Category Archives: Bird Anatomy

Anatomy: Culmen

Bird Anatomy

Culmen shown on European starling (photo by Chuck Tague)Winter is lousy for field work but it’s a good time to curl up with a book and learn something, so in that spirit I’ve decided to (finally!) learn more about bird anatomy. 

Yes, I’ve watched birds for decades but that doesn’t mean I know the scientific names for the parts of a bird.  During research on various blogs I’ve encountered many technical names, but what do they mean? 

Maybe the names stump you, too.  Why not make this a group project?  So here’s the first in a weekly series on bird anatomy. 

What is a culmen?  It sounds vaguely like… ummmm…. “culminate,” a related word. 

Answer:  It’s “the dorsal ridge of the bird’s bill.”  For us laypeople, it’s the top of the beak from the head to the tip, as shown by the green line. 

I encountered “culmen” when I looked for the length of the pileated woodpecker’s beak.  The answer was “the male’s culmen is 43-56 mm” so I had to look up two things:  the meaning of culmen and the conversion from millimeters to inches.

The shape of the culmen is a useful field mark for identifying birds.  Some bills (culmen) curve up as on American avocets, some are straight, and some curve down as on the long-billed curlew.

So now you know.

(photo by Chuck Tague with graphics added by Kate St. John)

Disease links T.Rex to raptors

Bird Anatomy, Birds of Prey, Musings & News, Peregrines
Hypothesized Trichomonas-like infection in T. rex (Illustration by Chris Glen, The University of Queensland from plosone.org)
Hypothesized Trichomonas-like infection in T. rex (Illustration by Chris Glen, The University of Queensland from plosone.org)

14 October 2009

For years people believed the holes in the jawbones of many Tyrannosaurus rex skeletons were evidence of fighting, even though they were too round and perfect for violent combat.  Recently paleontologists re-examined the holes with a new theory in mind and published their findings on PLoS One.

What lead them to the discovery was this thought:  Where have we seen holes like this before?  We’ve seen them on the jawbones of modern day birds of prey who suffered from a common avian parasitic infection called trichomoniasis.

Raptors, including peregrine falcons, catch trichomoniasis by eating diseased prey.  Peregrines are susceptible to it because they eat pigeons who carry the disease without showing symptoms.  Trichomoniasis invades the mouth and throat causing lesions which eventually penetrate to the bone.  The lesions block the throat making it hard to swallow and the raptor dies of starvation. 

When the paleontologists compared the holes on the tyrant dinosaur jawbones to those of raptors who had trichomoniasis, everything matched up.  The illustration at right shows how the infection would have looked on Tyrannosaurus rex with lesions both inside and outside mouth.  (Ewwww!)  Just like raptors, the tyrant dinosaurs would have caught it through feeding on diseased meat or by snout to snout contact. 

To me, the cool part of this discovery is that modern day birds are close enough to T.rex that they still suffer from a tyrant dinosaur disease. 

And it solved another mystery for me.  When peregrine falcon chicks are banded, the veterinarians always swab their throats with a long Q-tip to test for disease.  Now I know at least one of the diseases they’re looking for.

For more information on this discovery, click here or on the illustration to read the original article at PLoS ONE. 

(Illustration of trichomoniasis in T.rex, based on photographs of living birds suffering from the disease and bird necropsies, by Chris Glen, The University of Queensland.  Article Citation: Wolff EDS, Salisbury SW, Horner JR, Varricchio DJ (2009) Common Avian Infection Plagued the Tyrant Dinosaurs. PLoS ONE 4(9): e7288. doi:10.1371/journal.pone.0007288)