Several weeks ago I photographed and observed the outsides and insides of the body of a beautiful thrush. The thrush was found dead by a friend of mine. We sketched, looked closely, and dissected the bird, trying to see its body with fresh eyes. We were trying to notice details and ask our own questions about what we saw. We weren't using a manual or a textbook; just our eyes. As a result, we saw a lot.

We saw things we didn't yet have words for. Our seeing came before our language. When we noticed something and made connection to ideas we've heard about or considered before, we cooed with wonder. We were making discoveries with our eyes first, instead of looking for clearly deliniated anatomical structures someone else told us to look for in a manual or dissection guide.

With our eyes we saw different types of feathers and elastic skin that seemed to help the thrush flap it's wings. We saw rings around it's wind pipe, the black textured insides of it's stomach, its shimmering lungs, and whiskers around it's beak. We also saw things that we had previously "learned" but not reallyknown before. We discovered the proportions of its leg bones, their thinness, its tiny hip socket, its large heart, and how its muscles threaded from its chest to the top of its wings.

Here's some of what we saw the day we looked inside a beautiful thrush. It was quite an intimate and sacred activity to look inside another being.

Around the beak, this thrush had what I would describe as… whiskers.

I had never known that these structures existed in some bird species. I associate whiskers (aka vibrissae) solely with mammals — cats, dogs, manatees — not feathered creatures.

However, it turns out that these hair-like feathers, rictal bristles, are often thought of as being similar to whiskers. However, like whiskers, it's not totally clear what they do or how they work.

People have thought that they're used to help birds capture flying insect prey (acting like a net). However, experiemnts where rictal bristles have been cut off or taped down seem to show that this doesn't affect a bird's hunting ability. Some still speculate that they're used to detect airflow around the head and can help birds detect insects in that way.

Another hypothesis is that they protect a hunting-birds eyes form stinging prey parts or other debris that may come flying towards their face while they're hunting. Experiments have been done where dead birds with sticky stuff over their eyes have been put in wind tunnels with stuff flying towards their faces. Bird bodies with rictal bristles seem to have less stuff go in their eyes. So maybe that's part of their function. ¯\_(ツ)_/¯

Or, maybe they help birds get around in the dark. Experiments where birds were put in mazes in the dark showed that they did much better navigating the mazes when their rictal bristles were fully in tact. So are rictal bristles more like eyelashes or more like whiskers?

Whiskers are sensory structures that have have significant brain real-estate dedicated to sensory information they generate. It seems that the whiskers act as an array to communicate sensory information to their owners. They're actively moved by muscles and used to sense the world through coordinated "whisking" actions.

Whiskers are a relatively new sensory system in the mammal lineage. We know this because monotremes (platypi and echidnas), which branched from the other groups of mammals a long time ago, don't have whiskers. In marsupial and placental mammal lineages, the way in which whiskers are arranged is relatively conserved — with similar rows primarily along their mustaches.

In cats, these coarser modified hairs reside on the face (above the eye, the mustache region, and even on the back of their front legs!). Mice and rats also have most of their whiskers in the mustache region. Manatees are quite different — all of the hairs on their bodies are vibrissae — follicles with mechanoreceptors that are intensely innervated, with an extensive surrounding blood supply.

Rictal bristles are, like whiskers, surrounded mechanoreceptors called herbst corpuscles. Herbst corpuscules are collections of connective-tissue cells surrounding the end of a nerve cell. The connective tissue cells around the nerve-ending core are layered like an onion. When pressed, they deform and eventually press on a nerve ending, which passes information to the trigeminal nerve (a nerve we also have in our face), and eventually to the brain.

To really understand how these rictal bristle bird whiskes work, NI'm going to look into herbst corpuscules and get a better sense of them. I want to know how these little onion-receptors work.

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How beautiful are these chest feathers!? They look like tiny combs to me. I'm curious to know more about the difference between flight and non-flight feathers and why the coloring of birds evolved so that the chest is often different form that of the back int he wings. I'll eplore this more in an eploration of feathers.

So much about this bird's feet and legs struck us.

For starters, when you look at the joints, their not like ours. What may seem like an ankle (the part where all the toes meet) is actually some more toe bones. The long, thin, extended part of the leg you see in this photos is NOT their shin but the space between their foot and their ankle. Think about that. That means they basically have an extra leg joing that we don't have.

The leg parts between their ankles and their knees and their knees and their hips are all up under their feathers. You can't see them in this picture. I think I've read and talked about this fact before, but I never really knew it before looking closely at this thrush.

The stretch between the ankle and the knee, which is tucked under the feathers, has visible muscles, along with the short thigh stretch, all ending in a TINY ball that connects with the pelivs. This "ball" on the top of it's femur is so small, it feels like a paperclip with a bent notch. Our femurs are the biggest bones in our body and that ball at the heads of our thigh bones are much bigger and sturdier.

But birds don't use their legs as much as their wings. They're evolved to fly like we're evolved to walk and run. And so, their legs may be dainty but their weings incredibly muscular and built out.

So why do birds have these skin, naked tooth-pick legs? It's often said that it's for thermoregulation. They help birds dissipate heate and also are able to get incredibly cold and don't require much blood supply.

Whatever blood does flow to them is thought to engage in counter current exchange. Counter-current exchnage happens wehn warm blood coming from the body in an artery gives it's heat to cold blood coming back up from the feet in a vein. The feet and lower legs are kept incredibly cold so as not to let as much heat from the blood escape into the air — instead that heat goes to the blood in the vein making it's way make to the rest of the body and eventually the lungs and heart.

Perhaps a bird's lower "leg" (from the toes to the ankle) then is primarily some tough skin, thin, delicate bone, and blood vessles.

We saw on the bird's foot that it seemed to have toe-pads and scales! The skin of its legs and feet felt quite foreign to me — different from my own skin, with very little muscle underneath. I perceived it as much drier and stiffer. What is skin, anwyay? Why is my skin different from a birds?

Birds and us both have a surface layer of skin made up primarily of dead (i.e. cornified) cells that have been converted into a layer of cross-linked alpha-kertin proteins. However, birds have another kind of keratin in their skin — beta keratin, which is shaped in pleated sheets, not helices like alpha-keratin. And this shape-difference is why reptiles and birds have much stiffer skin than we do.

Something that's unclear is: are a bird's scale-covered feet descended directly from that of its reptilian ancestors or did they secondarily evolve from the beta-keratin in feathers, beaks, and claws? Supposedly there are genes that, when turned off, result in feathers growing on the legs and feet, suggesting that bird's naked, scaley legs secondarily evolved from former feathered skin.

I just couldn't believe that birds have tiny feathers around their eyes! They're so incredible! I didn't realize feathers got so small.

What is that white stripe under the wing for? What does it do? What does it signal?

…I have no idea and am going to keep hunting from some kind of explanation or come up with a hypothesis of my own:).

Besides seeing meat at the supermarket or observing birds from afar, I've never really touched or made detailed observaiton of a whole, in-tact bird body.

This bird's body had a layer of skin between it's back and it's wing, which was incredibly flexible. It was so elastic and soft. It's the part of the wing that's should be used for tagging according to this blog.

When we moved the wings with our hands to get a more tactile understanding of how they worked, this part of the wing felt much more prominant than I would have expected. It seemed to pull the distal parts of the arm back towards the body. Perhaps it also aids the wing in acting as an airfoil.

We were surprised by this yellow area. We thought it was fat — perhaps insulation. But actually, after research, it seems more likely that it's this bird's crop.

I associate yellow with fatty tissue and I'm not sure why a crop (an area birds use to hold food) would be surrounded by fat. More research required…

We couldn't believe it when we saw the birds windpipe (i.e. trachea) and it's voice box. There was something so intimate about seeing the place from which a bird's voice originates.

When we looked closely, we saw these black rings around the trachea and bronchi. We think these were cartilage rings which help to keep the pipes rigid and open.