12. Evolution of Birds

Black is White - Up is Down - Birds are Dinosaurs
Introduction

Archaeopteryx In 1861, only a few years after Darwin published On the Origin of Species, workers at a German limestone quarry made one of the most important fossil discoveries of all time: the 145 million-year-old Archaeopteryx. Notice the feathered wings and the long, stiff tail, indicating that this was a flying bird.

Besides the dinosaurs and the flying pterosaurs being so large, the large flying birds of the Cretaceous period is yet another group of terrestrial animals indicating that the atmosphere was much thicker during the Mesozoic era. Unfortunately most people are unaware that there were numerous exceptionally large flying birds during the Mesozoic era because paleontologists have misidentified these birds as being feathered dinosaurs.

The paleontology community refuses to recognize the incredibly large size of dinosaurs and pterosaurs as being a scientific paradox. In the minds of paleontologists they sincerely believe that they have explained how dinosaurs grew so large and they sincerely believe they have explained how gigantic pterosaurs were able to fly. But now they come to the problem of explaining the existence of the gigantic flying birds of the Cretaceous period. Their solution is to deny these birds existence. They say, that is not a large bird; that is a feathered dinosaur. But they have wings! Why would a dinosaur have wings? And to this these paleontologists say that their ‘feathered dinosaurs’ were using their wings for balance, or sexual display, or really anything imaginable except of course the possibility of using their wings for flying. In conclusion, according to paleontologists, there is nothing odd about there being monstrous size terrestrial animals roaming the earth millions of years ago, or that there were gigantic flying reptiles much larger than any bird, nor is there anything odd about there being extremely large flying birds with relatively small wings since we have relabeled these birds as being non flying feathered dinosaurs so that the problem goes away.

Paleontologists have made so many nonsensical and highly questionable claims in the effort to misidentifying large birds as feathered dinosaurs that it would be easier if they could just convince the public that there is really no difference between birds and dinosaurs; hence the reasons why paleontologists have been pushing the claim that birds are dinosaurs. Many scientists realize that paleontologists are misleading the public with their downplaying the significance of feathered wings and their claim that birds are dinosaurs, but it is difficult for these scientists to get a voice or raise questions because paleontologists ‘own’ the media and these paleontologists have repeated their bogus claims so many times. These paleontologists’ success in quieting dissension is not a triumph of science but rather a demonstration of the effectiveness of propaganda: if authorities repeat a lie often enough people will no longer question whether it is true.

I would rather have questions that cannot be answered, than answers that cannot be questioned.
Richard Feynman

For science to move forward, the ridiculous beliefs of the paleontology community need to be questioned and rejected, but to do this people need to relearn how to think for themselves. People need to develop their scientific thinking. They need to learn how to gather and examine evidence and then draw correct conclusions from that evidence, instead of just relying on authorities to tell them what to think.

Recognizing how birds evolved, what makes them superior fliers and just the fact that that there were large predatory birds flying about and often preying on dinosaurs, are some of the many fascinating aspects of the Mesozoic era.

People Are Fish

Birds are dinosaurs in the same way that people are fish. This is because of the classification rule that says if one classification of species evolves from another classification of species then technically the new classification is still a part of the original classification. Hence, since birds supposedly evolved from dinosaurs then technically birds are dinosaurs. Furthermore, since we can also state that dinosaurs are reptiles, we must likewise conclude that birds are reptiles. Do you see where this is going? Birds are dinosaurs, birds are reptiles, birds are amphibians, and finally birds are fish. And by the same logic we can declare that people are fish!

It is highly questionable if birds even evolved from dinosaurs, and even if this claim was true, placing birds and dinosaurs in the same classification nullifies the whole point of why we classify species. The reason we classify species is to expedite the process of understanding each individual species. Once a classification is assigned, we instantly gain significant knowledge about the species, and from that point on, we only need to describe the few remaining features that make the species unique among the other members of its classification.

By claiming that birds are dinosaurs, these paleontologists are engaging in a misleading game of semantics that does not contribute to the advancement of science.

When did science become mind games?

No, Birds Are Not Dinosaurs

Are we all going nuts, or are these leading authorities gaslighting the public when they tell us that birds are dinosaurs? It is gaslighting, and it does not require a paleontology degree to recognize that these 'Birds Are Dinosaurs' (BAD) paleontologists are misleading the public. A person just needs to look over the feathered dinosaur fossils to identify the numerous bird features before realizing that these are not dinosaurs; they are birds.

In their efforts to convince the public that the large flying birds of the Cretaceous period were feathered dinosaurs paleontologists are claiming that both birds and their feathered dinosaurs evolved from theropod dinosaurs of the early Cretaceous period. The main arguments clarifying why neither birds or ‘feathered dinosaurs’ could not have evolved from Saurischian theropod dinosaurs are as follows:

  1. Does Not Follow I - Expert paleobiologist Alan Feduccia has spent decades pointing out the evidence refuting the claim that birds evolved from dinosaurs. His published works cover everything from revealing the numerous conflicts in paleontologists’ evolutionary history of birds (phylogenetic systematics), their claimed improbable origins for flight, to the renaming of Jurassic and Cretaceous birds as feathered dinosaurs. His direct embryological research with ostriches shows that while both theropod dinosaurs and birds have a reduction of the digits from five down to three digits, they are not the same digits. While theropod dinosaurs have digits one, two, and three, birds have digits two, three, and four. This mismatch means that one group could not have evolved from the other.
  2. Does Not Follow II - The hips of theropod dinosaurs are distinguished by having a robust pubis bone that points downward and forward. This theropod dinosaur hip bears little resemblance to the hips of birds whose pubis bone is not nearly as robust and points to the rear. Zoologist Devon Quick and vertebrate paleobiologist John Ruben of Oregon State University found that the position of the thigh bone — the rear-pointing pubis — and muscles in birds are critical to their ability to have adequate lung capacity for sustained long-distance flight.

  3. Picture of Ornithischia and Saurischia hips, Models of T-Rex and Triceratops The 'Birds are Dinosaurs' paleontologists claim that birds evolved from the Saurischian dinosaurs shown on the right. However, the hip structure of birds more closely resembles the Ornithischian dinosaurs shown on the left. Birds needed a more open space to accommodate their large respiratory system, so the pubis is pointed backwards. On the other hand, theropods could have used the robust pubis bone that ends with a flattened boot, as this would have given them the ability to slide on their hips much like an alligator, providing an effective means of staying low and unseen while sneaking up on their prey.

  4. Bad Timing - Paleontologists are claiming that birds and ‘feathered dinosaurs’ evolved from early Cretaceous period theropod dinosaurs. However this is impossible since Archaeopteryx and numerous other bird species had already evolved at least forty million years earlier in the late Jurassic period and many if not most of these bird lineages continued on into the Cretaceous period.
  5. Failing Evolution Theory 101 - Claiming that a vertebrate can form wings by jumping numerous times until it sprouts wings is an excellent example of how evolution does NOT work! For a species to evolve a new feature, there must be some benefit throughout the evolution of the new feature, and there is no survival benefit that comes from jumping up and down on the ground that would encourage wings to form. This is in contrast to taking ever longer glides from one tree to another to either escape predators or to simply move more efficiently about a forest. The vertebrate’s ability to achieve this survival task improves with every bit of wing growth. Hence, every class of flying vertebrates has evolved by first becoming gliders before evolving into true flyers.

While the first three points highlight problems indicating that the claim 'birds evolved from early Cretaceous dinosaurs' is all but certain to be wrong, it is the last point that is upsetting simply because the Theory of Evolution is so crucial to the acceptance of science in our society. What should the public think about the Theory of Evolution when these 'scientists' so casually dismiss it because it does not fit their agenda? Creationists — anti-science religious people who also have their own agenda — have seized upon these paleontologists' claim that dinosaurs could 'evolve wings by jumping up and down' by asking the question 'What good is a half-formed wing?' By promoting a scientific claim that conflicts with the Theory of Evolution, these paleontologists have opened the door to attacks on the Theory of Evolution and science in general.

What is a Bird?

Bird features Chart of features that distinguishes birds from crocodiles: their closes living relatives.
University of Maryland Department of Geology

There is an expression “if it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck.” A similar statement could be said about birds in general.

Most biologists would say that birds are warm-blooded, egg laying vertebrates that have feathers, a beak, two wings and two feet. They may also add that birds have a high metabolism, a four chamber heart, a unique respiratory system, keen vision, and light hollow bones. Last and certainly not least, biologists would state that most birds can fly, although there are some birds that have lost their ability to fly.

It is so easy to identify modern birds that most children can do this; however, identifying who the first birds were is not so easy. Species may evolve considerably over time such that ancestral species will not have nearly all the features of present-day species. In this chain of evolving forms, how far back in time do we go before declaring that earlier ancestral species are unrecognizable as being birds? We need agreement on what the minimum critical features are that a species must have before we consider it a member of the bird community.

The task of determining a dividing line for declaring when a new species or group of species has come into existence is not as difficult as it may first seem. This is because evolution does not move forward at a constant pace; rather, its movement is more accurately described as fits and starts, known as Punctuated Equilibrium. It is common for species to remain unchanged for many millions of years until there is a breakthrough creating a new species. The breakthrough occurs when individuals cross a specific barrier that allows them to exist in a new environment. In the process of crossing this barrier, individuals quickly evolve to be better suited to their new environment. On a generation-to-generation basis, the evolution of a new species is so subtle that it is impossible to notice. Yet, from the perspective of geological time, it represents a dramatic jump; while looking at a timeline on the scale of millions of years we blink and suddenly we see a new species.

Flying Confuciusornis This is a drawing of Confuciusornis sanctus that flew during the early Cretaceous period.

For the feathered arboreal archosaurs of the Mesozoic era their big evolution moment came when they evolved from tree climbers to gliders to flyers. This is something that had already been done by the pterosaurs millions of years earlier so it is not like the feathered archosaurs did not have competition in the air. To compete in this new frontier of flying these earliest birds had to be better than the pterosaurs, and they were. It is because birds have feathers that they were able to compete with the already established pterosaurs.

While the evolution of the long light and strong flight feathers proved to be very advantageous for smooth aerodynamic flying, it was actually the insulating ability of simple body feathers that first set the birds apart from the pterosaurs. By providing superior insulation the body feathers set the stage for a whole host of evolutionary developments that gave birds superiority as hot blooded high powered fliers. The first birds are distinguished by having feathers indicating that they were warm blooded vertebrates along with whatever evidence there is indicating that these vertebrates were flying. Thus, if a fossil of a vertebrate shows both evidence of feathers and evidence that the vertebrate was flying then that vertebrate was a bird.

Birds (Aves) are advanced feathered archosaurs that fly, or at least had ancestors that flew.

What is a bird? What is a dinosaur? Why are definitions important? Sometimes mistakes that lead to disagreements occur when people are sloppy about how they define terms, while at other times there are those who intentionally engage in misconstruing terms for their own benefit. Paleontologists cannot explain the existence of large dinosaurs, flying pterosaurs, AND the exceptionally large flying birds of the Mesozoic era, and so they are trying to convince people that the large flying birds were non-flying feathered dinosaurs. Clear, rational, working definitions for terms such as birds and dinosaurs allow science to move forward by putting an end to these shenanigans.

Fossil showing the feathered wing of Confuciusornis Feathered wing of Confuciusornis

During the Cretaceous period, there were numerous birds that were substantially larger than modern flying birds. Apparently, when these species were first being discovered, paleontologists had difficulty accepting the evidence that they were flying birds, so they mislabeled them as dinosaurs. However, the evidence continued to come in, indicating that these 'dinosaurs' were actually large flying birds. Most problematic for the paleontologists was the evidence showing that either these large birds or their smaller close relatives had feathered wings and asymmetric feathers. So, the paleontologists yielded to the evidence showing that these vertebrates had feathers but continued to deny the fact that these birds could fly. In every description of these large flying birds, they finish their description by saying that despite the 'feathered dinosaur' having feathered wings, it is their opinion that it could not have flown. Let us take a closer look at the evidence indicating that many of the large vertebrates paleontologists are referring to as 'feathered dinosaurs' were actually flying birds.

Wings: Fossils of feathers, and likewise feathered wings, are not as likely to be preserved as well as bones, and yet there are still several fossils showing the feathered wings of the early Cretaceous 'feathered dinosaurs'. Either these wings are seen directly on these exceptionally large 'feathered dinosaurs', or at least on some of the smaller members within their species' family, such that no one contests the fact that all of the members of Troodontids, Dromaeosaurs, and Avialae had wings. Even though the wings on these birds were relatively small by today’s standards the size of their wings is appropriate for the much thicker Mesozoic atmosphere.

Paleontologists want to dismiss the idea that these were flying birds and so they introduced the slippery slope argument that these feathered vertebrates could have evolved their wings for sexual display or whatever. While nature is full of surprises the Theory of Evolution does not favor improbable explanations. Of the current 70,000 known species of vertebrates there are approximately twelve thousand winged species that fly: 10,500 birds and about 1,500 bats. There is not a single species that evolved wings for some purpose other than flying or at least gliding. This does not mean that it would be impossible for a species to evolve wings for some purpose other than flying, but it does say that it is so astronomically improbable of happening that we should not waste our time considering the possibility. Hence, if we discover a species with wings then we should conclude that it or its ancestors were using its wings for flying or at the very least gliding.

Drawing showing why feathers are asymmetric
Drawing identifying parts of a asymmetric

Asymmetric Feathers: The flight feathers of birds are asymmetric because the lifting pressure on the leading vane of the feather is much stronger than the lifting pressure on the trailing vane. The same principle applies to an airplane wing: there is at least as much lift on the forward one-fourth to one-third of the wing as there is on the remaining trailing portion of the wing. Whether it is a flight feather or the wing of an airplane, the main support tube needs to be placed one-fourth to one-third of the way back from the leading edge to counteract the lifting force. It is only the wing feathers of flying birds that experience these unbalanced lifting forces, so it is only these feathers that are asymmetric.

Image of several feathers Wing feathers are more likely to be asymmetrical than tail feathers.
Image by Beverly Buckley.

It is common practice in paleontology to assume that whatever features found on one member of a family or clade are shared among all the members of the family. Long asymmetric feathers, used by modern birds, are also found on the wings of Archaeopteryx and Confuciusornis, members of the Avialae family. Similarly, long asymmetric flight feathers are found on Microraptor of the Dromaeosaurid family and Troodontid of the Troodontidae family. It is collectively accepted that asymmetric flight feathers existed on all the members of the Troodontids, Dromaeosaurs, and Avialae families, thus favoring the belief that all of the members of these families were flying vertebrates.

Stiff Tail: The stiff tail of these fossilized vertebrates is the clincher in distinguishing whether the vertebrate was a flyer or grounded. Similar to the rudder and elevator on the tail of an airplane, the tail of a bird guides the direction of its flight. For this to work effectively, the bird’s tail needs to be stiff everywhere other than at its base. As the bird flies, the stiff tail changes the direction of its flight by deflecting the air that flows past the flying bird. By deflecting the air, a force is applied back on the tail, which turns the bird in the desired direction. In contrast, a flexible tail is not as effective in guiding a bird, as it yields or bends in response to the force applied by the wind.

Anchiornis Huxleyi: Late Jurassic feathered dinosaurs or ancestral bird Fossil shows Anchiornis Huxleyi of the Late Jurassic (160 mya). Being older than Archaeopteryx and having features such as a fused tail and feathers on all of its limbs means that it may actually deserve the title of being the ‘first bird’.

While modern birds and a few Jurassic and early Cretaceous birds used long stiff tail feathers as their rudder, most of the Jurassic and early Cretaceous birds had their tail vertebrae fused together to create a long, feather-covered rod that served as their rudder. Because fossilized bones are more likely to be preserved than feather imprints, the straight fused tail is an easily recognizable feature that can be used to identify vertebrates as birds. By using this identifier, we find that most, if not all, of the 'feathered dinosaurs' of the early Cretaceous period are actually flying birds. This fact is not surprising, as these vertebrates are all members of family groups that have already been identified as having at least one member showing well-defined feathered wings and asymmetric feathers.

Besides being far more likely to be preserved, the fused bony tail is just as effective as a feathered wing in distinguishing between flyers and non-flyers. While a stiff tail is extremely useful to a bird while flying, it can be a hindrance to any vertebrate on the ground. Most ground-dwelling vertebrates live in small dens and need to be able to turn around without being poked or having their tail bent or damaged. Similarly, when birds are not flying, they often hold their stiff tail feathers up at nearly a 45-degree angle to avoid this problem, whether on the ground or squatting on their nest. A stiff tail can be such an annoyance that if a bird evolves into a flightless species, it is more likely to lose its stiff tail before its shortened wings. Hence, the presence of a stiff tail is a strong indicator that the vertebrate is a flyer.

The reason many vertebrates have a flexible muscular tail is for propelling the animal through a thick fluid. However, while an oscillating tail can provide strong thrust when the animal is starting to move or moving slowly in a dense fluid, the ability of a flexible tail to provide positive thrust diminishes as the animal attempts to move at higher speeds through the fluid. For this reason, we see most animals using their tail to push themselves through water, but we do not see animals using a flexible tail to push themselves while flying through the air.

alligator on a dock An alligator’s flexible tail is it primary means of propelling itself through the water.
Public domain image by Photo by Shelly Collins on Unsplash
snake swimming in the water A snake is effectively a head attached to a long flexible tail, a flexible tail that it uses to propel itself through the water or over the land.
sparrow standing on a post When on the ground or near other objects, a stiff tail is more likely to be damaged than a flexible tail. This may be the reason why many birds hold their tail up high when they are on the ground.

Birds need to be moving fairly fast for their wings to generate enough lift for flying. Unlike an airplane's propeller, an oscillating flexible tail cannot move fast enough to be effective in pushing the flyer forward. Hence, birds do not have a flexible tail; instead, they have a stiff tail that they use only to determine the direction of their flight. Birds flap their wings to produce the forward thrust needed for flying.

'Feathered Dinosaur' named Zhenyuanlong Fossil of Zhenyuanlong suni of the Cretaceous period (125 mya). Zhenyuanlong was a 6-foot-long Velociraptor. Notice the fused vertebra tail along with the brownish tint silhouette in the shape of wings thus indicating that Velociraptor was a flying bird.

During the Mesozoic era, the atmosphere was much thicker than it is today, which influenced the anatomy of the animals of that time. Firstly, the dense atmosphere enabled even reptiles to fly. Similarly, birds also evolved, and they too were capable of flight, but because of the thickness of the Mesozoic atmosphere, these birds did not need their wings to be nearly as large as either the pterosaurs or modern birds. However, Mesozoic birds still required a stiff tail to direct their flight since they were flying at high enough speeds that a flexible tail would have been useless. This was not the case for dinosaurs, as they did not move nearly as fast as birds. At the dinosaurs’ typically slower speeds, a muscular flexible tail provided propulsion through the thick Mesozoic atmosphere. Whereas a modern alligator used its legs for the few steps it takes on the land and uses its tail while propelling itself in water, most dinosaurs used their flexible tails and rear legs simultaneously to propel themselves forward through the thick air and across the land.

Birds are advanced feathered archosaurs that fly, or at least had ancestors that flew. Dinosaurs, on the other hand, are an extinct group of unusually large archosaurian reptiles that had their hind legs extending directly beneath the body. These two groups share a common ancestry of archosaurian reptiles, so it is not surprising that they share many common features: both lay eggs, scales are typically found on dinosaurs, and there are also scales on the legs of birds. Additionally, members of each group can have either a mouth full of teeth or a beak. Because of this common ancestry it would not be shocking if paleontologists were to find a dinosaur that had feathers. However, if that 'feathered dinosaur' also flew, then it would not be a dinosaur; it would be a bird.

The Giant Flying Birds of the Cretaceous Period

troodontid Troodontid J. tengi was a three foot (0.9 m) tall bird of the early Cretaceous period. Troodontids are known for having a large brain, binocular vision, and asymmetrical flight feathers.

Birds had evolved by at least the mid to late Jurassic period, with some paleontologists claiming that birds may have existed as early as the late Triassic period. Thus, birds coexisted with dinosaurs and pterosaurs for most of the Mesozoic era. The first birds of the Jurassic period were small and unusual compared to modern birds; they had teeth instead of a beak, claws on their wings, a long stiff tail, and many had flight feathers on their rear legs. At the extinction event that ended the Jurassic period, many of these early bird species went extinct, but they were soon replaced by similar birds that emerged in the early Cretaceous period. The most notable difference about Cretaceous period birds is that many, if not most, were much larger. Like the dinosaurs and pterosaurs, many Cretaceous period birds were incredibly large compared to modern species.

Avialea chart

Originally, many of the species that paleontologists now classify as feathered dinosaurs were placed in 'waste basket' categories, indicating uncertainty about their identity and evolutionary relationships. However, it is now possible to reclassify nearly all of these specimens as either birds or dinosaurs, while also determining their proper place in taxonomy.

The paleontological community's insistence on depicting birds as evolving from theropod dinosaurs, coupled with their reluctance to acknowledge the existence of exceptionally large birds from the Cretaceous period, has led to significant confusion regarding the classification of various groups of birds and dinosaurs. Consequently, the phylogenetic trees depicting the evolution of birds often vary widely and can sometimes be nonsensical. For instance, it is not uncommon for these trees to depict a new family of birds evolving from another group of birds that do not appear in the fossil record until tens of millions of years later. Similarly, they tend to overlook late Jurassic birds such as the iconic Archaeopteryx, which lived between 160 and 145 million years ago.

To identify the earliest birds, we need to return to the most fundamental definition: if it has feathers and it flies, then it is a bird. This means that the lineage of birds begins in the mid to late Jurassic period, encompassing iconic species like Archaeopteryx, as well as more recently discovered ones such as Anchiornis huxleyi and Confuciusornis sanctus.

While many of these species became extinct at the end of the Jurassic period, a few families of birds managed to survive and thrive into the early Cretaceous period. These included Troodontids, Dromaeosaurs, and Avialae.

Besides wings, the fused tail is the most obvious indicator that a late Jurassic or early Cretaceous vertebrate is a flying bird. By being flexible only at the base, the fused tail acted like a rudder, guiding the direction of these birds as they flew through the air. Further confirmation of their flying nature comes from observing that the pubis bone of the hip is pointed backwards to accommodate the bird’s large respiratory system. Additionally, many, if not most, of these specimens show actual evidence of feathers, often in the form of outstretched wings. Please examine the fossil images to confirm for yourself that Troodontids, Dromaeosaurs, and Avialae were indeed true flying birds.

Several Predatory Birds of the Cretaceous Period The birds of the Dromaeosaurs family flew during the Cretaceous period, and many of them were considerably larger than modern flying birds. Despite their varying sizes, they shared striking similarities in shape and features: teeth instead of a beak, relatively small wings, deadly sharp talons, and a stiff tail. While paleontologists may initially envision only the smallest of these birds as capable of flight, calculations demonstrate that in a thick atmosphere, all of these birds were highly proficient fliers. They were formidable predators.
(Wikipedia creative commons file first uploaded by Fred Wierum)
fighting dinosaurs
This fossil is know as the ‘Fighting Dinosaurs’ even though it is actually the entangled remains of a dinosaur (Protoceratops) and a bird (Velociraptor). Similar to the killing strategy of present day eagles and hawks, the Velociraptor was attempting to make its kill by ripping its talons through the large arteries in the neck of its prey. However, in this dangerous world of frequent aero attacks, the Protoceratops had evolved a shield that made it difficult for the Velociraptor to get to the Protoceratops’ neck. This time the deadly encounter ended in a draw. Notice the stiff tail of the Velociraptor, indicating that it was a flying bird.
Dakotaraptor Dakotaraptor is one of the larger members of the Dromaeosaurs family of birds.
Drawing by Fred the Dinosaur Man.

Using the flight equations derived in chapter three we can calculate the power ratios of these feathered vertebrates based on best estimates of their weight, wingspan, and other factors important to flight. Using the Earth’s current sea level atmospheric density (1.2 kg/m3) the calculations show that it not be possible for these feathered vertebrates to fly in our present atmosphere. While on the other hand when the equations are reworked using the much higher density value of the thick Cretaceous atmosphere (660 kg/m3) the calculation show that these feathered birds of the Cretaceous period were very capable flyers.

Here are the equations used for making the flight calculations followed by a table giving the data input estimates along with the calculated values.

N = Fg (1 - ρF / ρS)

v_min =  [(2 W^2) / (3 A C b^2 ρ^2)]^1/4

P_T-min =  4/3 [ W^2 / (b^2 ρ v_min)]

Pav = 1.5[(69 W3/N2) W2]1/3

Flyer Weight
(N)
Front Area
Estimate
(m2)
Drag Coefficient
Estimate
(Front Area)
Wingspan
(m)
Speed
for least Power
(m/s)
Minimum Power
for Flight
(kW)
Available Power
(kW)
Power Ratio
Dakotaraptor
Thin Atm
3000 0.25 0.25 3.5 48 17 1.0 0.06
Dakotaraptor
Thick Atm
1020 0.25 0.25 3.5 2.1 0.10 1.0 10
In order to fly, a potential flying object needs a power ratio greater than one. The first time through the calculations are done based on the incorrect assumption that on Cretaceous atmosphere was similar to the present atmosphere. Using the current sea level atmospheric density of 1.2 kg/m3, the resulting value for the power ratio is only 0.06 thus indicating that it is falling far short of having enough power to fly in a thin atmosphere. However when the numbers are crunched again using the much higher density value of the Cretaceous period the power ratio comes out to 10 thus indicating that this bird was an extremely capable flyer in the much thicker atmosphere.
shark
Leopard Shark
Unlike other fish, sharks do not have an air-filled swim bladder to help ‘float’ their body, so sharks must use their pectoral fins as their wings to give them lift. The shark’s ‘wings’ are relatively small because small wings are all that are required when ‘flying’ in a dense fluid.

To better understand why these large birds had relatively small wings, let’s consider a present-day example of a vertebrate 'flying' in a dense fluid. A shark’s body is denser than the surrounding water, so if it did not swim, it would slowly sink to the bottom of the ocean. However, sharks do not sink because they have pectoral fins on their sides that act as effective wings, giving them lift as they propel themselves forward with their tail.

Think of a shark in the ocean as being similar to an airplane or bird in the atmosphere: all of these 'fliers' propel themselves forward so that fluid flows over their wings, producing the lift required to maintain their altitude. However, unlike airplanes and modern birds that fly in the thin atmosphere, sharks need only relatively small wings because they are flying in the much denser ocean water. This inverse relationship between the size of wings and the density of the fluid likewise applies to the birds that flew in the dense Cretaceous atmosphere. The extremely dense Cretaceous atmosphere was the reason why most of the birds of the Cretaceous period had relatively small wings.

In our comparison of the Mesozoic atmosphere to the present day ocean environment something else comes to our attention: the amount of life swimming in the ocean compared to how much live is crawling on the sea floor. It makes sense that the denser the fluid the larger percentage of life that will be flying or swimming in the fluid as opposed to just walking on the sea floor. Likewise in the Mesozoic world with its extremely thick atmosphere, flying is much easier than what it is today and so we should expect a larger percentage of vertebrates flying about than what we see in the atmosphere today. As a rough guess during the Cretaceous period as much as ten to thirty percent of terrestrial life mass was in the air at any given moment as opposed to just moving about on the land.

Once Again Defining A Bird

Head of Bald Eagle Beak of a Bald Eagle. A beak is better than teeth because a beak is just as strong as teeth and it is lighter; in most cases minimizing weight maximizes flying ability.
Image by Anrita

Some scientists seem to overly emphasize whether a vertebrate has a beak when defining a bird. However, besides modern-day birds, many living and extinct species possess a beak, including turtles, swordfish, numerous dinosaurs, most pterosaurs, and some amphibians. The evolutionary preference for a beak over a jaw full of teeth in flying animals is due to its lightness and strength, which improve aerodynamic efficiency. This could explain why both pterosaurs and birds initially had teeth but later evolved to have a beak. However, while a beak is a favorable feature, it is not essential.

Earlier arguments clarify what criteria should be used to identify a bird: having feathers and showing evidence of flying, or at least having ancestors that flew. This evidence of flying includes having feathered wings, asymmetric flight feathers, and a hinged stiff tail useful for guiding the flight. These features are extremely good since it appears to be true that all birds have these features and all non birds do not have these features. This statement cannot be said about all characteristics that are often used to identify birds.

In describing a bird, we might say that it lays eggs, is warm-blooded, or has a beak. Yet, just how useful are these identifiers? If we say that a bird is a vertebrate that lays eggs AND is warm-blooded then we have a useful identifier since there are only a few exceptions to this statement. However, we have to wonder how useful it is to say that a bird has a beak.

Claiming that birds have a beak fails miserably in both ways: numerous non-birds have a beak, and many extinct birds did not have a beak. The only reason all modern birds today have a beak is that only the Avialae family of birds survived the K-T mass extinction at the end of the Mesozoic era. If one of the non-beak bird families had survived the K-T extinction, we would not even consider a beak a defining feature of birds.

Phony ‘Feathered Dinosaurs’ That Have No Wings Or Feathers

Paleontologists have caused confusion by labeling two distinct groups as feathered dinosaurs. The first group comprises of large birds that lived throughout the Cretaceous period, as described in the previous section. The second group consists of theropod Saurischian dinosaurs from the late Cretaceous period. While these late Cretaceous theropods may have had some similarities to modern-day ostriches and possessed beaks, they were unequivocally not birds.

Dinosaur Feathers Look hard and squint. The evidence of Ornithomimus dinosaurs having feathers is supposedly inside the yellow lines.

A large group of birds, regarded as the first group of 'feathered dinosaurs,' emerged in either the late Jurassic or late Triassic periods. They coexisted with dinosaurs and pterosaurs before surviving the K-T extinction event and persisting to the present day. Although many early birds had a mouth full of teeth instead of a beak, they shared crucial avian characteristics with modern birds, including an Ornithischia hip structure, a stiff tail for flight guidance, body feathers, asymmetric flight feathers, and fully developed feathered wings.

The second group of 'feathered dinosaurs' likely evolved from theropod dinosaurs and existed during the late Cretaceous period. This group included species such as Therizinosaurus, Conchoraptor, Gigantoraptor, Corythoraptor, Oviraptor, Anzu, Ornithomimus, and others. Despite being labeled as 'feathered dinosaurs' by paleontologists, the evidence of them having feathers is either sparse or nonexistent. Unlike the first group, these late Cretaceous 'feathered dinosaurs' lacked avian characteristics such as a bird hip structure, stiff tail for flight guidance, flight feathers, and feathered wings. There is no evidence indicating that this second group of 'feathered dinosaurs' were capable of flight or had ancestors that could fly.

Several Ostrich Like Theropod Dinosaurs None of these dinosaurs show evidence of having wings, they do not have stiff tails, and they may not even have feathers. So why are paleoartists drawing these vertebrates this way?

Why is it that paleontologists are grouping together the large flying birds of the Mesozoic era and the late Cretaceous ostrich like dinosaurs under the same heading of feathered dinosaurs? Why is it that after describing the wings of every large Mesozoic era bird, paleontologists feel obligated to give their highly questionable opinion that these large birds must have been using their fully evolved wings for some purpose other than flying? Why is it that paleoartists show numerous ostrich like theropod dinosaurs as having feathered wings when there is no evidence supporting these claims? Why is it that paleontologists want to blur the distinction between birds and dinosaurs?

To summarize, paleontologists have cause confusion by burring the distinction between the large birds of the Cretaceous period with ostrich like theropod dinosaurs of the late Cretaceous period. None of the theropod dinosaurs that make up the second group and are being called feathered dinosaurs show any evidence of having wings, a stiff tail, or even evidence of well formed feathers. While it would not be shocking if paleontologists were to someday find one or more species of dinosaurs showing evidence of actual feathers, currently there is actually no such thing as a feathered dinosaur.

The Evolution of Modern Birds: Feathers and High Metabolism

Protoavis Paleontologist Sankar Chatterjee claims that the earliest known bird flew during the late Triassic period. He calls this bird Protoavis.

In response to the classic question of which came first, the chicken or the egg, the answer should be obvious: birds evolved from egg-laying archosaurs. However, the more difficult question is: which bird features evolved first on the evolutionary journey from advanced archosaurs to modern-day chickens?

Before birds, there were flying reptiles known as pterosaurs. Pterosaurs, like all reptiles, were most likely ectothermic, or ‘cold-blooded,’ meaning that their internal body temperature was typically nearly the same as the external temperature. In contrast, birds are distinguished from pterosaurs by being warm-blooded, or one could even say hot-blooded, considering how high their internal temperature is compared to mammals. But how do we know this?

While there are clearly advantages from being warm blooded there is also a price to be paid for this upgrade, and that is, an endothermic vertebrate needs to consume considerably more food to maintain its elevated temperature. In fact endothermic animals use far more calories to maintain an elevated temperature than they do for their physical activity. Hence, having some form of thermal insulation to slow down the loss of body heat to the surrounding environment is critical to the survival of endothermic vertebrates. This is why birds have feathers covering their body. Feathers are ideal for trapping air next to the body, and this trapped air is a very effective form of thermal insulation. Hence, the presence of feathers on the predecessors to birds indicates that these vertebrates were evolving an endothermic or warm-blooded metabolism.

Enzymes and Metabolism

Warm blooded vertebrates are able to achieve a much higher power output with the help of enzymes. Enzymes work within cells to move chemical reactions along at about a thousand times faster than normal. So enzymes are great for achieving higher metabolism. The only drawback is that the body needs to be kept within a narrow band of pH and elevated temperature in order for enzymes to work.

Flying is a power-intensive activity and so it requires flying animals to have a high level of relative power. The relative power of a vertebrate strongly correlates with the animal’s metabolism. Most scientists divide vertebrates into two broad categories: ectothermic, or ‘cold-blooded’ like reptiles, and ‘warm-blooded’ endothermic vertebrates like mammals. However, considering how much higher the internal temperature of most birds is compared to mammals, it would seem appropriate to classify birds as being ‘hot-blooded’. These differences in internal temperatures strongly correlate with each group’s metabolism, relative power, and flying capability. In our present time, reptiles have too low a metabolism to fly, while the warm-blooded flying mammals – bats – can fly, but they are usually rather small, whereas the ‘hot-blooded’ birds are by far the largest and most capable fliers.

Hierarchy of Flying Vertebrates

Flying Vertebrate Metabolism Thermal Insulation Notes Flying Ability
Birds Hot-Blooded
104 – 107oF
(40 – 42oC)
Feathers:
best insulation
Higher metabolism required
evolution of unique respiratory system
for greater oxygen intake
Birds rule the skies
Bats
(Flying Mammals)
Warm-Blooded
98.6oF
(37oC)
Hair:
good insulation
Evolved echolocation
for night flying to
advoid predatorily birds
Much smaller than birds
and not as fast
Reptiles Cold-Blooded
Temperature same
as environment
Scales:
poor insulation
Lower metabolism means
much lower food consumption
Currently reptiles are
incapable of flying

Like the parts of a well-tuned engine, every organ of an organism needs to make its full contribution so that the organism can achieve its maximum performance. The transition of birds from advanced archosaurs to the superb fliers of today required the evolution of many parts. Flying demands high power output, so birds need a high metabolism. A high metabolism necessitates maintaining elevated temperatures, which, in turn, require the effective insulation provided by body feathers. Additionally, a robust respiratory system is needed to keep up with the oxygen demand of the high metabolism.

The Evolution of Modern Birds: Oxygen Feeds the Fire

One challenge ancestral birds faced was providing enough oxygen to sustain the continuous high power output required for flight. Birds addressed this challenge by evolving a unique respiratory system.

Let’s first consider how the respiratory system works for terrestrial vertebrates that are not birds. When humans, as well as other mammals, reptiles, and extinct dinosaurs, take a breath, fresh air travels down the trachea to fill our lungs. Upon exhaling and contracting our lungs, the air in the trachea reverses direction to exit our body. However, since we can only partially contract our lungs, a significant portion, if not most, of the stale air remains in our lungs. This residual air then mixes with the fresh air that enters upon the next inhalation. As a result of this mixing of old and new air, the air inside our lungs has a lower level of oxygen than the air outside our body. This makes it more difficult for us, as well as other non-bird terrestrial vertebrates, to absorb oxygen into our blood.

Diagram of a Bird's Respiratory System A bird’s respiratory system differs from ours. In our system, air moves back and forth in our trachea as our lungs expand and contract. In contrast, in a bird’s respiratory system, air first travels down the trachea to the air sacs in the rear of the bird; it then passes through the lungs before moving to smaller sacs in the front or sides of the lungs, and finally exits the bird through its mouth. Because high oxygen air is constantly flowing through the lungs, the bird’s respiratory system is more efficient at extracting oxygen from the atmosphere.
Beautiful illustration by Lizzie Harper showing a duck’s anatomy. Red organ is the lungs while the blue organs are the air sacs. Waterfowl are able to float on water because air fills most of their interior.
swan Mute swan and two chicks.

In contrast to our back-and-forth breathing, a bird’s respiratory system utilizes numerous air sacs to ensure a continuous flow of oxygen-rich air over the capillaries in their lungs. When a bird inhales, air travels to the large posterior and abdominal air sacs near the rear of the bird. From there, it undergoes a one-way journey through the lungs, maintaining its high oxygen content. After exiting the lungs, the air passes to the forward anterior thoracic air sacs before being expelled back into the environment. Birds benefit from a constant unidirectional flow of air through their lungs, allowing them to extract a greater amount of oxygen from the atmosphere.

In addition to extracting more oxygen from the atmosphere, a bird’s unique respiratory system results in much of its interior being empty space. Consequently, birds have a significantly lower body density compared to other vertebrates. While the body density of other vertebrates is typically around 1.0 g/cm3 - about the same as water - most birds have a density that is about one half to one third of this value. This lower body density is the primary reason why waterfowl are capable of floating high on the water.

Surprisingly, there is a third major benefit that arises from a bird's unique respiratory system: the large air sacs located towards the rear of the bird assist in statically balancing the bird while it is in flight.

...

The Evolution of Modern Birds: Physics of Flying

Force vectors acting on an airplane while it is in steady constant speed flight. Force vectors acting on an airplane while it is flying level at a constant altitude and speed.

The Science of Flight Equations calculate the takeoff speed and power requirements of an airplane or flying vertebrate based on factors such as weight, wingspan, air density, and aerodynamic shape. However, determining if an animal or airplane is capable of flying involves more than just these calculations. These flying objects need to be statically balanced as they fly. Besides the upward lift from the wings being strong enough to overcome gravity and the forward thrust matching drag to maintain speed, these opposing forces either need to be directly in line with each other, or the torques that they create need to cancel each other out to prevent unwanted rotation. A statically balanced airplane will maintain stable level flight without the need for a pilot to make corrections.

Microraptor in flight showing its four wings Microraptor is just one of numerous late Jurassic and early Cretaceous birds that had excessive plumage on their rear legs and tail. These flight feathers were required to give the rear portion of these birds enough lift to keep the bird in the prone position while they were flying. Since these earlier times the center of mass of birds has moved forward and so modern birds no longer need this excessive plumage on the rear of their body in order to fly.

In the early evolution of birds, the feathered archosaurs that were gliding between trees were not statically balanced. Like most animals, the center of mass was near the center of their body or nearly centered between their rear and forward legs. This arrangement works well for an animal walking or climbing a tree but not for a vertebrate whose forward limbs are evolving into wings. If the center of mass is approximately midway between the rear and forward limbs while the center of lift is closer to the forward limbs—the wings—then the two opposing force vectors are not aligned. The consequence of this misalignment is that once the winged vertebrate makes a horizontal leap from one tree towards another, the rear of its body will begin falling in respect to the rest of its body. Because nothing is holding up the rear of its body, not long after leaping, the gliding animal will rotate from a prone position to nearly vertical. For short leaps, this was not a problem and, in fact, it was preferred: if the destination is the trunk of a nearby tree, it's much better to be able to stop the forward motion by landing on all four limbs rather than slamming into the tree headfirst. Only when the vertebrate attempts longer glides or tries to fly does this unwanted rotation become a serious problem.

The early birds solved this misalignment problem by evolving large tail feathers that provided lift to the rear of their body. Many of these early birds also had excessive plumage on their rear legs, in addition to the plumage on their stiff tail. These feathers on the rear of their body gave these early birds the extra lift needed to maintain their aerodynamic prone position while in flight. Reviewing the fossil evidence and pictures of these early birds, one can observe that all of them have excessive plumage on their stiff tail, and many also had plumage on their rear legs.

Early Cretaceous Bird Mistaken For Being a Feathered Dinosaur The plumage on the rear legs and tail would create air resistance drag working against their efforts if they were trying to run. But why would a vertebrate bother trying to run fast when it can fly?

The plumage on their rear legs is particularly revealing, indicating that these vertebrates spent more time flying or gliding rather than running on the ground. This excessive plumage would create significant air drag if they attempted to run, suggesting that if these birds needed to move quickly, they would certainly opt for flying rather than running.

What has changed so that modern birds no longer need excessive plumage on the rear of their body? It appears that modern birds no longer require this excess plumage for static balance. In other words, the center of mass for modern birds must have shifted forward, aligning the downward weight vector with the lifting force of the wings pointing upward.

But how did the center of mass move forward? As explained in the previous section, birds possess a unique respiratory system that occupies a significant amount of space within their bodies. Although this unique respiratory system has existed since the late Triassic period, it has undergone some changes over time. Initially, the air sacs were likely much smaller, but as vertebrates evolved the ability to fly, these air sacs began to enlarge, particularly the rear air sacs. Consequently, in addition to modern birds having a lower overall density, this lower density is primarily concentrated in the rear portion of their bodies. With the majority of the high-density muscle mass and organs located near the front, and the low-density air sacs in the rear, the bird’s center of mass has shifted forward.

RC airplane being supported with three fingers For better stability, cars are typically supported by four wheels while tables and other furniture are typically supported by four legs, nevertheless only three points of contacts are actually required to achieve stability. This RC airplane needs three spread out points where forces are applied to achieve stability and the same is true for full size airplanes and flying birds. In the picture this is the three fingers, while it flight the three points are the two wings and the rear horizontal stabilizer.

Flight stability is a desirable feature for both airplanes and flying animals. This means that an object flying at constant speed, direction, and altitude should have a natural tendency to maintain its constant speed, direction, and altitude without any correcting adjustments from the pilot. Thought must be given to the design of the aircraft and its proper loading so as to achieve this balance while the airplane is in flight.

To better understand what this means point a finger towards the sky and then try to balance something like a pencil on the tip of your finger. With only one point pushing up the object is going to fall to one side or another and so this is not a stable situation; the object will soon fall off your finger. To achieve stability in the x, z plane – z direction being vertical – we will need to use at least two fingers, like the peace sign, supporting our object and if we want complete stability in all directions of x, y, z we will need to use at least three finger tips to support our object.

The center of mass of an airplane typically lies between what appears to be the center of the airplane and its heavier components, such as the engine. The main wings are usually positioned directly above this point. At the tail, there is typically a horizontal stabilizer, which serves as the third point for maintaining stability. The purpose of the horizontal stabilizer is to ensure steady flight by preventing the airplane from pitching up or down. While it is possible to design an airplane with wings but no fuselage, this type of aircraft lacks strong flight stability.

Positioning the horizontal stabilizer at the tail of the airplane is advantageous because this design naturally corrects itself. If a gust of wind attempts to blow the airplane off course, it typically returns to its original level flight. However, there is another design option known as a canard airplane, where the horizontal stabilizer is placed at the front of the fuselage. Positioning the horizontal stabilizer in front of the main wing may seem odd and even potentially dangerous, and yet modern canard airplanes are often more efficient than traditional airplanes because all horizontal surfaces are providing positive lift.

Geese Flying Geese: Geese and swans achieve flight stability by having long necks. These ‘canard flyers’ are large birds that are capable of making long migration flights.
Wright Flyer 1905 Wright Flyer: the early Wright flyers had the elevator at the front of the airplane.
Swift Flying Swift showing the typical ‘T’ flying form of most birds and recreational airplanes

These two fundamental styles of airplanes – either positioning the stabilizer in the rear or in the front – also apply to flying vertebrates. The vast majority of small to medium, and sometimes large birds are stabilized by their tail while many of the larger migrating birds are stabilize by having an extremely long neck. Typically the birds that require some degree of maneuverability while flying will have the traditional ‘T’ profile using their tail as their stabilizer, while most large migrating birds will favor having a long neck such that the mass of their head acts as inertia stabilizer that keeps the bird level while flying.

The Wright brothers’ first airplane had a large horizontal stabilizer in the front and so it was a canard style airplane. While this design worked it did not work all that well because it is inherently unstable at faster speeds; once the airplane starts pitching either up or down it is far more likely to keep going off course instead of correcting itself. During the first flights of the Wright flyer this inherent instability was not so noticeable, but as the Wright brothers increased the power and speeds of their later airplanes this dangerous tendency to pitch required constant attention from the pilot to keep the airplane from crashing. By the time the Wright brothers finally switched to placing the horizontal stabilizer at the rear of their airplanes they were no longer the leaders in aviation technology.

Large Birds of the Cenozoic Era

Like the exceptionally large flying birds of the Mesozoic era there were also exceptionally large birds during the Cenozoic era, but they were different. As mentioned earlier, the Avialaes family of birds was the only one to survive the K-T extinction that ended the Mesozoic era and they were different from the Troodontidae and Dromaeosaurs birds of the Mesozoic era in that the Avialaes had a beak instead of a mouth full of teeth like the other birds, and since present-day birds belong to the Avialaes family all living birds have a beak. Another difference between Avialaes birds of the Cenozoic era and most Mesozoic-era birds is that Cenozoic-era birds typically have larger wings.

Yet, because the atmosphere was still much thicker than what it is now throughout most of the Cenozoic, many of the earlier Cenozoic birds grew to be much larger than present-day flying birds.

Pelagornis sandersi Pelagornis sandersi
Drawing by Rob Westdrop

There are only a few known species of large extinct flying birds from the Cenozoic era for which there are well-preserved fossils: Pelagornis sandersi, a large seabird that lived approximately 25 to 28 million years ago; Pelagornis chilensis, a slightly smaller seabird that lived five to ten million years ago; and Argentavis magnificens, a large South American vulture that existed only six million years ago. Pelagornis sandersi had a form similar to that of a Wandering Albatross but with an estimated wingspan of 6.4 meters it is nearly twice the size of the Albatross. Similarly, Argentavis had a wingspan of seven meters, more than twice the size of the largest similar-shaped flying South American bird, the Andean Condor. Undoubtedly, there were numerous other large extinct birds that flew during the Cenozoic era, but unfortunately, most of these fossils consist of no more than a few bones in damaged condition.

It will be helpful to first study the largest modern flying birds before investigating how the largest birds of the Cenozoic era were able to fly. This will give us a better perspective of flight limitations set by our current thin atmosphere. Once again the flight equations enable us to calculate flight capability of the largest flying animals. The results show that generally as the weight of a bird goes up its flying capability goes down until the heaviest birds can no longer fly.

Flyer Mass
(kg)
Wingspan
(m)
Speed for
least Power
(m/s)
Minimum Power
for Flight
(kW)
Available Power
(kW)
Power Ratio
Great Bustard 19 2.5 15 0.44 0.38 0.89
Andean Condor 14 3.0 12 0.20 0.32 1.6
Mute Swan 13 3.0 12 0.18 0.30 1.7
Dalmatian Pelican 15 3.5 11 0.18 0.33 1.9
Wandering Albatross 13 3.6 11 0.13 0.30 2.3
Marabou Stork 9.0 2.9 11 0.10 0.24 2.3
Bald Eagle 5.6 2.0 11 0.08 0.17 2.2
Blackston's Fish Owl 4.6 1.8 11 0.067 0.15 2.3
Bar-headed Goose 3.0 1.6 10 0.039 0.12 3.0

Comments Regarding the Largest Flying Birds

Marabou stork Marabou stork
Photo by Alpcem
Dalmatian Pelican Dalmatian Pelican
Photo by BarBus
Bar Headed Goose Bar Headed Goose
Photo by Lancier
Male Great Bustard Male Great Bustard
Photo by L Jargal

Great Bustards – Males are typically three to five times larger than females and this size difference between the sexes has caused some confusion about the flying ability of Great Bustards. Researchers have tracked Great Bustards migrating thousands of kilometers, but these bustards were all females that only weighed about 3.5 kg. Because male bustards are heavier their flying preference is similar to wild turkeys: They spend nearly all of their time walking on the ground while only occasionally making a short flight that places them out of the reach of predators.

Andean Condor – With the exception of when they are taking off, these large birds rarely flap their wings. Instead they typically get their lift by soaring over warm rising air.

Andean Condor in Flight Andean Condor in Flight

Mute Swans – While most swan species migrate, Mute Swans do not migrate. Perhaps it is because they do not need to migrate or fly that often that some individuals have grown extremely large: up to about 23 kg. These overgrown Mute Swans may be too heavy to fly.

Dalmatian Pelican – Many pelicans are surprisingly large and strong flyers.

Albatross – These are excellent fliers. They will usually go on migrations for multiple years where they are often fly continuously for days before taking a break to eat or float on the water. However, because they are large birds with narrow wings, when they do return to solid ground they need to land at high speeds and these high speed landings often give comical results.

Bar-headed Goose – These birds are noted for their ability to fly at high altitudes as they fly over the Himalayan mountains. Flying at such high altitudes test the limits of these birds’ ability because the thinner atmosphere requires the expenditure of more power to produce lift and yet the bird’s ability to produce this power is less because there is far less oxygen in the thin atmosphere.

Argentavis magnificens Argentavis magnificens compared in size to Andean Condor and typical size woman.
Drawing by Nobu Tamura

Having established the fact that in today’s atmosphere 15 kg is about as heavy as a bird can be and still be capable of flying, let’s now investigate how it was possible for flying birds to be much larger than this during the Cenozoic era.

Six million years ago a giant bird known as the Argentavis Magnificens flew in the Andes Mountains of South America. While it is known that the Argentavis had a wingspan of seven meters, we will have to do some calculating to come up with a reasonable estimate of its mass. Because Argentavis is relate to the Andean Condor in that they are both New World vultures and they even flew in the same geological location, we can get a good estimate of the Argentavis’ mass by simply scaling up the mass of the Andean Condor. Multiplying the 14 kg mass of the Andean Condor by the cubed of the wingspans (7m / 3m) gives us a value of 180 kg for the estimated mass of Argentavis Magnificens.

If we insert the Argentavis’ wingspan and mass estimates into the flight equations while assuming no change in the atmosphere’s density we get the 0.43 power ratio value thus validating our gut feeling that such a large bird would not be capable of flying in today’s atmosphere. So six million years ago the atmosphere was thicker than what it is today, but then we wonder if it is possible to calculate a rough estimate of just how thick the atmosphere was at this time, and yes we can. We notice the similarities between Argentavis and the Andean Condor: they had extremely similar shapes and they even flew in the same geological location. If we assume that the Argentavis was soaring in the same way as the Andean Condor then it should need the same power ratio of 1.6. By matching the power ratios and then working backwards with our flight equations, we produce the estimate that six million years ago the density of Earth’s atmosphere was 17 kg/m3.

Flyer Air Density
(kg/m3)
Mass
(kg)
Wingspan
(m)
Speed for
least Power
(m/s)
Minimum Power
for Flight
(kW)
Available Power
(kW)
Power Ratio
Condor (Thin Atm.) 1.2 14 3.0 12 0.20 0.32 1.6
Argentavis (Thin Atm.) 1.2 180 7 18.6 3.95 1.7 0.43
Argentavis (Thicker Atm.) 17 180 7 4.9 1.06 1.7 1.6

Large Flightless Birds

There are so many questions about flightless birds. Why would any bird species ever give up its ability to fly? How did these large flightless birds arrive at these remote locations? Could the loss of flying ability have been forced upon these birds? Why have so many flightless birds gone extinct?

Ostrich The ostrich is the largest and heaviest living bird. It cannot fly. The ostrich avoids predators by outrunning them.
Elephant Bird The elephant bird existed on the islands of Madagascar and went extinct around 1100. It is often considered the world’s largest bird.
Giant Haasts Eagle Attacking Two Moa Drawing shows a Giant Haasts Eagle attacking two Moa. Both of these species were native to New Zealand and both went extinct around 1400 following the arrival of the Māori.
Drawing by John Megahan

The fact that so many species of flying birds evolved into flightless birds is testament to the dramatic changes that can occur when a species adapts to a new environment.

As always, the golden rule of most animals’ survival involves obtaining the necessary food to reach reproductive maturity while avoiding becoming the food for somebody else. Usually, flying provides a tremendous advantage in achieving both of these goals. Flight enables birds to travel great distances in search of food, whether through seasonal migrations or daily foraging. Furthermore, since most vertebrates cannot fly, flying allows birds to easily maintain a safe distance from potential predators. Therefore, if a bird species is going to give up its ability to fly, it needs to be in a location where there is a continuous source of food within walking distance, and where predators are absent or relatively easy to avoid. There are only a few locations around the world that fulfill these requirements.

Flightless Bird Mass (Kg) Extinction Date Island or Region
Stirton's Thunderbird 500 30,000 years ago Australia
Elephant Bird 650 1100 Madagascar
Moa 250 1400 New Zealand
Dodo 13 to 20 1600 Mauritius
Great Auk 5 1844 North Atlantic
Ostrich 130 Still Alive Africa
Emu 45 Still Alive Australia
Cassowary 60 Still Alive New Guinea
Rhea 40 Still Alive South American
Emperor Penguins 25 to 45 Still Alive Antarctica

When volcanic islands form hundreds of miles from any other land, they develop their own unique ecosystems based on which species are the first to discover them. Birds, capable of flying long distances, are often among the first arrivals. Frequently, these early birds find an abundance of food within easy walking distance and no predators. If this situation persists for dozens of generations, these birds may lose their ability to fly simply because they never have a need to do so.

Finding a remote island is not the only way that a bird might lose its ability to fly. Because the feathers on birds provide excellent insulation, large birds can survive in environments that are too cold for other vertebrates. By establishing themselves in these cold environments, they will have few, if any, predators. This solves half the problem of survival, but what about food? It's likely that the ancestral birds to penguins were species whose primary diet consisted of the smaller fish swimming in the nearby ocean. These birds gradually adapted to colder climates near the ocean so that there was plenty of food and their breeding grounds would be free of predators, and in the process they lost their ability to fly.

An open grassland known as a savanna is another environment where a bird species may evolve towards becoming flightless. For a bird that primarily consumes plants, roots, and seeds, there is little benefit in flying over a savanna, as the food is readily available on the ground, and the food sources are consistent for several miles in every direction. While there are predators in the savanna, this is not a significant concern if a flightless bird can outrun them. While the cheetah, gazelle, and a couple other species are faster than an ostrich in a half mile to mile long sprint, only a pronghorn has a chance of keeping up with an ostrich over longer distances. Apparently, the ostrich does not tire as quickly as mammals due to its superior respiratory system.

Fastest Land Animal

While a race horse can outrun an ostrich for the first mile of a race, after about a mile the race horse will be exhausted while the ostrich could continue on at nearly the same high speed for ten, twenty, or thirty more miles without tiring. An ostrich could finish a 26 mile marathon in about 45 to 50 minutes.

Most flightless birds are quite large, so much so that even if they possessed full-sized wings, they would still be incapable of flying. For these large flightless birds, the most plausible scenario is that their ancestral species discovered a location where food was abundant and predators were scarce, and then over time these birds grew larger and heavier from over consumption until flying became so difficult that they eventually gave up trying. While their increased size made flying impossible, it also endowed them with the ability to run fast enough to escape predators. The only exception to this 'grow larger' trend is the small kiwi bird, which has managed to survive by adapting to a nocturnal lifestyle.

Great Auks The great auk was a large flightless bird native to the North Atlantic. It went extinct on July 3, 1844 when fishermen killed the last confirmed pair of great auks.

All of the flightless birds, whether recently gone extinct or still alive today, evolved during the Cenozoic era. Throughout this era, the atmosphere transitioned from being extremely thick to the relatively thin atmosphere we have today. While it is tempting to believe that this diminishing thickness of the atmosphere — thus making it more difficult to fly — could have played a role in grounding these birds, it is difficult to say whether this had an impact on the creation of flightless birds. It is possible that these various species of birds lost their flying ability in less than a few thousand years. If so, in this short time the slight change in the thickness of the atmosphere would have been negligible. Nevertheless, the diminishing thickness of the Cenozoic atmosphere does explain why many of the flightless birds that existed millions of years ago were larger than the largest flightless birds that exist today.

Being grounded does not necessarily mean that a species of bird is destined for extinction, but that is the usual outcome. The record of these extinctions leads to some interesting observations. Most of the bird species that were flightless on islands or isolated land masses survived and thrived because they were isolated from predators. However, this peaceful existence would come to an end the moment a predator, usually human, reached their isolated location. Sadly, it is easy to track the expansion of mankind with the extinction of each of these species of flightless birds.

Summary

There is overwhelming fossil evidence showing that many flying birds of the Cretaceous period were much larger than today's largest flying birds. However, most people are unaware of these Cretaceous birds because paleontologists mislabel the larger birds as being feathered dinosaurs. This mislabeling stems from paleontologists' reluctance to acknowledge the existence of these large birds because this challenges their beliefs about the Mesozoic era. These oversized birds, along with exceptionally large dinosaurs and flying pterosaurs, suggest significant differences in the Mesozoic environment that enabled terrestrial animals to grow exceptionally large. Admitting this mistake would advance science, but it probably would not benefit the careers of these paleontologists. Consequently, paleontologists are doing everything within their power to deny the fact that there were oversized flying birds during the Mesozoic era.

Archaeopteryx Archaeopteryx

The discovery of fossils of oversized flying birds is a source of cognitive dissonance for paleontologists. This conflict was partially resolved, at least in their minds, when they began labeling these large Cretaceous birds as non-flying feathered dinosaurs. However, this narrative didn't actually resolve anything since it left numerous unanswered questions, such as why these feathered dinosaurs had wings or why the feathers of these wings were asymmetric if they were not being used for flying. These incongruities should have ended their hypothesis of feathered dinosaurs. However instead of backing down, these paleontologists doubled down on their claim with several more highly questionable narratives. One of their false claims is that birds and feathered dinosaurs evolved from theropod dinosaurs, even though Archaeopteryx and other bird species had already evolved tens of millions of years earlier in the late Jurassic period. According to paleontologists, some theropod dinosaurs grew wings and evolved into birds by jumping up and down; it is a claim that is at odds with how evolution works. In the process of reject anything that conflicts with their beliefs, these paleontologists show an astonishing disregard for facts, evidence, reasoning, or fundamental scientific principles.

Earnest Rutherford is attributed to have said “all of science is either physics or stamp collecting” and while this remark is overly harsh to most science disciplines it is spot-on in describing paleontology. These glorified stamp collectors are good at digging up and displaying fossils in museums, but it’s a cringeworthy train wreck nearly every time they give their almost always misleading scientific opinions. In the process of denying the existence of the exceptionally large flying birds of the Cretaceous period, paleontologists have once again missed out on making some of the most significant scientific discoveries of our times.

There were at least three families of flying birds during the Cretaceous period of the Mesozoic era: Troodontids, Dromaeosaurs, and Avialae. The Troodontids and Dromaeosaurs were similar in that they had relatively small wings, a mouth full of teeth instead of a beak, and a straight bony tail covered with feathers that they used as a rudder to direct their flights. The Dromaeosaurs were deadly predators who preyed on small dinosaurs and possibly even some medium-sized dinosaurs. The Avialae family of birds may look more familiar to us since it is the only family of birds that survived the K-T mass extinction, and so they are still with us today.

“A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.” Max Planck

Society waits for paleontologists to either figure out these scientific paradoxes or admit that they are wrong, but unfortunately, neither of these outcomes is ever going to happen. Instead, with every new bit of evidence indicating that something was substantially different about the Mesozoic era, paleontologists will only become more extreme in their denial of reality. They started by claiming that there is nothing odd about terrestrial animals, the dinosaurs, being so incredibly large. Then they went on to claim that there is nothing odd about pterosaurs, giant reptiles flying about, when in fact both physics-based flight equations and experimental trials strongly showed otherwise. Now, these paleontologists are denying the previous existence of oversized flying birds by telling the public that these are not birds but instead feathered dinosaurs. Furthermore, in the latest development paleontologists are doubling down on their claim that Cretaceous birds are feathered dinosaurs by making the creepy Orwellian 'war is peace'-like assertion that birds are dinosaurs. The paleontology community’s continuous gaslighting — this twisting of reality — has damaged both the credibility of science and the collective sanity of our modern society.


External Links / References

Early Birds


Taxonomy & Phylogeny


Birds Are Not Dinosaurs


Feathers and Wing Design


Endothermic and Ectothermic (Warm and Cold Blooded) Vertebrates

Enzymes and Metabolism


Dromaeosaurids: Cretaceous Raptors

Troodontidae

Animals with Beaks



Phony 'Feathered Dinosaurs' That Have No Wings Or Feathers


Bird Respiratory


Physics of Flying Applied to Birds


Largest and Heaviest Flying Birds


Geological Ages


Largest Flying Birds of The Cenozoic Era


Fastest Land Animal


Flightless Birds


Gaslighting, Narcissism, and Propaganda