For the Birds Radio Program: Dissecting Birds
The inside story about birds. By the way, Laura never euthanizes birds. She dissects only birds that were brought to her already dead. (4:01)
Transcript
Now that I’ve started working on a Ph.D. in avian physiology, I’ve had to start dissecting birds to learn all the ins and outs of their amazing bodies. And amazing is the word for a bird’s body. Oddly enough, I never dissected a bird in the two ornithology courses I took. We made study skins, but we never actually had the time to look at the internal organs. After dissecting rats, fetal pigs, and frogs in college, reading about avian anatomy, and eating my share of chickens, I thought I pretty much knew what the innards of a bird looked like until I opened my first nighthawk last spring.
The first thing I did was to remove all the body feathers. That was enlightening in itself. The nighthawk is a chunky little bird with a big, thick neck–until you take off the feathers. It turns out that beneath the feathers, its neck is no wider than a drinking straw. Bird skin is much thinner than a mammal’s, in part because ounce for ounce, feathers provide much more protection than skin. And unlike fur, feathers on most birds don’t grow uniformly over all the body surface. They grow along distinct feather tracts, and just blowing the feathers aside you can see a lot of bare skin.
The longest flight feathers grow out of the bones that correspond to our human hands. The secondary flight feathers grow out of the radius and ulna. The humerus in a nighthawk is short and thick–the bone most people think of as the elbow is really the wrist. And what most pole think of as a bird’s knee is really its ankle.
Going beneath the skin, the first thing you come to is the pectoral muscle. On nighthawks, this is extraordinarily thick, powering wings that carry a Northland nighthawk all the way down to Brazil and then back again each year. Beneath the deep keel bone, things get really interesting. The huge red organs in the place where our lungs would be are the nighthawk’s liver lobes. The tiny heart was wedged in behind this, and then I came to the nighthawk’s largest organ, something taking up well over a third of the volume of the bird’s entire body cavity–its stomach. No wonder my nighthawks can eat so much in one sitting. The intestines are quite tiny, insects being relatively easy to digest.
Rright where the small intestine meets the large intestine, there are two interesting little branches called the caeca. No one knows for sure why nighthawks have caeca. They may harbor bacteria that break down the chitin in insect exoskeletons, or they may help the bird maintain a proper water balance. That is the question I hope to answer in my Ph.D. research.
Anyway, by this point in my dissection, I was completely bewildered about where the bird’s lungs were. It wasn’t until I teased the stomach out that I found them–much flatter than I could have imagined and beautifully woven into the dorsal ribs. When birds breathe in, air goes through the lungs and even beyond–into air sacs strategically placed in the body cavity and even in some of the bones. When the bird breathes out, the air sacs empty and the bird’s bloodstream takes in more fresh air from the lungs. This ability to absorb oxygen on both inhalation and exhalation makes a bird’s respiratory system much more efficient than any mammal’s.
All in all, a bird is as miraculous on the inside as it is on the outside. There is so much in this world to fill our minds and hearts–all we have to do is look around us.