Comparing skulls

Of all the bones in a bird’s body, surely those that comprise the skull are the most fascinating. It is impossible to look at a bird skull without recognizing features that are also found in the human skull.

During the middle decades of the 20th century, ornithologist Harvey Fisher published several articles about the anatomy of New World vultures. This family of birds includes 7 species, one of which is the California condor.

A 1944 article by Fisher is a detailed comparison of the skulls of New World vultures. The article includes fine illustrations, for which Fisher offers this acknowledgment:

The artist, Elizabeth Whitfield, has been most painstaking in her delineation of the skulls.

Below are 3 of Whitfield’s beautiful diagrams. The first shows a side view of the skulls of, from top to bottom, the turkey vulture, black vulture, king vulture, California condor, and Andean condor:
The illustrations above clearly show a distinctive feature of the New World vultures: the lack of separation between the nostrils that appears as a “window” in their skull.

Next are views, from above, of the skulls of the California condor and king vulture (upper row) and Andean condor and extinct Gymnogyps amplus (lower row):
The fossil skull of Gymnogyps amplus, a close relative of the California condor, is missing its beak.

Third, here are views from below the skulls of, from left to right, the king vulture, Gymnogyps amplus, California condor, and Andean condor:

The illustrations above make it clear that the 2 condors have substantially larger skulls than 3 of their living relatives. It is also clear that the skull of the Andean condor is larger than that of the California condor.

But the Andean condor seems small in comparison to the extinct Teratornis merriami, a close relative of today’s New World vultures:

The photo above was taken by Harry Swarth and is from his Guide to the Exhibit of Fossil Animals from Rancho La Brea (1915):

“Merriam’s teratorn” was identified by Loye Holmes Miller based on fossils excavated from what is popularly known as the La Brea tar pits. Even larger teratorns and other extinct relatives of the New World vultures have subsequently been described.

For more on the skull of the California condor, see a previous post: The skull.

Fisher, Harvey I. The skulls of the cathartid vultures. Condor. November 1944.

Swarth, H S. Guide to the exhibit of fossil animals from Rancho La Brea. Museum of History, Science and Art. 1915.

Miller, Loye Holmes. Teratornis: a new avian genus from Rancho La Brea. University of California Publications, Bulletin of the Department of Geology. 1909.