Passerine Anatomy & Physiology Basics

Key Points

  • Passerines or perching birds belong to order Passeriformes, a large, diverse, and widespread taxonomic group.
  • Most passerine birds are “songbirds” or oscines, which are renowned for their vocal ability due to a particularly complex syrinx that includes five or more pairs of syringeal muscles.
  • Although many passeriforms are omnivores, passerines employ a variety of nutritional strategies that also includes granivory, insectivory, and nectarivory. Consequently, the passerine gastrointestinal tract can show a high degree of diversity in structure and function.
  • The passerine ceca are small and vestigial.
  • The middle and caudal divisions of the kidney are fused in most passerine birds.
  • In many species, the distal end of the ductus deferens forms a mass of convolutions called the seminal glomus. During the reproductive season, the seminal glomus engorges creating a prominent, cone-shaped swelling called the cloacal promontory or protuberance.
  • Vivid red, yellow, and orange coloration on the feathers, beak, and/or legs of male songbirds occurs secondary to rising carotenoid levels, which in turn rise in response to testosterone.
  • Song is also considered a secondary sex characteristic in passerine birds as singing is induced by a rise in endogenous testosterone levels. Male birds produce more melodious songs; hens tend to produce a chirp or single-note call.
  • Although songbirds inherit a “song template”, chicks must hear the song of their species in order to copy it. Chicks can first memorize a song as early as 15-20 days of age but song development is not complete until later in life.

Perching birds or songbirds belong to order Passeriformes, which makes up the largest taxonomic group of birds. Passeriforms make up nearly 60% of all birds with over 5,000 species belonging to this group. If you are comfortable with psittacine anatomy and physiology, then you are well on your way to understanding passerines. LafeberVet has listed ten interesting, clinically significant facts about passerine anatomy and physiology . . .


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References

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Further reading

Australian Bird Study Association. Guide to sexing passerines by cloacal examination. ABSA web site. Available at https://absa.asn.au/wp-content/uploads/2019/11/Guide-to-Cloacal-Sexing.pdf. Accessed April 11, 2023.

Denbow DM. Gastrointestinal anatomy and physiology. In: Whittow GC (ed). Sturkie’s Avian Physiology. Academic, San Diego, CA. pp 299-325, 2000.

Drouin G, Godin JR, Pagé B. The genetics of vitamin C loss in vertebrates. Curr Genomics. 2011;12(5):371-8. doi: 10.2174/138920211796429736. PMID: 22294879; PMCID: PMC3145266.

Dumbacher JP, Wako A, Derrickson SR, et al. Melyrid beetles (Choresine): a putative source for the batrachotoxin alkaloids found in poison-dart frogs and toxic passerine birds. Proc Natl Acad Sci U S A. 2004;101(45):15857-60. doi: 10.1073/pnas.0407197101. Epub 2004 Nov 1. PMID: 15520388; PMCID: PMC528779.

El-Sayed AK, Hassan S. Gross morphological features of the air sacs of the hooded crow (Corvus cornix). Anat Histol Embryol. 2020;49(2):159-166. doi: 10.1111/ahe.12504. Epub 2019 Oct 15. PMID: 31617250.

Gaunt AS. An hypothesis concerning the relationship of syringeal structures to vocal abilities. The Auk. 1983;100(4):853-862. https://www.jstor.org/stable/4086413.

Goller F, Suthers RA. Role of syringeal muscles in gating airflow and sound production in singing brown thrashers. J Neurophysiol. 1996;75(2):867-76. doi: 10.1152/jn.1996.75.2.867. PMID: 8714659.

Gutherz SB, O’Connor PM. Postcranial skeletal pneumaticity in Cuculidae. Zoology (Jena). 2021;146:125907. doi: 10.1016/j.zool.2021.125907. Epub 2021 Feb 17. PMID: 33730625.

Larsen ON, Goller F. Direct observation of syringeal muscle function in songbirds and a parrot. J Exp Biol. 2002;205(Pt 1):25-35. doi: 10.1242/jeb.205.1.25. PMID: 11818409.

McGraw KJ, Ardia DR. Do carotenoids buffer testosterone-induced immunosuppression? An experimental test in a colourful songbird. Biol Lett. 2007;3(4):375-8. doi: 10.1098/rsbl.2007.0190. PMID: 17550877; PMCID: PMC2390673.

Mennerat A, Bonadonna F, Perret P, Lambrechts MM. Olfactory conditioning experiments in a food-searching passerine bird in semi-natural conditions. Behav Processes. 2005;70(3):264-70. doi: 10.1016/j.beproc.2005.07.005. PMID: 16144746.

Møller AP. Relative longevity and field metabolic rate in birds. J Evol Biol. 2008;21(5):1379-86. doi: 10.1111/j.1420-9101.2008.01556.x. Epub 2008 Jul 8. PMID: 18631214.

Pap PL, Osváth G, Aparicio JM, et al. Sexual dimorphism and population differences in structural properties of barn swallow (Hirundo rustica) wing and tail feathers. PLoS One. 2015;10(6):e0130844. doi: 10.1371/journal.pone.0130844. PMID: 26110255; PMCID: PMC4482263.

Peters A. Testosterone and carotenoids: an integrated view of trade-offs between immunity and sexual signaling. Bioessays. 2007 May;29(5):427-30. doi: 10.1002/bies.20563. PMID: 17450573.

Reyes L, Braun EJ. The functional morphology of the english sparrow cecum. Comp Biochem Physiol A Mol Integr Physiol. 2005;141(3):292-7. doi: 10.1016/j.cbpb.2005.05.053. PMID: 15996497.

Sayrafi R, Aghagolzadeh M. Histological and histochemical study of the proventriculus (Ventriculus glandularis) of common starling (Sturnus vulgaris). Anat Histol Embryol. 2020;49(1):105-111. doi: 10.1111/ahe.12495. Epub 2019 Sep 11. PMID: 31509272.

Scanes C, Dridi S (eds). Sturkie’s Avian Physiology, 7th ed. San Diego: Academic Press; 2021.

Wild JM, Botelho JF. Involvement of the avian song system in reproductive behaviour. Biol Lett. 2015;11(12):20150773. doi: 10.1098/rsbl.2015.0773. PMID: 26631245; PMCID: PMC4707696.

Whittaker DJ, Soini HA, Atwell JW, et al. Songbird chemosignals: volatile compounds in preen gland secretions vary among individuals, sexes, and populations. Behav Ecol. 2010;21(3):608-614. doi: 10.1093/beheco/arq033. Epub 2010 Mar 17. PMID: 22475692; PMCID: PMC2854530.

To cite this page:

Pollock C. Passerine Anatomy & Physiology Basics. July 15, 2012. LafeberVet Web site. Available at https://lafeber.com/vet/passerine-anatomy-ten-key-facts/