August 08, 2021

Deformed Duck Humerus, A Healed Long Bone Fracture

A few months ago, in an otherwise apparently standard Domestic Muscovy Duck (Cairina moschata var. domestica) skeleton, I came across an extremely deformed humerus.
On the left is the deformed humerus, on the right the bird's seemingly healthy humerus.

The humerus' deformity I believe to be the result of a healed bone fracture.

Below are long bones from various carnivorans, displaying different healed fractures. Not all the deformities are especially obvious, but D, a healed bobcat (Lynx rufus) femur, stood out as a similar level of deformed to my Muscovy humerus.

From Argyros, George & Roth, Aaron. (2016). Prevalence of healed long-bone fractures in wild carnivores from the northeastern United States. Journal of Zoo and Wildlife Medicine. 47. 879-882. 10.1638/2015-0180.1.

Although I am fairly confident the humerus is a healed fracture, and that is why it is deformed, I still have a lot of questions I, ideally, would of found answers to, and explored them more in this journal post. It's unclear what eventually killed the duck, but with how healed the humerus was, I assume it lived substantially long after the initial injury. I don't know what caused the injury, how long it could take for a fracture like this to heal, or what the duck's life was like after the injury.

The only other conclusion I have made from this aside from the fact the humerus is a healed fracture as opposed to say, a genetic deformity, is that this duck's prolonged survival to heal after a significant injury implies there are no alligators at the lake it lived. The article Noteworthy healed fractures in Some north american artiodactyla (Smith Grandstaff, B., Deeble, E., Parris, D.) studies artiodactyl skeletons with long bone injuries, and explains "these specimens demonstrate the resiliency of injured artiodactyls in wild populations with few large predators". I know I can't assume studies on deer and pronghorn can translate flawlessly to avians, but I have a hard time imaging an almost literal sitting duck could live long enough to permit healing if living among predators. No gators are observed there on iNaturalist, and I haven't heard reports of gators, though I know they aren't totally uncommon for the surrounding area. But, this duck does give me confidence there are no gators, at least at the time of the duck's life, at the lake. Guess that means I don't have to worry terribly much about the times I almost fall into lake looking for bones along the steep and rocky shoreline.

Though, back to the duck being an almost literal sitting duck, it is actually difficult to know how impaired it was by the wing bone injury.
The article Waders (Scolopacidae) surviving despite malaligned leg fractures in the wild: kinematics of bipedal locomotion (Reichert, J., Mayr, G., Wilke, T. et al.) explores the implications of healed long bone injuries in the wild on the function of the injured animals, describing information on the subject as "scarce". They studied wader leg injuries, and although the birds presumably had to make some life style changes to survive, their movement wasn't terribly impaired.

Well, that is about it for my findings. I was hoping to have have more for this, and not just post bizarre bone pictures without more context, and although I was able to find more context it wasn't all I hoped. At the very least I suppose it was validating to see Reichert, J., Mayr, G., Wilke, T. et al. describe information on the subject as scarce. I could find more on fractures healed with veterinary methods, but that is different than fractures healed in wild settings. I assume my duck here couldn't fly, but even that I can't be totally certain of. Also interesting to learn more places in osteology there are dearths of information.

Argyros, George & Roth, Aaron. (2016). Prevalence of healed long-bone fractures in wild carnivores from the northeastern United States. Journal of Zoo and Wildlife Medicine. 47. 879-882. 10.1638/2015-0180.1.

Reichert, J., Mayr, G., Wilke, T. et al. Waders (Scolopacidae) surviving despite malaligned leg fractures in the wild: kinematics of bipedal locomotion. Avian Res 8, 23 (2017).

Barbara Smith Grandstaff, Eric Deeble, and David C. Parris
School of Veterinary Medicine
University of Pennsylvania
Philadelphia, PA 19104
Bureau of Natural History
New Jersey State Museum
Trenton, NJ 08625

Posted on August 08, 2021 16:57 by lizardking lizardking | 1 observation | 0 comments | Leave a comment

June 18, 2021

Bird Skull and Pelvis vs Mammal Skull and Pelvis

When IDing bones, one of the most common mistakes I come across is confusion between bird and mammal skulls and pelvises. Not just confusing a bird pelvis for a mammal one, but often a bird pelvis for a mammal skull. Since this is so common, I decided to have a post with a more in depth explanation.

I will be using a Domestic Muscovy Duck (Cairina moschata var. domestica) and Gray Fox (Urocyon cinereoargenteus) to demonstrate.

From left to right: Duck pelvis, duck skull, fox skull, fox pelvis.
First I will start with the most common mistake of this order confusion, mistaking a bird pelvis as a mammal skull. Most of the confusion seems to come from the bird pelvis' acetabulum, circled below.
(see also, Parts of a bird pelvis:

(Left, duck pelvis, right, fox skull.)
This is where the femur articulates into the pelvis. However, its perfectly circle shape is often mistaken as an eye socket. As you can see on the fox skull, eye sockets aren't actually that clean and circle. It is a very common mistake though, and I will also detail some ways to tell the bone is a pelvis, and not a skull.

(Left, duck pelvis, right, fox skull.)
Both the duck pelvis and fox skull have a similar form, a wider posterior (back) and then a more narrow anterior (front), the fox's snout seeming analogous to the duck's anterior. That, however, when turned upside-down, is revealed to be not dental and nasal structures, but fused vertebra.

(Left, duck pelvis, right, fox skull.)
Bird bones have to be very efficient. Strong, supportive, but light weight. They have a lot of fusion, and the pelvic girdle is a great example of this. Much of the lower spine is fused to be part of the pelvis. So while the anterior of a mammal skull should have teeth or holes for teeth, the anterior of a bird pelvis -and its entire length- has fused vertebra.
Second is a less obvious, but still common, confusion.
When bird skulls have their beaks, they are typically easily distinguishable from mammal skulls. I have seen confusion when the bill is broken off, and also on occasion rabbit skulls being confused for avian. The easiest way to tell an avian skull from a mammalian one is the rounded "bump", or occipital condyle, on the skull, around the foramen magnum, or the opening at the back of the skull the spinal cord runs through. Birds have one, right under the center of the foramen magnum, and mammals have two, on either side of the opening.

Left, duck skull, single arrow pointing to it's single occipital condyle. Right, fox skull, arrows pointing to both occipital condyles.

And last is a less common, but still frequent cause of confusion, mistaking bird and mammal pelvis.

(Left, duck pelvis, right, fox pelvis)
As said above, bird bones have incredible efficiency of strength and lightness, and fusion is one mechanism that helps achieve this. Mammals don't have this same need, and the structure of their pelvises appear far more simplistic. Bird pelvic girdles have a lot of spine fused to the pelvic bones, where mammals lack any apparent vertebra in their structure.

(Left, duck pelvis, right, fox pelvis)
Also discussed earlier, the circle opening confused for an eye socket is actually the acetabulum, where the femur attaches to the pelvis. In mammals, this is less of an opening and more of a crater or indent. The spherical indent on the side of the pelvis is the fox's acetabulum.

This is an overview, a general explanation to help educate and also to explain my own personal ID corrections, but I can gladly explain aspects more in depth, and as always, I am always open to help with anything bird bone related. Lee Post has an excellent book that covers how to differentiate the entire avian skeleton from mammalian, The Bird Building Book.

Posted on June 18, 2021 18:31 by lizardking lizardking | 2 comments | Leave a comment

Great Blue Heron

Wish bone


sternum and vertebra


wing girdle;
humerus, coracoid, scapula

coracoid, scapula



both wings



Posted on June 18, 2021 17:32 by lizardking lizardking | 1 observation | 1 comment | Leave a comment

February 15, 2021

Differentiating Accipitriformes Skulls (Simplified, USA)

Skull images credit to and Royal CS Museums' Avian Osteology.
This is an incomplete and oversimplified guide, but helpful for me to review back to and potentially link to when IDing, or as a good introduction for people looking to start building knowledge on osteology of the skulls of birds of prey. Unfortunately I lack reference material for many of the unlisted Accipitriformes and they therefore had to be excluded, but this covers some of the most common. If anyone wants more specific advice, please comment or message me

Bald Eagle (Haliaeetus leucocephalus)

-Massive size (12 or more cm)
-Almost entirely, and in some specimen entirely, solid sheet of bone between eyes (circled)
-Extremely pronounced and thick beak


Golden Eagle (Aquila chrysaetos)

-About bald eagle sized (12 cm) but:
~Has perforation in sheet of bone between eyes
~Has smaller bill


[for a more in depth comparison of golden vs bald eagle skeletons, see]

Snail Kite (Rostrhamus sociabilis)

-Completely unique bill shape, exceptionally delicate and curved


Osprey (Pandion haliaetus)

-Round and almost circular nasal (circled)
-Particularly curved bill


Hen Harrier (Circus cyaneus)

-Comparatively slender frontal (circled)

( for harrier, other two skulls from skullsite)

Harris's Hawk (Parabuteo unicinctus)

-Yellow on bill sheath


(pictured is a red tailed hawk Buteo jamaicensis)

-Typically larger than Accipiter, but much smaller than Golden or Bald eagles
-More straight posterior
-More narrow opening in sheet of bone between eyes (circled)
-Nasal a "triangular oval", more open and clean


(Pictured is coopers hawk Accipiter cooperii)

-Wider and larger opening in between bone sheet that separates eyes
-More rounded posterior
-Nasals tend to vary across Accipiter, not as evenly shaped


Posted on February 15, 2021 23:19 by lizardking lizardking | 0 comments | Leave a comment

September 23, 2020

Duck Bone Identification Walk Through

In the process of removing a lot of young coconut palms from under our large coconut palm, some duck bones were unearthed.

Judging by the petite size (and a bit of hopeful bias) I initially thought they could be mallard (Anas platyrhynchos).
However, this was disproved almost immediately, ruled out by the sternum. I new mallards had wider xiphial areas (circled) than a handful of other waterfowl (Muscovy ducks, many geese, and swans, etc.), but I didn't realize just how wide. Not all mallards have the posterior lateral processes (in rectangle) connected to the xiphial area like this reference from the Ohio Virtual Museum, but they're all close. Certainly not a fit for the unknown sternum.
This would hold true for all Anas species, which eliminates them and leaves the two more likely options; a Muscovy Duck (Cairina moschata, specifically Cairina moschata var. domestica) or Egyptian Goose (Alopochen aegyptiaca).


So I got out Muscovy and Egyptian Goose bones for comparative analysis.

First lets start with the sternum.

The Egyptian Goose has a very broad xiphial area (circled) compared to my two Muscovy sternums (larger male, smaller female) and the unknown sternum. The Egyptian Goose sternum in general seems to be wider than the Muscovy and unknown, so it's looking to just be a petite Muscovy duck.

But then I went to the humerus.

(Male Muscovy duck is seen here)
In the square box is an indent known as the capital groove. The unknown humerus and Egyptian Goose humerus both seemed to be more dramatic than the Muscovy. Now I'm considering if this is a goose, not a duck.

On to the pelvis.

Circled on all pelvises is the ischiadic foramen, the opening (foramen) in the ischium of the pelvis. The humerus didn't convince me the unknown was a goose, but this pelvis is getting me there. The foramen of both the male and female ducks is larger, with an almost second foramen extending from the first. I have used such comparisons in my identifications before, so now I'm quite sure this unknown is actually an Egyptian Goose!

And now here comes the tarsometatarsus.

Uh oh. As I went into my box of goose bones to get the tarsometatarsus I immediately realized something was off. Was the unknown bone broken? When I got out the Muscovy tarsometatarsus, however, I realized that no, it was in fine shape. Dirty, yes, but not broken. Egyptian Geese apparently have very long tarsometatarsus, and this unknown bone was not that. And so this becomes a cautionary tale of the inherent randomness in nature, as well as the issues with using features very susceptible to ossifying and changing shape with age.

The unknown is most certainly a Muscovy.

The largeness of the foramen and vague difference in the humerus (which I struggle to find myself now reflecting after a few days) are just not strong enough to trump the wideness of the Egyptian Goose sternum, and, most of all, the size of the tarsometatarsus.
So how do we know what is actually reliable to determine as an identifiable trait?

I am not professional trained by any stretch. I have no formal education in what I do. Not until maybe a year into my self teaching did I buy a proper comparative osteology book, Osteology for the Archaeologist by Stanley J. Olsen.
However, even trained professionals use unreliable identification measures subject to the same issues with what I did with the foramen.
I learned somewhat early on into my studies that professionals often use palatal structures in identification, but that always seemed imprecise to me. I never bothered to study the bottom of bird skulls of IDing, and when people ask if that's an important view I'd say for some people, but I don't find it necessary. And, upon getting my first proper comparative osteology book, I realized I wasn't unjustified in my assumption. From Olsen's Osteology for the Archaeologist:

"It must be pointed out that there is some individual variation in this palatal complex, not only among bird groups, but also regarding the age of individual birds within these groups For instance, in the young of some gulls, crows, and hawks, the anterior margin of the pterygoid becomes detached from the rest and fuses with the palatine. These palatal types must be considered as of taxonomic value only when used as part of the diagnosis which is based on other osteological characters as well."

In short, things that can easily be subject to changes with age can be used for identification as a supplement, but certainly not alone. I personally think I'll retire using the shape of the ischiadic foramen to diagnosis species within a group, though I still intend to use it to differentiate between family groups I never encountered a problem with that thus far, but I suppose time will tell if that's reliable. But there is a much bigger different between a tiny coot ischiadic foramen than the ischiadic foramen of any waterfowl, even if the individuals experience variance.
I've also had issues with using pneumatization patterns for ID, which makes sense. Most bones as far as I'm aware tend to ossify or have changes in ossification with age, and therefore something as delicate as tiny holes in the bone would surely be subject to morphological changes with age. Younger ducks, I have found, tend to have more pneumatization on the bottom of the sternum than older ones. Which makes sense when you think about how many vertebrates ossify more with age.

Ultimately, I think only using one or two traits on one or two bones can always lead to issues, even if they don't experiences the issues discussed above. A well rounded look, exploration and analysis of whatever morphological features you have seems to be a good plan to make the more through ID possible.

Posted on September 23, 2020 02:37 by lizardking lizardking | 1 observation | 2 comments | Leave a comment

June 23, 2020

White ibis skeleton!

I can't express how insanely grateful I am to of found a white ibis (Eudocimus albus) skeleton.
This post will have more photos than those uploaded in my observation. Because white ibis are MBTA protected, I wasn't able to collect it, but I was able to do a set up sufficiently similar to what I do at home to photograph the skeletal elements to try and capture their measurements and morphological features.

I'll be more than happy to define all the terms I use, and correct any I might have misused.

Coracoid, ~4.4, 4.5 cm at longest point.
Ventral veiw.


Furcula (wishbone).

Humerus, ~10 cm.
Left humerus, posterior view.

Left humerus anterior view, right humerus posterior view.

~8.4 cm, 8.8 cm including anterior-most part of sternum, the manubrium.
Ventral view.

Dorsal view.

Emphasis on pneumatization

Lateral view, with coracoids, scapulas, humerus, and wishbone still articulated.

Emphasis on still articulated sternal ribs.

About two feet away, I found the pelvis and some vertebra, and about half a foot from there, the tarsometatarsus, and a few inches away from that the tibiotarsus.

Pelvis, ~8.6 cm.
Dorsal view.

Lateral view.

With tarsometatarsus and vertebra.
Ventral view.

Ventral, with focus on pubis.

Dorsal view.

Lateral view.

Tarsometatarsus (~6.1 cm, posterior view) and vertebra.

Tibiotarsus, ~11.5 cm.

Lateral views.

Emphasis on pronounced outer cnemial crest.

Emphasis on distal end.

And that's that! The associated observation has some more photos, including feathers, but many are the same.

Like how I can't properly express how grateful I was so find this, I also can't properly articulate how humbled I was. I spend hours going through observations of bird bones on iNaturalist, using hundreds of photographs and illustrations for reference from books both online and physical, museum and college collection databases, figures from scientific papers, shared photos from taxidermists, curators and collectors, anything I can get my hands on. I have a decent avian bone collection, consisting of countless Muscovy ducks, several chickens, a couple of feral pigeons, a collared dove, a monk parakeet, European starling, turkey and peacock.

And even with all of that, I was still tripping up and confused. I changed my ID 4 times, back and fourth between shorebirds and white ibis. Some specific features threw me, like the very strong transverse processes on the immediately post-acetabular vertebra (circled) that I am familiar with in shorebirds (comparison is a Glaucous Gull from, but in general I just felt clueless and bumbling.

The most important thing I think I learned that day wasn't any specifics about white ibis or great blue heron skeletal structure (more on the heron later, maybe tomorrow), of which I learned a great deal, but that I am still vastly ignorant. Every bird in my skeletal collection was found and cleaned by me or me and my sister, with the exception of the turkey, which I bought because I was having difficulties grasping their bones. It's incomplete, I don't have complete turkey skeleton money, but it has helped insurmountably. And the fact that the white ibis bones have also helped me understand so much, far more comprehensively than Olsen's Osteology for the Archaeologist or the Smithsonian's photographs ever could, was a rude awakening as to how stunted I am by not having access to physical references. Illustrations and pictures are helpful, but no substitute for the real thing. The ibis skeleton just felt so foreign, even though I've seen pictures and illustrations of them and even IDed some before.

There's obviously no easy solution to this, there's no way I could legally argue getting a collection permit for these things and the only museum that would have those reference materials near me is about 7 hours away by car. But I can hope to keep exploring and encountering new incredible finds. Studying avian osteology without many ways to ascertain physical bones to study sure isn't easy, but fortunately I like a challenge.

(In other news of personal osteological break throughs, I have finally found a photographic reference on an aningha pelvis. I'm sure a physical one would still blow my mind, but after only seeing illustrations for years it is still super impressive to see an actual photo.)

Posted on June 23, 2020 03:18 by lizardking lizardking | 1 observation | 3 comments | Leave a comment

May 31, 2020

Some Bird Sternums


Turkey (Meleagris gallopavo) sternum:

Peafowl (Pavo) sternum (male):

Domestic Chicken (Gallus gallus domesticus):

(from top to bottom)
Peacock, chicken, turkey.


Domestic Muscovy Duck (Cairina moschata domestica):

Chicken vs Muscoy duck:

Feral Pigeon (Columba livia domestica)
Monk parakeet/Quaker Parrot (Myiopsitta monachus)
Eurasian collared dove (Streptopelia decaocto)

Duck, chicken, pigeon, monk parakeet, collard dove:

Posted on May 31, 2020 04:39 by lizardking lizardking | 3 comments | Leave a comment

May 08, 2020

Another Duck Bulla Bone/Syrnix

As I said in my post Domestic Muscovy Duck Duck Quack Box/Bulla Bone/Syrnix, I feel there's a general lack of waterfowl syrnix references online. I shared mine, but it was not in prime shape. Fortunately, I now have a second Cairina moschata domestica quack box in much better condition than my previous one that I think would be very valuable to share.

The new one is one the left, the old one on the right.

I assumed my old one might have been so thin because of how I cleaned it, but it makes sense Muscovy voice boxes are so much thinner than other ducks (1, 2) when you think about their calls. Muscovy ducks make low, weak and breathy sounds, and aren't generally wont to vocalizations.

I'm thrilled at the concept of more obscure anatomical elements being able to be identified so precisely. If you're in Muscovy duck territory and find a disembodied voice box around an inch/3 centimetres long that is exceptionally paper-y and thin, the good likelihood (I assume) is that it would be a Muscovy. Very few ducks are as quiet as them.
It's easy to identify mute swan sternums on a similar principle; all other Cygnus species have a thick keel to store extra windpipe to project their calls, while mute swans are the most "mute" of swans and lack this anatomical feature. You can see that clearly here with a Whooper swan as comparison, but all other Cygnus have that extra windpipe storage.

If any other views or measurements could be helpful to you, comment or message me and I'll be more than happy to take pictures of whatever you need.

Posted on May 08, 2020 00:03 by lizardking lizardking | 3 comments | Leave a comment

March 24, 2020

February 29, 2020

Domestic Muscovy Duck Quack Box/Bulla Bone/Syrnix

Couldn't find any good reference images for duck "quack boxes" online, so I decided it was well overdo I post better images of mine. I have some floating around iNat comments, but I think a journal post will be much easier to access and reference.
I don't know how I only now just found it, but a quick Google search showed Jake's Bones also has some bulla bone images, in the blog post "Strange bones #7 - the strangest bone yet ?", so I'll share that here too.
*3/17/20 update, found another voice box reference at Zygoma here, species uncertain. I also have a second Muscovy duck voice box on the way, in better condition than the one in this post.

"Quack boxes", or the bulla/bulla bone, are the syrinx of waterfowl. Syrinx as a whole are interesting phenomenon, an anatomical feature exclusive to birds. If you're interested in reading a study about the avian syrnix being an evolutionary novelty, you can find that in full and for free here. It's really not a bad read, I'd recommended at least reading the abstract and figure descriptions and skimming though the rest. If there are anatomical terms in this post that seem confusing, they're probably defined somewhere in that study.

The syrnix is inherently unique to birds, but the waterfowl syrnix is unique among birds. Their voice box looks in ways quite literally like a box.
Mine is unfortunately broken in a few places, but is complete enough it should give a good idea of what the bulla looks like. I have an observation attached to this journal that is a length of domestic Muscovy duck windpipe which I think shows the cartilage rings very well, but it is from a different specimen than the one that gave me this bulla.

On the top of the duck bulla you can see how the cartilage rings feed into the vocal organ itself.

Sadly from the top view you can see a lot of the damage.

In the image below you can see the back is very broken.

So that's my domestic Muscovy duck bulla bone. If there are any views that you would find helpful, message me and I'll gladly take more pictures.

Posted on February 29, 2020 19:43 by lizardking lizardking | 1 observation | 1 comment | Leave a comment