How birds evolved big brains

Brain evolution traced from tyrannosaurs to modern crows

Date: April 23, 2020

Source: Bruce Museum 

An international team of evolutionary biologists and paleontologists have reconstructed the evolution of the avian brain using a massive dataset of brain volumes from dinosaurs, extinct birds like Archaeopteryx and the Great Auk, and modern birds.

The study, published online today in the journal Current Biology, reveals that prior to the mass extinction at the end of the Cretaceous Period, birds and non-avian dinosaurs had similar relative brain sizes. After the extinction, the brain-body scaling relationship shifted dramatically as some types of birds underwent an explosive radiation to re-occupy ecological space vacated by extinct groups.

"One of the big surprises was that selection for small body size turns out to be a major factor in the evolution of large-brained birds," says Dr. Daniel Ksepka, Curator of Science at the Bruce Museum and lead author of the study. "Many successful bird families evolved proportionally large brains by shrinking down to smaller body sizes while their brain sizes stayed close to those of their larger-bodied ancestors."

In order to understand how bird brains changed, a team of 37 scientists used CT scan data to create endocasts (models of the brain based on the shape of the skull cavity) of hundreds of birds and dinosaurs, which they combined with a large existing database of brain measurements from modern birds. They then analyzed brain-body allometry: the way brain size scales with body size.

Read more

How the development of skulls and beaks made Darwin's finches one of the most diverse species

Date:February 3, 2020

Source:University of Bristol

Darwin's finches are among the most celebrated examples of adaptive radiation in the evolution of modern vertebrates and now a new study, led by scientists from the University of Bristol, has provided fresh insights into their rapid development and evolutionary success.

Study of the finches has been relevant since the journeys of the HMS Beagle in the 18th century which catalysed some of the first ideas about natural selection in the mind of a young Charles Darwin.

Despite many years of research which has led to a detailed understanding of the biology of these perching birds, including impressive decades-long studies in natural populations, there are still unanswered questions.

Specifically, the factors explaining why this particular group of birds evolved to be much more diverse in species and shapes than other birds evolving alongside them in Galapagos and Cocos islands have remained largely unknown.

A similar phenomenon is that of the honeycreepers endemic to the Hawaiian archipelago. These true finches (unlike Darwin's finches which are finch-like birds belonging to a different family) radiated to achieve an order of magnitude more in species and shapes than the rest of the birds inhabiting those islands.

Continued

A New Study Helps to Explain the Evolution of Flightless Birds

Chardynne Joy H. ConcioApr 07, 2019 09:46 PM EDT

Large flightless birds are scattered across all but one of the world's southern continents. Since Darwin's era, people have wondered: How are they related? Ostriches, emus, cassowaries, rheas, and kiwis can't fly. Unlike most birds, their flat breastbones lack the keel that anchors the strong pectoral muscles required for flight. Their puny wings can't possibly lift their heavy bodies off the ground. These flightless birds, called ratites, are clearly different from other avian species.

Darwin noticed, and he predicted that ratites were related to each other. His contemporary, Thomas Huxley, found another commonality among them: The arrangement of bones in the roofs of their mouths appeared more reptile-like than that of other birds. At about the same time, another biologist, Richard Owen, assembled the remains of a giant ostrich-like fossil skeleton, the first extinct moa known to the western world. But a pesky detail puzzled Huxley--small, ground-dwelling South American tinamous--didn't seem to fit neatly with the ratites or other birds.

Tinamous fly, albeit reluctantly. And they possess keeled sternums, suggesting that they evolved with flying birds. But their palate bones match the ratites. Where do they belong? Scientists have debated this question for 150 years. Now, a new study analyzing the largest molecular dataset to date, clarifies the tinamous' place on the evolutionary tree and offers clues about the origins of flightlessness. Scientists probed almost 1,500 DNA segments from tinamous, emus, ostriches, the extinct little bush moas, and others, which have generally showed tinamous on the outskirts of the ratite group, relying solely on morphological traits like skeletal details. Other investigations of limited genetic information suggested tinamous were evolutionarily tangled with the flightless birds. "Fundamentally, the recent debate is about molecular data versus morphology," says Allan Baker, lead author of the study. "We can't both be right."

Continued

Darwin's finches have developed a taste for junk food, and it may be impacting their evolution

December 5, 2018 by Umass Boston Office Of Communications, University of Massachusetts Boston

A UMass Boston professor and his colleagues have published new research showing that feeding on human junk food may be altering the course of evolution in Darwin's finches.

Assistant Professor of Evolutionary Biology Luis De León says feeding on human foods is weakening natural selection on ground finch beaks, which is what drives the formation of new species in the wild. These findings, published in the journal Evolutionary Applications, suggest that the seemingly harmless activity of feeding birds might be altering the course of evolution in the iconic Darwin's finches in the Galápagos islands.

"If we continue to feed finches, we're not only affecting the individual species, but the processes that lead to the formation of new species," De León said. "We're getting in the way of evolution."

Galápagos finches are famed for being the inspiration behind Charles Darwin's pioneering work on evolution. They are an example of adaptive radiation, an evolutionary process that produces new species from a single, rapidly diversifying lineage. Their common ancestor arrived on the Galápagos about two million years ago, and since then Darwin's finches have evolved into more than a dozen recognized species differing in body size, beak shape, and feeding behavior.

De León and fellow researchers from UMass Amherst, Universidad San Francisco de Quito, McGill University, and Norwegian University of Science and Technology were on Santa Cruz Island when they found two forms of medium ground finches—a small and large version—while studying beak size at an isolated, pristine site.

Read more at: 

What homebody island birds could tell us about adaptation and evolution

13Aug, 2018

By Anne Manning

In nature, organisms are constantly adapting to their surroundings. It’s why animal or plant populations with the same set of genes will do different things in different environments.

These adaptive divergences can occur within fewer generations, and at smaller spatial scales, than classic evolutionary theory would have us believe. Launching a new study, Colorado State University biologists are diving into the question of just how small these scales could be. To find out, they’re studying a rare, isolated bird that, it turns out, is a bit of a homebody.

Researchers led by Cameron Ghalambor, professor in the Department of Biology, are launching a National Science Foundation-supported study of what evolutionary biologists term “microgeographic” adaptation strategies of island scrub-jays, North America’s only island-endemic bird. Island scrub-jays live exclusively on Santa Cruz Island, one of the Channel Islands off the southern California coast.

The study is aimed at understanding how isolated species like scrub-jays somehow manage to genetically diverge, creating sub-populations that reflect specific, adaptive traits. That’s despite living in an area of less than 100 square miles, with plenty of opportunity to interbreed. What the researchers learn could provide new insight into the mechanisms by which individuals in a single population diverge across habitats, and what that could mean for conservation biology, biodiversity and evolution.

Continued  

Climatic stability resulted in the evolution of more bird species

Date: July 17, 2017

Source:Umea University

More species of birds have accumulated in genera inhabiting climatically stable areas. This is shown by a new study from Umeå University.

"The explanation may be that a stable climate makes it more likely that diverging lineages persist without going extinct or merging until speciation is completed, and stability reduces the risk for extinction in response to climatic upheavals," says Roland Jansson, researcher from Umeå University who led the study.

How life has evolved from simple origins into millions of species is a central question in biology that remains unsolved. Advances in genomics and bioinformatics mean we now know a lot about the relationships among species and their origins, but surprisingly little is known about which environmental conditions that allows species to multiply.

Continued

Bird lovers help scientists discover secrets of beak evolution

Date: February 2, 2017

Source: University of Sheffield

Citizen scientists and bird lovers across the world have helped researchers to uncover new secrets about the evolution of bird's beaks over time in a ground-breaking study.

Researchers at the University of Sheffield asked the public to help measure beak shapes from more than 2000 bird species which have been 3D scanned from specimens at the Natural History Museum and the Manchester Museum.

Using the crowdsourced data, the team were able show that the diversity of bird beaks expanded early in their evolutionary history. The most unusual beak shapes often involved periods of exceptionally fast evolutionary change.

However, once extremes are reached, the changes to bird beaks over time became much smaller as birds filled ever-narrower evolutionary niches.

There are some examples -- such as birds who have evolved in comparative isolation on remote islands such as the Galapagos and the Hawaiian archipelago -- who have continued to evolve rapidly.

Gavin Thomas, the project lead from the Department of Animal and Plant Sciences at the University of Sheffield, said: "The shape of a bird's beak is an important indicator of the food it eats and the way it forages -- its ecological niche.



Read on

The South Hills Crossbill Is Evolving in a Seriously Bizarre Way

In the pine forests of Idaho, a bird called the South Hills crossbill is waging one seriously bizarre evolutionary war.

Over the last 5,000 years or so, the crossbill—so named because the two halves of its bill cross over each other instead of aligning—has menaced the lodgepole pine, developing an ever-bigger beak to break into the tree’s cones and steal its seeds. In response, the tree has evolved ever-thicker cone scales. And the South Hills crossbill evolves a bigger bill. And the tree responds. And on and on through the millennia.

That’s not the weird bit. Species evolving together like this is known as coevolution. Happens all the time. The weird bit is that the South Hills crossbill may have speciated without geographic isolation—which is sort of problematic for traditional evolutionary theory. Because while the South Hills crossbill was diverging from other crossbills, it did so while those other crossbills were freely flying through its territory, according to a study published today in Molecular Ecology. That adds to a growing body of evidence that in certain fascinating cases, you may not need geographic isolation to get a new species, challenging what was long gospel among many evolutionary biologists. Gasp—I know.

Continued 

Feral chickens spread light on evolution

Date:September 30, 2016

Source:Linköping University

Different genes are involved during the adaptation of a domestic animal to life in the wild than when a wild animal becomes domesticated. This is the conclusion of a study led by a researcher at Linköping University in Sweden and published in the journal Nature Communications. The results increase our understanding of what happens as a species evolves.

"There are large differences between tame chickens and wild ones. Studying the differences in their genetic material can teach us more about how genes influence animal appearance and behaviour. Although a lot is known about how we tame and domesticate animals, very little is known about the reverse, when domestic animals go back to the wild. We have examined this process at the genetic level when tame chickens are released into the wild," says researcher Dominic Wright, who has led the study.

For many thousands of years, humans have bred dogs, goats, chickens and other animals to make them suitable for use as domestic animals, in a process known as domestication. Humans have selected the individuals that possess desirable traits and bred them with similar individuals, such that the offspring possess the same traits. The genetic material of the animal has partially changed during the development of the species from its wild form to a domesticated one. The opposite process also takes place, when domesticated animals readapt to life in the wild, in a process known as feralization. By investigating what happens in an animal's genetic material, we can study whether the effects of domestication by humans are long-term or short-term. Can evolution go backwards?

Read on

Evolution of flight in birds

Date: July 18, 2016

Source: Queen's University

Research by post-doctoral fellow Alexander Dececchi challenges long-held hypotheses about how flight first developed in birds. Furthermore, his findings raise the question of why certain species developed wings long before they could fly.

Dr. Dececchi, a William E. White Post-Doctoral Fellow in the Department of Geological Sciences and Geological Engineering, used measurements from fossil records and data from modern birds to test the evolutionary explanation for the origin of birds. Dr. Dececchi and his colleagues determined that none of the previously predicted methods would have allowed pre-avian dinosaurs to take flight.

"By disproving the idea that the predicted models led to the development of flight, our research is a step towards determining how flight developed and whether it can evolve once or developed multiple times in different evolutionary lines," he says.

Dr. Dececchi and his colleagues examined 45 specimens, representing 24 different non-avian theropod species, as well as five bird species. After determining some critical variables from the fossils -- such as body mass and wing size -- they used measurements from living birds to estimate wing beat, flap angle and muscular output.

These values were used to build a model for different behaviours linked to the origins of flight such as vertical leaping and wing-assisted incline running (WAIR) -- a method of evasion for many ground-based modern birds that has become a favoured pathway towards the origin of flapping flight in the paleontological literature. They also tested if any species met the requirements to take-off from the ground and fly under their own power.

"We know the dimensions and we know how modern birds muscles and anatomy work," Dr. Dececchi says. "Using our model, if a particular species doesn't reach the minimum thresholds for function seen in the much more derived birds -- such as the ability to take off or to generate a certain amount of power -- it's safe to say they would not have been able to perform these behaviours or fly."

The researchers found that none of the behaviours met the criteria expected in the pathway models. In fact, they found that almost all the behaviours had little or no benefit, outside of those species which evolved right before the origin of birds. When looking at WAIR specifically -- the method that has been touted as an explanation for some early wing adaptations -- the researchers found that it only was possible in a handful of large winged, small bodied species such as Microraptor, but found no evidence to suggest its use was widespread.

Read on … 

Diet affects the evolution of birds

Date:April 13, 2016

Source:Universiteit van Amsterdam (UVA)

How diet has affected the evolution of the 10,000 bird species in the world is still a mystery to evolutionary biology. A study by Daniel Kissling of the Institute for Biodiversity and Ecosystem Dynamics (UvA) and colleagues from the University of São Paulo and the University of Utah shows how diet preferences have influenced bird diversification over millions of years. The findings were published in Nature Communications.

Since the seminal work by Charles Darwin, it is know that dietary habits of birds can affect the evolution of species, such as the beak sizes of Galapagos finches. However, birds show an astonishing diversity of species and dietary adaptations, ranging from very small nectar-feeding hummingbirds to large carnivorous eagles. How such diverse dietary preferences ultimately lead to differences in diversification dynamics (i.e. the balance between speciation and extinction) of different birds has not yet been examined.

Diet dataset

The researchers compiled an impressive diet dataset of almost all bird species in the world together with a large phylogenetic tree that represent the relatedness of all bird species. Using models of trait-dependent diversification, they then showed that omnivorous bird lineages (with species that feed on many different food items) have lower rates of speciation (i.e. generating less new species) and higher rates of extinction (i.e. losing more existing species) than species which prefer specific food items such as fruits, nectar, or insects. Furthermore, the researchers also found that over deep evolutionary time birds which are specialized on a particular food item often add other food items to their diets, resulting in evolving transitions into omnivory.

Continued ...

Research reveals trend in bird-shape evolution on islands

Date: April 12, 2016

Source: The University of Montana

In groundbreaking new work, Natalie Wright, a postdoctoral fellow at the University of Montana, has discovered a predictable trend in the evolution of bird shape.

Her research showing that birds on islands have evolved toward flightlessness was published April 11, 2016 in Proceedings of the National Academy of Sciences. Her partners include Christopher Witt of the University of New Mexico and David Steadman of the University of Florida.

"The search for general trends in evolution of animal shape, size and color, often comes up empty," Wright said. "Evolution tends to be unpredictable, leading toward different forms in different places. So it was gratifying to discover this trend among island birds."

Wright said it is widely known that particular types of birds tend to become flightless after they colonize islands that have no predators. Flightlessness has evolved over a thousand times, but it tends to evolve only from certain types of ancestors -- usually birds such as rails that already spend most of their time on the ground.

Wright wanted to know whether there are predictable evolutionary trends that apply to all island birds, the vast majority of which can still fly. Like the flightless species on their islands, they generally have fewer predators than their relatives on the mainland. But most species still need to fly in order to find food. So as part of Wright's doctoral research at the University of New Mexico, she focused on how flying birds evolved on islands and whether they exhibit similar changes to those seen in flightless island species.

Continued ...

Unique beak evolved with tool use in New Caledonian crow

Date: March 15, 2016

Source: Cornell University

Cornell researchers have quantified what makes the New Caledonian crow's beak different and how it got that way. Their findings were published March 9, 2016 in the journal Scientific Reports.

It was as plain as the beak on a bird's face. Cornell ornithologist and crow expert Kevin McGowan recalls the day in the late 1990s when he first saw stuffed specimens of the New Caledonian crow.

"I remember saying to a student, 'I don't know what this bird does, but it does something different from any other corvid on Earth because its bill is so weird,'" said McGowan, project manager for distance learning in bird biology at the Cornell Lab of Ornithology.

In 2000, McGowan read a paper by Gavin Hunt, a senior research fellow at the University of Auckland, New Zealand, on tool use by these crows and he had an insight into the New Caledonian crow's unusual beak.

Now, Hunt, McGowan and a team of scientists from Japan have quantified what makes the New Caledonian crow's beak different and how it got that way. Their findings were published March 9, 2016 in the journal Scientific Reports.

"We used shape analysis and CT [computer tomography] scanning to compare the shape and structure of the New Caledonian crow's bill with some of its crow relatives and a woodpecker species with a similar foraging niche," said lead author Hunt.

"This study shows that the unique bill contributes to the birds' ability to use and probably make tools," he said. "We argue that the beak became specialized for tool manipulation once the birds began using tools, and that this enhanced tool manipulation ability may have allowed the crows to make more complex tools."

Read on ...

New basal bird from China reveals the morphological diversity in early birds

 Date: March 2, 2016

Source: Chinese Academy of Sciences Headquarters

A new species, Chongmingia zhengi, sheds light on the early evolution of birds. Phylogenetic analyses indicate that it is basal to the dominant Mesozoic avian clades Enantiornithes and Ornithuromorpha, and represents a new basal avialan lineage. This new discovery adds to our knowledge regarding the phylogenetic differentiation and morphological diversity in early avian evolution.

Over the past three decades, representatives of all major Mesozoic bird groups have been reported from the Early Cretaceous Jehol Biota of northeastern China. A new species, Chongmingia zhengi, reported in the journal of Scientific Reports on 25 January 2016, sheds light on the early evolution of birds. Phylogenetic analyses indicate that it is basal to the dominant Mesozoic avian clades Enantiornithes and Ornithuromorpha, and represents a new basal avialan lineage. This new discovery adds to our knowledge regarding the phylogenetic differentiation and morphological diversity in early avian evolution.

This new species, represented by a single new skeleton from the Early Cretaceous Jiufotang Formation of the Jehol Group in Dapingfang, Liaoning Province, China. The generic name is from the Mandarin word Chongming, referring to a Chinese mythological bird. The specific epithet is in honour of Mr. ZHENG Xiaoting for his generous contribution in the establishment of the Shandong Tianyu Museum of Nature.

The new specimen is a partial skeleton with associated soft tissues and gastroliths, missing the skull and most of the caudal vertebrae. Comparative studies indicate that it is a large non-ornithothoracine bird distinguishable from the known basal avialans by a combination of features.

The furcula of Chongmingia is rigid (reducing its efficiency), consequently requiring more power for flight. However, the elongated forelimb and the large deltopectoral crest on the humerus might indicate that the power was available. The unique combination of features present in this species demonstrates that numerous evolutionary experimentations took place in the early evolution of powered flight.

Continued ....

No bird brains - crows as clever as chimpanzees

 By Colin Fernandez

6:12 PM Saturday Mar 5, 2016

Crows and parrots have sophisticated thinking skills on a par with those of apes such as chimpanzees, researchers claim.

The birds' brains are about a tenth the size of the mammals' and their structures are completely different, but scientists believe they developed equal cognitive abilities through facing the same challenges in the wild over 300million years of evolution.

The new assessment of research results gathered in recent decades says bird cognition includes abilities such as delaying gratification - for example in hoarding food - and reasoning.

Corvids - the bird family that includes crows - are also known to use tools and think logically. Previous research, for example, has confirmed that a crow will drop stones into a beaker of water to raise its surface level so it can drink - a form of behaviour central to the Aesop's Fable The Crow and the Pitcher.

'The mental abilities of corvids and parrots are as sophisticated and diverse as those of apes,' the latest study says.

'Among other things, they are capable of thinking logically, of recognising themselves in the mirror and of empathy.'

The study highlights the fact that birds and apes use different brain structures to think.
Mammals' cognitive skills are controlled by a part of the brain called the neocortex, while crows and parrots manage complex mental tasks with a structure called the pallium.

Continued ...

Chicken study reveals evolution can happen much faster than thought

October 27, 2015

A new study of chickens overturns the popular assumption that evolution is only visible over long time scales. By studying individual chickens that were part of a long-term pedigree, the scientists led by Professor Greger Larson at Oxford University's Research Laboratory for Archaeology, found two mutations that had occurred in the mitochondrial genomes of the birds in only 50 years. For a long time scientists have believed that the rate of change in the mitochondrial genome was never faster than about 2% per million years. The identification of these mutations shows that the rate of evolution in this pedigree is in fact 15 times faster. In addition, by determining the genetic sequences along the pedigree, the team also discovered a single instance of mitochondrial DNA being passed down from a father. This is a surprising discovery, showing that so-called 'paternal leakage' is not as rare as previously believed.

The study is published in the online early version of the journal, Biology Letters.

Using a well-documented 50-year pedigree of a population of White Plymouth Rock chickens developed at Virginia Tech by Professor Paul Siegel, the researchers reconstructed how the mitochondrial DNA passed from mothers to daughters within the population. They did this by analysing DNA from the blood samples of 12 chickens of the same generation using the most distantly related maternal lines, knowing that the base population had started from seven partially inbred lines. A selective mating approach within the population started in 1957, resulting in what is now an over tenfold difference in the size of the chickens in the two groups when weighed at 56 days old.

Read more at:

Advances in genetic studies of birds are changing ornithology research

Date:October 21, 2015

Source:Central Ornithology Publication Office

How do birds evolve over generations? How do different bird populations diverge into new species? Ornithologists have been asking these questions since the days of Darwin, but rapid advances in genetic sequencing techniques in the last few years have brought answers more in reach than ever. A Review forthcoming inThe Auk: Ornithological Advancesdescribes some of the newest and most exciting developments in the field of "high-throughput sequencing," a collection of techniques for studying broad regions of a genome rather than individual genes.

High-throughput sequencing has been dropping in cost and complexity; once only available to large research consortiums, these methods are now feasible for smaller labs that were previously limited to working with individual genes or with mitochondrial DNA. "It's like going from seeing with a few light sensitive cells that can only detect the difference between night and day to a fully formed eye that can see all of the stars in the night sky," says David Toews of the Cornell Lab of Ornithology, the lead author of the Review.

Because high-throughput sequencing data looks at many genes instead of just a few, it makes it easier to identify very subtle genetic differences between populations, such as the genetics underlying small differences in plumage patterns between different subspecies of Wilson's Warbler. It can also provide a fresh look at the genetic changes that occur in "hybrid zones," where the ranges of closely related species overlap and members of the species breed freely with each other, such as where Black-capped and Carolina Chickadees meet in Pennsylvania. The process of one species splitting into two, such as what may be happening with the coastal and inland subspecies of Swainson's Thrush, is another intriguing area for study.

Continued ...

Darwin's finches have reached their limits on the Galapagos Islands

Date: June 23, 2015

Source: University of Groningen

Summary: The evolution of birds on the Galapagos Islands, the cradle of Darwin's theory of evolution, is a two-speed process. Most bird species are still diversifying, while the famous Darwin's finches have already reached an equilibrium, in which new species can only appear when an existing one becomes extinct. This finding expands the classical theory on island evolution put forward in the 1960s. The study is published online on June 23 in Ecology Letters.

Islands are seen as natural laboratories for the study of evolution. They form isolated ecosystems with barriers to migration. Classical Island Theory predicts that a dynamic equilibrium will occur between immigration and extinction of species. Recent theory adds that as species diversity increases, ever more ecological niches become occupied, which has a negative effect on immigration (new immigrants from outside of the Galápagos cannot settle) and diversification (radiation into new species is blocked).

Continued ...

What drives the evolution of bird nest structures?

Date:May 6, 2015

Source:Central Ornithology Publication Office

Summary:How to protect your chicks from predators? Build a dome over them! There is tremendous diversity among the nests of birds, in nest location, structure, materials, and more, but we know very little about the forces that shaped the evolution of this incredible variety. A new study finds that domed-shaped nests arose as a result of species transitioning to nesting on the ground, where the risk from predators is greater.

Continued ...

Fearless birds and big city spiders: Is urbanization pushing earth's evolution to a tipping point?

Date:

February 18, 2015

Source:

University of Washington

Summary:

That humans and our cities build affect the ecosystem and even drive some evolutionary change is already known. What's new is that these evolutionary changes are happening more quickly than previously thought, and have potential impacts on ecosystem function on a contemporary scale. Not in the distant future, that is -- but now.

Continued ...