Birgita Hansen, Federation University AustraliaImagine having to fly non-stop for five days over thousands of kilometres of ocean for your survival. That’s what the Latham’s Snipe shorebird does twice a year, for every year of its life.
This migratory shorebird, similar in size to a blackbird, completes this gruelling migration to warmer climes, where it prepares itself for its return flight and the next breeding season.
Unfortunately, their wetland habitat is now being lost to development and other pressures, putting this tough little bird at risk.
Latham’s Snipe breeds in northern Japan and parts of eastern Russia during May-July and spends its non-breeding season (September to March) along Australia’s eastern coast.
Like other migratory shorebirds, it has incredible endurance, undertaking a non-stop, over-ocean flight between its breeding and non-breeding grounds.
It arrives at its destination severely malnourished and spends the Australian summer months building up its strength and body fat to complete its long return flight.
Unlike many other migratory shorebird species in Australia, you won’t find Latham’s Snipe in large flocks enjoying picturesque estuaries and bays. Instead, it hides away in thickly vegetated wetlands during the day to avoid local predators.
Their characteristic brown mottled feathers help them hide in wetlands.
Large eyes high on their heads allow them to see far and wide. Their exceptional eyesight helps them constantly scan for dangers at night, when they forage for food in open wet and muddy areas.
Latham’s Snipe is the ultimate sun-seeker. It breeds in the northern hemisphere when the snows have melted and the weather is warm, then returns to the southern hemisphere to take advantage of spring rains, warmer weather and food-rich wetlands.
It spends its entire time in Australia feeding, resting and growing new flight feathers in preparation for the long haul back to Japan in autumn.
No food and nowhere to rest
Latham’s Snipe, formerly known as the Japanese Snipe, was once a popular game bird. Hunting and wetland loss during the 20th century have contributed to a decline in Latham’s Snipe in south-eastern Australia.
The signing of the Japan Australia Migratory Bird Agreement in 1981 has stopped snipe hunting in both countries. However, their wetland habitat continues to be lost due to land development and drying of wetlands.
Imagine flying for five days straight, arriving at your destination emaciated and exhausted, only to find your habitat has disappeared. No food and nowhere to rest. This is the crisis facing Latham’s Snipe and many other migratory shorebird species.
No formal protection for many of its wetlands
Under the Australian government Environment Protection and Biodiversity Conservation Act, any grouping of 18 or more snipe at a wetland site is considered nationally important. Unfortunately, however, development on snipe habitat still occurs.
In 2014 — triggered by a plan to allow housing construction on an important snipe wetland area — a team of passionate researchers and citizen scientists banded together to initiate a monitoring program of Latham’s Snipe in south-west Victoria.
After the first year of the monitoring, the Latham’s Snipe Project expanded to other parts of the country with help from a large number of dedicated volunteers and professionals.
The story from this monitoring is still unfolding but two clear patterns are emerging:
Latham’s Snipe often congregate in urban wetlands; and
the majority of these important wetlands have no formal protection from development or disturbance.
7,000km, non-stop, in three days
Between 2016 and 2020, the Latham’s Snipe Project started tagging snipe with small electronic devices to try and learn about their migratory routes.
The team uncovered an amazing migration from a female snipe captured in Port Fairy. She left her breeding grounds in northern Japan and flew directly to south-east Queensland in three days, a non-stop flight of around 7,000km. A trip that might normally take around five days, this incredible individual did in three.
This is one of the fastest bird migrations on record and highlights how demanding these over-ocean migrations are. It also shines the spotlight on the critical importance of good quality wetland habitat when the snipe return to Australia.
Urban development continues to threaten Latham’s Snipe habitats. Several snipe sites in eastern Australia are at risk from housing developments and large infrastructure projects.
However, a different way of doing things is possible.
Eco-friendly developments like the Cape Paterson Ecovillage in Victoria provide hope. Here, researchers and citizen scientists have worked with the developer to help design conservation areas within the development to protect and restore wetlands for snipe.
Such progress is heartening, but a critically important next step is to make changes to local planning schemes that explicitly recognise wetlands for Latham’s Snipe.
Gregory Moore, The University of MelbourneThe housing market in most parts of Australia is notoriously competitive. You might be surprised to learn we humans are not the only ones facing such difficulties.
With spring rapidly approaching, and perhaps a little earlier due to climate change, many birds are currently on the hunt for the best nesting sites.
This can be hard enough for birds that construct nests from leaves and twigs in the canopies of shrubs and trees, but imagine how hard it must be for species that nest in tree hollows.
They are looking for hollows of just the right size, in just the right place. Competition for these prime locations is cut-throat.
Sulphur-crested cockatoos battling for spots
Sulphur-crested cockatoos, Cacatua galerita, are relatively large birds, so naturally the hollows they nest in need to be quite large.
It can take 150 years or more before the hollows in the eucalypts that many native parrot species nest in are large enough to accommodate nesting sulphur-crested cockatoos. Such old trees are becoming rarer as old trees on farms die and old trees in cities are cleared for urban growth.
In late winter, early spring you quite often find sulphur crested-cockatoos squabbling among themselves over hollows in trees.
These squabbles can be very loud and raucous. They can last from a few minutes to over an hour, if the site is good one. Once a pair of birds takes possession and begins nesting, they defend their spot and things tend to quieten down.
The stakes are high, because sulphur-crested cockatoos cannot breed if they don’t have a nesting hollow.
In parts of southeastern Australia, rainbow lorikeets, Trichoglossus moluccanus (and/or Trichoglossus haematodus), have expanded their range over the past couple of decades. It is not uncommon to see sulphur-crested cockatoos in dispute with them over a hollow.
The din can be deafening and if you watch you will see both comedy and drama unfold. The sulphur-crested cockatoos usually win and drive the lorikeets away, but all is not lost for the lorikeets.
Sometimes the hollows prove unsuitable — usually if they are too small for the cockatoos — and a few days later the lorikeets have taken up residence. Larger hollows are rarer and so more highly prized.
How hollows form
Many hollows begin at the stubs of branches that have been shed either as part of the tree’s growth cycle or after storm damage. The wood at the centre of the branch often lacks protective defences and so begins to decay while the healthy tree continues to grow over and around the hollow.
Other hollows develop after damage to the trunk or on a large branch, following lightning damage or insect attack. Parrots will often peck at the hollow to expand it or stop it growing over completely. Just a bit of regular home maintenance.
Sulphur-crested cockatoos can often be seen pecking at the top of large branches on old trees, where the branch meets the trunk. They can do considerable damage. When this area begins to decay, it can provide an ideal hollow for future nesting.
Sadly, for the cockatoo, it may take another century or so and the tree might shed the limb in the interim. Cockatoos apparently play a long game and take a very long term perspective on future nesting sites.
Which trees are best for hollows?
In watching the local battles for parrot nesting sites, some tree species are the scenes of many a conflict.
Sugar gums, Eucalyptus cladocalyx, were widely planted as wind breaks in southern Australia and they were often lopped to encourage a bushier habit that provided greater shade.
Poor pruning often leads to hollows and cavities, which are now proving ideal for nesting — but it also resulted in poor tree structure. Sugar gums are being removed and nesting sites lost in many country towns and peri-urban areas (usually the areas around the edges of suburbs with some remaining natural vegetation, or the areas around waterways).
Old river red gums, (Eucalyptus camaldulensis) growing along our creeks and rivers are also great nesting sites. They are so big they provide ideal sites for even the largest of birds.
These, too, are ageing and in many places are declining as riverine ecosystems suffer in general. Even the old elms, Ulmus, and London plane trees, Platanus x acerifolia — which were once lopped back to major branch stubs each year, leading hollows to develop — are disappearing as they age and old blocks are cleared for townhouses.
Cavities in trees are not that common. Large cavities are especially valuable assets. They are essential to maintaining biodiversity because it is not just birds, but mammals, reptiles, insects and arachnids that rely on them for nesting and refuge.
If you have a tree with a hollow, look after it. And while some trees with hollows might be hazardous, most are not. Every effort must be made to ensure old, hollow-forming trees are preserved. Just as importantly, we must allow hollow-forming trees to persist for long enough to from hollows.
We consider our homes to be our castles. Other species value their homes just as highly, so let’s make sure there are plenty of tree hollows in future.
When we opened a box supplied by museum curators, our research team audibly gasped. Inside was a huge Australian magpie nest from 2018.
It was more than a metre wide and made up of the strangest assortment of items, including wire coat hangers, headphones, saw blades and plastic 3D glasses — a mix of detritus reflecting our modern lifestyle.
We estimate that today, around 30% of Australian bird nests incorporate human-made materials (primarily plastics). We also noted a steady increase in nest parasites over this period.
It’s clear the types of debris the birds use has reflected changes in society over time. They highlight the unexpected and far-reaching ways Australians impact their environment, and put birds in danger.
The first synthetic item
Birds and humans have been sharing spaces and habitats throughout history.
It’s well known birds incorporate material from their environment into their nests, making them ideal indicators of environmental changes and human activity. It’s also well known, particularly among scientists, that museum collections can provide unique insight into environmental changes through time and space.
With this in mind, our international team investigated Australian museum bird nest specimens collected between 1823 and 2018. Sourced from Museums Victoria and CSIRO’s Crace Site in Canberra, we inspected a total of 892 nests from 224 different bird species.
Australian birds generate an amazing array of nest types. Rufous fantails, for example, build delicately woven structures made of fine grass and spiderwebs, while welcome swallows and white-winged choughs create nests out of mud, which dry incredibly hard and can be used year after year.
Before the 1950s, human-made debris found in the nests consisted of degradable items such as cotton thread and paper.
This changed in 1956, when we found the first synthetic item in a bird nest from Melbourne: a piece of polyester string. This appearance correlates with the increased availability of plastic polymers across Australian society, seven years after the end of the second world war.
Australian magpies earn their name
We also determined, based on collection date and using historical maps, whether the nests came from natural, rural or urban landscapes. And it turns out the nest’s location, when it was built, and the species that made it largely determined whether human-made materials were present.
Our study found nests built close to urban areas or farmland after the 1950s by birds from the families Craticidae (Australian magpies and butcherbirds), Passeridae (old world or “true” sparrows) and Pycnonotidae (bulbuls) had significantly more human-made debris.
Familiar to many an urban bird enthusiast, these species tend to adapt quickly to new environments. The incorporation of human materials in nests is likely one example of this behavioural flexibility.
The research team also had access to ten bowerbird bowers from the family Ptilonorhynchidae, spanning more than 100 years. Male bowerbirds are known for creating elaborate structures, decorated with a range of colourful items to attract a mate.
In the 1890s, the birds decorated their bowers with natural items such as flowers and berries. Newspaper scraps were the only human-produced items we identified.
This changed dramatically 100 years later, where the most sought-after items included brightly coloured plastics, such as straws, pen lids and bottle caps.
But there are tragic consequences
When birds weave non-biodegradable materials — such as fishing line and polymer rope — into their nests, it increases the risk of entanglement, amputation and even accumulation of plastics in the gut of nestlings.
For example, we found evidence of one pallid cuckoo juvenile dying in 1981 after it was entangled in plastic twine used by its adoptive bell miner parents.
Plastic was not the only issue. We found the prevalence of nest parasites that attack the young chicks also increased by about 25% over the last 195 years.
Nest parasites can kill huge numbers of nestlings. Recent research into the forty-spotted pardalote in Tasmania, a threatened species, has shown nest parasites kill up to 81% of its nestlings.
What has caused this increase isn’t clear. However, the team determined it wasn’t directly linked to urban or rural habitat type, or the presence of human-made materials in the nest. This goes against the findings of other studies, which show a decrease of parasites in nests that incorporated items such as cigarettes.
Interestingly, we did find eucalyptus leaves might deter parasites, as nests that incorporated them were less likely to show evidence of parasitism.
It may be, therefore, that sticking with certain natural materials is not only better for the safety of nest inhabitants, but also may have an added effect of pest control.
Stop littering, please
While most are aware of how plastics harm sea life, our study is one of the first to show the impact goes further to harm animals living in our own backyard. If the trend continues, the future for Australian birds looks bleak.
However, we can all do something about it.
It is as simple as being responsible for our rubbish and supporting proposed legislation and campaigns for moving away from single-use plastics.
The team had access to nests from 224 different species, which equates to only about a quarter of Australia’s total of 830 bird species.
We focused on the Atlantic Forest in Brazil, a biodiversity hotspot with 1,361 different known species of wildlife, such as jaguars, sloths, tamarins and toucans. Habitat loss from expanding and intensifying farmland, however, increasingly threatens the forest’s rich diversity of species and ecosystems.
We researched the value of paddock trees and hedges for birds and bees, and found small habitat features like these can double how easily they find their way through farmland.
This is important because enabling wildlife to journey across farmlands not only benefits the conservation of species, but also people. It means bees can improve crop pollination, and seed-dispersing birds can help restore ecosystems.
Lone trees in paddocks, hedges and tree-lined fences are common features of farmlands across the world, from Brazil to Australia.
They may be few and far between, but this scattered vegetation makes important areas of refuge for birds and bees, acting like roads or stepping stones to larger natural habitats nearby.
Scattered paddock trees, for instance, offer shelter, food, and places to land. They’ve also been found to create cooler areas within their canopy and right beneath it, providing some relief on scorching summer days.
Hedges and tree-lined fences are also important, as they provide a safe pathway by providing hiding places from predators.
For our research, we used satellite images of the Atlantic Forest and randomly selected 20 landscapes containing different amounts of forest cover.
We then used mathematical models to calculate the habitat connectivity of these landscapes for three groups of species — bees, small birds such as the rufous-bellied thrush, and large birds such as toucans — based on how far they can travel.
And we found in areas with low forest cover, wildlife is twice as likely to move from one natural habitat to another if paddock trees and hedges can be used as stepping stones.
We also found vegetation around creeks and waterways are the most prevalent and important type of on-farm habitat for wildlife movement. In Brazil, there are legal protections for these areas preventing them from being cleared, which means vegetation along waterways has become relatively common compared to lone trees and hedges, in places with lower forest cover.
Insights for Australia
While the contribution of lone trees, hedges and tree-lined fences towards conservation targets is relatively low, our research shows they’re still important. And we can apply this knowledge more widely.
For example, in Australia, many koala populations depend on scattered trees for movement and habitat. In 2018, CSIRO researchers in Queensland tracked koalas using GPS, and found koalas used roadside vegetation and scattered trees for feeding and resting significantly more than they expected.
Likewise, lone trees, hedges and tree-lined fences can also facilitate the movement of Australian fruit-eating birds such as the olive-backed oriole and the rose-crowned fruit dove. Improving habitat connectivity can help these birds travel across landscapes, feeding and dispersing seeds as they go.
In fragmented landscapes, where larger patches of vegetation are hard to find, dispersing the seeds of native plants encourages natural regeneration of ecosystems. This is a key strategy to help achieve environmental restoration and conservation targets.
Policies overlook lone trees
In Brazil, there’s a strong initiative to restore natural areas, known as the Brazilian Pact for Restoration. This pact is a commitment from non-government organisations, government, companies and research centres to restore 15 million hectares of native vegetation by 2050.
However, the pact doesn’t recognise the value of lone trees, hedges and tree-lined fences.
Likewise, the Brazilian Forest Code has historically provided strong legal protection for forests since it was introduced. While this policy does value vegetation along waterways, it overlooks the value of lone trees, hedges or tree-lined fences.
These oversights could result in poor connectivity between natural areas, seriously hampering conservation efforts.
Australia doesn’t fare much better. For example, in Queensland, the native vegetation management laws protect only intact native vegetation or vegetation of a certain age. This means scattered, but vital, vegetation isn’t protected from land clearing.
Helping your local wildlife
But farmers and other landowners in Australia can make a big difference through land stewardship grant schemes (such as from Landcare) and private land conservation programs (such as Land for Wildlife or conservation covenants).
These schemes and programs can help landowners finance revegetation and protect native vegetation. Grants and programs vary by state and territory, and local council.
So think twice before you remove a tree or a hedge. It might be a crucial stepping stone for your local birds and bees.
The authors gratefully acknowledge the contributions of Dr Flávia Freire Siqueira who led this research collaboration, and co-authours Dr Dulcineia de Carvalho and Dr Vanessa Leite Rezende from the Federal University of Lavras.
David Haworth, Monash UniversityThe black swan is an Australian icon. The official emblem of Western Australia, depicted in the state flag and coat-of-arms, it decorates several public buildings. The bird is also the namesake for Perth’s Swan River, where the British established the Swan River Colony in 1829.
The swan’s likeness has featured on stamps, sporting team uniforms, and in the logo for Swan Brewery, built on the sacred Noongar site of Goonininup on the banks of the Swan.
But this post-colonial history hides a much older and broader story. Not only is the black swan important for many Aboriginal people, it was also a potent symbol within the European imagination — 1500 years before Europeans even knew it existed.
Native to Australia, the black swan or Cygnus atratus can be found across the mainland, except for Cape York Peninsula. Populations have also been introduced to New Zealand, Japan, China, the United Kingdom and the United States.
Right now, the breeding season of the black swan is in full swing across southern Australia, having recently ended in the north. In waterways and wetlands, people are seeing pairs of swans — a quarter of which are same-sex — tending carefully to their cygnets, seeing off potential threats with elaborate triumph ceremonies, or gliding elegantly across the water, black feathers gleaming in the winter sun.
Yet once upon a time in a land far away, such birds were described as rare or even imaginary.
The impossible black swan
In the first century CE, Roman satirist Juvenal referred to a good wife as a “rare bird in the earth, and very like a black swan”.
Casual misogyny aside, this is an example of adynaton, a figure of speech for something absurd or preposterous — like pigs flying, or getting blood from a stone.
Over the centuries, versions of the phrases “black swan” and “rare bird” became common in several European languages, describing something that defied belief. The expressions made sense because Europeans assumed, based on their observations, that all swans were white.
Around the same time that Juvenal coined these phrases, Ptolemy devised a map of the world that included an unknown southern continent, Terra Australis Incognita. Many believed this distant southland was populated with monsters and fabulous races, like the Antipodes, imagined by Cicero as “men which have their feet planted right opposite to yours”.
In a quirk of history, both the impossible black swan and the hypothetical southland were indeed real. Even more unbelievably, they would be found at the same geographic coordinates.
Once they were white
Black swans are significant totems for many Aboriginal people and incorporated within songlines and constellations (where they are called Gnibi, Ginibi, or Gineevee).
Yet the Noongar people in WA, and the Yuin and Euahlayi in New South Wales, tell ancestral stories about white swans, which had most of their feathers torn out by eagles.
In the Noongar story Maali, the swan, is proud and boastful of its beauty, and has its white feathers ripped out by Waalitj, the eagle, as punishment. In the Yuin story the swan, Guunyu, humble and quiet, is attacked because the other birds are jealous of his beauty.
And in the Euahlayi story, two brothers are transformed into swans, or Byahmul, as part of a robbery. Later they are attacked by eagles as an act of revenge.
In each story, after the swans have their white plumage torn out, crows release a cascade of feathers, turning the swans black, except for their white wing tips. Their red beak still shows blood from the attack.
These stories are keenly observant of, and offer an explanation for, the black swan’s colouration. They acknowledge the possibility swans could be white — even though it’s unlikely First Nations people observed white swans in their surroundings prior to British settlement.
This contrasts starkly with the European assumption that, having never seen a black swan, they couldn’t possibly exist.
European assumptions were destined to shatter once Dutch ships began visiting Australia’s western coastline in the 1600s. Seeing the mythical black swan in the flesh must have been like seeing a unicorn emerge from the shadows of the forest.
In 1636, Dutch mariner Antonie Caen observed black birds “as large as swans” at sea off Bernier Island — probably the first recorded European sighting.
In 1697, Willem de Vlamingh’s expedition to the west coast sighted many swans on what they dubbed Swarte Swaane Drift or Black Swan River. Noongar people know this river as Derbarl Yerrigan. If de Vlamingh was amazed at the sight of black swans, he did not record it, simply noting, “They are quite black”. Three swans were captured and taken to Batavia (Jakarta), but died before they could be brought to Europe.
Reports of the black swan made it back to the Netherlands and then to England, but it took another century for its mythical status to dissipate completely.
English ornithologist John Latham gave the black swan its first scientific name, Anas atrata, in 1790. Yet knowledge of its existence was still not widespread.
In 1792, the botanist on Bruni d’Entrecasteaux’s expedition, Jacques Labillardiere, made note of black swans at Recherche Bay in Tasmania, apparently unaware they were already known to Europeans.
In 1804, Nicolas Baudin’s expedition brought the first living specimens to Europe. These became part of the Empress Josephine Bonaparte’s garden menagerie at the Château de Malmaison.
The black swan had migrated from myth to the far edge of reality, joining the kangaroo and the platypus as awe-inspiring wonders from the distant, topsy-turvy southland — real, but only just.
Good versus evil
Black swans never established large populations in the wild after being brought to Europe. It’s speculated this is because black animals were considered bad omens, in league with witches and devils, and often driven away or killed.
Beliefs like these reflect the ancient assumption, found everywhere from the Dead Sea Scrolls to Star Wars, that darkness and the colour black represent evil and corruption, and that light and the colour white represent goodness and purity.
Frantz Fanon once argued that “the colonial world is a Manichean world”, in which light and dark, white and black, and good and evil are starkly divided. These divisions have been deeply implicated in the histories of colonialism and racism — often with devastating consequences.
Two swans, one dancer
The symbolic contrast of light and dark features heavily in Pyotr Ilyich Tchaikovsky’s most famous ballet, Swan Lake. Prince Siegfried falls in love with Odette, the innocent and virtuous white swan. But he is tricked into promising himself to her double, the seductive and malevolent Odile.
The ballet’s story was inspired by a long tradition of European fairy tales depicting Swan Maidens, but Tchaikovsky was also reportedly inspired by the life of King Ludwig II of Bavaria, known as the Swan King. Both Ludwig II and Tchaikovsky were caught between the societal pressure to marry and their own same-sex desires.
The roles of Odette and Odile are often played by the same ballerina, a tradition that started in 1895, two years after Tchaikovsky’s death. But it was not until 1941 that Odile was first depicted wearing black, and afterwards became known as the black swan.
Swan Lake suggests a Manichean worldview in which good and evil are polar opposites, as far away from each other as Europe is from the Antipodes. By having the same ballerina portray both roles, the ballet also suggests the world is not so simple — things can be black or white, or both at once.
False black swans
For 1500 years, Europeans had been spectacularly wrong about the black swan. Once its existence was accepted, its transmogrification from myth to reality became a metaphor within the philosophy of science. The black swan had shown the difficulty of making broad claims based on observable evidence.
Austrian philosopher Karl Popper used the black swan in 1959 to illustrate the difference between science that can be verified versus science that can be falsified.
To verify that all swans are white is practically impossible, because that would require assessing all swans — yet a single black swan can disprove the theory. In 2007, essayist and mathematic statistician Nassim Nicholas Taleb argued organisations and individuals should be robust enough to cope with “black swan events”: consequential but unexpected moments in history.
This Australian winter, those enjoying the sight of black swans and their cygnets might assume, based on observable evidence, that all Australian native swans are black. But as black swans have shown, and as Taleb argued, we should expect the unexpected.
Last month, some four centuries after Europeans were awe-struck by the sight of black swans on our waters, Tasmanian fisherman Jake Hume rescued a white-plumaged black swan, the only one known to exist.
The swan is not an albino, because it still has pigmentation around its beak and eye. Its white feathers are the expression of a rare genetic mutation. First sighted in the area in 2007, the bird was found riddled with shotgun pellets. It is recovering in Bonorong Wildlife Sanctuary until ready to be released.
Simultaneously a black swan, a white swan, and a metaphor, this assumption-shattering “rare bird” captures the complex cultural history surrounding this species.
Seabirds journey vast distances across Earth’s seascapes to find food and to breed. This exposes them to changes in ocean conditions, climate and food webs. This means their biology, particularly their breeding successes, can reveal these changes to us on a rare, planet-wide scale.
We collated and analysed the world’s largest database on seabird breeding. Our findings reveal a key message: urgency in the Northern Hemisphere and opportunity in the south.
The Northern Hemisphere ocean systems are degraded and urgently need better management and restoration. Damage to Southern Hemisphere oceans from threats such as climate change and industrial fishing is accelerating, but opportunities remain there to avoid the worst.
Oceans at a crossroads
Seabirds often travel far across the planet. For example, many sooty shearwaters breed in New Zealand, yet travel each year to the productive waters of the northeast Pacific. Arctic terns migrate even further, travelling each year between the Arctic and Antarctic.
Scientists often use satellite-derived data sets to determine, for example, how the oceans’ surfaces are warming or how ocean food webs are changing. Few such data sets span the globe, however, and this is where seabirds come in.
Over its long journey, a seabird eats fish and plankton. In doing so, it absorbs signals about ocean conditions, including the effects of pollution, marine heatwaves, ocean warming and other ecological changes.
Seabird breeding productivity (the number of chicks produced per female per year) depends on the food resources available. In this way, seabirds are sentinels of change in marine ecosystems. They can tell us which parts of oceans are healthy enough to support their breeding and which parts may be in trouble.
In some cases, seabirds tell us directly about major distress in the oceans. This was the case in 2015-16, when around a million emaciated common murres died, many washing up on beaches from California to Alaska. The seabirds experienced severe food shortages caused by an acute marine heatwave.
In other cases, seabird health can hint at longer-term and more subtle disruption of ocean ecosystems, and we are left to decipher these messages.
In this task, seabird breeding provides important clues about marine food webs that are otherwise difficult or impossible to measure directly, especially at global scales. Thankfully, seabird scientists around the world have consistently measured breeding productivity over decades.
Our research team included 36 of these scientists. We collated a database of breeding productivity for 66 seabird species from 46 sites around the world, from 1964 to 2018. We used the data to determine whether seabirds were producing relatively more or fewer chicks over the past 50 years, and whether the risk of breeding failure was increasing or decreasing.
In the Northern Hemisphere, breeding productivity of plankton-eating birds such as storm petrels and auklets increased strongly over 50 years, but breeding productivity of fish-eating birds declined sharply.
In the Southern Hemisphere, by contrast, breeding productivity of plankton-eating seabirds declined weakly, but increased strongly for fish eaters.
In short, fish-eating seabirds in the north are in trouble. Decreasing breeding productivity leads to population declines, and the low breeding rate of seabirds (many species only have one chick per year) means populations recover slowly.
More worrying, though, were our findings on the risk of breeding failure.
In the Southern Hemisphere, the probability of breeding failure was low throughout the study period. The same was true for Northern Hemisphere plankton feeders. But fish eaters in the north showed dramatically increasing risk of breeding failure, most acutely in the years since 2000.
Importantly, increasing risk of breeding failure was also much higher for seabirds that feed at the ocean’s surface, such as black-legged kittiwakes, compared with those that feed at greater depths, such as puffins.
Unfortunately, these results match what we know about human-caused damage to the ocean.
First, many pollutants such as plastics collect close to the ocean surface. They are often eaten by surface-feeding seabirds, potentially hampering their ability to produce chicks.
Similarly, the rate of ocean warming has been more than three times faster, and the change in number of marine heatwave days twice as large, on average, in the Northern than Southern Hemisphere over the past 50 years.
Likewise, northern oceans have sustained industrial fisheries for far longer than those in the south. This has likely reduced food supplies to Northern Hemisphere fish-eating seabirds over longer periods, causing chronic disruptions in their breeding success.
But human impacts in the Southern Hemisphere are accelerating. Ocean warming and marine heatwaves are becoming more intense, and industrial fisheries and plastic pollution are ever-more pervasive.
We must heed the warnings from our seabird “canaries”. With careful planning and marine reserves that take account of projected climate change, the Southern Hemisphere might avoid the worst consequences of human activity. But without action, some seabird species may be lost and ocean food webs damaged.
In the Northern Hemisphere, there is no time to waste. Innovative management and restoration plans are urgently needed to avoid further deterioration in ocean health.
If you’ve lived through a mouse plague, you’ve seen this, and smelled the stench of mice dying of poison baits.
As a desperate measure to help combat the mouse plague devastating rural communities across New South Wales, the state government yesterday secured 5,000 litres of bromadiolone. This is a bait that’s usually illegal to roll out at the proposed scale.
This is a bad idea. While bromadiolone effectively kills mice, it also travels up the food chain to poison predators who eat the mice, and other species. And these predators, from wedge-tailed eagles to goannas, are coming out in droves to feast on their abundant prey.
When your prey is everywhere
Animal plagues in Australia are fuelled by the “boom and bust” of rainfall.
We have natural, flood-driven population explosions of the native long-haired rat, with accompanying booms of letter-winged kites, their predator. We also have locust plagues when the conditions are right, leading to antechinus or mice plagues which eat the locusts.
Since at least the late 1800s, we’ve had terrible plagues of the introduced house mouse (Mus musculus). But rarely has it been this bad, with conditions currently seeming worse than the last plague in 2011, which caused over A$200 million in crop damage alone.
High numbers of birds of prey — nankeen kestrels, black-shouldered kites and barn owls — are often reported feasting on plague mice.
Snakes, goannas, native carnivores such as quolls, and feral cats and foxes, also take advantage of the abundant food. Pets, especially cats and some dogs, are highly likely to consume mice under these conditions, too.
Poisoning the food web
Laying out poison baits is one way people try to end mouse infestations and plagues. So-called “anticoagulant rodenticides” are divided into first and second generations, based on when they were first synthesised and the differences in potency.
Second generation anticoagulant rodenticides have higher toxicities than first generation, and are lethal after a single feed. First generation rodenticides, on the other hand, require rodents to feed on them for consecutive days to be lethal.
But mouse-eating predators are highly exposed to second generation rodenticides. For most animal species, the lethal doses of rodenticide aren’t yet known.
A scientific review from 2018 documented the poisoning of 31 bird, five mammal and one reptile species. Second generation aniticoaugulant rodenticides were implicated in the death of these animals.
Our research from 2020 found urban reptiles are highly exposed to second generation rodenticides, too. This includes mouse-eating snakes, called dugites, which had up to five different rodent poisons in them.
We also found poisons in frog-eating tiger snakes, and in omnivorous bobtail skinks which eat fruit, vegetation and snails. This is even more concerning because it shows how second generation rodenticides can saturate the entire foodweb, affecting everything from slugs to fish.
Bromadiolone is particularly dangerous, even to humans
Five thousand litres of the poison can treat around 95 tonnes of grain, and the government will provide it for free to primary producers once federal authorities approve its use.
Bromadiolone is usually restricted to use in and around buildings. But given the widespread impacts on wildlife, using bromadiolone at the proposed scale will do more harm than good.
Past research on bromadiolone has shown residues persist for up to 135 days in the carcasses of voles (another rodent species). In international studies, bromadiolone has been found in the livers of a host of birds of prey, including a range of owl species, red kites, sparrowhawks and golden eagles.
And it’s not just a problem for wildlife, humans are also at risk of exposure. For example, we can get exposed from eating eggs from chickens that feed on poisoned mice, or more directly from eating other animals that may have ingested poisoned mice.
A 2013 study looked at chicken eggs for human consumption, and detected bromadiolone in eggs between five and 14 days after the chicken ingested the poison. It’s not yet clear how many of these eggs we’d have to eat for us to get sick.
So what are the alternatives?
There are highly effective first generation rodenticides that provide viable solutions for managing mouse plagues. They may take a little longer to kill mice, but the upshot is they don’t stick around in the environment. A 2020 study found house mice in Perth didn’t have genetic resistance to first generation rodenticides, which suggests they’re effectively lethal.
Another approach has been to use zinc phosphide, a poison which is unlikely to secondarily poison other animals that eat the poisoned mice. However, zinc phosphide is still extremely toxic and will kill sheep, cows, pets and even humans if directly eaten.
Rolling out double-strength zinc phosphide may be the lesser of the evils in causing secondary poisoning, but only if used very carefully.
And another way to help control the mouse plague is to limit food resources for mice on farms. Farmers can minimise grain on ground, and Australia should invest in research for grain storage facilities that are less permeable to mice.
Mouse plagues are a regular cycle in Australia. Natural predators not only help create healthy, natural ecosystems, but also they help with mouse control. Second generation rodenticides will only destroy and weaken the predator populations we need to help us combat the next plague.
Like many endangered species, Aotearoa’s flightless and nocturnal kiwi survive only in small, fragmented and isolated populations. This leads to inbreeding and, eventually, inbreeding depression — reduced survival and fertility of offspring.
Mixing kiwi from different populations seems a good idea to prevent such a fate. But translocating kiwi in an effort to mate birds that are not closely related can come with the opposite risk of outbreeding. This happens when genetically distant birds breed but produce chicks with lower fitness than either parent.
Translocations have been part of the kiwi conservation effort for decades. We also have many genetic studies of the five species of kiwi in New Zealand.
But our research, which synthesised available genetic studies, shows we don’t yet have enough genetic information to predict translocation outcomes and manage genetic diversity to achieve safe and sustainable conservation practices.
Kiwi are cherished by all cultures in New Zealand as a symbol of a unique natural heritage. For Māori, kiwi are a taonga (treasure) and of vital importance to hapū (sub-tribal groups) and iwi (tribes) across Aotearoa.
Our research is the culmination of more than two decades of close collaboration and inclusion of mātauranga Māori (traditional knowledge) to improve conservation outcomes — for mana tangata (people with authority over land), for kiwi and for other species across the globe.
In the early 20th century, there were still millions of kiwi roaming the bush. But Pākehā settlers accelerated the destruction of New Zealand’s forests and introduced invasive predators, including stoats and ship rats, which are now a major threat, particularly to kiwi chicks.
Today there are fewer than 70,000 kiwi in the wild, and populations are declining in areas without predator control. The forests, wetlands and pastures where kiwi once lived have been milled, drained and ravaged by introduced browsers such as goats and deer.
Kiwi are also not immune to climate change, with worrying mortality events during recent severe droughts. In these new and changing conditions, kiwi face many challenges: new predators, new diseases, new seasonal events, new foods.
Genetic diversity provides a buffer against such challenges and better chances of survival for a species. One way to maintain genetic diversity is through mating between individuals that are not closely related.
But most kiwi live in groups of fewer than 100 birds. We have confined them to pockets of favourable habitat. As a result of well-meant conservation management to protect the birds from mammalian predators, we have moved them to safe havens on offshore islands or patches of remnant forests that effectively function as “mainland islands”, cut off from other habitat.
Call for more genetic research
One way to avoid inbreeding depression is to mix individuals from distant populations that have different genes and could provide the basis for genetic rescue. But some are opposed to such mixing because it raises the risk of outbreeding depression, which is particularly high if the parental populations differ in their adaptations to their respective environments.
Kiwi populations have evolved to adapt to local conditions on timescales of tens of thousands of years. This means one population of the same species may have adapted in different ways to another. For example, populations of North Island brown kiwi (Apteryx mantelli) are found from the warm lowlands of Te Tai Tokerau/Northland to the sub-apline volcanic plateau near Mount Ruapehu.
For decades the Department of Conservation (DOC) and community groups have been translocating kiwi all over Aotearoa. We need more gene sequencing research of such populations to investigate the effects of inbreeding and outbreeding.
Decision making in the absence of sufficient genetic information risks leading to management strategies that are inadequate or even harmful for future population sustainability.
Working with Māori
Māori, the Indigenous people of Aotearoa, are kaitiaki (guardians) of the kiwi. Whakapapa, a key concept of relatedness in te ao Māori (Māori world view), means Māori culture has a deep understanding of ideas described in western science as genetic diversity, inbreeding and hybridisation.
But hapū and iwi are not always consulted about conservation interventions, even though their role as co-managers of taonga species is well established in Te Tiriti o Waitangi.
In 2013, my research group teamed up with two hapū (Te Patukeha and Ngāti Kuta) to develop a management plan for the North Island brown kiwi in their area. A century of well-intentioned but somewhat random mixing of different North Island brown kiwi populations during translocations has effectively produced both “randomised experimental” and “control” groups.
We have also recruited support from other hapū and iwi in Tai Tokerau and have now started to analyse genetic information from several sites, using the latest techniques to investigate the genetic make-up of the birds. This research will shed new light on the effects of years of breeding in populations that started with kiwi from a single source versus those that started with mix-provenance birds.
We need to save North Island brown kiwi, but we need to do it properly. And when conservation efforts succeed, it would be far better if we knew why they worked. If we do this research right, the conservation management of other species will benefit, across Aotearoa and the world, at a time of an accelerating extinction crisis.