Bird Flight Or My Contribution to Science

Wings and flight are at the very essence of what is a bird, are they not? Humans have long regarded birds as heavenly creatures for their ability to slip gravity, to defy our own terrestrial existence. During most of human history here on earth, we've looked at birds and particularly, bird's wings for inspiration to find ways to do that ourselves - giving us the dream of flight. Beyond the power of flight and travel, few of us ever considered there might be more to bird flight than meets the eye. What has perplexed us is how birds have the lung capacity to achieve not only flight itself, but the ability to span the globe on wings hardly larger than our own hands or on huge wings, fly at altitudes [And have been reported to fly to 33,000 feet (some 12,000 meters or more Protor and Lynch, Manual of Ornithology, 1993, pg 16).] and endure cold temperatures at which humans couldn't live. But we've never combined into the same thought bird's two advantages that enables birds to achieve the feats they do on the wing: the ability to fly at all and the ability to fly tirelessly. The two abilities are linked in a most unexpected way.

For many years scientists puzzled over the avian respiratory system and proposed novel and extremely complicated ideas to explain all the elements of the avian breathing such as the link at the bottom of this page.* I especially remember one long and credible explanation of bird respiration that appeared in Scientific American in the early 70's. The model bird was a duck standing on the ground and the hard-to-follow explanation for air flow and air sac function was a 'had to' read over and over again proposition in order to grasp the whole breathing cycle because to understand it, you had to consider chemistry, physics as well as biology. Realizing that birds have all these air sacs and pneumatic bones that intercommunicate with each other and are in turn connected to the lungs results in a confused mess to try to understand how the whole system functions, it being so alien to mammal's system. Needless to say, the author was trying to convince that birds received adequate O2 just by compressing its lungs with its feeble thoracic muscles attached to the ribs. In this scenario, birds inhaled and air via the lungs passed through the lungs to the air sacs and then out again (in stages) resulting in an exchange of atmospheric chemistry sufficient to enable birds to rise above the world's tallest summits and span oceans on just a few breaths of air. It was my understanding that the air sacs would be full of stale air as there was no physical ability to adequately compress the air sac. While none of that was claimed in the article - because it avian respiration was not as thoroughly understood then, what turns out true enough is a bird's ability to span oceans and scale peaks the like of which humans can only dream. There is that word again.

Our understanding about the respiration system of a bird at rest is complicated because we know birds don't have large muscular diaphragms - like we mammals - to inflate and deflate their lungs like a bellows as we do. That's why we now know that bird's weak chest muscles can't possibly generate sufficient air to enable energetic and sustained activity, even if, apparently, the air birds breath passes through their lungs twice. But the amount of energy a bird uses at rest is miniscule compared to that which would be needed in flight. What nagged me for years was the claim that a bird at rest, despite breathing only a small amount of atmosphere, used the same mechanism and respiratory system for flight. That is, that birds thoracic muscles was sufficient to move all the air needed for strenuous flight as well as for rest. Added to that of course, was the idea that air sacs in birds exchanged their dead air - air sacs being dead ends anyway - for fresh air strictly by chemical means. That's how I remembered the Scientific American articles' claim.

Still, this explanation worked for me (and apparently still does for legions of Ornithologists) until, in the late 1980s, I met Timothy Rowe, co-author with Lowell Dingus of The Mistaken Extinction - Dinosaur Evolution and the Origin of Birds. Tim invited me to a talk at annual convention of comparative anatomists at the University of Texas given by the late Farish Jenkins, a Harvard researcher. Dr. Jenkins discovered that the wishbone (furcula) of a flying bird functioned like a spring and aided the bird's muscles in lifting the wing for its wing beat cycle when flying. Dr. Jenkins had measured energy production in every muscle in the wing and determined its energy demand vs what was available via respiration demonstrated the furcula was an energy saving device and aid that helped enable a bird to fly without becoming exhausted. How he determined this was amazing. Dr. Jenkins had trained starlings to fly in a wind tunnel(not his innovation as Ornithologists have been flying budgies in a wind tunnel in 1966) and he filmed the birds while flying...with both normal and X-ray cameras. Using X-ray was Jenkin's innovation. What the developed film revealed was the function of the birds' bones and muscles during flight. In both regular film and X-Ray film you could see the bird up close and all the mechanics of flight provided by feather, bone, and muscle. But there was more and that's what I saw.

I watched in amazement as the starlings' wings - bones, muscles, and feathers - worked in unison during each and every up and down stroke of the wings (complete breath cycle from wing up to wing down). Most unexpected for me was the fact that the sternum rocked back and forth alternately depressing and allowing for expansion of the posterior and associated air sacs - the most prominent in birds. Since the air sacs are not muscular, they cannot expand and contract like the lungs (via thoracic muscles). It turns out that the action of the sternum assures the enlargement of the air supply, enabling a double passing of air through a bird's lungs providing for maximum gas exchange efficiency why in flight, but not when stationary. When at rest, the air sacs are not sufficiently depressed, instead, it was assumed for years that air exchange with the air sacs was chemical and not dynamic. Thus the ability - the need - of a bird to fly and the bird's need for maximum pulmonary efficiency for sustained flight are intricately connected. Bones, muscles, feathers, lungs and air sacs work together to produce a complicated, but amazingly most highly efficient breathing apparatus in the Animal Kingdom.

After the conference there was a reception for Dr. Jenkins at Tim and Elizabeth Rowe's home and Elaine and I were invited. There I explained what I had seen. Afterwards, once Dr. Jenkins had gone home, he refined his understanding of bird flight to include the evidence that the sternum in addition to the furcula directly enhance the ability of a bird to breathe and thus fly seemingly without reaching exhaustion as we would expect for ourselves - from our own understanding of mammal respiration and mobility. In other words, the bird respiratory system is bio-mechanical involving the bones, muscles, air sacs, and lungs to achieve maximum efficiency, not strictly anatomical like it is in mammals with only diaphragms and a set of closed lungs that allows short bursts of strenuous activity. Birds have to fly to breathe.

Many years ago a University of California, Davis, study demonstrated that cockatiels allowed to fly were more successful breeders than non-flying ones. This is not surprising. These revelations mean that flight is not an either or proposition for flying birds, but a necessary, if not an evolutionary (not to speak of revolutionary) advantage. Farish Jenkin's information has now made its way to ornithological and veterinarian texts in one form or another these days and I would expect further developments on the subject in the future. By 1993, Noble Proctor and Patrick Lynch in MANUAL OF ORNITHOLOGY - Avian Structure and Function, basing their comments on Jenkin's work, included the fact that the furcula (wishbone) acts in birds like a spring that not only aids birds in flight by reducing the work load required by the flight muscles, but also deflates the anterior air sacs resulting in a more complete exchange of respiratory gases. Now we know thanks to the conference I attended that birds have a highly efficient pulmonary system that operates best during maximum utilization. For flying birds, that means in flight. These revelations help explain bird's abilities to fly continuously for long periods of time. One species of shorebird, the Bar Tailed Godwit, migrates non stop across the whole Pacific Ocean between its Alaska breeding ground and its New Zealand winter hunting grounds! What, besides magic, would explain little shore birds' breath taking annual globe trotting migrations from northern and southern hemispheres, or the mind boggling knowledge that migrating birds such as geese routinely scale high mountain ranges around the world during their twice a year pilgrimages from breeding grounds to wintering grounds - and from basically sea level to Tibet in a matter of hours without using rising air currents or other 'energy saving' devices. Geese are not alone, as everyone knows, even the tiny hummingbirds span the Gulf of Mexico twice a year during their annual migrations; they are not alone, of course. Incidentally, there is another surprising ramification of the form, function and evolution of bird flight. This information has been generated by paleontologists and ornithologists regarding our understanding of the origin of birds - what they are and what animals were their ancestors and the like. The evidence such as the possession by dinosaurs of a furcula points to the fact - not the possibility - that birds are directly descended from dinosaurs, actually, just another type of Theropod related to the largest land predators ever!

After the conference, I did a couple of things to spread the word as to what we had seen and understood. I wrote an article for a parrot organization newsletter I edited describing the implications of the information as I understood it at the time. I also called a couple of friends - an ecologist and an ornithologist - to tell them what I had discovered. I sent my article to Dr. Catherine Toft at the University of California, Davis, and talked to Dr. John O'Neill at LSU and discussed my observations. Both scientists had collaborated with the parrot breeder organization whose newsletter I edited on a number of projects and I distinctly remembered Dr. O'Neill asking me if what I saw was true, what about non flying birds like Ratites, the Ostrich, Emus and the like. I told him that sounded like a good research project for him - X-ray those obligate bipedals while running on a tread mill!

Ornithologists are a hard headed group. Apparently, Ornithologists have yet to understand how birds are able to achieve the feats of flight they do around the world and research continues to probe into the avian respiratory and cardiovascular system in search of clues to solving the mystery of flight. Recent research is still mostly focused on energy generation, chemical exchange and cardio function without incorporating the bio-mechanical evidence reveled by Dr. Jenkins. Blood components and mitochondria is under scrutiny as if the question of how birds achieve the feats they do cannot be explained simply by an understanding of their anatomy and the way their bodies work. BTW, in my opinion, the mystery of flight has been established without a doubt, without debate that a bird can fly without a wishbone, i.e., wishbone is not essential to a successful flight. Determining the function performed by the wishbone was Farrish Jenkin's first discovery.1 Adding my observation about the function of the sternum - in addition to securing the powerful flight muscles to the body serving as an integral part of the whole respiratory system - was his second important revelation.

1 http://articles.latimes.com/1988-09-19/local/me-1562_1_wind-tunnel

Even after Dr. Jenkin's ornithological research continues to center around blood chemistry (trying to reveal differences in avian hemoglobin/mitochondria and other highly technical, but ultimately invasive procedures to explain bird's flying ability. A sample of these efforts can be reviewed below but what I notice is a continuing reluctance to accept Dr. Jenkin's discoveries which really offer a much more simple explanation of how birds fly - and breathe.2

2 http://people.eku.edu/ritchisong/birdrespiration.html

*Sources:

https://www.palaeontologyonline.com/articles/2017/fossil-focus-archosaur-respiratory-system-breathing-life-dinosaurs/?doing_wp_cron=1572050458.9290409088134765625000

https://www.allaboutbirds.org/news/flight-of-the-kuaka-a-godwit-makes-the-longest-nonstop-flight-ever-recorded/

http://www.nytimes.com/2012/12/01/us/farish-jenkins-fossils-expert-dies-at-72.html

sad note added October 4, 2018: Obituary for Dr. Catherine Toft, University of California, Davis .

https://biology.ucdavis.edu/people/catherine-toft

https://news.nationalgeographic.com/news/2007/11/071108-dinosaurs.html

http://jeb.biologists.org/content/214/15/2455

Birds just have to fit into this diagram for us to understand the complexity of different species ability to fly high and widely.
http://jeb.biologists.org/content/jexbio/214/15/2455/F1.large.jpg

No statistical difference in lung size of high altitude and low altitude related species
http://jeb.biologists.org/content/220/6/1079?utm_source=TrendMD&utm_medium=cpc&utm_campaign=J_Exp_Biol_TrendMD_0

http://jeb.biologists.org/content/220/6/955?utm_source=TrendMD&utm_medium=cpc&utm_campaign=J_Exp_Biol_TrendMD_0

One flap, one breath but 5-6 fold increase in heart rate which keeps the chemistry constant at altitude
http://jeb.biologists.org/content/214/24/4071.long?utm_source=TrendMD&utm_medium=cpc&utm_campaign=J_Exp_Biol_TrendMD_0

Related: How birds fly high and far without drinking water:

http://articles.latimes.com/2011/sep/09/science/la-sci-migrating-birds-muscle-20110910

Compare this journal entry with this article. Notice any difference between the two?:

https://www.birdwatchingdaily.com/blog/2014/01/30/the-amazing-muscles-and-bones-that-make-birds-fly/

***Important Breaking News from the New York Times. Please read:

https://www.nytimes.com/interactive/2018/04/27/opinion/shorebirds-extinction-climate-change.html

Posted on December 31, 2017 06:35 PM by billarbon billarbon

Observations

Photos / Sounds

What

Gadwall (Mareca strepera)

Observer

billarbon

Date

November 2013

Place

Texas, US (Google, OSM)

Description

Winter visitors. One American Wigeon tagging along, bringing up the rear. And upon closer examination, there's a female Wigeon slightly ahead of the trailing male. At least one. Or two.

Photos / Sounds

What

Red-tailed Hawk (Buteo jamaicensis)

Observer

billarbon

Date

February 3, 2016 01:12 PM CST

Description

Red-tailed Hawk patrolling the Pedernales River valley checking me out.

Photos / Sounds

What

Sandhill Crane (Antigone canadensis)

Observer

billarbon

Date

March 11, 2014 07:30 PM CDT

Description

Spring migration back to the nesting grounds

Photos / Sounds

What

Osprey (Pandion haliaetus)

Observer

billarbon

Date

October 2017

Place

Texas, US (Google, OSM)

Description

Osprey fishing. Or, as this is October, you could say it's a headless Halloween Hawk! Boooo!

Photos / Sounds

What

Great Egret (Ardea alba)

Observer

billarbon

Date

November 8, 2017 01:28 PM CST

Description

flock flying over denuded bank of the Pedernales River at LCRA Nature Park.

Photos / Sounds

What

Gadwall (Mareca strepera)

Observer

billarbon

Date

December 13, 2017 01:51 PM CST

Tags

Comments

Must not overlook that birds are expert pilots, and find the best air to fly in. I think this is what our Canadas are doing when they fumble around for awhile each morning. Nevertheless, some species such as bar-headed geese that cross the Himalayas, are particularly adapted. Not just any bird can do it: doi: 10.1073/pnas.1017295108

Posted by ellen5 about 6 years ago

Thanks for the link. Of course, Bar-headed geese have to hurtle the world's highest peaks (not just the Himalayas) twice a year. Other species must also have to cross those mountains as well. I'm certain even passerines make it over some of those passes as well. But flying up from the Indian plain and scaling the Himalayas in a matter of hours with no tail wind is a feat to recon with. It's an awesome achievement. So too for our own species who fly the entire Gulf of Mexico in a single bound. Having a pulmonary system that is even more efficient under the stress of exertion is all the more remarkable. I think one of the details of this high flying business (besides being good pilots:-) is that even at these high altitudes (much higher than we could live or function at) one of birds major issues is heat exchange - birds generating great body heat even in sub zero air. And we think we have it bad on days like the last few here in Texas this New Year's Day. Birds, their flying and breathing systems are truly a work of nature to behold. Thanks for your comment.

Posted by billarbon about 6 years ago

That cold air is also excruciatingly dry, as winter joggers can attest. And so birds also have adaptations to hydrate those lungs (modified surfactants).
I work on cystic fibrosis and while doing some reading in that field learned that birds have tubular lungs, not alveolar like ours -- whole nother architecture.
http://people.eku.edu/ritchisong/birdrespiration.html

Posted by ellen5 about 6 years ago

I think this link, my second reference above, does a great job explaining avian respiration - and dinosaur, LOL. In fact, dinosaur respiratory system is what birds have, not the other way around according to the information on bird respiration. But yes, that air is dry and cold, just like we get when the arctic air sits on top of us. Avian lungs are so finely tuned that small amounts of toxic chemicals can kill a bird that wouldn't seem harmful to humans - witness the teflon™ crisis in pet birds a few years ago - and this sensitivity is why humans used birds to test air quality in constricted places like mines.

Also along these lines and something hardly ever mentioned is the obvious wind chills generated at altitude at flying speed. Regardless the species, birds' legs are often un-feathered and the scaly skin is exposed to those horrific temperatures and wind chills, yet, as we know waterfowl, raptors - all temperate (and some tropical) species regularly are active in the worst of conditions yet show little ill effects from their exposure.

Posted by billarbon about 6 years ago

Ellen5, And, despite the ambient temperature, flying birds have to deal with overheating, not over cooling. Migration is all about obtaining food rather than avoiding the cold. I mean, when birds migrate to and from their breeding grounds, it's still cold in the layers of the atmosphere where they fly (most efficiently as you point out). Often these birds are flying either with or against cold fronts and other inhospitable weather conditions - at least to us mammals. For me when it gets cold outside or I have to sleep outside in the cold, I want my down filled sleeping bag, thank you. Or when working outside on cold days like the last few, putting on my down filled jacket w/hood. Talk about keeping warm!

Posted by billarbon about 6 years ago

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