Most native bird species are losing their homes, even the ones you see every day



Eastern-yellow robin. Some 60 per cent of the native birds of south-east mainland Australia have lost more than half of their natural habitat.
Graham Winterflood/Wikimedia Commons

Jeremy Simmonds, The University of Queensland; Alvaro Salazar, The University of Queensland; James Watson, The University of Queensland, and Martine Maron, The University of Queensland

Across parts of Australia, vast areas of native vegetation have been cleared and replaced by our cities, farms and infrastructure. When native vegetation is removed, the habitat and resources that it provides for native wildlife are invariably lost.

Our environmental laws and most conservation efforts tend to focus on what this loss means for species that are threatened with extinction. This emphasis is understandable – the loss of the last individual of a species is profoundly sad and can be ecologically devastating.




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But what about the numerous other species also affected by habitat loss, that have not yet become rare enough to be listed as endangered? These animals and plants — variously described as “common” or of “least concern” — are having their habitat chipped away. This loss usually escapes our attention.

These common species have intrinsic ecological value. But they also provide important opportunities for people to connect with nature – experiences that are under threat.

A chain used for land clearing is dragged over a pile of burning wood at a Queensland property.
Dan Peled/AAP

The “loss index”: tracking the destruction

We developed a measure called the loss index to communicate how habitat loss affects multiple Australian bird species. Our measure showed that across Victoria, and into South Australia and New South Wales, more than 60% of 262 native birds have each lost more than half of their original natural habitat. The vast majority of these species are not formally recognised as being threatened with extinction.

It is a similar story in the Brigalow Belt of central New South Wales and Queensland. The picture is brighter in the northern savannas across the top of Australia, where large tracts of native vegetation remain – notwithstanding pervasive threats such as inappropriate fire regimes.




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We also found that in some areas, such as Southeast Queensland and the Wet Tropics region of north Queensland, the removal of a single hectare of forest habitat can affect up to 180 different species. In other words, small amounts of loss can affect large numbers of (mostly common) species.

Our index allowed us to compare how different groups of birds are impacted by habitat loss. Australia’s iconic parrots have been hit hard by habitat loss, because many of these birds occur in the places where we live and grow our food. Birds of prey such as eagles and owls have, as a group, been less affected. This is because many of these birds occur widely across Australia’s less developed arid interior.

This map shows the number of bird species affected by habitat loss in any region. Grey zones indicate parts of Australia where habitat loss has not occurred. Blue zones have up to 90 species affected by habitat loss, yellow is up to 120 species affected, while the highest category, red, is up to 187 species affected.
Conservation Biology

Habitat loss means far fewer birds

Our study shows many species have lost lots of habitat in certain parts of Australia. We know habitat loss is a major driver of population declines and freefalling numbers of animals globally. A measure of vertebrate population trends — the Living Planet Index — reveals that populations of more than 4,000 vertebrate species around the world are on average less than half of what they were in 1970.

In Australia, the trend is no different. Populations of our threatened birds declined by an average of 52% between 1985 and 2015. Alarmingly, populations for many common Australian birds are also trending downwards, and habitat loss is a major cause. Along Australia’s heavily populated east coast, population declines have been noted for many common species including rainbow bee-eater, double-barred finch, and pale-headed rosella.

Decling common species – rainbow bee-eater (left); double-barred finch (top right); pale-headed rosella (bottom right)
Jim Bendon, G. Winterflood, Aviceda



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This is a major problem for ecosystem health. Common species tend to be more numerous and so perform many roles that we depend on. Our parrots, pigeons, honeyeaters, robins, and many others help pollinate flowers, spread seeds, and keep pest insects in check. In both Europe and Australia, declines in common species have been linked to a reduction in the provision of these vital ecosystem services.

Common species are also the ones that we most associate with. Because they are more abundant and familiar, these animals provide important opportunities for people to connect with nature. Think of the simple pleasure of seeing a colourful robin atop a rural fence post, or a vibrant parrot dashing above the treetops of a suburban creek. The decline of common species may contribute to diminished opportunities for us to interact with nature, leading to an “extinction of experience”, with associated negative implications for our health and well-being.

We mustn’t wait until it’s too late

Our study aims to put the spotlight on common species. They are crucially important, and yet the erosion of their habitat gets little focus. Conserving them now is sensible. Waiting until they have declined before we act will be costly.

These species need more formal recognition and protection in conservation and environmental regulation. For example, greater attention on common species, and the role they play in ecosystem health, should be given in the assessment of new infrastructure developments under Australia’s federal environment laws (formally known as the Environment Protection and Biodiversity Conservation Act 1999).

We should be acting now to conserve common species before they slide towards endangerment. Without dedicated attention, we risk these species declining before our eyes, without us even noticing.The Conversation

Jeremy Simmonds, Postdoctoral Research Fellow in Conservation Science, The University of Queensland; Alvaro Salazar, Postdoctoral Research Fellow, The University of Queensland; James Watson, Professor, The University of Queensland, and Martine Maron, ARC Future Fellow and Professor of Environmental Management, The University of Queensland

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

Hot as shell: birds in cooler climates lay darker eggs to keep their embryos warm


The colour and brightness of birds’ eggs plays a key role in keeping them at the right temperature.
Anne Kitzman / Shutterstock

Phill Cassey, University of Adelaide and Daniel Hanley, Long Island University Post

Birds lay eggs with a huge variety of colours and patterns, from immaculate white to a range of blue-greens and reddish browns.

The need to conceal eggs from predators is one factor that gives rise to all kinds of camouflaged and hard-to-spot appearances.

Yet our research, published today in Nature Ecology & Evolution, shows that climate is even more important.

Dark colours play a crucial role in regulating temperatures in many biological systems. This is particularly common for animals like reptiles, which rely on environmental sources of heat to keep themselves warm.




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Darker colours absorb more heat from sunlight, and animals with these colours are more commonly found in colder climates with less sunlight. This broad pattern is known as Bogert’s rule.

Birds’ eggs are useful for studying this pattern because the developing embryo can only survive in a narrow range of temperatures. But eggs cannot regulate their own temperature and, in most cases, the parent does it by sitting atop the clutch of eggs.

In colder environments, where the risk of predators is lower and the risk of chilling in cold temperatures is greater, parents spend less time away from the nest.

We predicted that if eggshell colour does play an important role in regulating the temperature of the embryo, birds living in colder environments should have darker eggs.

The average colour of eggshells in different areas around the world.
Wisocki et al. 2019 ‘The global distribution of avian eggshell colours suggests a thermoregulatory benefit of darker pigmentation’, Nature Ecology & Evolution, Author provided

To test the prediction, we measured eggshell brightness and colour for 634 species of birds. That’s more than 5% of all bird species, representing 36 of the 40 large groups of species called orders.

We mapped these within each species’ breeding range and found that eggs in the coldest environments (those with the least sunlight) were significantly darker. This was true for all nest types.

We also conducted experiments using domestic chicken eggs to confirm that darker eggshells heated up more rapidly and maintained their incubation temperatures for longer than white eggshells.




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Our results show that darker eggshells are found in places with less sunlight and lower temperatures, and that these darker colours may help keep the developing embryo warm.

How future climate change will affect eggshell appearance, as well as the timing of reproduction and incubation behaviour, will be an important and fruitful avenue for future research.The Conversation

Phill Cassey, Assoc Prof in Invasion Biogeography and Biosecurity, University of Adelaide and Daniel Hanley, Assistant Professor, Long Island University Post

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

How barnacle geese adjust their migratory habits in the face of climate change



Shutterstock

Thomas Oudman, University of St Andrews

The climate is changing at an unprecedented rate, and so are the environments of many plant and animal species. Populations die out in places that become intolerable, and thrive in other places that have become more benign.

But for many species, population growth in new places does not keep up with the decline elsewhere. For some species, such as polar bears, such benign places do not even exist. And even if they do, species still face a significant problem: they need to find them.

This problem is perhaps more serious for migratory animals, which have to adjust to not one, but several changing environments that they visit throughout the year. Even after finding a new habitat one year, they must find it again the next, and every year after that. How on earth do these creatures know where to go?

This question is not trivial: many migratory populations are declining. What seems to be killing them is their inability to adjust to multiple changing habitats at once. The problem might be that it is hard for them to learn new migratory habits.

Geese lead the way

But a few migratory species are thriving. Among them are barnacle geese, a small-sized goose that winters in Europe and traditionally breeds on the Arctic tundras of Siberia, Svalbard and Greenland. So, how are they doing so well?

The barnacle goose faced extinction in the 1950s.
Shutterstock

We barely know the exact routes of many migratory species, let alone how these have changed over time. But here, barnacle geese are the exception. Ever since their near extinction in the 1950s, when fewer than 500 geese were left, scientists have been monitoring their numbers. The geese were observed in their wintering area at the Solway Firth, between Scotland and England, all along the Norwegian coast during spring migration and up to Svalbard.

Each spring from the 1970s onwards, researchers went to Helgeland on Norway’s west coast to observe the geese arriving from the UK to fill their bellies on grass. These fat reserves are essential to complete the second part of their journey north to Svalbard, where they breed.

In the early 1990s, bird researchers discovered a handful of barnacle geese in Vesterålen, 350km to the north-west of Helgeland, while they were counting pink-footed geese – another vulnerable goose population. Since then, the number of barnacle geese in Vesterålen in spring has been increasing steadily.

From the 2000s onwards, goose observers at the traditional feeding site in Helgeland started to see numbers go down. Currently, the majority of the whole population (now 40,000 birds strong) stops off in Vesterålen.

Rapid adjustments? Certainly. The number of geese in Vesterålen in spring has actually grown faster than can be explained by the birth rate alone, meaning that what we’re seeing is not just “the survival of the fittest”. In addition, many individual geese must have switched to feeding in Vesterålen later in life.

Barnacle geese calling.
Juha Saari/Xeno-Canto, CC BY-SA1.4 MB (download)

Along with counting geese, international research groups have been catching geese in the breeding areas on Svalbard since the 1960s, fitting juvenile geese with plastic leg rings with letter codes. This allowed goose observers along the Norwegian coast to actually know which bird they were looking at, and even how old it was.

Since 2000, these observers have gathered enough observations of ringed barnacle geese each year to allow proper calculations. This has enabled us to show that geese are indeed switching to Vesterålen in big numbers. In addition, the probability for individual geese to move to Vesterålen has been increasing, and young birds are far more likely to switch than older ones.

Adapting to climate change

So are these changes a response to climate change? We analysed the grass growth during the feeding period at both locations, which we could estimate from daily temperature and sunshine levels. The start of grass growth in spring has advanced more than three weeks since the 1970s, leading to a strong increase in grass availability during the goose staging period in spring at both locations. But availability is not all that counts.

Barnacle geese arrive in Norway at the end of April. In the 1970s, the snow usually had just melted at that time, and the first grass shoots were coming up. In recent years, the grass was already long when the geese arrived, and contained more cellulose. This is much more difficult for geese to digest than young grass, resulting in a lower rate of fat storage.

Vesterålen is further north, and spring starts much later than in Helgeland. This means that due to climate warming, the annual timing of grass growth in Vesterålen now is how it used to be in Helgeland. Fresh new grass now is just emerging in Vesterålen when the geese arrive, enabling the geese to gain weight fast. So yes, the switch makes sense.

Does that mean that the geese know that the new place is better? Not necessarily. Most of the switchers are young birds, which do not have much experience. Instead, we think that they follow experienced birds to Vesterålen, perhaps after they have arrived in Helgeland to find there is not enough food to go around. Geese operate in families, staying close to their long-term partners and relatives. They might exchange more information than we know.

It’s the group travelling that does the trick for geese, allowing them to profit from the discoveries of others. The question that remains is why other bird species have not evolved in the same way. Perhaps geese have always lived in a more dynamic environment than other migratory species.

Think of shorebirds, which have been dependent on the same shorelines and inter-tidal areas for thousands of years. For them, the current rate of climate change might be something they have not evolved to deal with. Perhaps we are creating a world in which all birds would be better off acting like geese.The Conversation

Thomas Oudman, Postdoctoral Researcher, School of Biology, University of St Andrews

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

How birds become male or female, and occasionally both


Jenny Graves, La Trobe University

The highly unusual “semi-identical” Australian twins reported last week are the result of a rare event. It’s thought the brother and sister (who have identical genes from their mother but not their father) developed from an egg fertilised by two different sperm at the same moment.

In humans, it’s the sperm that determines whether an embryo is pushed along a male or female development pathway. But in birds, it’s the other way around. Eggs are the deciding factor in bird sex.




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There are other fascinating aspects of bird sex that are not shared with humans. Female birds seem to have some capacity to control the sex of their chicks. And occasionally a bird that is female on one side and male on the other is produced – as in recent reports of this cardinal in the United States.

A half-male, half-female cardinal was recently spotted in Pennsylvania.

X and Y, Z and W chromosomes

So what is it about bird chromosomes that makes bird sex so different from human sex?

In humans, cells in females have two copies of a large, gene-rich chromosome called X. Male cells have one X, and a tiny Y chromosome.




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Birds also have sex chromosomes, but they act in completely the opposite way. Male birds have two copies of a large, gene-rich chromosome called Z, and females have a single Z and a W chromosome. The tiny W chromosome is all that is left of an original Z, which degenerated over time, much like the human Y.

When cells in the bird ovary undergo the special kind of division (called “meiosis”) that produces eggs with just one set of chromosomes, each egg cell receives either a Z or a W.

Fertilisation with a sperm (all of which bear a Z) produces ZZ male or ZW female chicks.

Birds can control the sex of their chicks

We would expect that, during meiosis, random separation of Z and W should result in half the chicks being male and half female, but birds are tricky. Somehow the female is able to manipulate whether the Z or W chromosome gets into an egg.

Most bird species produce more males than females on average. Some birds, such as kestrels, produce different sex ratios at different times of the year and others respond to environmental conditions or the female’s body condition. For example, when times are tough for zebra finches, more females are produced. Some birds, such as the kookaburra, contrive usually to hatch a male chick first, then a female one.




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Why would a bird manipulate the sex of her chicks? We think she is optimising the likelihood of her offspring mating and rearing young (so ensuring the continuation of her genes into future generations).

It makes sense for females in poor condition to hatch more female chicks, because weak male chicks are unlikely to surmount the rigours of courtship and reproduction.

How does the female do it? There is some evidence she can bias the sex ratio by controlling hormones, particularly progesterone.

How male and female birds develop

In humans, we know it’s a gene on the Y chromosome called SRY that kickstarts the development of a testis in the embryo. The embryonic testis makes testosterone, and testosterone pushes the development of male characteristics like genitals, hair and voice.

But in birds a completely different gene (called DMRT1) on the Z but not the W seems to determine sex of an embryo.

In a ZZ embryo, the two copies of DMRT1 induce a ridge of cells (the gonad precursor) to develop into a testis, which produces testosterone; a male bird develops. In a ZW female embryo, the single copy of DMRT1 permits the gonad to develop into an ovary, which makes estrogen and other related hormones; a female bird results.

This kind of sex determination is known as “gene dosage”.

It’s the difference in the number of sex genes that determines sex. Surprisingly, this mechanism is more common in vertebrates than the familiar mammalian system (in which the presence or absence of a Y chromosome bearing the SRY gene determines sex).

Unlike mammals, we never see birds with differences in Z and W chromosome number; there seems to be no bird equivalent to XO women with just a single X chromosome, and men with XXY chromosomes. It may be that such changes are lethal in birds.

Birds that are half-male, half-female

Very occasionally a bird is found with one side male, the other female. The recently sighted cardinal has red male plumage on the right, and beige (female) feathers on the left.

One famous chicken is male on the right and female on the left, with spectacular differences in plumage, comb and fatness.

The most likely origin of such rare mixed animals (called “chimaeras”) is from fusion of separate ZZ and ZW embryos, or from double fertilisation of an abnormal ZW egg.

But why is there such clear 50:50 physical demarcation in half-and-half birds? The protein produced by the sex determining gene DMRT1, as well as sex hormones, travels around the body in the blood so should affect both sides.




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There must be another biological pathway, something else on sex chromosomes that fixes sex in the two sides of the body and interprets the same genetic and hormone signals differently.

What genes specify sex differences birds?

Birds may show spectacular sex differences in appearance (such as size, plumage, colour) and behaviour (such as singing). Think of the peacock’s splendid tail, much admired by drab peahens.

You might think the Z chromosome would be a good place for exorbitant male colour genes, and that the W would be a handy place for egg genes. But the W chromosome seems to have no specifically female genes.

Studies of the whole peacock genome show that the genes responsible for the spectacular tail feathers are scattered all over the genome. So they are probably regulated by male and female hormones, and only indirectly the result of sex chromosomes.The Conversation

Jenny Graves, Distinguished Professor of Genetics, La Trobe University

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

For the first time we’ve looked at every threatened bird in Australia side-by-side



File 20181126 140522 1v2gsvv.jpg?ixlib=rb 1.1
Success with conservation of Kangaroo Island’s Glossy Black-Cockatoos can now be compared with other bird conservation efforts around the country.
Ian Sanderson/Flickr, CC BY-NC-SA

Stephen Garnett, Charles Darwin University; Alienor Chauvenet, Griffith University; April Reside, The University of Queensland; Brendan Wintle, University of Melbourne; David Lindenmayer, Australian National University; David M Watson, Charles Sturt University; Elisa Bayraktarov, The University of Queensland; Hayley Geyle, Charles Darwin University; Hugh Possingham, The University of Queensland; Ian Leiper, Charles Darwin University; James Watson, The University of Queensland; Jim Radford, La Trobe University; John Woinarski, Charles Darwin University; Les Christidis, Southern Cross University; Martine Maron, The University of Queensland; Molly K Grace, University of Oxford; Paul McDonald, University of New England, and Sarah Legge, Australian National University

Glossy Black-Cockatoos used to be common on South Australia’s Kangaroo Island until possums started eating their eggs and chicks. After volunteers helped protect nest hollows and erect safe nest boxes, the population more than doubled.

But how do you measure such success? How do you compare cockatoo nest protection with any other investment in conservation?

Unfortunately, we have few ways to compare and track the different efforts many people may be making to help conserve our natural treasures.

That’s why a group of us from a dozen Australian universities along with scientists and private researchers around the world have created metrics of progress for both our understanding of how to manage threats of different intensity, and how well that management has been implemented. We also provide guidance on what still needs doing before a threat no longer needs active management.

For the first time, we looked at every threatened bird in Australia to see how well – or not – they are managed. Hopefully, we can use this to avoid compounding our disastrous recent track record of extinctions in Australia.




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The state of Australian birds

What we did differently was collect the same data across different species, which meant we could compare conservation efforts across all bids.

The mallee emu-wren is unique to Australia and endangered due to habitat loss.
Nik Borrow/Flickr

When we applied these metrics to Australia’s 238 threatened bird species, the results were both encouraging and daunting. The good news is that we understand how to reduce the impact of about 52% of the threats – although of course that means we know little about how to deal with the other 48%.

But the situation is decidedly worse when we consider how effectively we are putting that research into practice. Only 43% of threats are being managed in any way at all – and just a third of the worst threats – and we are achieving good outcomes for just 20%.

But at least we now know where we are. We can celebrate what we have accomplished, appreciate how much needs doing, and direct our efforts where they will have the greatest benefit.

The threats to our birds

Introduced mammals, particularly cats, have been (and continue to be) a significant threat to Australian birds. Although we have successfully eradicated feral animals on many islands, saving many species, they remain a grave threat on the mainland.

The effect of climate change is becoming the top priority threat for the future. About half of all threatened birds are likely to be affected by increases in drought, fire, heat or sea level. Given the policy prevarication at a global level, targeted research is essential if birds are to be helped to cope.

By looking at multiple species, we can also identify what helps successful conservation. Monitoring, for instance, has a big impact on threat alleviation – better monitored species receive more attention.

The orange-bellied parrot is amongst Australia’s most critically endangered birds.
sompreaw/Shutterstock

There is also – unsurprisingly – a strong connection between knowledge of how to manage a threat and successful application of that knowledge. Often policy people want instant action, but our work suggests that action before knowledge will squander money.

Where to from here?

So what can we use this analysis for? One use is helping species close to extinction.

Using the same approach for multiple species groups, it is apparent that, while birds and mammals are in a parlous state, the most threatened fish are far worse off. We can also identify some clear priorities for action.

Finally, we must acknowledge this work emerged not from a government research grant, but from a non-government organisation (NGO). BirdLife Australia needed an overview of the country’s performance with threatened birds and was able to draw on the volunteered skills of biologists and mathematicians from around the country, and then the world.




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Indeed, one of the future projects will be using the new assessment tool to see just how much of the conservation action around the country is being driven by volunteers, from the many people who contributed their knowledge and skills to this paper through to those keeping glossy black-cockatoo chicks safe on Kangaroo Island.The Conversation

Stephen Garnett, Professor of Conservation and Sustainable Livelihoods, Charles Darwin University; Alienor Chauvenet, Lecturer, Griffith University; April Reside, Researcher, Centre for Biodiversity and Conservation Science, The University of Queensland; Brendan Wintle, Professor Conservation Ecology, University of Melbourne; David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University; David M Watson, Professor in Ecology, Charles Sturt University; Elisa Bayraktarov, Postdoctoral Research Fellow in Conservation Biology, The University of Queensland; Hayley Geyle, Research Assistant, Charles Darwin University; Hugh Possingham, Professor, The University of Queensland; Ian Leiper, Geospatial Scientist, Charles Darwin University; James Watson, Professor, The University of Queensland; Jim Radford, Principal Research Fellow, Research Centre for Future Landscapes, La Trobe University; John Woinarski, Professor (conservation biology), Charles Darwin University; Les Christidis, Professor, Southern Cross University; Martine Maron, ARC Future Fellow and Associate Professor of Environmental Management, The University of Queensland; Molly K Grace, Postdoctoral Fellow in Zoology, University of Oxford; Paul McDonald, Associate professor, University of New England, and Sarah Legge, Associate Professor, Australian National University

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