to be extinct for more than 60 years, the ivory-billed woodpecker has become the species most people associate with extinction in the Americas. The huge appetite for lumber to rebuild after the American Civil War led to the destruction of the ivory-billed woodpecker’s habitat and its primary food source, beetle larvae. Demand from collectors increased as it became rarer, speeding its extirpation. Although in 2004, a large woodpecker was spotted that some thought to be the ivory-billed variety, no indisputable evidence has emerged to confirm its existence.
