Category Archives: blog

Secrets of flocking by birds and fish revealed —

Watching thousands of birds fly in a highly coordinated, yet leaderless, flock can be utterly baffling to humans. Now, new research is peeling back the layers of mystery to show how exactly they do it — and why it might be advantageous to fly right.

Mathematical models show that the birds’ complicated collective behavior can be the consequence of a few simple rules of the road — or sky.

“Initially in [the] 1930s, people thought it might be telepathy that guided flocks of birds. Now we know self-organization is at the heart,” said Charlotte Hemelrijk of the University of Groningen in the Netherlands.

Flock of Auklet

Flock of Auklet

Hemelrijk has studied schools of fish and flocks of starlings — birds that can gather in flocks as large as 30,000 individuals.

“Each day they flap around for 30 minutes in the evening before sleep, and it’s just spectacular the way they do this,” Hemelrijk said.

And while fish generally only made long skinny shapes as they swam, the shapes that the bird flocks could take — elongated, bulbous, hourglass, and constantly shifting — were incredibly diverse. This motivated Hemelrijk to work, collaborating with a computer programmer to create a new model that figured out the underlying logic of the starlings’ flight.

She found that even in giant flocks, each bird maintained just about the same speed and only interacted with about seven neighbors as it swooped and dove. As the birds rolled through a turn, the shape of the flock changed from wide and flat to long and narrow. Additionally, birds that are flying abreast each other end up in a single file line when they turn. The research was published in the journal PLoS One.

The benefits of flocking are still being determined. In one study that measured the heart rate of pigeons, birds consumed more energy when they were forced to fly closer to each other.

“Clearly for some birds, flying together is costing them energy, so the question remains: why do they do it?” said Geoffrey Spedding, a professor of mechanical and aerospace engineering at University of Southern California. “It could be that flocking is a social phenomenon as well as mechanical one — something like getting on the treadmill at lunch for exercise.”

Spedding said that the study of flocking can be applied to lots of other fields.

“Suppose I want to make a flock of flying machines that can sense an environment and manage coordination among individuals. A good place to start would some rules of interaction in birds that can equally apply to our artificial devices,” Spedding said.

Gathering in flocks could also raise the overall intelligence of the group. According to a study in the Proceedings of the National Academy of Sciences, larger groups of great and blue tits are better at solving problems than smaller ones.

“For one thing, when there are more birds around, each bird doesn’t have to be as vigilant for predators, so they can devote more attention to the task,” said Julie Morand-Ferron, a researcher at Oxford University’s zoology department.

Social birds can learn quickly from each other, so having one whiz kid present among the group can improve the situation for everyone. In the experiments, the researchers created a lever-pulling device that the birds had to operate to get a food reward. They found that as the size of the groups increased individual birds got more food in return for the time they spent mastering the device.

Morand-Ferron said it’s not clear if larger groups work better for all types of birds, but that several species have had the same outcomes.

“Technical innovation is a new benefit to flocking that had not been described in the wild before,” Morand-Ferron said. (Phys.org)

Female warblers live longer when they have help raising offspring —

Seychelles warbler (CC BY-SA 3.0) (Author - Remi Jouan)

Seychelles warbler (CC BY-SA 3.0)             (Author – Remi Jouan)

Death is, unfortunately, an inevitable consequence of life. In most animals growing old is accompanied by progressive deterioration in health and vitality, leading to an increasing likelihood of death with age.

However, within populations of a single species there is lots of variation in when individuals start to deteriorate in later life. Why some individuals of the same species age faster than others is one of the biggest unanswered questions in biology. It’s also one that has massive implications for healthcare and society. Understanding why individuals age differently may allow us to promote longer and healthier lifespans in humans and other animals.

The environment that an individual experiences as it strives to survive and reproduce appears to be a major driver of individual variation in ageing. We are all familiar with the idea that some people look like they have “had a hard life”, while others are “young for their age”. Scientists and medics sometimes refer to an individual’s biological age. An individual has a biological age of 70 if their health and condition resembles that which we would expect of a 70 year old – whatever their actual age is.

It’s thought that a lot of this variation in ageing originates because individuals experience different levels of physiological stress as they go through life. We now need to figure out which factors explain these differences, at what point they have an effect in the course of a life, and how they can be avoided or mitigated.

Research on a small bird could help us understanding this process of ageing – and the unlikely benefits of childcare.

How our cells record ageing

Investigating the causes of ageing within natural populations – where individuals are exposed to realistic variation in stresses and do not benefit from any intervention or medication – is important, but very tricky. Wild living individuals have to be tracked throughout their lives to assess the environmental and social conditions they experience, and their subsequent health and survival.

Our long-term study of the Seychelles warbler (Acrocephalus sechellensis), also known as Seychelles brush warbler – a small, tropical songbird – on the island of Cousin in the Indian Ocean is a useful case study for understanding the ageing process. Since the 1990s, all the warblers on this tiny island – just 40 football fields in size – have been fitted with coloured leg rings so they can be tracked and identified. Birds don’t disperse on or off this isolated island so we were able to follow them from birth to death. We also monitored their health, reproduction and survival, which all decline rapidly in elderly individuals.

We also measured the warbler’s telomeres – repetitive DNA sequences which protect the ends of chromosomes but shorten in response to physiological stress. Telomere shortening has been shown to be a useful marker of biological condition and ageing in various animals, including humans. In the Seychelles warbler, telomere length predicts future survival. By measuring the telomere shortening that occurs in response to any given experience we can determine the impact that specific factors have on ageing.

Our previous studies on the Seychelles warbler have already found that certain factors influence the rate at which individuals age. For example, having a territory surrounded by unrelated and unfamiliar neighbours leads to more territorial fights, and hence more rapid telomere shortening. Growing up in a territory with limited food availability also has a detrimental impact on later ageing.

Our recent paper in Nature Communications has focused on how raising offspring is stressful and may lead to premature ageing – something that may not surprise many parents. Due to a lack of space on Cousin, many adults can’t find a territory in which to pair up and breed. Instead, these individuals may join up as subordinates to a dominant breeding pair within an already established territory – often the one in which they were born. They then sometimes help the dominant breeding pair raise their next batch of offspring—a process known as “cooperative breeding“.

Our analyses showed that the dominant birds that receive help have less telomere shortening than those that are left to do all of the parenting work themselves. This help also results in better survival of the dominant females. Therefore, we can see that the help that the dominant breeding birds received reduced the stress of breeding and delayed ageing, at least in females. The dominant males don’t appear to benefit from receiving help as much, probably because in the Seychelles warbler males invest much less energy in raising chicks than females do.

Our study confirms a long-held hypothesis that cooperative breeding – which is the norm in humans – can reduce the health costs to parents of raising young and may, therefore, slow down ageing. This could explain why more social species tend to have longer life-spans.

Our findings in the Seychelles warbler have identified the costs of more rapid ageing in overworked parents. These costs, and how individuals differ in what they experience and when, can help explain why there is so much variation in how individuals age in later life. (Phys.org)

Invasive plants are dyeing woodpeckers red —

Northern flicker pair - female (left), male (right)(Author - David Margrave)

Northern flicker pair – female (left), male (right)(Author – David Margrave)

An ornithological mystery has been solved! Puzzling red feathers have been popping up in eastern North America’s “yellow-shafted” population of Northern Flickers, but they aren’t due to genes borrowed from their “red-shafted” cousins to the west, according to a study in The Auk: Ornithological Advances. Instead, the culprit is a pigment that the birds are ingesting in the berries of exotic honeysuckle plants.

The Northern Flicker comes in two varieties—the birds of the west have a salmon pink or orange tinge to the undersides of their wings, while the eastern birds are yellow. Where the two populations meet in the middle, they frequently hybridize, producing birds with a blend of both colors. For years, however, flickers far to the east of the hybrid zone have been popping up with red-orange wing feathers. The prevailing explanation has been that they must somehow have genes from the western population, but Jocelyn Hudon of the Royal Alberta Museum and his colleagues have determined that the eastern birds’ unusual color actually has a different source: a pigment called rhodoxanthin, which comes from the berries of two species of invasive honeysuckle plants.

Hudon and his colleagues used spectrophotometry and chromatography to show that rhodoxanthin, rather than the type of carotenoid pigment that colors western red-shafted birds, was present in the feathers of yellow-shafted flicker specimens with the aberrant red coloration. Data from a bird-banding station helped confirm that the birds acquire the red pigment during their fall molt about early August, which coincides with the availability of ripe honeysuckle berries. The honeysuckles have also been implicated as the source of unusual orange feathers in Cedar Waxwings.

“At one point considered valuable wildlife habitat and widely disseminated, the naturalized Asian bush honeysuckles are now considered invasive and undesirable in many states. This is clearly not the last we have heard of aberrantly colored birds,” says Hudon. “The ready availability of a pigment that can alter the coloration of birds with carotenoids in their plumages could have major implications for mate selection if plumage coloration no longer signaled a bird’s body condition.”

“This is the pinnacle of a lengthy series of papers on the pigments deposited in primary feathers. Hudon et al. make use of the most up-to-date spectrometric and biochemical analyses to identify and quantify the pigments,” according to Alan Brush, an expert on feather color and retired University of Connecticut professor who was not involved with the study. “In addition to demonstrating that the red pigments in the molting yellow-shafted feathers are derived from their diets, not the result of interbreeding with the red-shafted form, they illuminate the dynamic nature of pigment deposition during molt, an accomplishment in itself.” (Phys.org)

White storks hatch in UK wilderness for first time in six centuries —

White Stork  (CC BY-SA 3.0) (Author - Nevit)

White Stork (CC BY-SA 3.0)                                (Author – Nevit)

White stork chicks (Ciconia ciconia) have been hatched in the wild in the UK for the first time in what is thought to be more than 600 years.

The birds cracked out of their eggs at the Knepp Estate in West Sussex.

Observers witnessed the parents removing eggshells and then regurgitating food for the babies, the White Stork Project announced on Saturday (16 May 2020).

White stork (CC BY-SA 4.0) (Author - Soloneying)

White stork (CC BY-SA 4.0) (Author – Soloneying)

It is hoped the successful hatching will be the first step towards establishing the species in the south of England once again after a break of almost six centuries – the last chick to hatch on British soil is believed to have been born atop Edinburgh’s St Giles’ Cathedral in 1416.

Lucy Groves, project officer with the initiative, said: “After waiting 33 days for these eggs to hatch it was extremely exciting to see signs that the first egg had hatched on May 6.

“The parents have been working hard and are doing a fantastic job, especially after a failed attempt last year.”

She added: “These are early days for the chicks, and we will be monitoring them closely, but we have great hopes for them.

“This is just one step towards establishing this species in the south of England. It may be a small step, but it is an exciting one.

“This stunning species has really captured people’s imagination and it has been great following the sightings of birds from the project during the period of lockdown and hearing about the joy and hope they have brought to people.”

The project to breed wild white storks in the UK is a partnership of private landowners and conservation organisations including Cotswold Wildlife Park and Durrell Wildlife Conservation Trust.

It aims to restore a population of at least 50 breeding pairs across the south of England by 2030.

Isabella Tree, co-owner of Knepp – where large swathes of the 1,400 hectare site have been given over to such rewilding – said: “When I hear that clattering sound now, coming from the tops of our oak trees where they’re currently nesting at Knepp, it feels like a sound from the Middle Ages has come back to life.

“We watch them walking through the long grass on their long legs, kicking up insects and deftly catching them in their long beaks as they go – there’s no other bird that does that in the UK.

“It’s walking back into a niche that has been empty for centuries.” (The Independent) 

Flamingos apply natural makeup to look good and attract mates: study —

Greater flamingo   (pix SShukla)

Greater flamingo                                                       (pix SShukla)

Flamingos apply natural make-up to their feathers to stand out and attract mates, according to a study by Juan Amat, from the Estación Biológica de Doňana in Seville, Spain, and colleagues. Their research is the first to demonstrate that birds transfer the color pigments (carotenoids) from the secretions of their uropygial gland for cosmetic reasons. The uropygial or preen gland is found in the majority of birds and is situated near the base of the tail. The study is published online in Behavioral Ecology and Sociobiology, a Springer journal.

There is evidence that the color of feathers may change due to abrasion, photochemical change and staining, either accidental or deliberate. Some bird species modify the color of their feathers by deliberately applying substances that are either produced by the birds themselves or from external sources. Among the substances produced by birds are the secretions of the uropygial gland, which may be pigmented orange, red or yellow.

Amat and team studied seasonal variations in plumage color in relation to courtship activity of the greater flamingo (Phoenicopterus roseus) in Spain. They then looked for the pigments that may tinge the plumage both in the secretions of the uropygial gland and on the surface of feathers. They also observed whether the birds displayed a specific behavior to acquire and maintain the coloration of their feathers. Lastly, they compared the timing of cosmetic coloration with annual reproductive patterns – egg-laying specifically.

They found that the plumage of flamingos was more colorful during periods in which the birds were displaying in groups and faded during the rest of the year. This fading occurred shortly after the birds started to breed. They also found evidence that the birds transferred carotenoids from their uropygial gland to their feathers by rubbing their head on their neck, breast and back feathers. Because rubbing behavior was much more frequent during periods when the birds were displaying in groups and the color of the feathers faded after egg hatching, the authors believe that the primary function of cosmetic coloration in flamingos may be related to mate choice.

They conclude: “Our findings in flamingos have important implications for the theories of sexual selection and signaling, highlighting the key role of the manipulation of plumage color by the birds themselves to improve signal efficacy.” (Phys.org)

Sons or daughters Female finches use head colour to decide —

Red-headed Gouldian finch (Copyright Marc Gardner 2019)

Red-headed Gouldian finch (Copyright Marc Gardner 2019)

Researchers studying the behaviour of the stunningly coloured Gouldian finch (Erythrura gouldiae) have made an exciting discovery – females of the species deliberately overproduce sons when breeding with a male of a different head colour.

The two-year study, funded by the Australian Research Council, has produced the clearest evidence yet to show that birds are capable of deliberately biasing the gender of their eggs.

The findings have been published in the leading international journal Science.

Macquarie University biologists made the discovery following experiments with a captive population of Gouldian finches in the Hunter Valley. Gouldian finches are unique in that they can have either black or red heads, yet are still regarded part of the same species.

Two hundred female finches bred with a male of the same head colour and a male of a different head colour. Then, the researchers tested the effects by dyeing the heads of the male. 

Through their experiments the researchers established that the birds with the red heads and the birds with the black heads were genetically incompatible. When females were forced to mate with an incompatible male, or were tricked into thinking they were, they biased the gender of their eggs to produce more sons.

Sons resulting from genetically incompatible pairings have a much better chance of survival than daughters.

“Over eighty per cent of Gouldian finch chicks will be male if the father has a different coloured head to the female,” said lead author Dr Sarah Pryke.

“There’s no chemical or genetic interaction between the parents at work. Change the colour of the male’s head with dye and the sex ratio changes.

“Gouldian finches wear their genes on their head, so it’s relatively easy for a female to simply assess the genetic suitability of the male.”

The discovery suggests that across the animal kingdom females can have much more influence on the sex of their offspring than was previously thought possible.

“This shows that species are very complex and that genetic incompatibility between a male and female, even within a species, can be a major driving force in the evolution of behaviour,” Pryke said.

This work is also a reminder of the importance of endangered species for science as well as the environment. The Gouldian finch is one of Australia’s most endangered birds, with only a few thousand remaining in the wild.

“The study highlights just how little we know about this iconic Australian species,” said Mike Fidler, Director of the Save The Gouldian Fund.

“This discovery has important implications for how we conserve and ultimately save this finch.”

Professor Ben Sheldon, of the University of Oxford’s Edward Grey Institute, said the results demonstrated “hitherto unsuspected degrees of control over reproductive investment by female birds”.

“This work opens new possibilities in unravelling the mechanisms behind these striking behaviours, something which has up to now remained an unsolved mystery,” Sheldon said.

Sarah Pryke and Simon Griffith are ARC Research Fellows with the Department of Brain Behaviour and Evolution at Macquarie University. Animal behaviour is one of 19 Concentrations of Research Excellence (COREs) at Macquarie. (Phys.org)

Birds show good neighbourhood prevents ageing and is good for health —

Seychelles warbler (CC BY-SA 3.0) (Author - Remi Jouan)

Seychelles warbler                        (CC BY-SA 3.0)   (Author – Remi Jouan)

Birds that live next door to family members or to other birds are physically healthier and age more slowly, according to a research from the University of East Anglia (UEA).

The research, conducted in collaboration with colleagues at the universities of Leeds (UK) and Groningen (the Netherlands), published in the Proceedings of the National Academy of Sciences (PNAS).

Much like humans, many wild animals ‘own’ a private piece of land, or territory, that they rigorously defend against intruders. Having good neighbours that respect the territory boundaries means less work and stress for territory owners – but are some neighbours better than others? Good neighbours come in two varieties. Firstly, when neighbours are extended family members, they share genes and therefore refrain from fighting over space or intruding into each other’s territories. Second, if neighbours know each other well, they should keep the peace and cooperate with each other in order to prevent new neighbours, with whom they must resettle all the rules regarding territory boundaries, from moving into the neighbourhood.

Scientists studied a population of Seychelles warblers (Acrocephalus sechellensis), also known as Seychelles brush warblera small island bird, endemic to the Seychelles islands, to test whether territory owners with more related, or more familiar, neighbours had more peaceful territories and better health as a result. Territory owners were sometimes observed fighting with their neighbours, but never with family members or neighbours that they were neighbours with in previous years.

The researchers then measured the birds’ body condition and telomere length (sections of DNA that protect an individual’s genetic material but which erode faster during times of stress and poor health). Territory owners who had more relatives or familiar neighbours in their neighbourhood were in better condition and showed less telomere loss. If new or unrelated neighbours moved into the neighbourhood, territory owners lost condition and suffered more telomere shortening. Since telomere loss is a measure of how quickly an animal is ageing and may also predict how long that animal will live, the results show just how important keeping good neighbours can be. The scientists also found that the effect of having related or familiar neighbours was more important in densely-populated areas, where the number of neighbours (and hence the number of borders to maintain) is higher.

Lead author of the research, Kat Bebbington of UEA’s School of Biological Sciences, said: “Defending territory boundaries is crucial if animals are to hold onto valuable food and other resources.

“Territory owners who are constantly fighting with neighbours are stressed and have little time to do other important things – such as finding food and producing offspring – and their health suffers as a result.

“Interestingly, we show that it’s not just relatives that can be trusted, but also neighbours you get to know well over time. Something similar probably occurs in human neighbourhoods: if you’ve lived next to your neighbour for years, you are much more likely to trust each other and help each other out now and then.”

In a world where wild animals are increasingly squeezed into small areas of natural habitat, understanding how relationships between neighbours affect the health and lifespan of individuals is crucial. The discovery that territory owners can benefit from living next to relatives or familiar neighbours provides exciting new information about how conflict over space and resources can be resolved, the researchers said.

Kinship and familiarity mitigate costs of social conflict between Seychelles warbler neighbors is published in the journal Proceedings of the National Academy of Sciences (PNAS) on October 9, 2017. (Phys.org)

How do birds get their colors? —

 

Eclectus parrot (female); pix SShukla

Eclectus parrot (female)                                                                                     pix SShukla

An article in Physiological and Biochemical Zoology explores the role of melanins in creating complex plumage patterns in 9,000 bird species.

Birds’ feathers, or plumage, are some of the most strikingly variable animal characteristics that can be observed by the naked eye. The patterns that we see in bird’s feathers are made up of intricate combinations of mottles, scales, bars, and spots. But, how are these colors and patterns made?

Eclectus parrot (male); pix SShukla

Eclectus parrot (male);                               pix SShukla

We already know why birds have colored feathers. For many birds, plumage coloration may make them less visible to predators by helping them to blend in to their surroundings, or more appealing to potential mates by helping them to stand out from their peers. These aspects are well known. A greater mystery has been how the patterns are created on a cellular level.

Dr. Ismael Galván and his team of expert researchers studied plumage coloration to see what types of pigments were present in birds’ complex feathers patterns. Plumage coloration mainly happens courtesy of two types of pigments: melanins, which produce a range of black, grey, brown, and orange colors, and carotenoids, which are used by specialized feather structures to generate brighter colour hues.

Birds cannot produce carotenoids on their own. For feathers with bright colors, birds must consume food items that contain these pigments, and the carotenoids circulate through the bloodstream and to the feather follicles. Birds’ bodies do not have direct cellular control of synthesizing and depositing carotenoids; nor do they have control of the specialized feather structures, which react to the consumed carotenoids with a mechanism that is not regulated by specialized cells.

Melanins, on the other hand (or should that be “on the other wing”), are synthesized by in the birds’ bodies in special cells called “melanocytes,” which work together with feather follicles to achieve a fine control of pigmentation. Although studies frequently focus on carotenoids in bird coloration, Dr. Galván and group are the first to test whether melanins are indeed the only pigmentary element that birds’ bodies directly control on a cellular level.

Galván says, “Knowing beforehand that different pigments and structures produce different types of colors in feathers, we examined the appearance of the plumage of all species of extant birds and determined if the color patches that they contain are produced by melanins or by other pigmentary elements. We also identified those plumage patterns that can be considered complex, defining them as those formed by combinations of two or more discernible colors that occur more than two times uninterruptedly through the plumage.” This study was very large in scope, examining about 9,000 bird species, with the goal of supporting a general conclusion for all birds, to finally answer the question of how birds develop colorful and detailed patterns.

The team found that about 32% of the species studied have complex plumage patterns, with the vast majority of these complex patterns produced by melanins rather than carotenoids. Metaphorically, if the birds were artists, they would use carotenoids as a broad brush to produce color patches, with melanins as a detail paint brush to produce more intricate designs.

A few birds are exceptions to this rule: Three bird families do have complex plumage patterns without melanins. Fruit doves, cotingas and one type of stork have unusual colors that appear to be produced by their bodies making metabolic modifications to the carotenoid pigments that they consume. (Phys.org)

Ban wildlife markets to avert pandemics, says UN biodiversity chief —

Seafood section of Sanqi Baihui Market, Hall-1 (CC BY-SA 4.0)

Seafood section of Sanqi Baihui Market, Hall-1 (CC BY-SA 4.0)

The United Nations’ biodiversity chief has called for a global ban on wildlife markets – such as the one in Wuhan, China, believed to be the starting point of the coronavirus outbreak – to prevent future pandemics.

Elizabeth Maruma Mremathe acting executive secretary of the UN Convention on Biological Diversity, said countries should move to prevent future pandemics by banning “wet markets” that sell live and dead animals for human consumption, but cautioned against unintended consequences.

China has issued a temporary ban on wildlife markets where animals such as civets, live wolf pups and pangolins are kept alive in small cages while on sale, often in filthy conditions where they incubate diseases that can then spill into human populations. Many scientists have urged Beijing to make the ban permanent.

Using the examples of Ebola in west-central Africa and the Nipah virus in east Asia, Mrema said there were clear links between the destruction of nature and new human illnesses, but cautioned against a reactionary approach to the ongoing Covid-19 pandemic.

“The message we are getting is if we don’t take care of nature, it will take care of us,” she told the Guardian.

“It would be good to ban the live animal markets as China has done and some countries. But we should also remember you have communities, particularly from low-income rural areas, particularly in Africa, which are dependent on wild animals to sustain the livelihoods of millions of people.

“So unless we get alternatives for these communities, there might be a danger of opening up illegal trade in wild animals which currently is already leading us to the brink of extinction for some species.

“We need to look at how we balance that and really close the hole of illegal trade in the future.”

As the coronavirus has spread around the world, there has been increased focus on how humanity’s destruction of nature creates conditions for new zoonotic illness to spread.

Jinfeng Zhou, secretary general of the China Biodiversity Conservation and Green Development Foundation, called on authorities to make the ban on wildlife markets permanent, warning diseases such as Covid-19 would appear again.

“I agree there should be a global ban on wet markets, which will help a lot on wildlife conservation and protection of ourselves from improper contacts with wildlife,” Zhou said. “More than 70% of human diseases are from wildlife and many species are endangered by eating them.”

Mrema said she was optimistic that the world would take the consequences of the destruction of the natural world more seriously in the wake of the Covid-19 outbreak when countries returned to negotiate the post-2020 framework for biodiversity, billed as the Paris agreement for nature.

“Preserving intact ecosystems and biodiversity will help us reduce the prevalence of some of these diseases. So the way we farm, the way we use the soils, the way we protect coastal ecosystems and the way we treat our forests will either wreck the future or help us live longer,” she said.

“We know in the late 1990s in Malaysia with the outbreak of Nipah virus, it is believed that the virus was a result of forest fires, deforestation and drought which had caused fruit bats, the natural carriers of the virus, to move from the forests into the peat farms. It infected the farmers, which infected other humans and that led to the spread of disease.

“Biodiversity loss is becoming a big driver in the emergence of some of these viruses. Large-scale deforestation, habitat degradation and fragmentation, agriculture intensification, our food system, trade in species and plants, anthropogenic climate change – all these are drivers of biodiversity loss and also drivers of new diseases. Two thirds of emerging infections and diseases now come from wildlife.”

In February, delegates from more than 140 countries met in Rome to respond for the first time to a draft 20-point agreement to halt and reverse biodiversity loss, including proposals to protect almost a third of the world’s oceans and land and reduce pollution from plastic waste and excess nutrients by 50%.

A major summit to sign the agreement in October was scheduled in the Chinese city of Kunming but has been postponed because of the coronavirus outbreak. (The Guardian)

Feather color is more than skin deep —

Common or Red Crossbills (Male) (CC BY-SA 3.0) (Elaine R. Wilson, www.naturespicsonline.com)

Common or Red Crossbills (Male) (CC BY-SA 3.0) (Elaine R. Wilson, www.naturespicsonline.com)

Where do birds get their red feathers from? According to Esther del Val, from the National History Museum in Barcelona, Spain, and her team, the red carotenoids that give the common crossbill (Loxia curvirostra) its red coloration are produced in the liver, not the skin, as previously thought. Their findings, published online in Springer’s journal Naturwissenschaften, have implications for understanding the evolution of color signaling in bird species.

Carotenoids have important physiological functions, including antioxidant, immunomodulating, and photoprotectant properties. Carotenoid pigments are also used by many bird species as colorants, and are responsible for most of their red, orange and yellow coloration. In particular, carotenoid-red coloration in birds has been shown to act as an ornament, signaling the nutritional and health status of the individual and its ability to locate high quality resources. Recent studies have suggested that the transformation of carotenoid pigments takes place directly in the follicles during feather growth.

Del Val and her team show for the first time that, contrary to previous assumptions, the liver acts as the main site for the synthesis of carotenoids responsible for the birds’ coloration, not the skin.

The researchers examined the carotenoid content of the liver, blood, skin and feathers of seven common crossbills (finches) in which adult males display carotenoid-based coloration on the throat, breast and rump. They were particularly interested in the anatomical origin of the birds’ red plumage. They found the primary red feather pigment of male crossbills in the birds’ liver and blood, implying that the carotenoids are synthesized in the liver and then travel to the peripheral tissues via the bloodstream. 

Del Val concludes: “This surprising divergence with previous studies raises the question whether there are inter-specific differences in anatomical sites for conversion of carotenoids. Understanding inter-specific variation in mechanisms of color production may be the key to comprehend the different evolutionary pathways involved in color signaling.” (Phys.org)