Tuesday, July 31, 2018

Avian Nutrient Foramen (Canals)

I recently read an online article which defined scientific inquiry as being a gathering of information through the use of human senses — seeing, hearing, touching, tasting, and smelling. Inquiry encourages people to question, conduct research for genuine reasons, and make discoveries on their own.

In an inquiry-based learning, people aren't waiting for the teacher or someone else to provide an answer — instead, they are actively seeking solutions, designing investigations, and asking new questions.

There is no better place, in my opinion, for this type of inquiry-based learning than with the inner bird.

Just the other evening, while going over the bones of an American Robin ((Turdus migratorius), I noticed a peculiar hole located on its tibiotarsus, about a third of the way down the shaft roughly the same level as the end of the fibular crest. 

American Robin (Turdus migratorius)
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
No, its not the first time I have noticed such an opening, but it is the first time that I have ever made a concerted effort to learn more about their true purpose.   

All bones possess larger or smaller foramina (openings) for the entrance of blood-vessels; these are known as the nutrient foramina and are particularly large in the shafts of the larger long bones, where they lead into a nutrient canal, which extends into the medullary cavity. The nutrient canal (foramen) is directed away from the growing end of bone. The growing ends of bones in upper limb are upper end of humerus and lower ends of radius and ulna. In lower limb, the lower end of femur and upper end of tibia are the growing ends. The nutrient arteries along with veins pass through this canal. In long bones the nutrient canal is found in the shaft (source; Wikipedia).

Bone Nutrient Foramen Diagram
Image Credit: Wikipedia
https://avianmusing.blogspot.com/
Below are a few examples of nutrient canals from our above-mentioned American Robin, and an American Crow (Corvus brachyrhynchos); the humerus, coracoid, ulna and femur respectively. 

American Crow (Corvus brachyrhynchos) left, and American Robin (Turdus migratorius) bones with nutrient foramen
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
American Crow (Corvus brachyrhynchus) humerus nutrient foramen
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
American Crow (Corvus brachyrhnchus) coracoid nutrient foramen
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
American Robin (Turdus migratorius) ulna nutrient foramen
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
American Robin (Turdus migratorius) femur nutrient foramen
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
One of the more interesting bits of information to come about from my inquiry included a past study on the nutrient canal size of extant animals, in comparison to dinosaur fossils.

"One of the big controversies among paleobiologists is whether dinosaurs were cold-blooded and sluggish or warm-blooded and active. Could the size of the foramen be a possible gauge for dinosaur metabolic rate?", says Professor Roger Seymour from the University of Adelaide School of Earth & Environmental Sciences.

"On a relative comparison to eliminate the differences in body size, all of the dinosaurs had holes in their thigh bones larger than those of mammals," Professor Seymour says.

"The dinosaurs appeared to be even more active than the mammals. We certainly didn't expect to see that. These results provide additional weight to theories that dinosaurs were warm-blooded and highly active creatures, rather than cold-blooded and sluggish."

Professor Seymour says following the results of this study, it's likely that a simple measurement of foramen size could be used to evaluate maximum activity levels in other vertebrate animal groups, both living and fossils.

Wednesday, July 25, 2018

Cedar Waxwing (Bombycilla cedrorum). Are their wing-tips really made of wax?

The Cedar Waxwing (Bombycilla cedrorum) is arguably one of the most beautiful birds in North America. It is also one of the most common, occurring year-round in both rural and urban areas. 

Cedar Waxwing (Bombycilla cedrorum)
Image Credit: Wikipedia
https://avianmusing.blogspot.com/
Cedar Waxwings are very sociable, often seen in massive flocks. The sociality of individuals within winter flocks and the lack of territoriality during the breeding season also are associated with the reliance of this species on locally superabundant fruit crops. Voracious feeding on fruits by large flocks and a high degree of mobility make this waxwing an especially effective disperser of the seeds of fruiting plants (source: Birds of North America Online).

As its scientific name implies; cedrorum is Latin for "of the cedars", the Cedar Waxwings favorite food crop from the native red cedar tree.

Its common name “waxwing” also relates to the red cedar seed, which is covered in a white-waxy substance. The large consumption of cedar seed is believed to be a useful, and convenient source of wax secreted by the bird to the tips of their secondary feathers. 

Eastern Red Cedar (Juniperus viginiana)
Image Credit: illinoiswildflowers.info
https://avianmusing.blogspot.com/
Interestingly, the red secretions (colored by pigments found in other berries) on the secondaries of Cedar Waxwings increase in number and size with a bird's age. Experts suggest that the red waxy feather tips act as an important signal in mate choice and social organization.

Cedar Waxwing (Bombycilla cedrurum) secondary feathers
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
If we could for just a moment go back over these evolutionary steps; the cedar seed becomes covered in a protective wax, a Cedar Waxwing eats the wax covered seed, the ingested wax is secreted to the wingtip pigmented in red, finally giving rise to mate choice and social organization; it would be hard to argue against, or sway from this type of reasonable interpretation.

I agree, at first glance it does appear as if the wingtips were made out of a wax-like material, even under a stereo-microscope. But the more I thought about feather secretion, the more skeptical I became. Could wax really secrete out of the tip of a thin feather rachis? I had to have a closer look. 

Cedar Waxwing (Bombcilla cedrorum) secondary feather wingtip
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Sacrificing one of my own feathers, I focused my attention toward the base of this so-called secretion, looking for a telltale sign that may suggest a definitive droplet. What I discovered instead were actual feather barbs growing off the side of this wax-like base. Do feather barbs grow off wax secretions?

Cedar Waxwing (Bombycilla cedrurum) secondary feather wingtip
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Cedar Waxwing (Bombycilla cedrurum) secondary feather wingtip
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
There was also a pattern of barb termination characteristically seen at the tip of other feather rachises, where under a microscope one can observe two or three smaller barbs coming together to form the rachis tip. These terminal barbs seemed to grow normally onto and meet at the droplet. 

I also detected a blending of the rachises dark coloration directly onto the base of this wax-like substance. Is this significant? Can a feather rachis evolve odd looking appendages just about anywhere along its shaft? The answer to this question I believe is yes.

Back in August of 2017, I wrote an article about a similar appendage on the feather rachis of a deceased Hoatzin (Ophisthocomus hoazin). Here, I found not one, but three separate (different feathers) protrusions growing from the rachis itself, the black coloration bleeding into a lighter colored swelling. 

Hoatzin (Ophisthocomus hoazin) feather rachis
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Hoatzin (Ophisthocomus hoazin) feather rachis
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
The reason for this evolutionary accompaniment is still unclear, but it does appear to be a growth from the rachis, rather than from an outside source. See article below;


My continued examination of the droplet also included the handling and turning the feather on its side. Nowhere did this droplet feel like hard wax, nor was it stiff in any way. In fact, it felt thin as the rachis tip, soft and pliable. 

Cedar Waxwing (Bombycilla cedrurum) secondary feather wingtip sideview
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
The final inspection of the red droplet required total mutilation. This I did by pulling off the terminal half of the appendage and cutting it into a number of small pieces. What was revealed from the fragments, in my best judgement, were indications of tiny barb-like structures. Did the rachis reabsorb the barbs?

What does all this tell us about these red adornments on the waxwings secondary feathers? Are the tips secreted wax? Or are they simply an extension of the feather rachis itself?

In my opinion, the red tips at the end of the Cedar Waxwings secondaries are most likely a continuation of the feather, dominated, or reabsorbed by the rachis.

A “rachis dominated” feather is typically used to describe the rectrices of some 120 million-year-old Mesozoic birds. Below is a short remark, and a link to a past blog posting regarding this long extinct feather form. 

Changchengornis hengdaoziensis
Image Credit: Peter Schouten
https://avianmusing.blogspot.com/
Typically referred to as “rachis dominated”, the proximally ribbon-like portion of the feather in basal birds is a large rachis that continues almost to the end of the feather, distally bounded laterally by the vane, as in modern pennaceous rectrices. The rachis of the distally pennaceous portion is continuous through the unbranched vane portion of the feather in Mesozoic birds.

Sunday, July 22, 2018

Avian Mud Nests

The American Cliff Swallow (Petrochelidon pyrrhonota) is one of the most social land birds of North America. These birds typically nest in large colonies, and a single site may contain up to 6,000 active nests. Cliff Swallows originally were birds of the western mountains, where they still nest underneath horizontal rock ledges on the sides of steep canyons in the foothills and lower elevations of the Sierra Nevada and Rocky and Cascade mountains. In the past 100 to 150 years, these birds have expanded their range across the Great Plains and into eastern North America, a range expansion coincident with the widespread construction of highway culverts, bridges, and buildings that provide abundant alternative nesting sites. New colonies continue to appear each year in areas where Cliff Swallows were previously unrecorded as breeders (source: Birds of North America Online).


Cliff Swallow (Petrochelidon pyrrhonota) 1894
Image Credit: Wikipedia
https://avianmusing.blogspot.com/
This is the exact situation here in interior Connecticut, where twenty years ago Cliff Swallows were an uncommon sight and a bird worth reporting. Today, Cliff Swallows are a regular breeder in my area, but by no means nest in large colonies. At best, the species nesting status is believed limited, with a success rate that’s very low.

There are a few obvious reasons for this poor success rate. First; when Cliff Swallows do choose to nest in a colonial manner, they are widely spaced, making them more susceptible to nest predation by trained corvids, or nest displacement by aggressive House Sparrows (Passer domesticus).

If that doesn’t take them out, maintenance crews with water hoses often do, at private businesses where stucco and brick buildings are a favored foundation for their mud nests.

In this case, the second nesting attempt now becomes the alternative site, where Cliff Swallows search for out-of-the-way schools or libraries which bring less attention. This year’s second nesting attempt also brought with it some interesting personal observations.

The first dealt with the construction styles of both the first and second mud nests. Before losing their initial design, Cliff Swallows had affixed a narrow mud ledge below an overhang, extending the walls until a complete dome was created. With this plan came a narrow entrance tunnel, which pointed downward for added protection. 

Cliff Swallow (Petrochelidon pyrrhonota) Nest
Image Credit: http://www.ccbbirds.org
https://avianmusing.blogspot.com/
The second nest however is more rudimentary, again affixed to corner overhang, but this time in a less protective open cup. Constraint on available breeding time had led to a more limited construction method. 

Cliff Swallow (Petrochelidon pyrrhonota) Nest
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

The texture of the mud itself was also an interest of mine. How do swallows transport mud and create such wonderful surface designs? 

Cliff Swallow (Petrochelidon pyrrhonota) mud nest close up
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

Birds gather mud in their bills along the bank of a stream, lake, or temporary puddle, usually at a site within 0.5 km of the colony but sometimes several kilometers distant. A bird brings a mud pellet back to the colony and molds it into the nest with a shaking motion of the bill. The shaking causes a partial liquefaction of the mud, disperses moisture, and allows fresh mud to overrun small air spaces, resulting in a stronger structure when dry (source: Birds of North America Online). 

Cliff Swallow (Petrochelidon pyrrhonota) building nest
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Cliff Swallows (Petrochelidon pyrrhonota) building nest
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
This shaking motion and dispersal of moisture can be recreated by taking a handful of semi-moist dirt, packing it into a ball, alternating it from hand-to-hand, which turns the balls outer surface more wet.   

It’s an amazing construction method used also by the Barn Swallow (Hirundo rustica). Other birds incorporate mud into their nests, and when they do, depending on the location, appear to be more helpful. 

Barn Swallow (Hirundo rustica) and mud nest
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
The American Robin (Turdus migratorius) often uses the ledge located over my front door to raise young. Some robins use a mud base, others do not. Those that use mud, are almost always successful. Those that do not find it impossible to keep nest material secured to the ledge.

The Eastern Phoebe (Sayornis phoebe), like the Barn Swallow affix their nest to a roofs wood beam or pipe using a strong, adhering mud base.

The Rufous Hornero (Furnarius rufus) takes nest building with mud to another level. Rufous Horneros are incredible architects that build domed nests out of mud and straw; these nests are 20 to 30 cm in diameter and 20 to 25 cm tall.

Rufous Hornero (Furnarius rufus) and nest
Image Credit: Wikipedia
https://avianmusing.blogspot.com/
Recent studies suggest that the mud nest of the Rufous Hornero works as an incubation chamber that likely evolved to help resolve the incubation-foraging trade-off in the very seasonal and hot regions where the bird evolved. See study here; https://www.ncbi.nlm.nih.gov/pubmed/25526648

Friday, July 20, 2018

Dinosaurs. A Concise Natural History; Third Edition. A Pictorial Book Review.

The first time I ever set eyes on the book Dinosaurs. A Concise NaturalHistory; by David E. Fastovsky and David B. Weishampel, it was sitting behind the counter of a local museum called Dinosaur State Park, in Rocky Hill Connecticut.

Dinosaurs. A Concise Natural History. Third Edition.
By David E. Fastovsky and David B. Weishampel
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Curious, I asked a volunteer at the museum if the book was for sale. She replied no, but kindly asked if I would like to thumb through the pages. It didn’t take me long to realize that this publication was not going to be your traditional Dinosaur read. 

Dinosaurs. A Concise Natural History. Third Edition.
By David E. Fastovsky and David B. Weishampel
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Dinosaurs. A Concise Natural History. Third Edition.
By David E. Fastovsky and David B. Weishampel
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Published in 2016, Dinosaurs; A Concise Natural History is an innovative look at what is presently known about the evolution and extinction of dinosaurs, both avian and non-avian.

Designed and organized with the college student in mind, Dinosaurs (in their own words) promises to make science exciting and understandable to non-science majors through its emphasis on scientific concepts rather than endless facts. Fully updated and now integrating the theme of feathered dinosaurs, this beautifully illustrated, lively and engaging text will encourage students to ask questions and think like a scientist.

I couldn’t agree more, that’s exactly what this book has accomplished. Below is a brief example of what is to be expected within the pages of this book.

Stuff n’ feathers!

A look at the modern biota, without understanding its evolutionary history (preserved in the fossil record) leads to some very erroneous ideas about the “why” of many features. For example, pneumatic bones and feathers are commonly singled out as marvelous adaptations to maintain lightness and permit flight. Well, they surely are marvelous, they clearly maintain avian lightness, and there is no doubt that feathers work well for flight. But did pneumatic bones and feathers evolve for lightness and flight, respectively?

In both cases, now that we have a sense of bird ancestry, the answer is a resounding, “No”! Hollow bones are a saurischian character (even the names Coelophysis and Coelurosauria contain a reference to the hollow bones in these non-flying dinosaurs), and pneumaticity is likely related to efficient breathing (as implied above, we will see this again in immense, ponderous sauropods which you can safely assume didn’t fly). Avian pneumaticity likely developed long before there were things we would call birds. Modern birds inherited pneumaticity, unidirectional breathing, feathers and a host of other “bird” features from non-avian theropods, even though these features were further refined in modern birds.

Most of us would say that the purpose of feathers is flight. We agree; feathers are used for flight, but we doubt that they evolved for that purpose, particularly as many non-flying, non-avian dinosaurs had them. This, in turn, provides a real insight into what the origin of feathers was all about. One striking feature of all feathered dinosaurs, flying or no, are skeletal designs suggesting very active, commonly predatory, lifestyles. With feathers most primitively appearing on non-flying theropods, we infer that feathers likely provided the insulation that is a prerequisite for warm-bloodedness, allowing theropods to maintain high levels of activity for extended periods of time; an attribute that was eventually used for flight. Feathers undoubtedly were useful in a cursorial, predatory lifestyle. It is perhaps not coincidence that the most highly evolved feathers are flight feathers; other feathers, such as monofilamentous feathers and down, likely represent earlier stages in feather development, and graced the coats of more primitive non-avian theropods.

But insulation for warm-bloodedness as the real reason for the origin of feathers doesn’t completely satisfy, either, because many of the early feathers that we’ve seen are monofilamentous and may not have insulated very well. But as we all know, modern birds are brightly colored, highly social, and visually acute. Moreover, we know that at least some non-avian theropods were highly social creatures. We also know that ancient feathered theropods, non-flying and flying, had distinctive patterns and colored markings. Could feathers, at first, have been at least as much for display as for insulation?

Recall that in Chapter 5 we discussed the sensory importance of feathers. Here, then, is a hypothetical, but plausible, scenario for the evolution of feathers: widely distributed (across the skin), monofilamentous feathers could have first arisen for tactile sensation. Color might have appeared as a byproduct, or an even driving force, of evolving theropod sociality, associated with denser packing of the feathers. Still more densely packed, multifilamentous (downy) feathers might then (or concurrently) have evolved as a means of insulation. And finally, flight feathers may have ultimately evolved, associated with small size and a very active lifestyle. That is simply a scenario; however, what we know for sure, now, is that early feathers weren’t about flight!

This sort of clear and concise (as the books title implies) writing occurs throughout the entire book. Each chapter, such as; Who are the Dinosaurs? Theropoda III: the origin and early evolution of birds, and Ornithopoda: mighty Mesozoic masticators, contain chapter objectives, summaries, selected readings and topic questions. 

Dinosaurs. A Concise Natural History. Third Edition.
By David E. Fastovsky and David B. Weishampel
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

The graphic design of this publication is also wonderful. With its mix of easy to interpret cladograms, color CT-scans and excellent fossil photographs, every page seems to offer new and exciting visual information. 

Dinosaurs. A Concise Natural History. Third Edition.
By David E Fastovsky and David B. Weishampel
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

If that wasn’t enough, British freelance paleoartist John Sibbick provides a number of original black-and-white reconstructions of prehistoric life. Sibbick’s use of scientifically accurate environments, and animal behavior in his artwork is some of the best I have ever seen. Wow! 

Dinosaurs. A Concise Natural History. Third Edition.
By David E. Fastovsky and David B. Weishampel
Artist: John Sibbick
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Dinosaurs. A Concise Natural History. Third Edition.
By David E. Fastovsky and David B Weishampel
Artist: John Sibbick
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
On its third printing since 2009, Fastovsky and Weishampel do their best to stay up-to-date with today’s new scientific developments.

No longer is it just about digging up prehistoric bones from the ground. Dinosaur study instead deals with more far- reaching topics such as brain reconstructions (Stegosaurus), jaw mechanics (Heterodontosauridae and Ceratopsian), thermoregulation, nesting and feather coloration. All of these are effectively touched upon in this book.

Dinosaurs. A Concise Natural History. Third Edition.
By David E. Fastovsky and David B. Weishampel
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
One has to wonder, is another update and edition not far on the horizon? Recent discoveries in 100 million-year-old Burmese amber may set the wheels further in motion.

A personal favorite of mine was the section on Mesozoic birds. Fastovsky and Weishampel do a very nice job describing some of the critical steps in early avialan evolution. The evolution of Aves from the primitive avialan condition, represented by Archaeopteryx, through the remarkable avian discoveries recently made in China, culminates in an easy to decipher cladogram on page 182. 

Dinosaurs. A Concise Natural History. Third Edition.
By David E. Fastovsky and David B. Weishampel
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Dinosaurs. A Concise Natural History, is without a doubt, one of the more lively and interesting Dinosaur books on the market. I highly recommend it. 

Friday, July 13, 2018

House Wren (Troglodytes aedon); Avian Tool Maker? Or not?

A couple years ago, I wrote a story about the unusual nesting behavior of the much-maligned House Wren (Troglodytes aedon). See posting here: https://avianmusing.blogspot.com/2016/06/hostile-house-wrens.html

The wren’s habit of destroying the nests and eggs of other birds is well known among researchers and birdwatchers alike. Once the male lays claim to its breeding territory, a series of potential nest sites will become established. During that time, he will also actively search and eliminate any nearby competitor, either by taking over an existing nest or by simply removing their eggs. In my yard, victims of the House Wren have included the Black-capped Chickadee (Poecile atricapillus), Tree Swallow (Tachycineta bicolor) and Eastern Bluebird (Sialia sialis). 

Tree Swallow (Tachycineta bicolor) eggs destroyed by House Wren (Troglodytes aedon)
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

What is not well known about House Wrens is that they themselves are victims of the same nest and egg destruction from other predators, especially woodpeckers (Melanerpes spp.). This is exactly what I observed last week when the alarm calls of two wrens suddenly rang out, alerting me to the presence of a Red-bellied Woodpecker (Melanerpes carolinus) clinging precariously to the front of an occupied nest box. Undeterred by the mobbing of nearby birds, the much larger woodpecker proceeded to remove some of the nesting material before flying off.

This attack had, for the time being, put a stop to all visible House Wren activity. As a precautionary measure, I waited three days before opening the box to confirm its continued use, or disuse. It turns out that the nest was completed, but not yet active, resulting in no casualties to nestlings or egg loss. 

Curious about its construction, the nest appeared to be a jumble of different sized sticks, loosely piled to the top of the entrance hole. I removed the entire nest and brought it to work, consulting Birds of North America Online to find out if there was anything special about the House Wrens building methods.

Not surprising, information about the structure and composition of the nest is well studied, including the mention of spider cocoons placed in the box to control mite numbers. 

Spider Cocoons that were placed in a House Wren (Troglodytes aedon) Nest Box
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

It was also cited that the male during nest building may add as much as 400 sticks to a box. In my estimation, that seemed a bit much, so I took it upon myself to deconstruct the entire nest, separating each and every stick, placing them together in like-sized units. 

Disassembled House Wren (Troglodytes aedon) stick nest
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
The first thing that struck me about the nest material was the size of the larger sticks. With some measuring over 6 inches (153mm) long, I thought, what would inspire a wren to use such a lengthy branch?

It didn’t take me long to discover the answer to this question. A quick look at its second nest revealed that the larger sticks act as a side anchor to the platform.


House Wren (Troglodytes aedon) Nest with larger sticks
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

Fortunately, I was in the right place at the right time to witness and photographically document this extraordinary stick insertion. 

House Wren (Troglodytes aedon) adding large stick to nest box
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
House Wren (Troglodytes aedon) adding large stick to nest box
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
House Wren (Troglodytes aedon) adding large stick to nest box
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
But there were even more interesting questions to be had. The smaller sticks, numbering at 492, made up a good portion of the platform itself. Interestingly, many of the smaller sticks (297 to be exact) exhibited an obvious bend to one part of its length. In addition to the shape, the smaller sticks were amazingly consistent in size, measuring either one inch (25mm), two inches (50mm) or three inches (75mm), end-to-end. 


House Wren (Troglodytes aedon) nest box material 
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
Another interesting feature showed that approximately 1/5th of the 492 sticks had freshly sheared off ends. Did the wrens knowingly gauge the size of each chosen stick? Were the sticks intentionally manipulated to fit its current needs? Does this imply a form of tool making by the wrens? 

House Wren (Troglodytes aedon) sticks with freshly sheared off ends
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/
The remaining nest material consisted of 182 medium sized sticks (4inch/102mm), 86 large sticks (5.8inch/147mm), 82 tiny twigs (1/2 inch/6mm), 97 rootlets and small feathers and 103 pieces of grape vine, cedar needle, grasses that made up the nest cup.

Together, the House Wren nest contained a conservative estimate of 1,042 pieces of material, far beyond the 400 or so mentioned in Birds of North America Online.

The idea that these birds may actually be “tool makers”, as well as “tool users”, is something to strongly consider. Despite the nests chaotic appearance, the wren has selected uniquely curve-shaped sticks, mentally categorized the smaller sticks into three advantageous lengths, while at the same time manipulating many of them to their desired size by shearing off the ends of the branches.

Does this type of behavior signify “tool maker”; “tool user”? Are these sticks that were purposely manipulated actual tools? I'm not a hundred percent sure. The information provided below seems to both support, and not support the House Wren as a “tool maker” and “tool user”.

Tool use is found in at least thirty-three different families of birds. A Bearded Vulture dropping a bone on a rock would not be considered using a tool since the rock cannot be seen as an extension of the body. However, the use of a rock manipulated using the beak to crack an ostrich egg would qualify the Egyptian Vulture as a tool user. Many other species, including parrots, corvids and a range of passerines, have been noted as tool users. Bird nests show a great diversity in complexity. Many birds (and other animals) build nests. It can be argued that this behavior constitutes tool use according to the definitions given above; the birds "carry objects (twigs, leaves) for future use", the shape of the formed nest prevents the eggs from rolling away and thereby "extends the physical influence realized by the animal", and the twigs are bent and twisted to shape the nest, i.e. "modified to fit a purpose". The complexity of bird nests varies markedly, perhaps indicating a range in the sophistication of tool use. For example, compare the highly complex structures of weaver birds to the simple mats of herbaceous matter with a central cup constructed by gulls, and it is noteworthy that some birds do not build nests, e.g. emperor penguins.

The classification of nests as tools has been disputed on the basis that the completed nest, or burrow, is not held or manipulated.

Perhaps the best known and most studied example of an avian tool user is the woodpecker finch (Camarhynchus pallidus) from the Galápagos Islands. If the bird uncovers prey in bark which is inaccessible, the bird then flies off to fetch a cactus spine which it may use in one of three different ways: as a goad to drive out an active insect (without necessarily touching it); as a spear with which to impale a slow-moving larva or similar animal; or as an implement with which to push, bring towards, nudge or otherwise maneuver an inactive insect from a crevice or hole. Tools that do not exactly fit the purpose are worked by the bird and adapted for the function, thus making the finch a "tool maker" as well as a "tool user" (source: Wikipedia).

Saturday, July 7, 2018

Andaman Treepie (Dendrocitta bayleyii). 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
Photo Credit: Paul Cianfaglione
https://avianmusing.blogspot.com/

Species; Andaman Treepie (Dendrocitta bayleyii)

Andaman Treepie (Dendrocitta bayleyii)
Image Credit: Wikipedia
https://avianmusing.blogspot.com/
Introduction; The Andaman Treepie (Dendrocitta bayleyii) is a species of bird in the family Corvidae. First described by Robert Christopher Tytler in 1863, it is endemic to the Andaman Islands of India, where its natural habitat is subtropical or tropical moist lowland forests. It is threatened by habitat loss. The scientific name commemorates the Anglo-Indian statesman Edward Clive Bayley.

Andaman Treepie (Dendrocitta bayleyii)
Image Credit:http://orientalbirdimages.org
https://avianmusing.blogspot.com/
Description; 32cm. The smallest treepie of this genus. Unmistakable: Large white wing patch, pale yellow eye, dark bluish-grey head and neck, blackish on face and forecrown, dark tawny-brown upperparts, black wings, bright rufous rump, long black tail. Sexes similar. Juveniles have a browner hood and a dark olive iris.


Behavior; No information about diet, feeds probably omnivorous. Usually seen in small groups of up to 20 birds, often in bird waves with Andaman Drongos. Breeding recorded from March to May. The nest is a flimsy structure made of fine twigs and placed about 5m above the ground hidden in a tree. Lays 3 eggs. A resident species.

Andaman Treepie (Dendrocitta bayleii)
Image Credit: http://orientalbirdimages.org
https://avianmusing.blogspot.com/

Habitat; Moist lowland forests. Favors stands of largest trees.

Justification of Red List category; This species is considered to have a very small population size and is likely declining as a result of habitat loss within its range. It is therefore now listed as Vulnerable. Population size: 250-999. Population trend: Decreasing.

Source:

Birdforum.net/opus/Andaman Treepie.

Wikipedia

The Life of Birds by David Attenborough, 1998.