Mouse plague: bromadiolone will obliterate mice, but it’ll poison eagles, snakes and owls, too


Masked owl (Tyto novaehollandiae), one of many birds of prey at great risk of secondary poisoning
Belinda Davis, Author provided

Robert Davis, Edith Cowan University; Bill Bateman, Curtin University; Damian Lettoof, Curtin University; Maggie J. Watson, Charles Sturt University, and Michael Lohr, Edith Cowan UniversityIt’s the smell that hits you first. The scent of urine and decomposing bodies. Then you notice other signs: scuttles and squeaks, small dead bodies leaking blood, tails sticking out of hubcaps.

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.

Wedge-tailed eagle
Wedge-tailed eagles are among the predators that take advantage of the house mouse plague.
Shutterstock

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.

Bobtail skink
Bobtail skinks don’t eat poisoned mice, but they’ve still been found with poison in their systems.
Shutterstock

Bromadiolone is particularly dangerous, even to humans

The NSW government secured bromadiolone baits as part of its $50 million mouse plague support package for regional communities.

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.

Flock of chickens
Humans can be exposed, too, by eating the eggs of chickens that ate the mice.
Shutterstock

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.The Conversation

Robert Davis, Senior Lecturer in Wildlife Ecology, Edith Cowan University; Bill Bateman, Associate professor, Curtin University; Damian Lettoof, PhD Candidate, Curtin University; Maggie J. Watson, Lecturer in Ornithology, Ecology, Conservation and Parasitology, Charles Sturt University, and Michael Lohr, Adjunct Lecturer, Edith Cowan University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Despite major conservation efforts, populations of New Zealand’s iconic kiwi are more vulnerable than people realise


Willowbank Wildlife Reserve, CC BY-ND

Isabel Castro, Massey University

Kiwi chick
Kiwi are moved between populations to lower the risk of inbreeding.
Maungatautari Ecological Island Trust, CC BY-SA

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.




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Kiwi whakapapa under threat

Before humans arrived in Aotearoa, kiwi populations numbered around 12 million. They were dispersed across most of the country.

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.

The remains of a kiwi
Introduced predators, including stoats and rats, are a major threat to kiwi.
Shutterstock/Lakeview Images

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.




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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.

Conservation workers holding a kiwi chick
Kiwi being released on an offshore island sanctuary.
Shutterstock/Naska Raspopina

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.

bbb
kiwi Shaun lee.
Flickr/Shaun Lee, CC BY-SA

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.

Our team is now comparing the precise genetics of mixed-background birds currently thriving on Ponui Island in the Hauraki Gulf with the control populations in Te Tai Tokerau and Taranaki, from which the Ponui Island kiwi have been drawn.

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.The Conversation

Isabel Castro, Associate Professor in Ecology and Zoology, Massey University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The secret life of puddles: their value to nature is subtle, but hugely important


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Gregory Moore, The University of MelbourneIt’s official: Australians endured the coldest, wettest summer in at least five years thanks to La Niña, a climate phenomenon over the Pacific Ocean.

Before we knew it, autumn rolled in bringing more rain. Tragically, it led to widespread flooding across New South Wales, but elsewhere it helped to create more puddles. In our urban environments puddles are inconvenient: they can damage property and block our paths. But from a biological perspective, puddles are very important components of microhabitats and biodiversity.

We know for many animals — including birds and pets — puddles are a ready source of drinking water and provide a much-needed bath after a hot and dusty day. They’re also well known for providing water-reliant species such as mosquitoes with opportunities for breeding, and many of us may remember watching tadpoles developing in puddles as children.

But puddles make more nuanced and subtle contributions to the natural world than you may have realised. So with more rain soon to arrive, let’s explore why they’re so valuable.

Rainy day on Swanston St, Melbourne
Puddles are getting harder to find in urban environments.
Shutterstock

Take a closer look

Puddles are a diverse lot. They can be small or large, shallow or deep, long lasting or gone in a matter of hours. If you look closely at a puddle you will often find it is not even, especially on a slope.

Puddles consist of small, naturally formed ridges (berms) and depressions (swales). The berms form from silt and organic matter like leaf litter, which act as mini dams holding back the water in the swales behind them.

Berms and swales can be hard to see, but if you look closely they’re everywhere and contribute to the retention of water, affecting the depth, spread and the very existence of the puddle.

All of this means they meet the needs of different species.

Flooded country path
The tiny ridges and depressions in puddles can make a big difference to wildlife.
Shutterstock

On rainy days you may have seen birds such as magpies feeding on worms that wriggle to the surface. Worm burrows can be two to three metres deep and many species might come to the surface to feed on leaf litter.

Worms emerge during and after heavy rain when water floods their burrows and soil becomes saturated. The worms won’t drown but they do need oxygen, which is low in very wet soils.

Often in drier weather, getting a worm is not as easy as you might think — not even for the legendary early bird. So when heavy rain drives worms to the surface, it’s party time for birds that feed on them, and they make the most of the opportunity.

A spotted pardalote near a puddle
A spotted pardalote inspecting puddle.
Shutterstock

Swales in puddles often persist for days, which allows water-dependent insects to breed. Mosquito larvae, for instance, live in water for between four and 14 days, depending on temperature (so if you’re worried about mozzies, then remember puddles have to persist for days before the pesky pests emerge).

Tadpoles take between four and 12 weeks to develop into frogs, and requires a deeper, long-lasting puddle. But these puddles are becoming rarer in urban areas, and so it’s not often you see tadpoles or frogs in our suburbs.

Why seeds love them

Puddles also provide small, but important, reservoirs where seeds of many plant species germinate. In some cases, the seeds have chemical inhibitors in them, which prevent the seeds from germinating until after a period of heavy rainfall.

Then, the inhibitors are leeched from or diluted within the seeds, allowing them to germinate. Many desert species have this adaptation, including Australian eremophilas (emu bush).




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In other cases, plants that grow all year round (annoyingly, weeds among them) need the dose of water puddles provide to kick start their very rapid growth and reproduction.

Easily germinated plants (such as tomatoes and cabbages) and ornamental flowering plants (such as hollyhocks and delphiniums) often require just a little extra water to trigger the whole germination process.

Important growing opportunities for iconic trees

Puddles also provide more subtle opportunities for wildlife. Take Australia’s iconic river red gums (Eucalyptus camaldulensis) as an example. River red gums are water-loving trees that can withstand up to nine months of inundation without getting stressed.

River red gum
Puddles can wash away plant-inhibiting chemicals from the soil.
Shutterstock

What’s not so well known, however, is river red gums produce chemicals that rain washes from their leaves, accumulating beneath the tree. These chemicals can inhibit the growth of plants, such as weeds, under the canopies.

This effect — where chemicals produced by one plant have an effect on other plants — is called “allelopathy”. Many wattle species produce allelopathic chemicals and so do some important food plants, such as walnuts, rice and the common pea.

River red gum allelopathic chemicals can prevent the trees’ own seedlings from growing near them. So river red gums require floods to wash the chemicals from the soil away. This mechanism allows river red gums to germinate and regenerate when the soil is wet, and in places away from the competition of mature trees.




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Puddles can do the same thing, on a small scale, ensuring trees have plenty of opportunities to persist in the wild. This pattern of regeneration is important to provide a mosaic of species and trees of different ages, making up a diverse range of habitats for other wildlife.

Puddles are no piddling problem

A muddy golden retriever playing in a puddle
Puddles are becoming harder to find in the suburbs.
Shutterstock

As property developers iron the creases from our created landscapes with much less open space and more paved surfaces, puddles are becoming harder to find close to home.

Taking away puddles removes a whole range of microhabitats, jeopardising the chances of a diverse range of species to breed and persist, especially in urban areas. These days, any loss of biodiversity is worrying.

So when you’re next out and about after or during heavy rain, keep an eye out for puddles.

Remember the life that depends on them and, if you can, try not to disturb them. Perhaps capture the joy of jumping over — rather than in — them. They are not just a nuisance, but a key to a nuanced and biodiverse local community.The Conversation

Gregory Moore, Doctor of Botany, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Only the lonely: an endangered bird is forgetting its song as the species dies out


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Ross Crates, Australian National University; Dejan Stojanovic, Australian National University; Naomi Langmore, Australian National University, and Rob Heinsohn, Australian National UniversityJust as humans learn languages, animals learn behaviours crucial for survival and reproduction from older, experienced individuals of the same species. In this way, important “cultures” such as bird songs are passed from one generation to the next.

But global biodiversity loss means many animal populations are becoming small and sparsely distributed. This jeopardises the ability of young animals to learn important behaviours.

Nowhere is this more true than in the case of regent honeyeaters. In a paper published today, we describe how a population crash to fewer than 300 has caused the species’ song culture to break down.

In healthy populations, the song of adult male honeyeaters is complex and long. But where the population is very small, the song is diminished and, in many cases, the birds have adopted the song of other species. Sadly, this makes the males less attractive to females, which may increase the chance the regent honeyeater will become extinct.

A soft, warbling song

singing honeyeater
Population decline is damaging song culture in regent honeyeaters.
Murray Chambers

Since 2015, we have monitored the regent honeyeater – a critically endangered, nectar-feeding songbird. The birds once roamed in huge flocks between Adelaide and Queensland’s central coast, tracking eucalyptus blossom.

As recently as the 1950s, regent honeyeaters were a common sight in suburban Melbourne and Sydney but are now extremely rare in both cities.

Extensive postwar land clearing has destroyed regent honeyeater habitat and caused the population to plummet. Most breeding activity is now restricted to the Blue Mountains and Northern Tablelands in New South Wales.

Regent honeyeaters are most vocal during the early stages of their breeding season. Before the population decline, the birds were known for their soft, warbling song produced with characteristic head-bobbing. But with few birds left in the wild, their song is changing – with potentially tragic consequences.

Finding their voice

Birdsong is one of the most well-studied examples of animal culture. Young songbirds learn to sing by listening to, repeating and refining the songs of older flockmates.

Song-learning is often completed in first year of life, after which a birds’ song is “fixed”.

Despite the increasing number of endangered bird species, there is surprisingly little research into how declines in population size and density might damage song culture in wild birds. We sought to explore whether this link existed in regent honeyeater populations.

Male regent honeyeaters sing to secure breeding territories and attract mates. We classified the songs of 146 male regent honeyeaters between 2015 and 2019. We made or obtained high-quality recordings of 47 of these in the wild, and more in captivity. This included wild birds found by the general public and reported to BirdLife Australia. We quickly chased up these public sightings to record the birds’ songs before they moved on.

We noted the location of each male and tracked its breeding success. We also recorded the songs of captive-bred regent honeyeaters that were part of a reintroduction program.




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Changing tunes

Our research showed the songs of remaining wild males vary remarkably across regions. For example, listen to the “proper” song of regent honeyeaters occurring in the Blue Mountains west of Sydney, where most of the remaining population occur:

Regent honeyeater singing a ‘proper’ song.
Author provided121 KB (download)

You’ll notice they sound noticeably different to the small number of males hanging on 400km to the north, near Glen Innes. Although these males still sound like a regent honeyeater, their songs are slower and have a different melody:

Regent honeyeater singing a slower song.

Across the species’ entire range, we found 18 males whose songs sounded nothing like a regent honeyeater. Instead, they closely resembled those of other bird species. Five male regent honeyeaters had learned the song of the little wattlebird:

Regent honeyeater singing the song of the little wattlebird.

Four males had learned songs of the noisy friarbird. Others sounded like pied currawongs, eastern rosellas or little friarbirds:

Regent honeyeater singing the song of a little friarbird.

There are isolated cases of individual songbirds mistakenly learning the song of a different species. But to find 12% of males singing only other species’ songs is unprecedented in wild animal populations.

We believe regent honeyeaters are now so rare in the landscape, some young males are unable to locate adult males from which to learn their song. Instead, the young males mistakenly learn the songs of different bird species they’ve associated with when developing their repertoires.

Evidence suggests this song behaviour is distinct from the mimicry common in some Australian birds. Mimicry involves a bird adding the songs of other birds to its own repertoire – and so, not losing its original song. But the regent honeyeaters we recorded never sang songs that resembled that of their species.




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Small honeyeater on a branch
Female regent honeyeaters avoid males with unusual songs.
Shutterstock

Also, mimicry in other species has typically evolved because it increases breeding success. However in regent honeyeaters, we found the opposite. Even among males that sounded like a regent honeyeater, those whose songs were unusual for the local area were less likely to impress, and be paired with, a female. Females that did couple up to males with unusual songs were less likely to lay eggs.

These data suggest the loss of song culture is associated with lower breeding success, which could be exacerbating regent honeyeater population decline.

A captive-breeding program is a key component of the regent honeyeater recovery plan. However our research showed the songs of captive-bred regent honeyeaters were shorter and less complex than their wild counterparts:

The song of a captive-bred regent honeyeater.

This may affect the breeding success of captive-bred males once they’re released to the wild. Consequently, we’re teaching captive juveniles to sing correctly by playing them our recordings of “proper” songs from wild birds in the Blue Mountains.

The honeyeaters’ final song?

Maintaining animal cultures in both wild and captive populations is increasingly recognised as crucial to preventing extinctions. These cultures include not just song, but also other important behaviours such as migration routes and feeding strategies.

The loss of the regent honeyeater song culture may be a final warning the species is headed for extinction. This is an aspect of species conservation we can’t ignore.

We must urgently restore and protect breeding habitats, protect nests from predators and teach captive-bred birds to sing. We must also address climate change, which threatens the species’ habitat. Otherwise, future generations may never hear the regent honeyeater’s dulcet tones in the wild.




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The Conversation


Ross Crates, Postdoctoral fellow, Australian National University; Dejan Stojanovic, Postdoctoral Fellow, Australian National University; Naomi Langmore, Research Fellow, Australian National University, and Rob Heinsohn, Professor of Evolutionary and Conservation Biology, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Birds on beaches are under attack from dogs, photographers and four-wheel drives. Here’s how you can help them


An adult fairy tern feeding a chick.
Claire Greenwell, Author provided

Claire Greenwell, Murdoch University

Environmental scientists see flora, fauna and phenomena the rest of us rarely do. In this new series, we’ve invited them to share their unique photos from the field.


Each year, oystercatchers, plovers and terns flock to beaches all over Australia’s coastline to lay eggs in a shallow scrape in the sand. They typically nest through spring and summer until the chicks are ready to take flight.

Spring and summer, however, are also when most people visit the beach. And human disturbances have increased breeding failure, contributing to the local contraction and decline of many beach-nesting bird populations.

Take Australian fairy terns (Sternula nereis nereis) in Western Australia, the primary focus of my research and photography, as an example. Their 2020-21 breeding season is coming to an end, and has been relatively poor.

Courting pair of Fairy Terns on the beach
Australian fairy tern pair. Males feed female mates, helping to supplement nutrients and energy for egg production.
Claire Greenwell

Fox predation and flooding from tidal inundation wiped out several colonies. Unfathomably, a colony was also lost after a four-wheel drive performed bog-laps in a sign-posted nesting area. Unleashed dogs chased incubating adults from their nests, and photographers entered restricted access sites and climbed fragile dunes to photograph nesting birds.

These human-related disturbances highlight the need for ongoing education. So let’s take a closer look at the issue, and how communities and individuals can make a big difference.

Nesting on the open beach

Beach-nesting birds typically breed, feed and rest in coastal habitats all year round. During the breeding season, which varies between species, they establish their nests above the high-water mark (high tide), just 20 to 30 millimetres deep in the sand.

Fairy Tern sitting on eggs
Eggs are sandy coloured and have a mottled appearance, which help them to blend in with the environment.
Claire Greenwell
Two Fairy Tern chicks. Down feathers are lightly coloured and mottled to help increase camouflage.
Fairy tern chicks crouch close to the ground to hide from predatory birds. Down feathers are lightly coloured and mottled to help increase camouflage.
Claire Greenwell

Some species, such as the fairy tern, incorporate beach shells, small stones and organic material like seaweed in and around the nest to help camouflage their eggs and chicks so predators, such as gulls and ravens, don’t detect them easily.

An adult Fairy Tern moving shell material around the nest site to increase camouflage of the eggs.
An adult fairy tern moving shell material around the nest site to increase the camouflage of its eggs.
Claire Greenwell

While nests are exposed and vulnerable on the open beach, it allows the birds to spot predators early and to remain close to productive foraging areas.

Still, beach-nesting birds live a harsh lifestyle. Breeding efforts are often characterised by low reproductive success and multiple nesting attempts may be undertaken each season.

Eggs and chicks remain vulnerable until chicks can fly. This takes around 43 days for fairy terns and about 63 days for hooded plovers (Thinornis rubricollis rubricollis).

Adult Fairy Tern feeding a chick
Eggs and chicks are vulnerable until chicks are capable of flight.
Claire Greenwell

Disturbances: one of their biggest threats

Many historically important sites are now so heavily disturbed they’re unable to support a successful breeding attempt. This includes the Leschenault Inlet in Bunbury, Western Australia, where fairy tern colonies regularly fail from disturbance and destruction by four-wheel drives.

Species like the eastern hooded plover and fairy tern have declined so much they’re now listed as “vulnerable” under national environment law. It lists human disturbance as a key threatening process.




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Birds see people and dogs as predators. When they approach, nesting adult birds distance themselves from the nest and chicks. For example, terns typically take flight, while plovers run ahead of the threat, “leading” it away from the area.

When eggs and chicks are left unattended, they’re vulnerable to predation by other birds, they can suffer thermal stress (overheating or cooling) or be trampled as their cryptic colouration makes them difficult to spot.

Silver Gull carrying away a Fairy Tern chick
Natural predators such as silver gulls readily take eggs and chicks when left unattended.
Claire Greenwell

Unlike plovers and oystercatchers, fairy terns nest in groups, or “colonies”, which may contain up to several hundred breeding pairs. Breeding in colonies has its advantages. For example, collective group defence behaviour can drive off predatory birds such as silver gulls (Chroicocephalus novaehollandiae).

However, this breeding strategy can also result in mass nesting failure. For example, in 2018, a cat visiting a colony at night in Mandurah, about 70 km south of Perth, killed six adults, at least 40 chicks and led to 220 adult birds abandoning the site. In other instances, entire colonies have been lost during storm surges.

Adult Fairy Terns mobbing a juvenile Crested Tern
Adult fairy terns engaged in group defence or ‘mobbing’ to drive away a juvenile crested tern from a colony.
Claire Greenwell

Small changes can make a big difference

Land and wildlife managers are becoming increasingly aware of fairy terns and the threats they face. Proactive and adaptive management combined with a good understanding of early breeding behaviour is helping to improve outcomes for these vulnerable birds.

Point Walter, in Bicton, WA, provides an excellent example of how recreational users and beach-nesting birds can coexist.

Point Walter, 18 km from Perth city, is a popular spot for picnicking, fishing, kite surfing, boating and kayaking. It’s also an important site for coastal birds, including three beach-nesting species: fairy terns, red-capped plovers and Australian pied oystercatchers (Haematopus longirostris).

Point Walter, Bicton with kite surfers and kayakers
Point Walter is a popular recreational site in Perth. Recent effective management, including seasonal closures, have enabled fairy terns, red-capped plovers and Australian pied oystercatchers to nest at the end of the sand bar.
Claire Greenwell

The end of the sand bar is fenced off seasonally, and as a result the past six years has seen the number of terns increase steadily. For the 2020-2021 season, the sand bar supported at least 150 pairs.

The closure also benefits the local population of red-capped plovers and Australian pied oystercatchers, who nest at the site each year.

Fairy Tern chick being brooded by its parent.
Fairy tern brooding (sitting on) its chick.
Claire Greenwell
An adult Australian Pied Oystercatcher teaching its offspring to hunt for prey.
An adult Australian pied oystercatcher teaching its offspring to hunt for prey.
Claire Greenwell

What’s more, strong community stewardship and management interventions by the City of Mandurah to protect a fairy tern colony meant this season saw the most successful breeding event in more than a decade — around 110 pairs at its peak.

Interventions included temporary fencing, signs, community education and increased ranger patrols. Several pairs of red-capped plovers also managed to raise chicks, adding to the success.

These examples highlight the potential for positive outcomes across their breeding range. But intervention during the early colony formation stage is critical. Temporary fencing, signage and community support are some of our most important tools to protect tern colonies.

So what can you do to protect beach-nesting birds?

Fairy Tern chick
A fairy tern chick at a site dedicated to fairy tern breeding.
Claire Greenwell
  • share the space and be respectful of signage and fencing. These temporary measures help protect birds and increase their chance of breeding success

  • keep dogs leashed and away from known feeding and breeding areas

  • avoid driving four-wheel drive vehicles on the beach, particularly at high tide

  • keep cats indoors or in a cat run (enclosure)

  • if you see a bird nesting on the beach, report it to local authorities and maintain your distance

  • avoid walking through flocks of birds or causing them to take flight. Disturbance burns energy, which could have implications for breeding and migration.




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The Conversation


Claire Greenwell, PhD Candidate, Murdoch University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Look up! A powerful owl could be sleeping in your backyard after a night surveying kilometres of territory



Nick Bradsworth, Author provided

Nick Bradsworth, Deakin University; John White, Deakin University, and Raylene Cooke, Deakin University

Picture this: you’re in your backyard gardening when you get that strange, ominous feeling of being watched. You find a grey oval-shaped ball about the size of a thumb, filled with bones and fur — a pellet, or “owl vomit”.

You look up and see the bright “surprised” eyes of a powerful owl staring back at you, with half a possum in its talons.

This may be becoming a familiar story for many Australians. We strapped tracking devices to 20 powerful owls in Melbourne for our new research, and learned these apex predators are increasingly choosing to sleep in urban areas, from backyard trees to city parks.

These respite areas are critical for species to survive in challenging urban environments because, just like for humans, rest is an essential behaviour to conserve energy for the day (or night) ahead.

Our research highlights the importance of trees on both public and private land for wild animals. Without an understanding of where urban wildlife rests, we risk damaging these urban habitats with encroaching development.

One owl, one year, 300 possums

Powerful owls are Australia’s largest, measuring 65 centimetres from head to tail and weighing a hefty 1.6 kilograms. They’re found in Australia’s eastern states, except for Tasmania.

Powerful owl with half a common ringtail possum
Powerful owl at roost with half a common ringtail possum (probably saving it for later).
Nick Bradsworth

These owls have traditionally been thought to live only in large old-growth forested areas. However, Victoria has lost over 65% of forest cover since European settlement, and because of this habitat loss, the owls are listed as threatened in Victoria.

Their remaining habitat is extremely fragmented. This means we’re finding owls in interesting places — from dry, open woodland to our major east coast cities. This is likely due to the high numbers of prey, such as possums, that thrive alongside exotic garden trees and house roofs.




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Powerful owls usually eat one possum per night, or 250-300 possums per year — mostly common ringtail and brushtail possums in Melbourne. They’re often seen holding prey at their roosting spots, where they’ll finish eating in the evening for breakfast.

This has ecosystem-wide benefits, as powerful owls can help keep overabundant possums in check. Too many possums can strip away vegetation, causing it to die back, which stops other wildlife from nesting or finding shelter.

Tracking their nocturnal haunts

But powerful owls are extremely elusive. With low populations, locating owls and researching their requirements is very difficult.

So, to help narrow down the general areas where powerful owls live in Melbourne, we used species distribution models and sought help from land management agencies and citizen scientists.

Over five years, we deployed GPS devices on 20 Melburnian owls to find how they use urban environments. These devices automatically record where the owls move at night and rest during the day.

We learned they fly, on average, 4.4 kilometers per night through golf courses, farms, reserves and backyards looking for dinner and defending their territory. One owl along the Mornington Peninsula travelled 47 km over two nights (possibly in search of a mate). Another urban owl called several golf courses in the Melbourne suburb of Alphington home.

Choosing where to sleep

After their nightly adventures, the owls usually return to a number of regular roosting (resting) spots, sometimes on the exact same branch. The powerful owl chooses roosts that protect them against being mobbed by aggressive daytime birds, such as the noisy miner and pied currawong.

A powerful owl showing defensive behaviour towards nearby pied currawongs trying to mob it.

We found the owls used 32 different tree species to roost in: 23 were native, and nine were exotic, including pine and willow trees. This shows powerful owls can adapt to use a range of species to fit their roosting requirements, such as thick foliage to hide in during the day.

Owls will generally roost in damp, dark areas during summer, and in open roosts in full or dappled sunlight during winter to help regulate their body temperature.




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Our research also shows rivers in urban environments are just as important as trees for roosting habitat.

Rivers are naturally home to a diverse range of wildlife. Using trees near rivers to rest in may be a strategic decision to reduce time and energy when travelling at night to find other resources, such as prey, mates and nests.

Rivers that constantly flow, such as the Yarra River, are a particular favourite for the owls.

A powerful owl surrounded by leaves
Powerful owl at roost among dense Kunzea vegetation.
Nick Bradsworth

The urban roost risk

These resting habitats, however, are under constant pressure by urban expansion and agriculture. Suitable roosting habitat is either removed, or degraded in quality and converted to housing, roads, grass cover or bare soil.

We found potentially suitable roosting habitat in Melbourne is extremely fragmented, covering just 10% of the landscape because owls are very selective about where they sleep.

Although there might be the odd suitable patch (or tree) to roost in urban environments, what’s often lacking is natural connectivity between patches. While owls are nocturnal, they still need places to rest in the night before they settle down in another spot to sleep for the day.

A pair of powerful owls with beady eyes sitting at their roost
The classic ‘surprised’ powerful owl expression at a roost.
Nick Bradsworth

Supplementing habitat with more trees on private property and enhancing the quality of habitat along river systems may encourage owls to roost in other areas of Melbourne.

Powerful owls don’t discriminate between private land and reserves for roosting. So conserving and enhancing resting habitats on public and private land will enable urban wildlife to persist alongside expanding and intensifying urbanisation.

So what can you do to help?

If you want powerful owls to roost in your backyard, visit your local indigenous nursery and ask about trees local to your area.

Several favourite roost trees in Melbourne include many Eucalyptus species and wattles. If you don’t have the space for a large tree, they will also roost in the shorter, dense Kunzea and swamp paperbark (Melaleuca ericifolia).

Planting them will provide additional habitat and, if you are lucky, your neighbourhood owls may even decide to settle in for the day and have a snooze.




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The Conversation


Nick Bradsworth, PhD Candidate, Deakin University; John White, Associate Professor in Wildlife and Conservation Biology, Deakin University, and Raylene Cooke, Associate Professor, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.