Translator Disclaimer
1 April 2008 The Trouble with Tertials
Author Affiliations +

The term "tertials" is usually used to denote the most proximal secondaries, commonly three, that cover the bases of primaries on a folded wing and frequently differ from other secondaries in molt sequence (Jenni and Winkler 1994, Pyle 1997). Secondaries, including tertials, are typically attached to the ulna (Van Tyne and Berger 1959). Tertials are often depicted connecting to the ulna's olecranon process (e.g., Wray 1887, Kortright and Shortt 1943, Lucas and Stettenheim 1972) but have been shown to occasionally attach to the skin surrounding the olecranon (Berger and Lunk 1954).

The term "tertials" is also a synonym for "tertiaries" (Thomson 1964, Baumel et al. 1993). Tertiaries are analogous to secondaries but more proximal and attached to tissues superficial to the humerus (Baumel et al. 1993). Tertiaries are most often indicated as enlarged flight feathers in long-winged birds such as those in the Diomedeidae and Cathartidae (Van Tyne and Berger 1959) and are frequently referred to as "humerals" (e.g., Wray 1887, Tickell 2000). They also have been designated by their synonym, "tertials" (Fisher 1942). The term "tertials" can, therefore, be used contradictorily to represent exclusively ulnar feathers as well as feathers that are exclusively humeral.

(Van Tyne and Berger 1959) and (Baumel et al. 1993) noted that referring to proximal secondaries as "tertials" is technically inaccurate. Similarly, describing humerals as "tertiaries" incorrectly implies that they are in a continuous series with primaries and secondaries (Lucas and Stettenheim 1972). These discrepancies are among several that have long prompted some researchers to abandon "tertials" and "tertiaries" as ornithological terms (e.g., Wray 1887, Thomson 1964; for reviews, see Berger and Lunk 1954, Van Tyne and Berger 1959). However, using the term "tertials" to indicate innermost secondaries is solidly entrenched within the ornithological literature. Ornithologists investigating molt sequences so consistently designate the most proximal secondaries as "tertials" (e.g., Jenni and Winkler 1994, Pyle 1997) that it is justifiably accepted as accurate terminology within their field of study. Replacing "tertials" with a different term would, therefore, be disruptive and burdensome.

An uncomplicated solution would be to no longer define "tertials" and "tertiaries" as synonyms and to discontinue use of the term "tertiary" to represent a type of feather. Adopting the most common application of "tertials" as the correct term for the modified proximal secondaries that cover portions of the folded wing and frequently differ in molt sequence from other secondaries would create no problem for most ornithologists or birders. The little-used term "tertiaries" could then be discarded in favor of "humerals" for denoting feathers analogous to secondaries but positioned along the humerus (e.g., Tickell 2000). Differentiating these terms as proposed above would resolve a problem in avian terminology with little adjustment required by either professional or citizen ornithologists.

Acknowledgments.—This paper benefited from editorial suggestions by P. Pyle, A. Lindsay, and two anonymous reviewers. J. Hinshaw and D. Willard verified the absence of quill knobs on Laysan Albatross (Phoebastria immutabilis) and Andean Condor (Vultur gryphus) humeri, respectively. I appreciate all of their efforts on my behalf.


  1. J. J. Baumel, A. S. King, J. E. Breazile, H. E. Evans, and J. C. Vanden Berge , editors. 1993. Handbook of Avian Anatomy: Nomina Anatomica Avium. 2nd ed.Nuttall Ornithological Club. Cambridge, Massachusetts. Google Scholar

  2. A. J. Berger and W. A. Lunk . 1954. The pterylosis of the nestling Coua ruficeps. Wilson Bulletin 66:119–126. Google Scholar

  3. H. I. Fisher 1942. The pterylosis of the Andean Condor. Condor 44:30–32. Google Scholar

  4. L. Jenni and R. Winkler . 1994. Moult and Ageing of European Passerines. Academic Press. London. Google Scholar

  5. F. H. Kortright 1943. The Ducks, Geese and Swans of North America. 2nd ed.American Wildlife Institute. Washington, D.C. Google Scholar

  6. A. M. Lucas and P. R. Stettenheim . 1972. Avian Anatomy: Integument, Part I. Agriculture Handbook, no. 362. U.S. Government Printing Office. Washington, D.C. Google Scholar

  7. P. Pyle 1997. Identification Guide to North American Birds, Part 1: Columbidae to Ploceidae. Slate Creek Press. Bolinas, California. Google Scholar

  8. A. L. Thomson , editor. , ed 1964. A New Dictionary of Birds. McGraw-Hill. New York. Google Scholar

  9. W. L N. Tickell 2000. Albatrosses. Yale University Press. New Haven, Connecticut. Google Scholar

  10. J. Van Tyne and A. J. Berger . 1959. Fundamentals of Ornithology. Wiley. New York. Google Scholar

  11. R. S. Wray 1887. On some points in the morphology of the wings of birds. Proceedings of the Zoological Society of London 1887:343–357. Google Scholar

Scott Hickman "The Trouble with Tertials," The Auk 125(2), 493, (1 April 2008).
Received: 1 August 2007; Accepted: 1 January 2008; Published: 1 April 2008

Back to Top