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.

A cockatoo sits in a hollow.
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.




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


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.

A rainbow lorikeet shelters in the hollow of a tree.
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.

A cockatoo sits in a hollow.
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).

A rainbow lorikeet hides in a hollow.
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.




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


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.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.

Dynasties: Lions may disappear without urgent funding for conservation


Niki Rust, Newcastle University

In part three of the BBC’s new nature series Dynasties, the protagonists, Charm and Sienna, show us how hard it is to be a successful lioness in a land filled with enemies.

Under constant threat of marauding hyenas and cub-killing male lions, the two mothers have to fight for their lives to ensure their offspring have a chance of making it to adulthood. But the episode also shows us that the biggest enemy of lions isn’t other wild predators – it’s humans.

Down from as many as 200,000 lions a century ago, some experts believe that we could now have as few as 20,000 individuals remaining in the wild – and that number is likely to be falling by the day. Worryingly, the general public are mostly unaware of their precarious conservation status. We have done a bad job of showing the perilous state of these big cats.

The lion’s kingdom under siege

Lions face attack by humans on many fronts. Panthera, a wild cat conservation organisation, believes the most serious causes for their decline include habitat loss, humans killing them to protect their livestock, wild prey depletion, accidental snaring, poorly managed trophy hunting and the illegal wildlife trade.

Since their threats are so varied, there is no single solution for protecting lions and overcoming these threats will be no mean feat. It will require locally-tailored solutions that fit each specific context. For instance, for lions that reside alongside people in areas outside national parks, research has shown that it is absolutely vital to reduce the perceived costs of lions to local people, like livestock depredation, while increasing their benefits, such as income from photographic tourism or trophy hunting.

Tourists gather to spot lions on safari in the Maasai Mara park.
Wikimedia Commons/Bjørn Christian Tørrissen., CC BY-SA

For lions inside protected areas, some experts argue that we must fence lions in to stop them causing problems with people. However, this has earned criticism from others, who believe that fences incur significant ecological and economic costs by disrupting the migration of herbivores. The issue over “to fence or not to fence” has turned into a bit of cat fight and shows the political nuances and ecological complexities of conserving such a charismatic species.

In a bold attempt to reunite conservationists, Pride, the Lion Conservation Alliance, has brought together five lion NGOs to pool their efforts and share funding. It may come as no surprise that, like the species they’re fighting to conserve, they have realised the benefits of coming together and working as a team rather than competing.

A lion always pays his debts

Focusing on lion populations in Kenya, Mozambique, Tanzania and Zambia, their community conservation efforts empower locals to be stewards of wildlife. By turning lion poachers into guardians, their initiatives have reduced lion killing by up to 99% in some of the areas in which they work.

By building on the cultural significance of lion hunts, young warriors that would usually show their bravery by killing lions are now employed to track lions and monitor their activities. They also inform their community if lions are approaching so that farmers can guard their livestock.

While TV shows such as Dynasties are helping to raise the profile of this threatened carnivore, what the lion needs now more than anything is funding. Conserving lions is an expensive business: one recent paper showed that to effectively manage the protected areas where lions currently reside would require a whopping US$0.9 billion to US$2.1 billion in additional income per year – on top of the money that is already raised.

The areas where lions are known to have lived in the past (red) versus where they survive today (blue).
Wikimedia Commons/Tommyknocker.

Where this cash comes from remains a bit of a mystery. We have to go beyond financing conservation from the meagre income of photographic tourism in national parks. Solutions could involve more corporate partnerships and financially linking lion lovers in the West to Africans living with lions.

An idea from Sir David Attenborough himself argues that companies that use lions in their marketing should pay for lion conservation. What is abundantly clear is that if we want lions to have a future, we must start stumping up the cash for their conservation.

Many commentators have suggested BBC’s Dynasties takes on the gripping, conflict-ridden format of storytelling that Game of Thrones perfected. If this is the case, humans would surely play the vicious and selfish King Joffrey. It is us, after all, who terrorise lions the most. But it is us, too, who have the power to guarantee their survival.The Conversation

Niki Rust, Postdoctoral Researcher, Newcastle University

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

Explainer: how does the sea ‘disappear’ when a hurricane passes by?


Darrell Strauss, Griffith University

You may have seen the media images of bays and coastlines along Hurricane Irma’s track, in which the ocean has eerily “disappeared”, leaving locals amazed and wildlife stranded. What exactly was happening?

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These coastlines were experiencing a “negative storm surge” – one in which the storm pushes water away from the land, rather than towards it.


Read more: Irma and Harvey: very different storms, but both affected by climate change


Most people are familiar with the idea that the sea is not at the same level everywhere at the same time. It is an uneven surface, pulled around by gravity, such as the tidal effects of the Moon and Sun. This is why we see tides rise and fall at any given location.

At the same time, Earth’s atmosphere has regions where the air pressure is higher or lower than average, in ever-shifting patterns as weather systems move around. Areas of high atmospheric pressure actually push down on the ocean surface, lowering sea level, while low pressure allows the sea to rise slightly.

This is known as the “inverse barometer effect”. Roughly speaking, a 1 hectopascal change in atmospheric pressure (the global average pressure is 1,010hPa) causes the sea level to move by 1cm.

When a low-pressure system forms over warm tropical oceans under the right conditions, it can intensify to become a tropical depression, then a tropical storm, and ultimately a tropical cyclone – known as a hurricane in the North Atlantic or a typhoon in the northwest Pacific.

As this process unfolds, the atmospheric pressure drops ever lower and wind strength increases, because the pressure difference with surrounding areas causes more air to flow towards the storm.

In the northern hemisphere tropical cyclones rotate anticlockwise and officially become hurricanes once they reach a maximum sustained wind speed of around 120km per hour. If sustained wind speeds reach 178km per hour the storm is classed as a major hurricane.

Surging waters

A “normal” storm surge happens when a tropical cyclone reaches shallow coastal waters. In places where the wind is blowing onshore, water is pushed up against the land. At the same time the cyclone’s incredibly low air pressure allows the water to rise higher than normal. On top of all this, the high waves whipped up by the wind mean that even more water inundates the coast.

The anticlockwise rotation of Atlantic hurricanes means that the storm’s northern side produces winds blowing from the east, and its southern side brings westerly winds. In the case of Hurricane Irma, which tracked almost directly up the Florida panhandle, this meant that as it approached, the east coast of the Florida peninsula experienced easterly onshore winds and suffered a storm surge that caused severe inundation and flooding in areas such as Miami.

The negative surge

In contrast, these same easterly winds had the opposite effect on Florida’s west coast (the Gulf Coast), where water was pushed offshore, leading to a negative storm surge. This was most pronounced in areas such as Fort Myers and Tampa Bay, which normally has a relatively low tide range of less than 1m.

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The negative surge developed over a period of about 12 hours and resulted in a water level up to 1.5m below the predicted low tide level. Combined with the fact that the sea is shallow in these areas anyway, it looked as if the sea had simply disappeared.


Read more: Predicting disaster: better hurricane forecasts buy vital time for residents.


As tropical cyclones rapidly lose energy when moving over land, the unusually low water level was expected to rapidly rise, which prompted authorities to issue a flash flood warning to alert onlookers to the potential danger. The negative surge was replaced by a storm surge of a similar magnitude within about 6 hours at Fort Myers and 12 hours later at Tampa Bay.

The ConversationRising waters are the deadliest aspect of hurricanes – even more than the ferocious winds. So while it may be tempting to explore the uncovered seabed, it’s certainly not wise to be there when the sea comes rushing back.

Darrell Strauss, Senior Research Fellow, Griffith University

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