Monday, February 29, 2016

If it looks like an albatross and flies like an albatross, then it probably is a duck?



     The last time that I could remember purchasing a new North America field guide was way back in 2000, when the much anticipated Sibley Guide to Birds came out. Since then, the urge to add more field guides to my library has waned, replaced instead by such topics as bird origins and ornithology texts.  

     But when I took the kids to a Barnes & Noble the other day, I ended up doing the unthinkable; I purchased a new field guide to the birds of North America. No, I didn’t need a new guide to help me with identification, or a book which had better range maps. What I did need in this new field guide was a list of North American bird species in the most up-to-date, and correct taxonomic order. 

     In the years following the first Sibley publication, birdwatchers have had to contend with a number of changes to the AOU Checklist of North American Birds. No longer were loons and grebes found on the opening pages of field guides. They were replaced in 2003 by the Anseriformes and Galliformes. In 2006, a new family called Stercorariidae was established, containing the skuas and jaegers, and then moved to follow the Laridae (preceding Alcidae). In 2012, the Falconiformes (American Kestrel, Merlin, Gyrfalcon and Peregrine Falcon) were relocated to a position between the woodpeckers and flycatchers. Plus a myriad of other scientific name changes, lumps and splits.

     Many of these changes can be directly attributed to the development of new technologies. In 1952, the discovery of the genetic material DNA shifted the evolutionary study of birds from behavior and physiology, down to the methods that occur at the molecular level.   

     Best known of these studies is the Sibley-Ahlquist bird taxonomy, conducted in the late 1970’s through the 1980’s. Their technique is known as DNA-DNA hybridization. In his book, The Inner Bird, Anatomy and Evolution, Gary Kaiser fully describes this technique;

     {DNA consists of two complementary strands that separate (melt) at a specific temperature when the molecule is gently heated. If you mix the separated strands with a similarly treated sample from another species, the strands re-bond at specific points in an attempt to reconstruct their original complementary nucleotide pairs. The new double strand will then melt at a temperature because the re-bonding cannot be perfect between strands from different species. The greater the genetic similarity between the two samples, the greater the frequency of bonding. Increased levels of bonding create a more stable molecule, which melts at a higher temperature. DNA from distantly related birds melts at a lower temperature because there is less bonding}.   

     In 1966, Willi Hennig proposed another solution to the problems plaguing traditional taxonomy, he called his approach phylogenetic systematics, otherwise known as cladistics. Cladistics is defined as; {an approach to biological classification in which organisms are categorized based on shared derived characteristics that can be traced to a group’s most recent common ancestor and are not present in more distant ancestors}.

     Paleontologist have so far had the most success with cladistics, using the method to set out the various diagnostic features of ancient birdlife. The willingness to work and increase the number of osteological characters in their studies have enabled researchers to show strong support for their results.

     As a collector of fossil bird bones, I often seek out these morphological studies as a way to bring credibility to an acquisition and to further my knowledge of a particular species. My latest acquisition was that of a single bone, a tarsometatarsus of a purported pseudo-toothed bird from Morocco.

Pseudo-toothed Bird Tarsometatarsus
Photo Credit: Paul Cianfaglione

Could I dig up (no pun intended here) some credible information on this rare fossil bone?

     Pseudo-toothed birds (Odontopterygiformes) are an extinct group of very large seabirds with massive tooth-like spikes along their bills. They lived between 58 and 2.5 million years ago and are known to have had a worldwide distribution. At first glance, pseudo-toothed birds look very much like a giant albatross with a saw-toothed bill.
Image property of Estelle Bourdon

The tooth-like protrusions were hollow outgrowths of the maxilla and mandible, lacking all of the characteristic tooth tissues. Since the protrusions were hollow and easily broken off, this seabird would have likely specialized in soft-bodied prey items like squid. 

Pseudo-toothed Bird maxilla
Photo Credit: Paul Cianfaglione
Pseudo-toothed Bird maxilla
Photo Credit: Paul Cianfaglione
  

     The skeleton of a pseudo-toothed bird was highly pneumatized, with extended wing bones. Wingspans of these birds are estimated to be close to 6 meters long, making them one of the largest flying birds to ever have lived.

     Information concerning my fossil was found in the book, “Living Dinosaurs, The Evolutionary History of Modern Birds”. A chapter titled “The Pseudo-toothed Birds and their Bearing on the Early Evolution of Modern Bird’s by Estelle Bourdon (page 209-234) provided not only excellent text, but a helpful comparative image of the bone in question. However, since my fossil tarsometatarsus is missing half of its proximal end and there is damage to the trochlea of the 4th digit (cracked and pushed against trochlea metatarsi 3), there may not be enough of the key characteristics present to make a positive identification.  

     Bourdon’s examination of available pseudo-toothed bird material has concluded that there are two recognized morphotypes; Dasornis and Pelagornis/Osteodontornis. A couple interesting features distinguish the two pseudo-toothed forms. Peculiarities of the humerus of Pelagornis/Osteodontornis likely prevented this morphotype to sustain flapping flight, which had them relying almost entirely on winds to provide lift. It also had shorter and stouter legs and was possibly clumsy on land. The morphology of the humerus in Dasornis allowed the bird to use some level of flapping fight.

     The picture below is a comparison photo of the right tarsometatarsi in dorsal view of (from left to right), (E) Pelagornis/Osteodontornis, (F) Dasornis, and my unidentified left tarsometatarsi from Morocco (fig.8.2, pg.211).


The scale bar between E and F equals 10mm, making the pictured fossils roughly 100mm long. The unidentified Moroccan fossil measures approximately 90mm. Note the stoutness of E and the side-by-side similarities in structure of Dasornis and the fossil.

     My second photo comparison is the distal ends of the right tarsometatarsi in plantar view of Dasornis and the unidentified Moroccan fossil (pg. 216).


Bourdon’s only mention of the tarsometatarsus in the chapter describes character 71 in her phylogenetic analysis; {plantar side of trochlea metatarsi III prominent, elongated with pointed extremity, slightly oblique; foramen vasculare distale in low position with a recessed opening}. Due to the fragile condition of the fossil, the bone was stabilized with an adhesive to avoid further damage. The matrix covering the vasculare distale could not be removed. The plantar side of trochlea metatarsi III (Moroccan bone) exhibited a pointed extremity and was slightly oblique.

     So is this fossil tarsometatarsus from the pseudo-toothed bird Dasornis? Based on its similar size, similar structure and similar characters on the plantar side of trochlea metatarsi III, I would like to think it’s possible.

Image Property of Researchgate.com


     Bourdons analysis in 2005 comprised of 21 taxa and 128 osteological characters. Her phylogenetic study, including part of the pseudo-toothed birds from the Paleogene phosphates of Morocco, has shown that the pseudo-toothed birds are sister to the Anseriformes (Boudon 2005).


Their structural appearance to the albatrosses is classic case of convergent evolution! Interestingly, a recent study of the brain and endocranium of pseudo-toothed birds also supports the close relationship with ducks (Milner and Walsh, 2009).

     Another extinct bird with pseudo-toothed serrations on their bill was called the moa-nalo. This goose-like duck from the Hawaiian Islands went extinct soon after the arrival of Polynesian settlers. Some moa-nalo fossils have been found to contain traces of mitochondrial DNA which were compared to living duck species (Wikipedia).  
Image Property of David Eickhoff

     Paleontologists have made great strides sorting out the relationships of extinct birds, using little more than osteological evidence. Conversely, our understanding of the evolutionary history of today’s living birds has been a bit more problematic. Although past taxonomists have always recognized morphological differences between species, such as Old World and New World vultures, the amount of time and work needed to create a change was never fully acted upon.  

     Fortunately, todays technologies are finding new ways to approach classification difficulties. Whether it be biomolecular genetics or cladistics, computers have now made it easier and faster for researchers to obtain results from their phylogenetic studies. This will surely create new breakthroughs in avian evolution and classification. In the future, it may be necessary to update a field guide every three years, rather than the sixteen it took me to become current. Or as technology races ahead, the hard copy guide may go the way of the pseudo-toothed bird and moa-nalo. This would certainly be a sad day.

Wednesday, February 17, 2016

Birds with false teeth


     It’s three below zero on a clear February morning. A warm discharge from a factory pipe creates open water in an otherwise frozen Connecticut River. As the steam rises, six Common Merganser (Mergus merganser) come into view, diving and hunting in this areas only reliable fishing-hole. 

     Within moments, a drake slowly emerges, hauling an oversized fish to the water’s surface. The prey item struggles desperately to free itself from the mergansers grip, still the bird magically holds on. In one quick motion, the merganser lifts the fish vertically into the air, and swallows it whole.

     Also known as the sawbill, the Common Merganser is an expert pursuit predator with a penchant for fish. Its slender, serrated bill is perfectly designed for grasping slippery prey and holding on. The backward pointing serrations of the rhamphotheca (horny sheath of keratin that covers the bill) extends back from the base of the bill to the hooked tip. Interestingly, mergansers also have serrated bony edges on the maxilla that correspond with the rhamphotheca serrations.
Image Property of Jaime Headden
"Bite Stuff" Blog

     But are the serrations on bird bills only used for catching fish? The answer to this question is a surprising no!

     A couple years ago, I had the opportunity to tour the bird skin collection at the Yale Peabody Museum in New Haven, Connecticut. Rare specimens of Brown Kiwi (Apteryx australis), Southern Cassowary (Casuarius casuarius) and Pel’s Fishing Owl (Scotopelia peli) were certainly some of the tours highlights, but what really caught my eye that evening was a tray of Blue-crowned Motmot’s (Momotus momota).

     Native to the forests of Central and South America, the Blue-crowned Motmot is recognized by its brilliant plumage of yellow, greens and blues. Its central tail feathers are bare spines, which hang like the pendulum of a clock. Most interesting of all were the serrated edges of its upper bill.
Blue-crowned Motmot
Yale University Collection
Photo Credit: Paul Cianfaglione

With a diet consisting of wriggling waxworms, earthworms and small reptiles, it’s no wonder the motmot has evolved a merganser-type hunting apparatus.  

     Even more unexpected was finding bill serrations on the skull of an Emu (Dromaius navahollandiae). This 6-foot tall ratite is endemic to the continent of Australia.
Emu
Photo Credit: Paul Cianfaglione

Emus are known for traveling long distances to reach abundant feeding areas. Once there, Emus will seek out both native and introduced plants such as Acacia, Casuarina and fresh grass shoots. The tiny serrations (photo below) on the mandible help the Emu clip and feed on plants more easily.  
Emu bill serrations
Photo Credits: Paul Cianfaglione
  

Monday, February 15, 2016

Birds with weapons



     Wild Turkeys (Meleagris gallopavo) are commonly found throughout my home state of Connecticut. Turkey observations become more conspicuous during the breeding season when males start gobbling and displaying for the females. As these displays and threats begin to intensify, fighting will break out with males attempting to grab hold of each other’s beak or the skin on the back of their opponent’s neck. Turkeys may also use their wings to flail at a rival and in some instances start kicking each other, using leg spurs as a weapon.

     One of the most overlooked aspects of bird study is the fact that many species possess defense weaponry. These weapons can be found on both the wings (bird hands) and legs, and come in the form of spurs, spikes and even knobs.

     Best known of these birds is the Southern Cassowary (Casuarius casuarius), native to the forests of New Guinea and northeastern Australia. Cassowary feet are powerfully built with a straight spear –like claw up to 5 inches on the inner toe. When provoked, cassowaries are known to strike and injure both people and dogs with this dagger claw.

     The turkey spur (pictured below) is an outgrowth of bone, placed nicely toward the middle of the tarsometatarsus. The bone spur is covered in a sheath of keratin, growing longer and sharper through life. Leg spurs are found mainly on males, used solely for breeding competition and territorial disputes.
Wild Turkey Tarsometatarsus
Pleistocene aged fossil
Photo Credit: Paul Cianfaglione


     Even more remarkable are the wing spurs, spikes and wrist knobs belonging to several living and extinct species of waterfowl, plovers and jacanas. Birds such as the Spur-winged Goose (Plectropterus gambensis), Southern Screamer (Chauna torquata), Masked Lapwing (Vanellus miles), Torrent Duck (Merganetta armata) and Northern Jacana (Jacana spinosa) all have wing weaponry, but differ in the size of the extension and area of emergence.


     The Spur-winged Goose is Africa’s largest goose species. It’s solid, conical spur (extension of the radiale) have sharp keels which are effectively used against all competitors and predators. It has rightly gained the reputation as “the most dangerous of all waterfowl”.

     The Southern Screamer, one of a small group of South American waterfowl, have not only one, but two equally impressive wing spikes. The screamers spikes (pictured below) project from the base of the alula, as well as from the distal end of the major metacarpal.

Southern Screamer
Photo Credit: Paul Cianfaglione
See Darren Naish Blog here:


     Strangest of all birds is the extinct flightless ibis, Xenicibis xympithecus (aka; Club-winged Ibis), which lived in Jamaica 10,000 years ago. See Darren Naish Blog here:


This bird exhibited a thick-boned, curved carpometacarpus. The radius was stronger than most of today’s birds, with a wrist that was entirely mobile. These flog -like weapons were most likely used between members of their own species (breeding season), rather than a tool for predatory gain. Evidence linked to the use of these wing clubs comes from findings of healed wing fractures.
Both images property of Nicholas Longrich
Yale University

     Aside from the extinct flightless ibis, the idea that flying birds evolved functional spikes and clubs on their forelimbs seems incredibly risky. In most instances, birds that break a wing in the wild stand little chance for continue survival. Interestingly, birds like the Southern Screamer and Northern Jacana, who rely on flight for feeding and predator evasion, evolved the role of avian cavalier.

     On the flip side of this is the American Robin (Turdus migratorius), who lacks wing spurs and spikes altogether, but still vigorously uses their forelimbs to fight for females during the breeding season. Wing-thrashing and auditory slaps often cause me to wince at the possibility of an on-the-spot injury. But thankfully, I have never witnessed a robin get hurt during these give-and-take poundings.   

Friday, February 5, 2016

Hawk Eyes

        
     We have all heard at some point in our lives the saying “eyes as sharp as a hawks”, to describe someone who notices everything. People generally use this expression freely, assuming, but not knowing, how sharp a hawks eyes really are.
     Birdwatchers who spend a great deal of time in the field with “real” hawks can attest to a raptors superior visual hunting abilities. They often recall familiar tales of perch hunting hawks catching mice along highway medians or of the Ospreys incredible proficiency at spotting fish just under the water’s surface.
     As a long-time birdwatcher myself, I find many of these accounts to be pretty much normal behavior. Despite these well-known hunting techniques, some observations can still stop me in my tracks and cause me stare in absolute amazement. Such was the case last weekend in my Canton, Connecticut yard.
DSCN0278
Red-tailed Hawk
Photo Credit: Paul Cianfaglione
     I had just started to clear some weeds from the flower garden, when out from under my feet came a scurrying meadow vole. It managed to escape from harm’s way by scampering across my driveway to the base of an old oak tree. At about that same moment, a Red-tailed Hawk flew in from a distant perch, settling on a low branch to have a closer look. In spite of my direct presence, the hawk’s focus and determination to find the vole allowed me to walk slowly to the garage and retrieve my camera.
     When the vole failed to show, the hawk flew back in the direction of its hunting perch. I continued on with my yardwork, but held in my mind the image of this last encounter. I kept thinking to myself, how on earth did this hawk see a black vole dash across a black driveway from a distance of over two-hundred yards away? How did it detect a vole’s momentary movement when there were so many other distractions about us? Did the hawk anticipate my disturbance in the garden as a potential feeding opportunity? This was certainly no ordinary roadside picking or a blindsided hit on a city park squirrel. This to me was a hawk’s true visual sharpness on full display!
     So how does a hawk pull off such a feat? Predatory birds typically have larger eyes than other species of similar body size. A Red-tailed Hawks eye is over twice the size of that of a Ruffed Grouse. Because a larger eye resolves objects at greater distances, a large predator can see a sparrow (or in this case a vole) at a much greater distance than a sparrow can see another bird of its own size (Kaiser, G. W. 2007. The inner bird: anatomy and evolution). This kind of increased ability to resolve small objects is particularly useful to birds that attempt to fly through forests at high speeds (I have always been amazed at that ability too!). Forward facing eyes also provides hawks with great binocular vision, necessary for judging distances properly. Think of it this way, it’s like being able to see your world through the lens of a spotting scope, all of the time!
     With a yard filled with stone walls, patches of weeds and woods, we have our fair share of voles. In fact, I see voles in my yard almost every day. So the next time I flush a vole from a garden bed or stone wall, I’m going to remember to look over my shoulder. You never know who may be watching your every move!

Avian foot sollerets



     As a longtime and active birder, I’m aware of birdlife no matter what the situation may be. Such was the case last month along a busy city street in Hartford, Connecticut. Out of the corner of my eye, I noticed a pile of black feathers lying motionless upon the sidewalk. An American Crow, a perfect specimen, was placed into the back of my truck and taken home to Canton, Connecticut.  
     In past encounters with this species, the American Crow has never been one to allow a close study. At my feeders, crows typically fly off with a glance of an eye. So to have finally placed one in the palm of my hands, I felt moved and honored for sure.  
     The crow’s large size and wingspan, its beautiful plumage and strong beak were quite impressive. But what really caught my attention was its feet. With its long claws and sizeable scales, this bird was certainly prepared to conquer any landfill or city street.


DSCN9008
American Crow Foot
Photo Credit: Paul Cianfaglione

     Bird feet are an exciting aspect of avian study. The ability to forage on the ground is a behavior used by over 75% of today’s birds. As an adaptation to its diverse feeding environments, birds have evolved a variety of tough plating of scales (also called scutes) that not only strengthens the foot, but also resists wear.
     The topography of our crow’s foot is classified as Scutellate-booted. The overlapping scales along the anterior side of the foot as well as the long, single boot covering the backside of the tarsus is easy to notice. The non-imbricating tuberculate (bumpy) scales on the plantar side of the foot is less noticeable on the crow, but more obvious on the metatarsal and digital pads of the Dark-eyed Junco below.
Dark-eyed Junco Foot
Photo Credit: Paul Cianfaglione

     Another interesting term that refers to the covering of the avian foot includes reticulate. Reticulate feet are characterized by small, unevenly arranged scales that are found on such species as plovers and parrots.
     A bird species most direct contact with its environment is by way of its feet. Whether it be the double-scratch behavior of an Eastern Towhee, the long reach into a thorny bush by a hungry Cooper’s Hawk or a woodpeckers search for insects across rough tree bark, a birds feet are armed and ready for all of nature’s challenges.