Buzzard skeletons (and bird skeletons in general)

I don't really write much about bird skeletons because complete ones are so hard to find. Bird bones are smaller, lighter, easier to break (and eat) and more likely to get scattered about, and often the way the birds get killed destroys some of the bones. Every single time I go to the pheasant woods near my village I find bones from pheasants killed by foxes but I hardly ever find the skulls.

That's why I was so excited when dad came back from a walk (my leg is still to weak to do proper walks)  and said he had found a buzzard skeleton. Buzzards are medium-sized birds of prey, bigger than most raptors like sparrowhawks, but still only small when compared to golden or white-tailed eagles. But not only had he found a buzzard skeleton - he had got all the major bones !

Buzzards are common near where I live because they like to live in pheasant woods. They are also one of the birds I have seen very close up because in October 2010 I found an ill buzzard in the pheasant woods which we took home for the SSPCA to take into their animal hospital.

The other important thing about buzzards is that you can only take their bodies or bones if you can be sure they died naturally. In reality this is almost impossible to prove. Some gamekeepers don't like buzzards so they either leave out poison in animal carcasses to poison them, or they shoot them. Luckily dad had taken lots of pictures of the site. He had found it at the bottom of a fallen down tree at the edge of Quoiggs Wood. 

The bones were complete and all together in a pile. It looked as if the buzzard had just died there. There were no signs of bones from poisoned carcasses nearby , and no damage on the bones to suggest it had been shot. It wasn't as clear-cut as the buzzard skeleton with the broken neck, or the buzzard I am rotting down at the moment which was mobbed, but I know the area, I don't think there is much active gamekeepering there, I've never heard of any poisonings  and I'm pretty sure it died naturally and that I'm okay to keep the bones.

Because a lot of birds are roughly the same size, the skull is the best place to identify the bird. Both the skull and lower jaw were here:

Dad knew just from the size of the skull it was a buzzard. It is 7.3cm long and 4.3cm wide, which is slightly smaller than the figures on Skullsite.com.

Dad did what I do, which is carefully work through the pine needles with a knife looking for bones. He put all the bones he found into his yellow collecting box then brought it home.

There was no soft tissue on the bones but a bit of muck so I cleaned by simmering for a few hours with biological washing powder in my S6 cleaner, then left them to dry for a few days: (the big bone at the top is from something else I was working on, otherwise it would be an odd-shaped buzzard)

The skeleton wasn't complete, but all the major bones were there. I've named this skeleton Churchill. Here are Churchill's bones:

The skull

Bird skulls are a lot more delicate than mammal bones, because they need to be light, and there is no need to have thick jaw bones for teeth because birds don't have any. You can tell from looking that this is a raptor (bird of prey) because of the short hooked beak. Other types of birds (like gulls) have hooked beaks too but their beaks are much longer. 

Otherwise, they are generally laid out the same way as mammal skulls with a rounded braincase at the back (with a hole for the spine), holes from the braincase into the eyes (for optic nerves) and nostrils at the form with thin, lacy bone behind. Generally in birds, the two eye sockets are separated by a thin piece of bone, whereas mammals usually have more inbetween.

The 'eyebrows' (thin bits of bone at the front of the eye socket) are missing, as is the quadrate bone (the rectangularish bit of bone which hinges the jaw and skull at bottom right) but these often get lost. You can see them in another of my buzzard skulls here though.

Shoulders and chest (sternum and pectoral girdle)

In most mammals (including humans) the bone in the middle of the chest (called the sternum) is thin, made out of cartilage, and is flat. In birds, the sternum is MASSIVE by comparison. Look at this roe deer ribcage next to a pink-footed goose:

That's because birds need different muscles to mammals. Imagine humans spent their time clapping their hands with straight arms; that's pretty much what birds do when they fly. The muscles that pull in the arms (or wings) are attached on the sternum, so birds to have evolved to have a much wider sternum which allows more muscle attachment, with a raised ridge in the middle. 

The ridge works the same way as a saggital crest on the top of a skull of some meat-eating mammals (like badgers and big cats) because it allows stronger muscles to attach. Some scientists can even make guesses about a species just from the bird sternum, to guess how strong it was at flying.

One of the weirdest sternums I have is from a whooper swan I found in 2011, where the inside of the keel is hollow, and the bird's windpipe folds inside. You can read about that here.

The highest part of the ridge (also called a keel) is usually closer to the head, and the lower end of the keel is closer to the feet. The wavy edges are where the ribs attach.

Coracoids are unusual bones. I have only found them in bird skeletons but some mammals are supposed to have them. They are short but strong, almost as thick as the wing and leg bones.  They have one smooth curved edge, and a hook at the other. There is a notch about two thirds of the way up, and a hole inside the hook which doesn't go all the way through the bone.

Because a flying bird had stronger muscles on the chest, these pull and stress the skeleton in different ways to mammals. The coracoids go from the top of the sternum up to the shoulders to offer support and stop the shoulders being pulled together as the bird flaps its wings.

The furcula is one of my favourite bones and I have written about it before. You only find them in dinosaurs and birds (and some scientists argue that birds are dinosaurs). The wishbone from your Christmas turkey is a furcula. 

The human equivalent of the furcula are the collarbones (clavicles) which go on the front top of your shoulders into your chest.

The furcula is like two collarbones fused together, and its job is to support the coracoids, even though it is much thinner. It goes from the claw end of the coracoids, bending back towards the sternum, like this:

The last major bones in the pectoral girdle are the scapulas (or scapulae, because it's Latin), which are the shoulder-blades. They are long, narrow, thin bones, a lot different to mammal scapulas (which I wrote about here) with not a lot of room for muscle attachment. The ones on my eider duck skeleton are much longer still but still as narrow.

I couldn't find anywhere to find out how to 'side' (work out what side they go on) bird scapulas, so they may be the wrong way round. UPDATE: By using "Bird Bones Form Archaeological Sites" (recommended in the comment) - I worked out that the top bone is the right scapula, and the bottom one is the left.

This is how those four bones go together (with the humeruses at the side too). I may not have got this precisely right, so don't copy it down for your final year vet exams or anything. (UPDATE: from looking at "Bird Bones From Archaeological Sites", I think everything is the right way round).

The wing bones

The wing bones of a bird are a lot like a human's arms, and some of the bones have the same names. The first bone from the shoulder on a bird, which is like the upper arm bone, is called the same thing, the humerus. Like the mammal one it has a broad, smooth end (like the back of a spoon) which joins onto the scapula and coracoid. The humerus below is the right one, and the right hand end is the one at the shoulder.

The next two bones have the same name as in mammals too, the radius and ulna. This is the forearm in humans. It looks thick and strong with lots of space for muscle attachments.

The ones below are the left radius and ulna:

For both bones in the picture the 'elbow' end is on the left and the 'wrist' end is on the right. These are much thinner, possibly because a buzzard keeps its wings fairly straight so doesn't need the 'arm wrestling' muscles you need if your forearm moves in a different way to your upper arm.

The last major bone in the wing is the carpometacarpus. There is no equivalent bone in humans, but the name is from the carpals (small wrist bones) and metacarpals (bones between wrist and knuckles) which are separate in most mammals but in birds are all joined together. This one is the left carpometacarpus, with the wrist end on the left.

There are other smaller bones that come afterwards, which are called the phlanges, same as in human fingers. Dad didn't find those and he didn't find the toe bones either.

The hips (pelvic girdle)

The pelvic girdle is massively different to the hips on mammals. They are often misidentified as skulls because of the smooth bone and the hip sockets look like eye sockets. Birds have evolved (from dinosaurs) so that the bottom of the spine is fused together, and that is fused onto both sides of the hips. 

The leg bones

The femurs are almost identical to mammal femurs, with a ball at the top to go in the socket of the hip. Just the same as mammals, the left femur is on top, with the hip end on the left here:

The next bone down is the equivalent of the lower leg in humans which has two bones called the tibia and fibula, but in birds the big tibia-like bone is called the tibiotarsus. This shows the left tarsometatarsus. The thin bone joined to it is still called the fibula because the scientists were too tired to come up with an even more complicated name for it after typing out "tibiotarsus" a few times. In this picture the knee end is on the left and the ankle end is on the right.

The final major bone in the bird leg is the tarsometatarsus because calling it anything shorter would just be too easy. This one is the left one. In mammals this would be called the metatarsals, and go between ankle and toe knuckle. The bits on the left are where the toe bones (claws) attach:

Now a bit of a moan

I don't often moan a lot, but all this stuff was really difficult to find out. Every webpage I went to seemed to want to make things more and more complicated and a lot of them might have well been written in Greek or something. 

Coracoids are hardly ever mentioned by name, like they are Lord frigging Voldemort, and bird scapulas might as well be in witness protection because they are mentioned even less, and when they are, it's like this which is virtually unreadable: 

In other tetrapods it joins the scapula to the front end of the sternum and has a notch on the dorsal surface which, along with a similar notch on the ventral surface of the scapula, forms the socket in which the proximal end of the humerus (upper arm bone) is located. The acrocoracoid process is an expansion adjacent to this contact surface, to which the shoulderward end of the biceps brachiimuscle attaches in these animals. In birds (and generally theropods and related animals), the entire unit is rigid and called scapulocoracoid.

Oh brilliant, Wikipedia, I'll be sure to tell all my friends about that.

Anyway, it seems there is a lot more about mammal skeletons on the internet, and a lot less stupid science nonsense when describing them. If you don't have somewhere that describes bones in a simple way, then how do you get kids (or even adults who aren't scientists) interested ? Anyway, rant over.

Big thanks to Ben Garrod of Ben's Bones and Meike Roth and John R. Hutchison (of What's In John's Freezer) who helped me identify stuff on Twitter. This page was really really useful to 'side' the bones as well, and Psydrache's post on her articulated buzzard helped too !

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