Looking Good, Part I — Pectinate Claws (Avian Edition)


Pectinate claw of the Great Egret (Casmerodius albus egretta) amongst the downy plumes.  Image credit: Yale Peabody Museum / Curious Sengi.

Astute birdwatchers might have noticed that some bird species have comb-like serrations running along one edge of a toe claw.  This feature, termed the pectinate claw, has long been assumed to be used just like combs we use for our own hair — to keep clean and look good.


The Magnificent Frigatebird (Fregata magnificens), called the “Frigate Pelican” by Audubon, swoops down from the skies in this print from the masterwork “Birds of America.”  Image credit: John J. Audubon’s Birds of America at Audubon.org.

Upon seeing the Magnificent Frigatebird (Fregata magnificens), John James Audubon (1785 – 1851) remarked:

I have frequently observed the Frigate Bird scratch its head with its feet while on the wing; and this happening one day, when the bird fell through the air, as it is accustomed to do at such times, until it came within shot, I killed it when almost over my head, and immediately picked it up.  I had been for years anxious to know what might be the use of the pectinated claws of birds; and on examining both its feet with a glass, I found the racks [sic] crammed with insects, such as occur on the bird’s head, and especially around the ears. . . . I now therefore feel convinced, that, however useful this instrument may be on other occasions, it is certainly employed in cleansing parts of the skin of birds which cannot be reached by the bill (Audubon 1835).


Pectinate claws emerge as a flange of the keratinous sheath.  They occur on the middle toe of each foot (Clayton et al. 2010; Bush et al. 2012).  Great Blue Heron (Ardea herodias).  Image credit: Yale Peabody Museum / Curious Sengi.

The function seems as self-evident to Audubon as it is to us — the pectinate claw combs out all those nasty ectoparasites (i.e., external parasites), especially the feather lice that eat precious down feathers.  Most birds have a little overhang at the tip of the beak for picking out and shearing apart lice, but a special foot comb would be ideal for reaching the head and neck areas inaccessible to the beak during preening (Clayton et al. 2010; Bush et al. 2012).  However, this tidy hypothesis quickly runs into some problems.


The serrations of the pectinate claw can occur in a variety of shapes (Clayton et al. 2010), including the more curved, spatulate forms seen here in the Great Egret (Casmerodius albus egretta).  Image credit: Yale Peabody Museum / Curious Sengi.

The first is that pectinate claws occur only sporadically throughout the avian phylogenetic tree.  A review of 118 bird families found that only 17 possessed pectinate claws.  This was a diverse assemblage that included herons, nightjars, owls, frigatebirds, terns, grebes, and cormorants.  Curiously, only one family of passerines, the dippers (Clincidae), were observed to have pectinate claws; passerines  constitute the bulk of species diversity amongst birds.  Even so, within each family, only a handful of species might have this feature.  And within certain species, the appearance of the pectinate claw was variable among individuals (Clayton et al. 2010).


The removal of ectoparasites is most widely believed to be the function of pectinate claws, but alternative hypotheses include roles in feeding, removing powder down, or straightening rictal bristles of the face (Clayton et al. 2010).  Detail of Montane Nightjar (Caprimulgus poliocephalus).  Image credit: Yale Peabody Museum / Curious Sengi.

So if the pectinate claw served such a vital function as stripping the feathers of harmful parasites, we should expect to find them consistently across a wide swath of bird diversity.  Instead, the pectinate claw seems to have evolved independently numerous times at very spotty intervals.


The pectinate claw of the Barn Owl (Tyto alba insularis) becomes fully formed at about two years of age (Bush et al. 2012).  Image credit: Yale Peabody Museum / Curious Sengi.


This captive barn owl demonstrates how handy it is to use your feet to groom your face!  Image credit: YouTube.

Another source of doubt cast upon the role of pectinate claws in removing ectoparasites comes from a study of Barn Owls (Tyto alba pratincola).  While owls with the most number of teeth on their pectinate claws were categorically the least likely to have lice infestations, there was no correlation between the number of lice and the number of teeth on the claw (Bush et al. 2012).  Foot claws are undoubtedly a critical tool in keeping a bird groomed, but given the rather ambiguous conclusions reached by researchers involved in these correlative studies, without experimental manipulation — e.g., filing off the teeth of the pectinate claw and comparing parasite loads between individuals  — there is little convincing evidence that pectinate claws function specifically to comb out ectoparasites (Clayton et al. 2010; Bush et al. 2012).


Detail from Audubon’s color plate of the “Frigate Pelican”, which highlights his efforts to understand why frigatebirds have both pectinate claws and rudimentary partially-webbed feet.  How to explain this amalgamation of what he perceived as characteristically terrestrial and aquatic features?  Image credit: John J. Audubon’s Birds of America at Audubon.org.

As a coda, there is a fascinating tangent related to Audubon’s particular interest in the feet of the Magnificent Frigatebird.  His attention was drawn to the presence of the pectinate claw, a trait he considered characteristic of terrestrial upland birds, and the partially webbed feet characteristic of an aquatic animal.  According to Weissman (1998), Audubon was able to reconcile the presence of both features by seeing frigatebirds as a transitional form between land and seabirds.  While that relationship does not hold in light of modern analysis of anatomical and genetic characters, it is worth taking note that Audubon, like some of his contemporaries, was beginning to think in quasi-evolutionary terms well before Darwin.


Audubon, John James.  1835.  Ornithological biography, or an account of the habits of the birds of the United States of America.”  Vol. 3.  Edinburgh:  Adam & Charles Black.

Bush, Sarah E. et al. 2012.  “Influence of Bill and Foot Morphology on the Ectoparasites of Barn Owls.”  The Journal of Parasitology 98 (2):  256 – 261.

Clayton, Dale H. et al. “How Birds Combat Ectoparasites.”  The Open Ornithology Journal 3:  41 – 71.

Weissmann, Gerald.  1998.  Darwin’s Audubon:  Science and the Liberal Imagination.  Cambridge, MA:  Perseus Publishing.


Nose Dive: Falcons & Gannets


The Peregrine Falcon (Falco peregrinus) is famous for being one of the fastest animals in the world.  Image credit: Yale Peabody Museum / Curious Sengi.

Of all the powers of the animal world that humans have envied and engineered into submission, nothing has become a more overdone trope of this desire than the flight of birds.  In our endeavor to understand flight, we have broken down the components of aerodynamics into something we can quantify, calculate, and model.  This approach has obviously worked quite well for us.  Just think about how a Boeing 747 jumbo jet can haul passengers from the East to West Coast of America in about six hours.  The same journey would have taken wagon-driving pioneers months of life-threatening travel through forests, endless plains, deserts, snowy mountains, more deserts, and more mountains.

With our highly engineered view of flight, we tend to look back at living organisms and try to find elements of evolutionary design that seem perfectly adapted to certain modes of life.  For example, let’s take a look at the nostrils of two very different birds, the Peregrine Falcon (Falco peregrinus) and gannets (Family Sulidae).

The Peregrine Falcon is a small North American raptor famous for its incredible high-speed dives.  These dives, or stoops, are generally reported to clock in at 200 mph (320 km/h).  This makes the Peregrine one of the fastest animals on Earth, “a feathered bullet dropping out of the sky (Hagler 2012).”  Traveling at such speeds requires many modifications, including some less obvious ones like redirecting airflow into the nostrils for breathing.  It is repeatedly said that the force of air entering the nose at 200 mph would cause the lungs to explode.  In order to prevent this from happening, there are bony tubercles in the nares that act as baffles to safely regulate the passage of air into the respiratory system.  As a matter of fact — according to these often repeated anecdotes — the nostrils of Peregrine Falcons inspired the design of inlet cones for supersonic jet engines.

That’s a cool fact, but what does it really mean?


The dive of the Peregrine Falcon is called the “stoop.”  During the stoop, the falcon strikes its prey — usually birds — with intense and often lethal force.  There are reports that the strike is enough to knock off the heads of prey animals.  Image credit: PBS Nature.

To begin with, traveling at high speeds will not cause lungs to explode.  Quite the opposite.  There are two physical principles to keep in mind here:  (1) the Bernoulli Effect where higher air speed results in lowered air pressure and (2) the energetically favored direction is always from high to low.  As the Peregrine Falcon reaches top speed during the stoop, the increasing air speed encountered by the nares will result in a drop in air pressure.  Inhalation relies upon relatively high pressure air outside the body rushing into the low pressure area of the lungs.  Eventually, the air pressure outside the stooping falcon will approach equilibrium with the air pressure inside the lungs, making breathing very difficult.  Think about how it is harder to breathe when facing into a strong wind, sticking your head out a car window on a freeway (not necessarily recommended), or riding a fast boat.  The presence of bony tubercles in the falcon’s nose act to slow down the airflow, increasing the air pressure, and allowing air to be drawn into the body.  Seems like a clever bit of evolutionary adaptation to extreme high speed flight.


The bony tubercle appears as a bump in the center of the nostril of this Peregrine Falcon.  Image credit: Yale Peabody Museum / Curious Sengi.

red tail

Compare the lack of a narial tubercle in an unrelated raptor, the Red-Tailed Hawk (Buteo jamaicensis calurus).  Image credit: Yale Peabody Museum / Curious Sengi.

This tidy story is somewhat disrupted once we take a look at the phylogenetic distribution of narial bony tubercles.  The Peregrine Falcon shares this morphological feature with all members of the Family Falconidae, which includes raptors of a wide variety of shapes, sizes, and flight abilities.  At one end of the spectrum is the Peregrine Falcon that knocks its bird prey out of the air.  At the other are the caracaras, which soar at a leisurely pace searching for carrion, much like vultures.  This leaves us with a puzzle:  if the tubercles within the nostrils of the Peregrine Falcon are adaptive for respiration at extreme flight speeds, why do all members of the Falconidae possess these tubercles?  It is possible that narial tubercles were present in the common ancestor of all Falconidae and, therefore, all its descendants still carry this feature.  Perhaps the tubercles evolved to serve a different function — such as sensing airspeed or temperature — and this existing structure was modified with a new purpose in the Peregrines.  The conclusion is that we do not fully understand why the bony tubercles of the nostril appear in the Falconidae and what adaptive purpose (if any) it may serve.

falcon skull

The bony tubercle is apparent in the nostril of this American Kestrel (Falco sparverius sparverius).  All members of the Family Falconidae share this morphological feature regardless of flight speed.  Image credit: Yale Peabody Museum / Curious Sengi.

caracara skull

The bony tubercle is faintly visible in the skull of this Crested Caracara (Caracara cheriway cheriway).  Unlike the Peregrine, the Caracara is a slow, soaring bird often found on the ground and scavenging carrion.  It is possible that the bony tubercle changes in size and shape depending on the flight behavior, but this has not been proven yet.  Image credit: Yale Peabody Museum / Curious Sengi.

Perhaps we felt confident in stating the purpose of the Peregrine Falcon’s unusual nostrils because we saw how engineers solved the problem of regulating air intake in jet engines in a very similar way.  In the post-WWII years, military aircraft were breaking more speed records with an ever sophisticated understanding and use of rocketry, but aircraft could only travel so fast until the engines would choke and then stall.  It was soon discovered that instead of passing through the cylinder of the jet engine, air flow was being diverted away, taking with it the oxygen necessary for combustion.  This is the same problem caused by the Bernoulli Effect and the flow from high to low pressure discussed earlier.  The addition of cone-shaped structures in the engine’s inlet generates shockwaves that slow down airflow and allow the engines to continue running.  The inlet cone innovation made supersonic flight possible.  In 1947, Chuck Yeager was able to take a Bell X-1 experimental plane faster than the speed of sound, i.e., Mach 1, which is a blinding 768 mph (1235 km/h) at sea level.

ramjet diagram 1024 C

Schematic drawing of a cross-sectioned jet engine.  When faced with supersonic speeds, air entering into the engine (left) needs to be slowed down in order to pass through the engine and allow combustion to take place.  This slowing down of the airflow is achieved by the introduction of the inlet cone (labeled here as “inner body”).  Image credit: Phillip R. Hays via History of the Talos Ramjet Engine.

The similarity between the design of the inlet cone in supersonic jet engines and the bony tubercle in the nostrils of Peregrine Falcons make for another tidy story where Nature directly informed engineering.  Though I was unable to find any literature that proved experimental research was done on the aerodynamics of falcon nostrils, it does not preclude the possibility that a casual observation inspired an idea.


SR-71 Blackbird was introduced in 1966 by Lockheed’s Skunk Works division, a secretive branch dedicated to advanced technology research. The Blackbird was indeed like nothing ever seen before in terms of aircraft design, prompting conspiracy theorists to claim it was reverse engineered from UFOs.  Definitely not alien technology, but note the presence of conical projections from the air intake of the engines mounted on the wings.  These inlet cones, similar to the bony tubercles seen in Peregrine Falcon nostrils, allowed the Blackbird to fly in excess of Mach 3.  So what came first:  did Nature inspire the engineering?  Or did engineering inspire our interpretation of the Peregrine Falcon?  The Blackbird was retired in the late 1990s. Image credit: Wikimedia Commons.

Another fast flyer encountering extreme physical forces are gannets.  These seabirds have been observed plunge diving from a height of about 100 feet (30 m), drawing their wings back and configuring their bodies into a tight, streamlined shape to pierce the surface of the water where they capture fish.  At the moment of impact with the water, gannets can be traveling at 54 mph (86.4 km/h, or 24 m/s).  (There are macabre data collected from 169 suicides of people jumping off the Golden Gate Bridge in San Francisco.  Impact velocity was calculated to be approximately 33 m/s.  Almost 100% of jumps were fatal, with a vast majority of deaths caused by the impact itself.)  Like the Peregrine Falcon, gannets have evolved a suite of features that allow them to cope with such intense hunting strategies.  As many human swimmers have experienced, how does the gannet dive without getting water up the nose?


Image credit: BBC Earth.

Gannets are believed to bypass the problem by losing the external nares entirely.

As embryos in the egg, gannet nostrils develop identically to  many other bird species, with the nostril openings and immediate vestibular cavity sealed by a plug of epithelial tissue.  While this plug breaks down a little bit later in development to open up the nares, it remains in gannets.  Eventually, the gannets’ external nares are overgrown with bone and covered by the keratinous sheath of the beak, the rhamphotheca.  Interestingly, while the nostrils are completely occluded and there is no flow of air through the nasal cavity, gannets still retain well-developed olfactory structures.


No external nares seen here on this Peruvian Booby (Sula variegata), which belongs to the same family as gannets.  The nostrils would be positioned near the base of the upper beak, but in gannets and boobies, the nostrils are completely covered over by bone growth and the keratinous sheath of the beak.  Image credit: Yale Peabody Museum / Curious Sengi.


Nope, no nostrils in this view either! Image credit: Yale Peabody Museum / Curious Sengi.

How do gannets manage without nostrils?  Macdonald (1960) described secondary external nares — compensatory nostrils, if you will — formed by a gap at the corner of the mouth where the upper beak overhangs the lower.  This area of overhang is made from a bone called the jugal (equivalent to our cheekbone), which is covered by a hinged plate of keratin.  These two elements are loosely connected to the rest of the skull and are likely to collapse against the sides of the beak from the external pressure of water when diving, thus passively closing up these secondary external nares.


Australasian Gannet (Morus serrator).  Note the keratinous plate of the beak underneath the black patch of the eye (it is a narrow triangular shape with a sharp point oriented anteriorly towards the tip of the beak).  Macdonald identifies this as the site of a secondary external naris, a permanent gap between the upper and lower beak covered by a collapsible “jugal operculum.”  Image credit: Yale Peabody Museum / Curious Sengi.

The total loss of nostrils in gannets seems to be a great way to prevent water from forcibly entering the nose during plunge diving and potentially causing damage or water entering the respiratory system.  However, Macdonald noticed some interesting patterns in other unrelated diving birds.  Cormorants (Family Phalacrocoracidae) certainly dive, but from the water’s surface, not from the air.  Despite this more gentle entry into the water, cormorant nostrils are small and almost completely occluded.  In contrast, the Brown Pelican (Pelecanus occidentalis) is a heavy-bodied plunge diver with open nostrils.  The nostrils are surrounded by a flap of skin that might push up against the nostril and seal it like a valve under external water pressure.

To say that the complete narial occlusion in gannets is directly correlated to plunge diving would be ignoring some of the complexities of the story.  We could interpret the near-total loss of nostrils in the cormorant as a remnant from a plunge diving ancestor.  Or it could evolved for a different reason entirely.  The alternative mechanism for closing up the nares in the Brown Pelican is suggestive that there is an adaptive advantage to not getting water up your nose when diving.  In addition, the employment of a different solution to the same problem suggests that there are negative trade-offs involved with losing nostrils.  For example, seabirds need salt-secreting glands to rid their bodies of the excess salt they ingest.  These glands usually empty out through the nostrils.  Gannets have relatively small salt-secreting glands and must discard concentrated salts from their mouths.

gannet skull_01

Skull of the Northern Gannet (Morus bassanus).  During development, bone has overgrown the site of the external nares.  The long, thin bone projecting behind the mandible is the jugal.  Image credit: Yale Peabody Museum / Curious Sengi.

gannet skull_02

Faced with only skeletal material of extinct animals, paleontologists must be extra careful in interpreting the function of anatomical structures and extrapolating behavior.  Even in a modern animal, like this Northern Gannet, it would be a dangerous oversimplification to state that occluded nostrils are directly related to plunge diving.  Image credit: Yale Peabody Museum / Curious Sengi.

Interpreting the function of anatomical structures is always going to be more nuanced than saying “structure X is perfectly adapted to serve purpose Y.”  The biological world is far removed from the world of engineering design.  In our interpretations, we have to take into account the baggage and constraints imposed by evolutionary history, experimentally prove that a given structure does have a function that enhances performance, and keep in mind that trade-offs exist.


Hagler, Gina.  2012.  Modeling Ships and Space Craft:  The Science and Art of Mastering the Oceans and Sky.  New York:  Springer.

Macdonald, Helen.  2006.  Falcon.  London:  Reaktion Books.

Macdonald, J.D.  1960.  “Secondary External Nares of the Gannet.”  Journal of Zoology 135 (3):  357 – 363.

Ropert-Coudert, Yan et al. 2004.  “Between air and water:  the plunge dive of the Cape Gannet Morus capensis.”  Ibis 146:  281 – 290.

Scholz, Floyd.  1993.  Birds of Prey.  Mechanicsburg, PA:  Stackpole Books.

Scothorne, R.J.  1958.  “On the anatomy and development of the nasal cavity of the gannet (Sula bassana L.).”  Journal of Anatomy 92 (4): 648.

Snyder, Richard G. & Clyde C. Snow.  1967.  “Fatal Injuries Resulting from Extreme Water Impact.”  Aerospace Medicine 38 (8):  779 – 783.

Supersonic speed.”  Wikipedia: The Free EncyclopediaJou.  Wikimedia Foundation, Inc.  Last modified 21 August 2016.  Web.  Accessed 25 August 2016.

Hands Behind the Masterpiece: Audubon’s “Birds of America”

Lush and beautiful.  Dynamic.  Faintly fragrant with the mystery and romance of the man who created it.  This is the enormous double elephant folio, Birds of America, by artist, naturalist, and outdoorsman John James Audubon (1785 – 1851).


“Blue Grosbeak,” Image credit: Yale Peabody Museum / Beinecke Library / Curious Sengi.

In order to realize his ambition to publish illustrations of every living bird species in America, Audubon was forced to leave the depths of a frontier wilderness and the nascent cities of a new republic.  In Britain, Audubon had a chance to find wealthy subscribers to fund and talented printers to produce his masterwork.  Birds of America was ultimately entrusted to the London engraver Robert Havell, Jr. (1793 – 1878).  The project encompassed the production of 435 hand-colored plates with text and accompanying figures, printed in four volumes in double elephant folio size:  26 ½ by 39 ½ inches.  This endeavor would take a team of fifty men over fourteen years to produce.



Color plates were generated in a multi-step process that involved engraving a copy of Audubon’s original watercolor image onto a copper plate, printing, and hand-coloring.   Work on the 400+ plates began in 1827 with the illustration of a Wild Turkey and was finished in 1838.  Image credit: Yale Peabody Museum / Curious Sengi.

Of the 180 original copies of the double elephant folio, about 110 still survive today and are sought out as great treasures.  In 2010, Sotheby’s in London broke the record for any printed work when a copy was auctioned to a bird-loving art dealer for £7.3 million ($11.5 million).  In contrast, a Shakespeare 1623 First Folio sold for a paltry £1.5 million at the same auction.


The Hooping Crane [sic]. Image credit: Yale Peabody Museum / Beinecke Library / Curious Sengi.


Havell’s engraving were based upon watercolors like this one that Audubon provided.  The lively gestures and life-like poses characteristic of Audubon’s work is attributed to his method of using freshly shot birds supported by wire armatures.  Image credit:  New York Historical Society.

As cherished and celebrated as the folio volumes are, the original copper engraved plates have met with an extraordinary history of their own.  After Birds of America was printed in London, the plates were shipped to New York and stored in a warehouse which burned down in 1845, damaging a good number of them.  After that episode, the plates were stored in a special fire-proof storage vault Audubon had constructed on his property.  By 1869, Audubon’s impoverished widow, Lucy, was forced to sell the plates as mere scrap metal to Ansonia Brass & Copper Company in Connecticut.


Copper plate engravings, such as this one of American Scoter Ducks, were made by Robert Havell, Jr. of London.  He and his father were both printer/artists who specialized in natural history images.  Havell would later leave London and move to upstate New York, where he is buried in Sleepy Hollow Cemetery.

Not all the copper plates were melted down, however.  Charles Cowles recounts the extraordinary story:

At that time I was about fourteen years old.  I was beginning the study of taxidermy and was naturally deeply interested in birds.  I happened to be at the refinery watching the process of loading one of the furnaces, and noticed on one of the sheets of copper that a man was throwing into the furnace, what appeared to me to be a picture of a bird’s foot.  I took the plate from him, cleaned it with acid, and thereupon discovered the engraving [of the Black Vulture]. . . . I appealed to the superintendent, but without avail.  I next brought the matter to. . . . my father, from whom I received no encouragement. . . . I appealed to my mother and interested her to such an extent that she drove to the factory and looked at one of the plates.  She of course recognized that they were Audubon plates; and instructions were given by my father to keep them intact.  (Quoted from Deane 1908.)


Could this be the very same Black Vulture plate snatched from the furnace by an astute teenage boy? One shudders at the thought of what could have been lost.  Image credit: Yale Peabody Museum / Curious Sengi.

The surviving plates were then distributed to various museums, universities, and individuals.  The clever young Cowles talks of two plates that “. . . particularly struck my fancy, so much so that when the plates were first discovered I managed to secure them on the quiet, cleaned them myself and hid then; and when the plates were distributed no one knew of the existence of these two and they later became my property (quoted from Deane 1908).”

Approximately 80 plates survive today.  In 1985, to celebrate the 200th anniversary of Birds of America, a handful of plates in the care of the American Museum of Natural History in New York City were taken back to London for restoration and a special limited edition of reprints, which were quickly snapped up by wealthy enthusiasts.  But this masterpiece has not been completely sequestered by private collectors.  A number of copies of the double elephant folio are on public display at various universities and museums.

Read, view, and download high-resolution images from Birds of America via the Audubon Society webpage.

Images from this post were taken at the “Audubon and the Double Elephant Folio” exhibit at the Yale Peabody Museum.


The double elephant folio is huge!  These dimensions were adopted according to Audubon’s plan to have each bird depicted at life size.  Image credit:  Yale Peabody Museum / Beinecke Library / Curious Sengi.



Deane, Ruthven.  1908.  “The Copper-Plates of the Folio Edition of Audubon’s ‘Birds of America,’ with a Brief Sketch of the Engravers.”  The Auk 25 (4):  401 – 413.

Hart-Davis, Duff.  2005.  Audubon’s Elephant:  America’s Greatest Naturalist and the Making of the “Birds of America.”  New York:  Henry Holt and Company, LLC.

Reyburn, Scott.  7 December 2010.  “‘Birds of America’ Book Fetches Record $11.5 Million.”  Bloomberg.  Accessed 1 May 2016.

Thomas, Michael.  2006.  “The extraordinary tale of an eight point eight million dollar book.”  In Consuming Books:  The Marketing and Consumption of Literature.  S. Brown, ed.  London:  Routledge.  Pp. 32 – 45.


Notes from the Field No. 2: Erstwhile Pets

Scarritt Pocket

Mammal fossils lured paleontologists to Oligocene age rocks in Patagonia of Chubut Province, Argentina. The deposits pictured here were discovered by G.G. Simpson heading the Scarritt Expedition in 1934.  This photograph comes from a modern paleontological expedition revisting the area.  Image credit: Vucetich et al. 2014. “A New Acaremyid Rodent (Caviomorpha, Octodontoidea) from Scarritt Pocket, Deseadan (Late Oligocene) of Patagonia (Argentina).”  Journal of Vertebrate Paleontology 34 (3): 689 – 698.

In the 1930s, the reknowned American paleontologist George Gaylord Simpson (1902 – 1984) led a number of fossil hunting expeditions with the American Museum of Natural History to Patagonia in the southern end of South America.  Simpson was very much interested in an assemblage of ancient mammals living in “splendid isolation” on the island continent of South America.  His research centered upon these endemic radiations and their eventual fate when a narrow landmass, the Isthmus of Panama, arose at the end of the Pliocene (approximately 3 million years ago) and began the Great American Faunal Interchange.  While searching for evidence from this epic story of South-meets-North, the expedition lightened their days enjoying the antics of local wildlife they adopted as camp pets.

The vast plains of Patagonia are a barren and savage waste in which man seems an interloper.  Here in the far south of South America nature never smiles. . . Yet Patagonia has its own children, living in constant fear and combat, but somehow contriving to flourish and finding in this desolation a home suited to their own wild temperaments. . . .

Simpson in the Field with Jacket

Simpson at the dig.  A skeleton is carefully excavated, covered in shellac, and bandaged for safe transport.  Image credit: Simpson 1932.

We caught one of the babies [a Darwin’s Rhea, Rhea pennata] and christened him Charita. . . . [he] soon forgot his brothers and sisters and lived with us contentedly, a silly creature with feet much too big for it, its body the size and shape of the egg from which it came (where the neck and legs fit in I do not see), covered with soft down, dark brown and striped with white like a skunk.  His idea of heaven was to wedge himself tightly between two hot pans beneath the camp stove.  When deprived of his sensuous pleasure, he divided his time between trying to crawl into our pockets and trying to scratch his head, laudable ambitions neither of which was ever wholly achieved. . . . He used to sleep with one of us, and soon became a real member of the family.  His cry was a sad whistle, slurring down the scale and ending with a pathetic tremolo. . . . he would come running whenever we called him and would carry on long conversations with us.

Charita the Rhea Chick

Expedition members tended to name their pets after the local language — in this case, “Charita” referred to “ostrich chicks in general.”  Of course, Charita was not actually an ostrich, but a related ratite indigenous to South America known as a rhea.  Drawing by E.S. Lewis.  Image credit: Simpson 1932.

Our long favorite was a pichi [i.e., armadillo] named Florrie. . . . She came to tolerate us as servitors but never displayed any demonstrative affection.  One can no more pet an armadillo than one can pet an egg or, more aptly, a tortoise, and her own attitude was always one of vapid selfishness.  Yet she fully earned her keep.  As she wallowed in a saucer of condensed milk we laughed more at than with her.  She never learned to lap it up cleanly with her long tongue, but must always get her sharp, flexible snout in it too, so that attempts to breathe resulted in convulsive coughs and mighty blowing of bubbles.  She would start to wander off, then suddenly remember the milk, dash back to it in the most business-like way and start drinking again, only to lose interest, wander off again, and repeat the whole process several times.

There was always something vague about Florrie.  Her thick skin seemed to be an index to her mentality and emotions.  Almost the only real emotion she betrayed was when first captured.  Then, if touched, she would suddenly jump, at the same time emitting a convulsive wheeze, a maneuver as disconcerting as the explosion of a mild cigar.  Later she ceased to bother.  If she wandered off when let out, it was rather from absent-mindedness than from any active dislike for our society.  She seemed to think with her nose, and when thus let out for exercise she would trot busily from bush to bush, poking her nose into the ground beneath and sniffing violently.  Once she got away altogether and for several days we mourned her for lost, when one morning she wandered back into camp with her usual air of preoccupation.  The cook, whose special friend she was, swore that she returned for love of us, and another said she had returned for free meals, but I maintain that she had simply forgotten that the camp was there two minutes after she left it, and stumbled on it again quite by accident in the course of one of her sniffing parties.

Florrie the Armadillo

Drawing by E.S. Lewis.  Image credit: Simpson 1932.

These erstwhile pets shared in the daily life of the expedition.  What, if anything, was planned for their ultimate fate is a bit more ambiguous.  Simpson devotes a great deal of space in this popular account to the culinary merits of the local wildlife (a hallowed tradition in scientific expeditions) and both rheas and armadillos were eaten regularly.  Whether the men planned to abandon the animals, eat them, take them back to New York, or have them prepared as museum specimens, that decision soon became moot.  For “. . . .Charita met an untimely end.  He developed an unwholesome appetite for kerosene and, one day, finding a whole pan of this delightful beverage unguarded, he overindulged.  All afternoon, he wandered about vaguely as if something was very much on his mind, or stomach, and next morning he was dead.”  Likewise, Florrie, who was a cheerful presence in camp for several months, ended up being accidentally crushed to death.  Despite these unhappy ends, it is clear that the hapless bumblings of animals like Charita and Florrie were the focus of much entertainment and affection during the long months of isolation grueling in the field.  

Quotation Source

Simpson, George Gaylord.  1932.  “Children of Patagonia.”  Natural History 32 (2):  135 – 147.

Figures: Horned Screamer Gives Directions

Anhima cornuta drawing wing outstretched

Image credit: Naranjo 1986.

“Yes, officer — they headed that way.  I hope you catch those capybaras. . .  they looked shifty as f**k.”


About This Image

This figure comes from a behavioral study of Horned Screamers (Anhima cornuta) and shows a lateral one-wing stretch, a type of comfort behavior exhibited by animals loafing around, preening and relaxing.  The odd, thumb-like projection is probably one of the bony metacarpal spurs typical of screamers.  The drawings were made from tracings of 35 mm photographs taken in the field.

These birds do indeed share habitat with giant semi-aquatic rodents, the capybaras.

Learn more about Horned Screamers in a previous post here.

Image Source

Naranjo, Luis G.  1986.  “Aspects of the Biology of the Horned Screamer in Southwestern Colombia.”  The Wilson Bulletin 98 (2):  243 – 256.

Screaming Unicorns: Anhima cornuta

Anhima cornuta by Eduardo Carrion Letort via PBase

Image credit: Eduardo Carrión Letort via PBase.

There is strange honking cry haunting the humid, primaeval wetland forests of the Amazon Basin.  It comes from an appropriately antiquarian-looking beast, the Horned Screamer (Anhima cornuta).

Neither quite like a turkey nor quite like a goose, screamers belong to the Galloanserae, which branches off between the oldest living group of birds, the Palaeognathae (e.g., ostrich, cassowary, kiwi, tinamou), and the Neoaves, which represent over 95% of all extant bird species.  The middle child of modern bird diversity, Galloanserae itself consists of such familiar and often under-appreciated denizens such as chickens, turkeys, quail, pheasants, ducks, and geese.


Image credit: Yale Peabody Museum / Curious Sengi.

Horned screamers have a rather mind boggling list of anatomical oddities*, but the most obvious is that single thin horn growing out of the top of the head.  Though no published studies specifically examine the function of the horn, it is most likely a display structure since the first appearance of the horn correlates with sexual maturity and many social interactions are marked with a certain amount of head bobbing.  The horn continues to grow throughout life and has been measured to lengths of 15 cm; however, the tip is prone to breaking off.

* Wicked bony carpometacarpal spurs projecting out of the wings!  No uncinate processes on the ribs!  Crackly pneumaticized skin!


Image credit: Yale Peabody Museum / Curious Sengi.

Anhima cornuta variations

Many variations in the shape of the horn from a population of birds observed in southwestern Colombia.  Image credit: Naranjo 1986.

There is currently no firm consensus about the nature of the Horned Screamer’s horn.  Stettenheim (2000) claims this is a cornified structure growing from the skin and not a feather modified into a bare shaft.  This hypothesis is consistent with Stettenheim’s emphasis on the incredible lability of avian integument to generate novel structures.  In opposition is Prum (2005), who interprets these horns as “entirely tubular feathers”; likewise, this supports Prum’s larger corpus of work on the tubular model of feather development and growth.


Though the horn is attached to the skull on the left, the horn seems only to be loosely connected to the bone as it is often observed to waggle freely with the movement of the skin. The skull on the right shows a distinct boss or bump where the horn would be positioned.  Image credit: Yale Peabody Museum / Curious Sengi.

While the exact identity and function of the horn remain somewhat mysterious, early observers of the bird could not help ascribing mythical properties to the horn.  In 1659, Otto Keye published a book entitled Het waere Onderscheyt tusschen Koude en Warme Landen, which described the Dutchman’s adventures in Surinam.  In this book, the Horned Screamer is described as using the horn to fight its enemies, but more significantly, the horn was stirred into the waters to purify it of all poisons before the bird took a drink.  This behavior is suspiciously similar to that of the unicorn, which was believed in Europe to possess such a powerful innocence and purity that it could cleanse polluted waters with a touch of its fabled horn.

Unicorn is Found Tapestry_detail

Detail from the famous series of Unicorn Tapestries.  The unicorn kneels down to purify the waters with his horn for the benefit of all his fellow creatures.  Hunting dogs and their masters lurk in the corners.  Image credit: “The Unicorn is Found” from The Unicorn Tapestries, Netherlands, 1495 – 1505 via Metropolitan Museum of Art.


Image credit: Yale Peabody Museum / Curious Sengi.

The Horned Screamer is currently listed by the IUCN as a species of least concern, despite some previous concern about habitat loss and population decline.  May this delightfully bizarre bird continue long-lived and glorious!


The Horned Screamer is honored as a heraldic device in the coat of arms for the Brazilian municipality of Tietê in São Paulo state. Image credit: Wikimedia Commons.



Barrow, James H., Jr., J.M. Black, & W.B. Walter.  1986.  “Behaviour patterns and their function in the Horned Screamer.”  Wildfowl 37:  156 – 162.

Naranjo, Luis G.  1986.  “Aspects of the Biology of the Horned Screamer in Southwestern Colombia.”  The Wilson Bulletin 98 (2):  243 – 256.

Penard, Thomas E. & T.C. Penard.  1924/1925.  “Historical Sketch of the Ornithology of Surinam.”  De West-Indische Gids, 6de Jaarg.:  145 – 168.

Prum, Richard O.  2005.  “Evolution of the Morphological Innovations of Feathers.”  Journal of Experimental Zoology 304B:  570 – 579.

Schufeldt, R.W.  1901.  “On the Osteology and Systematic Position of the Screamers (Palamedea: Chauna).”  The American Naturalist 35 (414):  455 – 461.

Stettenheim, Peter S.  2000.  “The Integumentary Morphology of Modern Birds — An Overview.”  American Zoologist 40:  461 – 477.