Tuesday, March 28, 2017

"Naked Birds"; how people see and value avian life



I've been involved in one way or another with birds my whole life. Birdwatching, education, conservation projects, bird sanctuary manager, travel; you name it, I’ve had my hands in it.

Today, my interests in birds lie mainly in their origin and evolution. But this hasn’t stopped me from keeping abreast of present-day issues related to birds.

So, when I hear people out in the field talk about birds, or write questionable comments on the internet with regards to them, my ears quickly prick up.

One of those comments was the inspiration for today’s blog posting.

Recently, a series of photos were posted to Facebook showing a European Starling being pinned down under the talons of a Sharp-shinned Hawk. They were grisly images of a struggling starling being slowly eaten alive by a hawk. Before posting, the photographer was kind enough to warn people about the graphic nature of the images, but also went out of his way to assure people that it was O.K for this to be happening, since the starling is an invasive species and needs to be controlled. In many minds, the less we have of this aggressive bird, the better off we are.

 
European Starling
Photo Credit: Paul Cianfaglione

My own reaction to the Facebook post was pretty much middle-of-the-road. I fully understood the photographers position, as well as anyone else who may have felt saddened over the starling’s loss. People value certain birds over others for various reasons. Native versus introduced, beauty over ordinary, rare as opposed to commonplace.

As I just mentioned, putting a price tag on a bird’s head is highly subjective. But what if I told you that I think every bird is deeply the same, would you be surprised? Could you ever accept the fact that the starling is just as valuable to our world as a Scarlet Tanager?? Let me then ask you this, have you ever admired a bird for something other than its flamboyant plumage? By concentrating on appearance alone, we sometimes lose sight of the fundamental characteristics of birds.

Before I attempt to open your mind to these seemingly ridiculous claims, let’s put ourselves into a hypothetical situation. You are in a Natural History Museum, in front of a display case. In it are two birds perched on a faux branch, one is a European Starling, the other is our Scarlet Tanager. At once, your eyes gravitate toward the more esthetically pleasing tanager. Its brilliant red plumage, combined with black wings and bill, jump out and pull you in for a closer look. You read its placard and discover it’s a neo-tropical migrant, and nests nearby at a favorite state park. The tanager draws a momentary pause of admiration and awe. 


Scarlet Tanager
Photo Credit: Wikipedia
The starling placard on the other hand reads; set loose in New York's Central Park in the early 1890s, commonly found in cities, aggressive toward native birds, often displacing them from natural nest cavities. Compared to the tanager, not a flattering description. No wonder birders often refer to starlings as “feathered rats”.

But what if we take that same situation, turn it around, and remove each and every feather from the two birds. No placards. How would you react? Do your eyes now drift over to the starling’s long yellow bill, heavily armored feet and larger size? Does its size and adornments in any way distract you from the unimpressive featherless tanager?  

Bird Mummy
Scarlet Tanager
Photo Credit: Paul Cianfaglione
In a weird way, the two birds now look somewhat similar. No more distinctively colored plumage, no defining field marks, missing tail feathers and truly bald head. Gone are the pre-misconceptions.

If this type of “naked” bird exhibit ever did come to fruition, there would certainly be some backlash from the general public.

In fact, there were some strong views recently posted to the internet when a Twitter user dug up and decided to share “naked” Barn Owl images with the rest of the world.

Featherless Barn Owl
Photo Credit:http://sarcasmsociety.com

"I just googled what owls look like without feathers and I am severely shook," a person wrote.

Another was quoted as saying; we're sure she was 'shook,' because as it turns out, beneath those lovely feathers lies a demon hell-bird with black, soulless eyes that can show you how you'll die years before it actually happens (end quote).

It’s actually very easy to forgive people for such strong resentment, bird lovers are not use to seeing their favorite wood warbler plucked clean like a supermarket chicken.

But if we take a more scientific approach to these shocking images, we may start to see and value birds, even the more deplorable ones, a bit more differently.

For this, I’d like to turn to one of my favorite books by Gary Kaiser called; The Inner Bird, Anatomy and Evolution. In it, Kaiser nicely describes what we should be thinking about if confronted with an image, or display case filled with “naked” birds. Remember, the evolutionary success of birds comes down to its bodies highly centralized structure. Kaiser writes;

Although the outer cloak of feathers is an important part of the animal, all living functions are the responsibility of the inner bird. The inner bird is a strange goblin-like creature that manipulates its appendages by pulling on long tendons just as the human operator within the muppet Big Bird pulls on a network of internal wires and strings. The puppeteer gets to enjoy an independent existence when he sheds his casing at the end of the workday, but the plumage of the inner bird is part of an integrated whole animal.

Suggesting that we should look at the inner bird as a puppeteer behind a screen of feathers may seem an extreme point of view but it does not overstate the case. The muppet analogy extends beyond the feathered suit to the bird’s basic design. In mammals, the limbs are moved by muscles that are distributed over the whole skeleton so that they lie close to the joints they move. There is ample additional room on the limbs for generous blood supplies and even stores of fat.

In birds, the muscles are remote from the joints and the limbs often appear thin and sticklike. Even the fleshier wings are little more than nubs, with no more tissue than is needed to carry and manipulate the feathers during flight. The limbs are not one of the places where a bird can store its reserves of fat, and they offer little space for blood vessels or nerves. Because the muscles are collected together in a dense mass and anchored as close as possible to the body’s core, they often lie far from their point of action and depend on long tendons to carry out their responsibilities. Tendons from muscles along the breastbone move the wing, while others along the backbone move the tail. Even the muscles that curl the toes are mounted high on the leg.

Though we can’t see the tendons, blood vessels and nerves under the skin, we can certainly see the centralized structure that characterizes the inner-bird strategy for flight.

For those who seek a greater meaning to a bird’s existence than just field marks and conservation issues, featherless images may be what is finally needed to strike a chord in one’s mind.

 
Featherless Lovebird
Photo Credit:https://www.buzzfeed.com/laurenstrapagiel/naked-bird
Stripped of feathers and pre-misconceptions, and back on a level playing field, the European Starling, Brown-headed Cowbird and Mute Swan are no longer invasive species, parasites or eye sores, but are instead viewed as 150 million-year-old evolutionary success stories.   

The scientific consensus at this time is that birds are a group of theropod dinosaurs that evolved during the Mesozoic Era. Because beneath the feathers, beneath the skin, birds share many unique skeletal features with dinosaurs including the neck, pubis, wrist (semi-lunate carpal), arm and pectoral girdle, shoulder blade, clavicle, and breast bone. Non-avian dinosaurs were even feathered.

Finally, I would like to say a few words about invasive species. I do not advocate at all the introduction of exotic animals into non-native habitats. In a world where forests, fields and wetlands are being lost at an uncontrollable rate, these exotic animals only make life tougher for native birds and conservationists alike. The pre-misconceptions I alluded to about the European Starling was not to ignore the problems they cause, but to simply recognize the bird for what it is; a survivor in life’s race.

Wednesday, March 15, 2017

Fossil Birds of China, A Pictorial Book Review



Have you ever known about, or wanted a particular book, but never got around to buying it? It just sits there in the back of your mind, returning again and again for serious consideration, until you finally purchase it some years later. That’s exactly how I acquired my latest out-of-print book called, Fossil Birds of China.

Fossil Birds of China, Book
Photo Credit: Paul Cianfaglione
Published in 2003 in both Chinese and English, Chief Compiler Hou Lianhai puts together a well-organized look (234 pages) at the early stages of fossil bird discovery in China. It’s a fairly large paperback book measuring in at 280x210 mm, made of high quality, thick paper stock.

The contents of this book include reconstructions of 53 fossil birds, classified as Archaeornithes, Enantiornithes and Ornithurae. Each one is represented in full color by its original fossil holotype, skeletal drawing and life painting.

 
Eoenantiornis buhleri
Fossil Birds of China
Photo Credit: Paul Cianfaglione

In addition to the fossils and incredible paleoart, the book provides pertinent information to go along with its discovery. This includes its scientific name, etymology, locality, preservation and diagnosis.

The diagnosis was easy to understand and interesting to me, something you don’t get in every bird evolution book. In contrast to long-worded scientific papers, the Fossil Birds of China provides a concise and welcome account of the most important and obvious skeletal features. For instance, the diagnosis for Sinornis santensis reads like this; Medium sized bird. Rostrum short. Teeth and pelvis similar to that of Archaeopteryx. Gastralia present. Second digit twice as wide as first digit. Digit 1 reduced. Small and curved claws present on digits 1 and 2. Tarsometatarsus fused proximally. Pygostyle present.

 
Sinornis santensis
Fossil Birds of China
Photo Credit: Paul Cianfaglione
However, not all information in this book is correct. The description of Confuciusornis dui states that its teeth on the lower jaw differ from that of Confuciusornis sanctus. Did Confuciusornis sanctus have teeth? Of course not, and neither did Confuciusornis dui. But C. dui did differ in smaller adult size and had an upturned bill tip (mentioned), indicative of a unique diet.

Confuciusornis sanctus
Fossil Birds of China
Photo Credit: Paul Cianfaglione
It’s easy to forgive such inaccuracies with past fossil interpretations. Even today, I’m currently reading a paper titled, Taxonomical Reappraisal of Cathayornithidae (Aves: Enantiornithes) Min Wang and Di Liu (2015). In the reappraisal, researchers point out that the unfused pygostyle originally described in the holotype of Cathayornis, was instead its partial left femur.

 
Cathayornis yandica
Fossil Birds of China
Photo Credit: Paul Cianfaglione
The artistic reconstruction of early birds in Fossil Birds of China is second-to-none. Both Anderson Yang and Zeng Xiaolian help bring the fossils back to life in colorful, yet believable and in tastefully done settings. Despite the limited amount of information available, and their lack of paleontological training, the artists did an extraordinary job painting the birds and environment as it existed 130 million-years-ago.

Imaginative at times, researchers and artists place Jibeinia luanhera, with its Blue Jay colored tail, high in a tree nest, despite any evidence of this occurring during the Mesozoic.


Jibeinia luanhera
Fossil Birds of China
Photo Credit: Paul Cianfaglione
Like Jibeinia’s tail, there were other ancient birds with colors reminiscent of today’s extant species. Confuciusornis chuonzhous was a dead ringer for North Americas Greater Roadrunner, while Longipteryx chaoyangensis was identical to the Eurasian (Common) Kingfisher.   

 
Confuciusornis chuonzhous
Fossil Birds of China
Photo Credit: Paul Cianfaglione
The Fossil Birds of China also has a wonderful section on Paleogene bird fossils. This was the first time I realized that extinct giant bird Diatrymiformes were found in Asia, plus a host of the other earliest relatives of today’s birds. Many of the species are represented and identified by a single bone.

I highly recommend this book on two accounts. First, found in this book are the clear, close-up images of fossil holotypes, which are sometimes hard to come by, even on the internet. Except for Luis Chiappe’s book Glorified Dinosaurs (2009) and Birds of Stone (2016), most fossil images are unsatisfactorily set on averaged sized pages. This was a nice feature of the book.

The second is the paleoart. I’m not saying that all of the paintings are accurate portrayals of the species, but they do let one’s imagination run wild, giving the reader an opportunity to pass their own judgements about how ancient birds looked and lived.  

 
Boluochia zhengi
Fossil Birds of China
Photo Credit: Paul Cianfaglione
The Fossil Birds of China is a nostalgic look at the beginnings, of what has turned out to be, a treasure trove of continued scientific discovery. If you can find it, buy it!


Largirostrornis sexdentornis
Fossil Birds of China
Photo Credit: Paul Cianfaglione

Thursday, March 9, 2017

Avian Sesamoid Bones

The identification and analysis of avian remains from local sites provides me with a variety of useful information. In my quest to learn more about the origin of birds, a hands-on study of the internal workings of a bird, in my opinion, is an essential first step. Without this basic knowledge of the inner bird, it would be nearly impossible to navigate your way through the technical jargon of online papers or books discussing the latest of fossil finds.

But acquiring a bird skeleton is no easy task. Finding a dead bird along a roadway can sometimes take months. When I do locate a specimen, I like to use a method called maceration to clean a bird. With maceration, bones are cleaned of tissue by bacteria; it is a rotting process. I place the bird in water (outside!) in a Tupperware container with holes drilled into the cover. Every few days, the remains are strained through a metal colander, and the water replaced. Warm-weather maceration is optimal for the bacteria to live, digest and multiply.

My final product is spread out, dried and placed into a riker-box for future comparative studies.


Those that are complete skeletal specimens often reveal puzzling bones, bones that are not typically depicted in ornithology, or even osteology guides. Some of these odd bones were eventually identified as hyoid apparatuses and unusually shaped phalanxes. But the most frustrating of bones (to secure and I.D.) are the ones that look like grains of sand or round nodules. These are called sesamoid bones.


Yellow Warbler Hyoid Apparatus
Photo Credit: Paul Cianfaglione
In anatomy, a sesamoid bone is a bone embedded within a tendon or a muscle. It is derived from the Latin word "sesamum" (sesame seed), due to the small size of most sesamoids. Often, these bones form in response to strain. Sesamoids act like pulleys, providing a smooth surface for tendons to slide over, increasing the tendon's ability to transmit muscular forces (Source: Wikipedia).

Although they are a special structure that is technically independent of the main skeleton, sesamoids begin their development much like regular bony tissue. Specialized bone-generating cells gather at the appropriate point and are nurtured by a locally enhanced blood supply. After initial mineralization, there is a period of remodeling so that the new bone can meet any special role it might play in the movement of neighboring bones (Source: Kaiser, G. 2007. The Inner Bird, Anatomy and Evolution).

The patella, better known as the kneecap, is probably the most familiar of sesamoid bones. The two (probable) American Crow patella, pictured below, were identified by using comparative images on the internet. However, locating other information regarding avian sesamoid bones is what I would describe as challenging at best.  

 
American Crow Patella
Photo Credit: Paul Cianfaglione

Lesser known sesamoid bones also appear in tendons some distance away from joints. Albatrosses have an interesting sesamoid in the wing. It is a rather long bone that runs across the tendons within the sheet of skin (propatagium) that extends from the shoulder to the wrist. The spar of bone helps keep the surface of the patagium stiff and smooth so that flight remains efficient, just as similar structures help to smooth a boat’s sail.

Another type of bony growth develops in the ligaments that lie along the backbone. These bones take the form of very long, flexible splints that lie parallel to the tendons. They help restrain the flexibility of the back without making it completely rigid. Similar supporting structures are widespread in the long tails and long necks of dinosaurs (Source: Kaiser, G. 2007. The Inner Bird, Anatomy and Evolution).   

 
Red-tailed Hawk vertebrae with flexible splints
Photo Credit: Paul Cianfaglione

The wrist is another area within the bird that seems to require a specialized sesamoid bone. In a guide called Avian Osteology (Glibert, M. 1996), two small peculiar bones, the scapholunar and the cuneiform, are clearly depicted in the right-wing elements of a duck species. In books about the origin of birds, paleontologists often refer to the wrist bones as the radiale and ulnare. Embryologists use slightly different terms. But are any of these wrist bones really sesamoids, and why so many confusing names?

Fortunately, I was able to locate a wonderful paper in PLOS Biology titled New Developmental Evidence Clarifies the Evolution of Wrist Bones in the Dinosaur–Bird Transition, where researchers Alexander O. Vargas and colleagues combine both embryological and fossil research on wrist bones to provide a more integrated view of their evolution and a proposed revised nomenclature.

I have included a link below to the full study as well as a few paragraphs and images. However, I encourage you to read the complete article, where researchers
have documented the loss and fusing of wrist bones, and the incredible evidence of a bone being re-acquired (a rare evolutionary reversal) during the course of this transition.   


Abstract

From early dinosaurs with as many as nine wrist bones, modern birds evolved to develop only four ossifications. Their identity is uncertain, with different labels used in palaeontology and developmental biology. We examined embryos of several species and studied chicken embryos in detail through a new technique allowing whole-mount immunofluorescence of the embryonic cartilaginous skeleton. Beyond previous controversy, we establish that the proximal–anterior ossification develops from a composite radiale+intermedium cartilage, consistent with fusion of radiale and intermedium observed in some theropod dinosaurs. Despite previous claims that the development of the distal–anterior ossification does not support the dinosaur–bird link, we found its embryonic precursor shows two distinct regions of both collagen type II and collagen type IX expression, resembling the composite semilunate bone of bird-like dinosaurs (distal carpal 1+distal carpal 2). The distal–posterior ossification develops from a cartilage referred to as “element x,” but its position corresponds to distal carpal 3. The proximal–posterior ossification is perhaps most controversial: It is labelled as the ulnare in palaeontology, but we confirm the embryonic ulnare is lost during development. Re-examination of the fossil evidence reveals the ulnare was actually absent in bird-like dinosaurs. We confirm the proximal–posterior bone is a pisiform in terms of embryonic position and its development as a sesamoid associated to a tendon. However, the pisiform is absent in bird-like dinosaurs, which are known from several articulated specimens. The combined data provide compelling evidence of a remarkable evolutionary reversal: A large, ossified pisiform re-evolved in the lineage leading to birds, after a period in which it was either absent, nonossified, or very small, consistently escaping fossil preservation. The bird wrist provides a modern example of how developmental and paleontological data illuminate each other. Based on all available data, we introduce a new nomenclature for bird wrist ossifications.

 
http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001957

Author Summary

When birds diverged from nonavian dinosaurs, one of the key adaptations for flight involved a remodelling of the bones of the wrist. However, the correspondence between bird and dinosaur wrist bones is controversial. To identify the bones in the bird wrist, data can be drawn from two radically different sources: (1) embryology and (2) the fossil record of the dinosaur–bird transition. Currently, identifications are uncertain, but new developmental data can help resolve apparent conflicts. The modern bird wrist comprises four ossifications, arranged roughly in a square with its sides running proximal/distal and anterior/posterior. Our study integrates developmental and paleontological data and clarifies the relationship between each of these four ossifications and those found in nonavian dinosaurs. This integrative approach resolves previous disparities that have challenged the support for the dinosaur–bird link and reveals previously undetected processes, including loss, fusion, and in one case, re-evolution of a transiently lost bone.

 
http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001957

The labelling of the ulnare reveals an apparent contradiction between palaeontology and developmental biology. Most paleontological papers identify the ulnare as present in the bird wrist. Previous embryological studies, however, described the embryonic ulnare was lost and “replaced” by a neomorphic “element x” or pseudoulnare. This complex process was not well documented, allowing for skepticism. According to our developmental data, “element x” is actually dc3, which becomes the posterior–distal ossification: Whether it is a replacement of the ulnare is debatable (see above sections, Figures 6 and 7). However, we fully confirm that the embryonic ulnare is lost in avian development. This provides a strong reason to reexamine the evidence in a broad set of fossil taxa for labelling this bone as being present in birds. Indeed, except in the earliest lineages of theropod dinosaurs and possibly the Ornithomimosauria, there is no evidence of an ulnare (brown in Figure 9). Importantly, there is no ulnare in the most bird-like dinosaurs (Oviraptorosauria, Dromaeosauridae, Troodontidae, which are known from several well-preserved, articulated specimens (Figure 9). In many theropods, the ulnare was mistakenly considered present, having been confused with other elements, such as the intermedium [56], distal carpal 2, and the posterior–distal dc3, which in modern adult birds fuses to the carpometacarpus. In early dinosaurs, some bird-like dinosaurs, and Mesozoic birds, dc3 is observable as a separate bone (blue in Figure 9) that has been variably labelled as the ulnare, “element x”], or dc3.

The proximal–posterior bone of the bird wrist (red in Figure 9) poses the greatest challenge to interdisciplinary integration. Paleontological data would seemingly exclude the hypothesis that it is a pisiform, because it provides evidence for its loss in the lineage leading to birds. Except for early theropods, and possibly the Ornithomimosauria, the pisiform is absent. The most bird-like dinosaurs show the presence only of the semilunate, the scapholunare (often labelled “radiale”), and occasional preservation of dc3, but no pisiform (Figure 9). Thus, if present, the pisiform must have been at least very small or nonossified, consistently escaping preservation. Developmental data, in turn, provide compelling evidence that the large posterior–proximal ossification of modern birds (often preserved in their fossil relatives) is in fact a pisiform in terms of its embryological position, its sesamoid nature, and its muscular connectivity. An integrative explanation for both developmental and paleontological evidence is that a large, ossified pisiform was reacquired in the evolution of birds, after a period in which it was at least strongly reduced (Figure 9). Its evolutionary reappearance as a large, posteriorly displaced proximal carpal occurred early in the evolution of birds, consistently observed in Mesozoic taxa such as the cretaceous long-tailed bird Shenzhouraptor sinensis, the basal pygostylians Sapeornis chaoyangensis, and Confuciusornis sanctus, personal observation). A bone in appropriate position has been reported in the Eichstätt specimen of Archaeopteryx, but not other specimens. In other Mesozoic taxa closer to modern birds (Ornithothoraces, this bone became v-shaped, like the pisiform of modern birds.

The ulnare, now called the pisiform, is indeed v-shaped in both modern birds and in the 120 million-year-old Enantiornithean bird fossil pictured here.

 
Northern Flicker Pisiform
Sesamoid Bone
Photo Credit: Paul Cianfaglione
Enantiornithean Bird Fossil Wrist
Photo Credit: Paul Cianfaglione

In accordance with the articles findings, we are now able to look at a modern bird’s wrist and realize that the two bones are really four bones, with distal carpal 2, and the posterior–distal dc3 having fused itself to the carpometacarpus.

 
Modern Bird Wrist Bones
Northern Flicker
Photo Credit: Paul Cianfaglione

The Enantiornithean fossil wrist appears to show four separate bones. The pisiform, which gives the bird wrist its bent shape and outward flexibility, re-evolves in the lineage leading to birds, after its apparent absence in the fossil record. If my identification of the pisiform on the fossil is correct, this would be one very old sesamoid bone!

This article on the identity and evolution of bird wrist bones brings to mind a couple of specific events in the history of bird origins.

The first, Heilmann and the thecodont hypothesis;

A turning point came in the early twentieth century with the writings of Gerhard Heilmann of Denmark. An artist by trade, Heilmann had a scholarly interest in birds and from 1913 to 1916, expanding on earlier work by Othenio Abel, published the results of his research in several parts, dealing with the anatomy, embryology, behavior, paleontology, and evolution of birds. His work, originally written in Danish as Vor Nuvaerende Viden om Fuglenes Afstamning, was compiled, translated into English, and published in 1926 as The Origin of Birds.

Like Huxley, Heilmann compared Archaeopteryx and other birds to an exhaustive list of prehistoric reptiles, and also came to the conclusion that theropod dinosaurs like Compsognathus were the most similar. However, Heilmann noted that birds had clavicles (collar bones) fused to form a bone called the furcula ("wishbone"), and while clavicles were known in more primitive reptiles, they had not yet been recognized in dinosaurs. Since he was a firm believer in Dollo's law, which states that evolution is not reversible, Heilmann could not accept that clavicles were lost in dinosaurs and re-evolved in birds. He was therefore forced to rule out dinosaurs as bird ancestors and ascribe all of their similarities to convergent evolution. Heilmann stated that bird ancestors would instead be found among the more primitive "thecodont" grade of reptiles. Heilmann's extremely thorough approach ensured that his book became a classic in the field, and its conclusions on bird origins, as with most other topics, were accepted by nearly all evolutionary biologists for the next four decades (Source; Wikipedia/Origin of Birds).

The second historical event, John Ostrom, Deinonychus and the dinosaur renaissance.

The tide began to turn against the 'thecodont' hypothesis after the 1964 discovery of a new theropod dinosaur in Montana. In 1969, this dinosaur was described and named Deinonychus by John Ostrom of Yale University. The next year, Ostrom redescribed a specimen of Pterodactylus in the Dutch Teyler Museum as another skeleton of Archaeopteryx. The specimen consisted mainly of a single wing and its description made Ostrom aware of the similarities between the wrists of Archaeopteryx and Deinonychus.

 
Image Credit: Wikipedia

Ostrom's recognition of the dinosaurian ancestry of birds, along with other new ideas about dinosaur metabolism, activity levels, and parental care, began what is known as the dinosaur renaissance, which began in the 1970s and continues to this day (Source; Wikipedia/Origin of Birds).