Tuesday, March 26, 2019

Avian Drop Foraging; a precursor to powered flight?

In recent years, increasing numbers of tourists have ventured to the New World tropics in search of exotic birds. Many, if not most of these people expect to find symbolic species such as trogons, tanagers, toucans and parrots.

Others, like myself, travel to the tropics with the hopes of adding knowledge about bird ecology and evolution, in this the richest of environments.

Of course, seeing cotinga’s and puffbirds for the first time is always an exhilarating and memorable experience. Some memories however are more vivid to me than others, including one that I experienced many years ago in a lush and humid Panamanian rainforest.

It was on an early morning walk down a beautiful forest trail, where I happened upon a rarely seen Great Tinamou (Tinamus major), searching for fallen fruits and seeds. Clearly surprised by our encounter, the bird quickly scurried off into the underbrush and out of sight.

As I continued my search for the tinamou in the dense undergrowth, my eyes were suddenly drawn to a Northern Barred Woodcreeper (Dendrocolaptes sanctithomae) perched motionless on a rotting log. Located directly next to the woodcreeper was an Ocellated Antbird (Phaenostictus mcleannani), also motionless. I thought to myself; what has drawn the attention of these two species?

Curious, I began to scan the surrounding area very carefully, until I came upon an active army ant colony. Initially, it was assumed that the woodcreeper and antbird were simply eating the ants. But as I continued to watch their behavior, I began to realize that that the birds were not feeding on the ants at all, but rather on the insects flushed by the swarming army ants. As a newcomer to tropical birding, their unusual behavior was beginning to make more sense.

Ant followers, as the woodcreeper and antbird are typically known, are birds that feed by following swarms of army ants (Eciton burchellii) and take prey flushed by those ants. The best-known ant-followers are 18 species of antbird in the family Thamnophilidae, but other families of birds may follow ants including thrushes, chats, ant-tanagers, cuckoos, and woodcreepers (source: Wikipedia).

Of particular interest to me was the exotically colorful antbird. In addition to its unique plumage and large area of blue facial skin, the Ocellated Antbird also takes part in an unusual method of hunting.   

Often referred to as drop-foraging, Ocellated Antbirds normally perch on stems and small tree trunks within one meter of the ground, sallying down to capture potential prey. Ocellated Antbirds are particularly adept at clinging to thin, vertical stems, with strong legs and toes. 

Ocellated Antbird (Phaenostictus mcleanni)
Image Property of: neotropical.birds.cornell.edu; Donald Kirker
https://avianmusing.blogspot.com/
Drop-foraging offers birds numerous benefits. In the case of the antbird, it allows for close approach and close inspection of army ant colonies, giving it a leg up (literally!) on the competition. It also helps the birds avoid becoming overrun, or stung by the swarming ants.

Closer to home, I see the same type of behavior in our neighborhood Eastern Bluebirds (Sialia sialis).

Research shows that drop-foraging constitutes the method of almost 100% of foraging attempts during the early breeding season. During the height of breeding season, 80% of bluebird foraging attempts are perch-to-ground movements. Hovering is uncommon. Younger fledglings hop along the ground to forage before acquiring adult drop-foraging habits (source: Bird of North America online).

Eastern Bluebird (Sialia sialis) Drop Foraging
Image Credit: Evan Hambrick
https://avianmusing.blogspot.com/

The benefits of this technique are similar to the antbirds, allowing the bluebird to scan a wider area for insects, while remaining at a reasonable striking distance. This is in direct contrast to other local species like the American Robin (Turdus migratorius) and Common Grackle (Quiscalus quiscula), who expend a great deal more energy on foot during hunting forays.

Clinging low to elevated stems and tree trunks also permits the birds to search their surroundings for potential predators.

So, how did this type of hunting method evolve? Is this behavior more of a recent development? Or are there any clues in the fossil record that may increase our understanding of this behavior, helping us to possibly answer questions about the origin of flight.

In the 2015 book-The Rise of Birds; 225 Million Years of Evolution, author Sankar Chatterjee goes to great lengths discussing the three competing models for the origin of avian flight.

Two theories have dominated most of the debates, the cursorial ("from the ground up") theory proposes that birds evolved from small, fast predators that ran on the ground; the arboreal ("from the trees down") theory proposes that powered flight evolved from unpowered gliding by arboreal (tree-climbing) animals.

A more recent theory, "wing-assisted incline running" (WAIR), is a variant of the cursorial theory and proposes that wings developed their aerodynamic functions as a result of the need to run quickly up very steep slopes such as trees, which would help small feathered dinosaurs escape from predators (source: Wikipedia, Origin of Birds).

Origin of Flight; From Rise of Birds, Chatterjee 2015
https://avianmusing.blogspot.com/
In short, Chatterjee clearly favor a “trees down” scenario, where the evolution of flight (and advanced feather development) happens solely in the trees, in a sequence of progression from climbing to jumping to parachuting to biplane gliding to monoplane gliding, soaring, flapping to complex maneuvering flight.

He downplays the cursorial theory by stating that it fails to explain fully why the primary vanes of Archaeopteryx are so asymmetrical and complex, a condition seen only in modern volant birds.

Chatterjee continues; If Archaeopteryx were a ground-dwelling bird, as John Ostrom depicted, it would have had hair-like feathers, like those of ostriches and rheas. The cursorial theory works against gravity and is energetically more expensive. The effects of gravity would create additional stress on proto-birds during takeoff. To overcome the added stress, the supracoracoideus pulley system would be required during takeoff; its lack in Archaeopteryx indicates that it took off from trees to become airborne, not from the ground.

The cursorial theory does not address the necessary transitional form between the preflight stage and the active, flapping flight stage; flight would thus have evolved rapidly, from jumping to active flying, almost by saltation without any intermediate gliding stage. This theory does not explain adequately the origin of feathers, endothermy, or brain enlargement and three-dimensional perceptual control (source: The Rise of Birds, Chatterjee, 2015).

But what if we factor in the evolutionary behavior of drop-foraging? Could this be the go-between behavior that the “ground up” theory is looking for?

Let us envision for a moment a small feathered coelurosaur, hunting in dense undergrowth. A distant crashing sound sends the dinosaur running to the nearest conifer (cycadeoids, etc.), where it uses its powerful legs to leap and grasp onto the tree’s rough trunk. It nervously scans the surroundings, at the same time periodically flapping one of its feathered arms to keep balanced, similar to a medium sized bird on a small tube-feeder.

Blue Jay (Cyanocitta cristata) on tube feeder
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
As the threat subsides, the hungry animal continues to search for prey. Once spotted, the dinosaur forcefully pushes off the trunk and into the air, flapping and gliding a short distance to the forest floor where it renews its pursuit.

For a ground-dwelling dinosaur in the earliest moments of avian evolution, there are a number of good reasons why it might have wanted to leap into the air, without feeling the need to stay there.

I see Archaeopteryx as a predominantly terrestrial predator, like today's Greater Roadrunner (Geococcyx californianus) who uses its feathered forelimbs and strong legs for leaping and rudimentary take-offs from ground level, to better access food and escaping predators.

Drop-foraging among small feathered coelurosaurs would involve vertical leaps from the ground, cling-perching on low stems and trees, balance-flapping, leaping again, controlled flapping and gliding descent; effectively explaining the origin of advanced feathers, brain enlargement and three-dimensional perceptual control, without the need of parachuting from great heights.

I could also imagine the early forms of enantiornithine and pygostylians birds utilizing this same foraging behavior, since all were most likely still tied to nesting and feeding upon the forest floor.  

Mesozoic Bird Drop Foraging
Image Property of: leaubellon.tumblr.com
Leaubellon
I often wondered if we could see any anatomical differences in the foot bones of antbirds, bluebirds or any other bark specialists, as a result of these unique actions. If so, how about in the fossil record.

White-breasted Nuthatch (Sitta carolinensis)
Image Property of: Stanislav Harvancik
https://avianmusing.blogspot.com/
As luck would have it, I remember years ago photographing a Chinese enantiornithine fossil with just that sort of anatomical anomaly.

Though it may have simply been an artifact of the preservation in the fossil, the ancient bird’s feet (foot) are a true eye-opener for the first-time observer!

Reminiscent of an aye-aye’s (Daubentonia madagascariensis) special thin middle finger, or Australian Striped Possum (Dactylopsila trivirgata) front forelimb, the fossil foot, at the slightest, may signal the start of a selected adaptation to dominant stem/trunk foot support. 

Enantiornithine Fossil Feet
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Enantiornithine Fossil Foot
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

Wednesday, March 13, 2019

Science Comics: Dinosaurs: Fossils and Feathers. A Pictorial Book Review.

As the father of three young kids, it’s not unusual for me to be spotted relaxing in the children’s section of our local bookstore. Where else can a busy parent go these days to find a coffee, and a much-needed mental break?! 

My last visit however was spent in a slightly different fashion, reading dinosaur books to a small (no pun intended!), but attentive audience. Browsing the stores selection, I was able to find the usual assortment of picture and pop-up books, as well as a variety of large format identification guides.

One of the books that clearly caught my attention was named; Science Comics. Dinosaurs: Fossils and Feathers (2016) by MK Reed and Joe Flood, which nicely combines scientific content with attractive and engaging illustrations. 

Science Comics. Dinosaurs: Fossils and Feathers by MK Reed and Joe Flood
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
An essential history lesson in comic strip style, I couldn’t help but notice how similar both the storyline and cast of characters were in this volume, in comparison to other science books on the topic of bird origins.

MK Reed does an outstanding job of presenting the facts in chronological order, rarely overlooking key historical points. By not jumping the gun on today’s feathered raptors, Dinosaurs: Fossils and Feathers is able to provide young readers with a flowing, easy to understand link between the study of dinosaurs and modern-day birds. 

Science Comics. Dinosaurs: Fossils and Feathers by MK Reed and Joe Flood
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Young readers will also be introduced to some lesser known figures through a series of important events such as the 1800’s Bone Wars, the discovery of Archaeopteryx, expeditions into the Gobi Desert of Mongolia, right up to the finding of Sinosauropteryx, a small theropod with feathers uncovered in China in 1996.

Science Comics. Dinosaurs: Fossils and Feathers by MK Reed and Joe Flood
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
How special was it for me to see the likes of Richard Owen, Georges Cuvier, Thomas Huxley, Othniel Marsh, Edward Drinker Cope, Franz Nopcsa, Roy Chapman Andrews and Jack Horner, as comic book heroes and villains! 

Science Comics. Dinosaurs: Fossils and Feathers by MK Reed and Joe Flood
Photo Credit: Paul Cianfaglione
 https://avianmusing.blogspot.com/
Written primarily for children ages 8 to 12, Dinosaurs: Fossils and Feathers touches upon other important topics like continental drift, soft tissue in bone, eggs and nests, the K-T boundary, and of course, feathered dinosaurs. Incredibly, at no point during the course of this comic book does the author waver from delivering accurate educational material. Very well done in my opinion. 

Science Comics. Dinosaurs: Fossils and Feathers by MK Reed and Joe Flood
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Joe Flood provides stellar artwork throughout the book. But my favorite illustrations were those of his that portrayed actual paleontological discoveries. Recreations of Velociraptor and Protoceratops locked in combat, along with nest attending Maiasaura and Oviraptors are key events in the history of the story of paleontology. 

Science Comics. Dinosaurs: Fossils and Feathers by MK Reed and Joe Flood
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Like the first Jurassic Park movie, Dinosaurs: Fossils and Feathers does a very nice job of mixing sound scientific facts into mainstream pop culture. For that reason alone, I would consider this book a classic, and important children’s science book.

Science Comics. Dinosaurs: Fossils and Feathers by MK Reed and Joe Flood
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
  

Thursday, March 7, 2019

Avian Inspired Poems. Field Lark, Meadow-Lark (Eastern Meadowlark).

Inspired by such works as Land-Birds and Game-Birds of New England by H.D. Minot (1877), and The Birds of New England by Edward A. Samuels (1870), is my attempt to bring their long-forgotten words, and place in time, back to life through a series of short poems and images. 

The Birds of New England by Edward A. Samuels (1870)
https://avianmusing.blogspot.com/

Common name in 1877:   Field Lark, Meadow-Lark

Common name in 2019:   Eastern Meadowlark, (Sturnella magna)

Allen & Ginter collector card circa late 1800's
https://avianmusing.blogspot.com/

Meadow-Lark

Fertile tracts of sunlit pasture, finds a nest upon the ground.

Meadow-Lark singing from a post, concerned it may be found.

Sweet-plaintive-music, a lisp that’s seems so pleasant.

Colors of the haying fields, a chest which bears a crescent. 

Beauty displayed in graceful flight, hovers before alighting.

Long grasses do they always trust, a walk that’s less inviting.

Threatened grassland habitat of the Eastern Meadowlark (Sturnella magna)
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

Wednesday, March 6, 2019

Whiskered Treeswift (Hemiprocne comate). All Birds Considered.

Inspired by David Attenborough’s book, The Life of Birds, is a monthly spin-off segment of my blog called “All Birds Considered”, which I hope will bring attention to some of the more unusual, and lesser known birds of our world.

The Life of Birds by David Attenborough
https://avianmusing.blogspot.com/
Species; Whiskered Treeswift (Hemiprocne comate)

Introduction; The Whiskered Treeswift (Hemiprocne comata) is a species of bird in the family Hemiprocnidae. It is found in Brunei, Indonesia, Malaysia, Myanmar, the Philippines, Singapore, and Thailand.

Description; 6”. Small size, 2 white stripes on face and bronzy brown plumage with metallic blue-back head, wings and tail diagnostic. Under tail coverts and spot at end of tertiaries white. Male has chestnut ear patch. Makes short, dashing flights from regular perch. 

Whiskered Treeswift (Hemiprocne comata)
Image Property of HBW Alive/Alex Berryman
https://avianmusing.blogspot.com/
Voice; The Whiskered Treeswift is quieter than the largest species of this family. The contact call between pair-members includes high-pitched “chew” or “kweeo”, and series of short notes “kwee kwee, kwi-kwi-kwi-kwi” or “she-she-she-SHEW-she”. These calls are uttered while the birds are flying or perched.

Behavior; The Whiskered Treeswift feeds primarily on insects. It hunts from perches where it sits in upright posture, and from where it can have a good all-round vision of the surroundings. 

Whiskered Treeswift (Hemiprocne comate)
Image Property of Ingo Waschkies/Oiseaux Birds
https://avianmusing.blogspot.com/
Very agile in flight, it chases insects and small flying arthropods, even amongst the foliage but well below the canopy. The preys are usually taken on the wing, but it also picks off the food items when perched, or by hanging from the tip of a small branch. It may perform short sallies from its perch, close to the surface of the vegetation.

Habitat; Its natural habitats are subtropical or tropical moist lowland forest, subtropical or tropical mangrove forest, and subtropical or tropical moist montane forest.

Conservation and population; Least Concern (IUCN 3.1). Bird Life International (2012). "Hemiprocne comata". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.

Source:

http://www.oiseaux-birds.com/card-whiskered-treeswift.html

Wikipedia

The Life of Birds by David Attenborough, 1998.

Tuesday, March 5, 2019

The Crow and the Pitcher (Jug). A fairytale comes to life.

The Crow and the Pitcher (Jug)

It was bone-dry in the countryside. There had been no rain for weeks on end now. For all the animals and birds, it had been a terrible time. To find even a drop of water to drink was almost impossible for them.

But the crow, being the cleverest of birds, always managed to find enough water to keep himself alive.

One morning, as he flew over a cottage, he saw a jug standing nearby. The crow knew, of course, that jugs were for water, and as he flew down, he could smell the water inside. He landed and hopped closer to have a look.

And sure enough, there was some water at the bottom. Not much maybe, but a little water was a lot better than no water at all.

The crow stuck his head into the jug to drink; but his beak, long though it was, would not reach far enough down, no matter how hard he pushed. He tried and he tried, but it was no good. However, he knew that one way or another he had to drink that water. He stood there by the jug, wondering what he was going to do. Then he saw pebbles lying on the ground nearby, and that gave him a brilliant idea.

One by one he picked them up and dropped them into the jug. As each pebble fell to the bottom, the water in the jug rose higher, then higher and higher, until the crow had dropped so many pebbles in that the water was overflowing. Now he could drink and drink his fill. What a clever crow, he thought as he drank. What a clever crow (source; Aesop’s Fables. Morpurgo M. 2004).

WHERE THERE’S A WILL, THERE’S A WAY. BUT IT HELPS IF YOU USE YOUR BRAIN. 

Crow and the Pitcher (Jug); Aesop's Fable
Illustrated by Milo Winter, 1919
https://avianmusing.blogspot.com/
Aesop's Fables, or the Aesopica, is a collection of fables credited to Aesop, a slave and storyteller believed to have lived in ancient Greece between 620 and 564 BCE. Of diverse origins, the stories associated with his name have descended to modern times through a number of sources and continue to be reinterpreted in different verbal registers and in popular as well as artistic media (source; Wikipedia).

Initially the fables were addressed to adults and covered religious, social and political themes. They were also put to use as ethical guides and from the Renaissance onwards were particularly used for the education of children.

Those of you who rarely observe bird behavior may find the above fable to be just that; a fable. As it turns out, this is not just a folktale. 

The Crow and the Pitcher (Jug)
Gallaher Ltd. trading card
https://avianmusing.blogspot.com/
In a book I’m currently reading titled; The Genius of Birds (2016), author Jennifer Ackerman describes a recent behavioral experiment conducted by University of Auckland researchers on the New Caledonian Crow (Corvus moneduloides).

(S.A. Jelbert et al., “Using the Aesop’s fable paradigm to investigate casual understanding of water displacement by New Caledonian Crows,” PloS One 9, no. 3 (2014): 1-9).

“New Caledonian Crows will do exactly that, drop stones into a water-filled tube to raise the water level. If given a choice between heavy objects and light ones, solid and hollow ones, the crows will spontaneously pick objects that will sink over those that will float. They know how to pick their material and will select the right option 90 percent of the time. This suggests that the crows understand water displacement, a fairly sophisticated physical concept, on par with the comprehension of a child five to seven years old. It also suggests that they’re able to grasp the basic physical properties of objects and make inferences about them.” (source: The Genius of Birds. Ackerman J. 2016). 

New Caledonian Crow (Corvus moneduloides) 
Image Property of: Sarah Jelbert
https://avianmusing.blogspot.com/
Please see the video link below;

https://www.youtube.com/watch?v=ZerUbHmuY04

Thursday, February 28, 2019

Quill knobs; on a carpometacarpus?

“Believe nothing you hear, and only one half that you see.” A quote from the great American poet and author Edgar Allan Poe.

I couldn’t help but to think back to those exact words the other morning while reading Sankar Chatterjee’s book; The Rise of Birds, 225 Million Years of Evolution (2015).

Here, Chatterjee nicely illustrates (and labels) the anatomical similarities and differences between forelimbs of a dromaeosaur (Deinonychus), and a Golden Eagle (Aquila chrysaetos). 

Dromaeosaur and Golden Eagle (Aquila chrysaetos) forelimb comparisons
Image from: Rise of Birds by Sankar Chatterjee (2016)
https://avianmusing.blogspot.com/
Informative in so many ways, the diagram did however present one peculiar and curious detail. Highlighted on the carpometacarpus of the Golden Eagle were six conspicuously drawn quill knobs. Quill knobs, I questioned, on a carpometacarpus? Have I ever seen quill knobs on a carpometacarpus before?

Golden Eagle (Aquila chrysaetos) carpometacarpus 
Image from: The Rise of Birds by Sankar Chatterjee (2016)
https://avianmusing.blogspot.com/
Quill knobs are typically shown on the ulna, where they serve as attachment points where secondary flight feathers are affixed to the bone with ligaments.

Northern Flicker (Colaptes auratus) ulna quill knobs
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Taking Poe’s words to heart, I started to second guess my own knowledge of avian wing topography. Was I just plain careless over the years to have missed such an obvious feature? Or, was Chatterjee’s illustration a gross exaggeration.

As soon as I arrived home that evening, I pulled out a few (sixteen to be exact) bird bone specimens, systematically examining each and every one. What I discovered under the microscope was that most of the carpometacarpus’s lacked quill knobs altogether, with one bone holding a potential attachment point.

The carpometacarpus is unique to birds. It is the result of fusion of carpals and metacarpals. A carpometacarpus is reminiscent of a violin bow. The grip is composed of metacarpal I and has a pronounced pisiform process in the middle of its palmar surface and a metacarpal process extending radially. The bow is metacarpal II, and the much thinner metacarpal III represents the strings (source: Avian Osteology. Gilbert, Martin, Savage.1996).

Avian carpometacarpus
Image from: Avian Osteology, Gilbert, Martin, Savage. (1996)
https://avianmusing.blogspot.com/
Equally confusing is how the carpometacarpus is depicted in print while supporting most of the primary remiges. Some Ornithology manuals place the primary attachment directly on the slimmer metacarpal III, with the feather quills held firmly in place by the postpatagium. 

Rock Dove (Columba livia) wing anatomy
Image from; Manual of Ornithology, N.S. Proctor (1993)
https://avianmusing.blogspot.com/
Others, including a recent research paper (2016) on the flight feather attachment in rock pigeons, clearly shows the primaries attaching onto metacarpal II of the carpometacarpus. 
https://www.researchgate.net/publication/304192129

Carpometacarpus primary feather attachments
Image from; Tobin L. Heironymus

So, who do we believe here? Where do the primaries actually attach? Is Chatterjee’s illustration correct? If so, where are all the quill knobs?

As I had mentioned earlier, I did detect what looks to be an attachment scar on metacarpal II of the carpometacarpus on a Pleistocene-aged American Coot (Fulica Americana). 

Possible American Coot (Fulica americana) carpometacarpus quill scar
Photo Credit: Paul Cianfaglione
 https://avianmusing.blogspot.com/
If quill knobs did exist on the carpometacarpus, it makes more sense that they would be found on the wider and stronger metacarpal II. Chatterjee’s placement of the quill knobs (on metacarpal II) would therefore be correct, but to what extent.

After examining sixteen specimens myself, I still dispute the idea that quill knobs on a birds carpometacarpus are clear or apparent. Specimens that I inspected ranged in size from the large bodied Southern Screamer (Chauna torquata) and American Crow (Corvus brachyrhynchos), to the diminutive wood warblers and sparrows.

American Crow (Corvus brachyrhynchus), Northern Flicker (Colaptes auratus), American Coot (Fulica Americana)
carpometacarpus's (from top to bottom)
Photo Credit: Paul Cianfaglione
 https://avianmusing.blogspot.com/
Granted, sixteen specimens does not qualify me as an expert on this subject, nor prove anything either way. Maybe Golden Eagles, and other species, do have prominent quill knobs on their carpometacarpus. At this moment, I wouldn’t know.

My hope is to see more illustrations, like the one below, that show the correct position of the primaries in relation to the carpometacarpus.

Bird wing feather attachments
Image from; Tobin L. Heironymus


Tuesday, February 19, 2019

Avian Hypoglossal Nerve

The Blue Jay (Cyanocitta cristata) is a common bird of urban areas and rural farms throughout most of eastern North America. Unlike the Northern Flicker (Colaptes auratus), the jay is an avian generalist, with a sturdy but anatomically unremarkable body suited to exploit a wide variety of habitats and food sources.

Northern Flicker (Colaptes auratus)
Image Property of Audubon.org
https://avianmusing.blogspot.com/
Despite both being relatively the same size, it was interesting to be able to compare the contrasting forms and function of their skeletal structures. The most distinguishing feature to me was in the shape of their skulls and bills.

Blue Jay (Cyanocitta cristata) left, and Northern Flicker (Colaptes auratus) skulls
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
The feeding strategies of these superficially similar species places them in unique ecological niches.

In the hand, and side-by-side, the Northern Flickers skull has a noticeably longer bill, which it uses to hammer in the soil searching for ants. Flickers have a remarkable protractible tongue, derived by great elongation of the basihyal and part of the hyoid horns, that is characteristic of woodpeckers. The sticky tongue darts out as much as 4 cm beyond the bill tip as it laps up adult and larval ants (source: Birds of North America Online).

As a generalist, the Blue Jay uses its nicely proportional bill to feed on arthropods, acorns and other nuts, soft fruits, seeds, bird eggs, and small vertebrates, which it does so in trees and shrubs, and on the ground.

But I also noticed one other feature while I was looking at the Blue Jays skull under the microscope. Located toward the rear of the skull, near the foramen magnum, were a series of symmetrically placed holes (canals) perforating the skull. I thought, what purpose do these holes serve? 

Blue Jay (Cyanocitta cristata) skull foramen
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Blue Jay (Cyanocitta cristata) skull foramen
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
According to the Handbook of Avian Anatomy (Baumel & Witmer), the holes on either side of the occipital condyle represent the exit points for two nerves, the vagus nerve and the hypoglossal nerve. Although difficult to discern, and contrary to the Manual of Ornithology (Proctor N.S. 1993.), I believe the hypoglossal canals are the smaller holes closest to the occipital condyle. 

Handbook of Avian Anatomy/Baumel & Witmer
https://avianmusing.blogspot.com/
Bird Anatomy/Wikisource
https://avianmusing.blogspot.com/
Manual of Ornithology/Proctor N.S. 1993
https://avianmusing.blogspot.com/
The hypoglossal nerve is the twelfth cranial nerve, and innervates all the extrinsic and intrinsic muscles of the tongue, except for the palatoglossus which is innervated by the vagus nerve. It is a nerve with a solely motor function. The nerve arises from the hypoglossal nucleus in the brain stem as a number of small rootlets, passes through the hypoglossal canal and down through the neck, and eventually passes up again over the tongue muscles it supplies into the tongue. There are two hypoglossal nerves in the body: one on the left, and one on the right (source: Wkipedia).

This was very interesting. Given its daily dependence on its abnormally long tongue, one would think that the Northern Flicker should show dramatically larger hypoglossal canals (larger nerves) than the similarly sized Blue Jay. Unfortunately, this is not the case. The flicker and jay hypoglossal canals appear equal in size.

Northern Flicker (Colaptes auratus) skull foramen
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Northern Flicker (Colaptes auratus) skull foramen
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
The size of the hypoglossal canals has also been considered in other animals;

The size of the hypoglossal nerve, as measured by the size of the hypoglossal canal, has been hypothesized to be associated with the progress of evolution of primates, with reasoning that larger nerves would be associated with improvements in speech associated with evolutionary changes. This hypothesis has been refuted (source: Wikipedia).