Cockatoos and rainbow lorikeets battle for nest space as the best old trees disappear

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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.

Unfortunately, large hollows are only found in old trees.

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.

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.
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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.

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Don’t disturb the cockatoos on your lawn, they’re probably doing all your weeding for free

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Enter the rainbow lorikeets

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.

It is not uncommon to see sulphur-crested cockatoos in dispute with rainbow lorikeets over a hollow.
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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.

Every effort must be made to ensure old, hollow-forming trees are preserved.
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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).

Many species need hollows for nests.
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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.

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Read more:
The river red gum is an icon of the driest continent

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Protecting tree hollows

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.

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.

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Many New Zealand species are already at risk because of predators and habitat loss. Climate change makes things worse

Education Images/Universal Images Group via Getty Images

Cate Macinnis-Ng, University of Auckland and Angus Mcintosh, University of CanterburyIslands are biodiversity hotspots. They are home to 20% of the world’s plants and animals yet cover only 5% of the global landmass. But island ecosystems are highly vulnerable, threatened by habitat fragmentation and introduced invasive weeds and predators.

Climate change adds to all these stresses. In our recent paper, we use Aotearoa New Zealand as a case study to show how climate change accelerates biodiversity decline on islands by exacerbating existing conservation threats.

Many native birds are threatened by introduced predators such as rats, possums and cats.
Shutterstock/Imogen Warren

Aotearoa is one of the world’s biodiversity hotspots, with 80% of vascular plants, 81% of arthropods and 60% of land vertebrate animals found nowhere else.

Its evolutionary history is dominated by birds. Before the arrival of people, the only native land mammals were bats. But now, introduced predators threaten the survival of many species.

Complex interplay between many threats

Conservation efforts have rightly concentrated on the eradication of introduced predators, with world-leading success in the eradication of rats in particular.

Potential climate change impacts have been mostly ignored. Successive assessments by the Intergovernmental Panel on Climate Change (IPCC) highlight the lack of information for Aotearoa. This could be due to insufficient research, system complexity or a lack of impacts.

In the past, some researchers even dismissed climate change as an issue for biodiversity in Aotearoa. Our maritime climate is comparatively mild and already variable. As a result, organisms are expected to be well adapted to changing conditions.

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Read more:
Despite its green image, NZ has world’s highest proportion of species at risk

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Palaeo-ecological records suggest few species extinctions despite abrupt environmental change during the Quaternary period (from 2.5 million years ago to present). But past climate change provides an incomplete picture of contemporary change because it did not include human-induced threats.

Habitat loss and fragmentation, land‐use change and complex interactions between native species and introduced predators or invasive weeds all contribute to these threats.

How climate change affects biodiversity

Species respond to climate change by evolving physiological adjustments, moving to new habitats or, in the worst cases, becoming extinct. These responses then change ecosystem processes, including species interactions and ecosystem functions (such as carbon uptake and storage).

Methods for identifying climate change impacts are either empirical and observational (field studies and manipulative experiments) or mechanistic (ecophysiological models). Mechanistic approaches allow predictions of impacts under future climate scenarios. But linking species and ecosystem change directly to climate can be challenging in a complex world where multiple stressors are at play.

Tuatara survive only on a few offshore islands and in sanctuaries.
Shutterstock/Ken Griffiths

There are several well-known examples of climate change impacts on species endemic to Aotearoa. First, warming of tuatara eggs changes the sex ratio of hatchlings. Hotter conditions produce more males, potentially threatening long-term survival of small, isolated populations.

Second, mast seeding (years of unusually high production of seed) is highly responsive to temperature and mast events are likely to increase under future climate change. During mast years, the seeds provide more food for invasive species like rats or mice, their populations explode in response to the abundant food and then, when the seed resource is used up, they turn to other food sources such as invertebrates and bird eggs. This has major impacts on native ecosystems.

How masting plants respond to climate change is complex and depends on the species. The full influence of climate is still emerging.

Every few years, beech trees produce significantly higher amounts of seed.
Shutterstock/sljones

Indirect effects of climate change

We identified a range of known and potential complex impacts of climate change in several ecosystems. The alpine zone is particularly vulnerable. Warming experiments showed rising temperatures extend the overlap between the flowering seasons of native alpine plants and invasive plants. This potentially increases competition for pollinators and could result in lower seed production.

Some large alpine birds, including the alpine parrot kea, will have fewer cool places to take refuge from invasive predators. This will cause
local extinctions in a process know as “thermal squeeze”.

Small alpine lakes, known as tarns, are not well understood but are also likely to suffer from thermal squeeze and increased drought periods. Warmer temperatures may also allow Australian brown tree frogs to invade further into these sensitive systems.

The alpine parrot kea lives in New Zealand’s mountain ranges.
Shutterstock/Peter Nordbaek Hansen

Climate change disproportionately affects Indigenous people worldwide. In Aotearoa, culturally significant species such as tītī (sooty shearwater) and harakeke (flax) will be influenced by climate change.

The breeding success of tītī, which are harvested traditionally, is strongly influenced by the El Niño Southern Oscillation (ENSO) cycle. As ENSO intensifies under climate change, numbers of young surviving are decreasing. For harakeke, future climate projections predict changes in plant distribution, potentially making weaving materials unavailable to some hapū (subtribes).

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Traditional knowledge helps Indigenous people adapt to climate crisis, research shows

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Mātauranga, the Indigenous knowledge of Māori, provides insights on climate change that haven’t been captured in western science. For instance, the Māori calendar, maramataka, has been developed over centuries of observations.

Maramataka for each hāpu (subtribe) provide guidance for the timing of gathering mahinga kai (traditional food sources). This includes the gathering of fish and other seafood, planting of crops and harvesting food. Because this calendar is based on knowledge that has accrued over generations, some changes in timing and distributions due to environmental or climate change may be captured in these oral histories.

Climate change is here now

Future projections of climate change are complicated in Aotearoa — but it is clear the climate is already changing.

Last year was the seventh hottest on record for Aotearoa. Many parts of the country suffered severe summer drought. NASA captured images of browned landscapes across the country.

These images show how the Hawke’s Bay dried out between the summer (December to February) periods of 2019 (left) and 2020 (right).
NASA, CC BY-SA

Much of the focus of climate change research has been in agricultural and other human landscapes but we need more effort to quantify the threat for our endemic systems.

On islands across the world, rising sea levels and more severe extreme weather events are threatening the survival of endemic species and ecosystems. We need to understand the complicated processes through which climate change interacts with other threats to ensure the success of conservation projects.

While we focused on terrestrial and freshwater systems, marine and near-shore ecosystems are also suffering because of ocean acidification, rising sea levels and marine heatwaves. These processes threaten marine productivity, fisheries and mahinga kai resources.

And for long-term conservation success, we need to consider both direct and indirect impacts of climate change on our unique species and ecosystems.

Cate Macinnis-Ng, Associate Professor, University of Auckland and Angus Mcintosh, Professor of Freshwater Ecology, University of Canterbury

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

Drop, bears: chronic stress and habitat loss are flooring koalas

Koalas are stressed out by a range of pressures, from habitat loss to dog attacks.
Edward Narayan, Author provided

Edward Narayan, Western Sydney University

Koalas are under a lot of stress. Heatwaves, land clearing and even noise pollution are all taking a toll.

Each year, hundreds of koalas are taken to veterinary clinics after being rescued from roadsides or beneath trees, and the incidences increase during the summer months.

Chronic and ongoing pressures such as habitat destruction are overwhelming koalas’ ability to cope with stress. Koalas are nationally listed as vulnerable, so it’s important to understand how they are affected by threats that can reduce life expectancy and their ability to cope with problems.

What is stress?

The term “stress” was coined in 1936 by Hans Sayle after experiments on rats. Sayle demonstrated that the adrenal glands, which sit on top of the kidney and produce the stress hormones adrenaline and cortisol, can swell in response to any noxious stimulus or due to pathological state. In addition, there are changes in the tissues and glands involved in the basic functioning of the immune system, reproduction and growth.

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The short-term stress response is not necessarily bad, because it prepares the body to cope with external challenges. For example, tadpoles that are exposed to dragonfly nymphs grow larger and have bigger tail fins than other tadpoles.

However, chronic stress over a long time can seriously affect an animal’s health (humans included) and survival rates.

How do koalas respond to stress?

Koalas release the stress hormone cortisol in response to any unpleasant stimulus like being handled by humans (oddly, males are much more stressed by handling than females, unless the females are lactating).

Koalas have biological feedback mechanisms that can regulate the amount of cortisol they produce, so they can carry on with their day-to-day routine. However, if koalas are continuously stressed by something large and permanent, such as land clearing of their territory, it’s difficult for them to relax from a stressed state.

When this happens, the body undergoes a barrage of sub-lethal chemical changes. The resulting chronic stress can negatively affect the animals’ reproductive hormones and immune system function.

Koalas, like all animals that call Australia home, have basic physiological and behavioural adaptations needed for life in Australia’s often extreme environment. But human-induced threats such as land clearing continue to create ecological imbalances, and chronic stress makes it very difficult for koalas to cope with environmental change.

How much stress can a koala bear?

As my review of the research shows, the most common sources of stress for koalas are heat stress, car impacts and dog attacks. Foetal development of koalas could also be impacted by maternal stress due to lack of adequate food from gum trees in drought periods.

Urban and fringe zones (areas between rural and urban zones) are particularly stressful for koalas, with added pressures like noise pollution and a higher chance of land clearing.

All of these factors create a continual strain on koala physiology. The sight of a koala dead by the road is the distressing culmination of multiple, complex and dynamic environmental influences.

Clinical research has shown that wild koalas are suffering from chronic stress. Koalas are often rescued with signs of trauma, caused by car accidents, burns or dog attacks, which is very difficult to handle in veterinary clinics.

Koalas are a living treasure, the only extant representative of the family Phascolarctidae. They live exclusively on Australia’s east coast, but are considered rare in New South Wales and South Australia.

There are now numerous local dedicated koala conservation centres aimed at safeguarding their habitat and educating the public. Koalas also help increase public awareness of conservation among both young people and adults.

But more research is needed in studying how they respond to the stresses of life in a human-dominated landscape. Techniques such as non-invasive hormone monitoring technology can be used to provide a rapid and reliable index of how our koalas are being affected by stress.

Simply put, if land clearing is not reduced now we will continue to add invisible stress on koalas. Our children may one day be more likely to see a koala dead on the road than one happily cuddling their gum tree.

Edward Narayan, Senior Lecturer in Animal Science; Stress and Animal Welfare Biologist, Western Sydney University

This article was originally published on The Conversation. Read the original article.

Let’s get this straight, habitat loss is the number-one threat to Australia’s species

Brendan Wintle, University of Melbourne and Sarah Bekessy, RMIT University

Earlier this month, Australia’s outgoing Threatened Species Commissioner Gregory Andrews told ABC radio that land clearing is not the biggest threat to Australia’s wildlife. His claim caused a stir among Australia’s biodiversity scientists and conservation professionals, who have plenty of evidence to the contrary.

The ecologist Jared Diamond has described an “evil quartet” of threatening processes that drive species to extinction: habitat destruction; overhunting (or overexploitation); the presence of introduced species; and chains of linked ecological changes, including co-extinctions.

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Read more: Australia’s species need an independent champion

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In modern times we can add two more to this list. The first is catastrophic disease outbreaks, such as the chytrid fungus that has been instrumental in the catastrophic decline or extinction of almost 200 frog species, or the facial tumour disease that still threatens to
wipe out Tasmanian devils in the wild.

The second is human-induced climate change, which appears to have caused one extinction in Australian Territories and is predicted to result in many more.

So the evil quartet has now become an evil sextet. It sounds ugly because it is. But does habitat loss through land clearing still top the list? The answer, in short, is yes.

Land clearing threat

According to an analysis of data from the International Union for the Conservation of Nature (IUCN), habitat loss is the number-one threat to biodiversity worldwide. Many more species are affected by processes such as logging and land clearing for agriculture and housing than by invasive species, disease or other threats.

Number of amphibians impacted by key threats.
IUCN, Author provided

Number of mammals impacted by key threats.
IUCN, Author provided

Habitat loss is the top threat here in Australia too, an assessment that is backed up by the federal government’s State of the Environment Reports in 2011 and 2016.

Pressures affecting species on Australia’s list of nationally threatened species.
State of the Environment Report 2011, Author provided

Compared with the rest of the world, Australia’s introduction of feral predators such as cats and foxes has had a devastating impact on iconic small mammals such as bilbies, and birds such as night parrots. Nationally, we invest a large amount of resources (relative to other threats) in creating predator-proof havens for threatened animals to keep feral predators out of key areas.

But despite this, habitat loss and land clearing pose an even bigger threat to animals and plants alike. It is the single biggest factor adding to Australia’s list of threatened species list, especially given the recent return to record-breaking land clearing rates.

Interacting threats

Of course, the evil sextet do not operate independently; they gang up, often with devastating results. The joint impact of two threats is often larger than the sum of its parts. Habitat destruction is the gang leader that joins forces with other threats to accelerate the slide to extinction.

When habitats are intact, large and in good condition, the species that depend on them are much better equipped to withstand other threats such as bushfires or invasive species. But as habitat is destroyed and chopped into smaller fragments, species’ populations become smaller, more isolated, and more vulnerable to predation or competition.

Larger populations of animals and plants also generally have larger gene pools, making them more able to adapt to new threats before it’s too late. Small populations, on the other hand, are sitting ducks.

You can see where this is heading. It’s all about habitat loss, because habitat loss makes all other threats more acute.

Classic depiction of habitat fragmentation in Warwickshire between 400 AD and 1960.
Wilcove et al. Cons. Biol. (1986), Author provided

The political landscape

Habitat loss is a polarising political issue, which makes it hard to legislate against. Most habitat is lost through land clearing for agriculture and urban development.

The quality and effectiveness of land clearing policy and legislation in Australia has risen and fallen like the tide over the past four decades. After being the world’s largest land clearing jurisdiction behind Brazil in the post-war era, the Beattie government in Queensland introduced hugely improved land-clearing laws in the mid-1990s.

But under the Newman government, Queensland resumed its world leadership in habitat destruction. While Queensland may be the most extreme example, every Australian state and territory has witnessed similar policy uncertainty over the decades. Meanwhile, no federal environment minister has made significant inroads into the problem since the establishment of the 1999 Environment Protection and Biodiversity Conservation Act.

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Read more: More sightings of an endangered species don’t always mean it’s recovering

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Reducing the impact of land clearing is not a job for a fainthearted politician, given the likely objections from the powerful agriculture and development lobbies.

The federal government’s Threatened Species Strategy and Action Plan provided some excellent initiatives to shield our species from some threats, but action to reduce habitat loss is notably absent. The number-one cause of extinctions has simply not been addressed.

Of course, the outgoing Threatened Species Commissioner is right to acknowledge the impact that feral cats and foxes. But I hope that whoever next takes on the role will be prepared to deliver an unambiguous message about the biggest threat to our plants and animals, and to outline a strong vision for how we can address it.

Brendan Wintle, Professor of Conservation Ecology, University of Melbourne, University of Melbourne and Sarah Bekessy, Professor, RMIT University

This article was originally published on The Conversation. Read the original article.

Indonesia: Sumatran Elephant Facing Extinction

In Indonesia, the Sumatran Elephant is facing extinction, due to habitat loss. It would seem that is largely due to Palm plantations.

For more visit:
http://wwf.panda.org/wwf_news/?203227