Raptor Gastrointestinal Anatomy and Physiology

Key Points

  • The raptor bill plays a role in prehension and sometimes killing.
  • Hide and bone are pierced with the tip of the beak. Flesh is torn from the carcass by the sharp, cutting edges (tomia) of the bill in Falconidae and Accipitridae (falcons, hawks, eagles, and caracaras). Owls often swallow prey whole.
  • The tongue and oropharynx possess barbed papillae that facilitate manipulation of food into the throat.
  • Most diurnal birds of prey possess a well-developed crop or ingluvies. Owls lack a true crop and instead there is a fusiform widening of the esophagus.
  • Digestion of a protein-rich diet relies primarily on chemical action. This is reflected in a stomach that is relatively thin-walled, highly distensible, and sac-like. Since there is very little mechanical digestion, the glanduar stomach or proventriculus is often larger in proportion to the ventriculus.
  • The gastroduodenal contraction sequence in raptors is much simpler than that described in granivores. Peristaltic waves move directly from the proventriculus, through the isthmus, into the ventricles, and finally into the duodenum.
  • A pellet is a compacted mass of indigestible material, such as fur, feathers, grains, bones, teeth, and claws.
  • The final phase of gastric digestion in the raptor involves pellet formation within the ventriculus and egestion, also known as “casting”.
  • Ceca are small, vestigial, or absent in diurnal birds of prey, but large and well developed in strigiforms.

Raptors are a diverse group of birds consisting of three taxonomic orders: Strigiformes (owls), Falconiformes (falcons and caracaras), and Accipitriformes (hawks, eagles, and remaining families). Although the normal diet of free-living raptors varies considerably among species, all raptors hunt and feed on other animals. Meat and fish-eaters possess unique gastrointestinal characteristics that reflect their predatory lifestyle. This review article begins with unique features of the bill and oropharynx, then describes distinctive features of gastrointestinal tract before concluding with pellet formation and egestion and digestive strategies . . .


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Further reading

Balgooyen TG. Pellet regurgitation by captive sparrow hawks (Falco sparverius). Condor 1971;73:382-385.

Blanco G. Influence of diet on the gastrointestinal flora of wintering red kites. Eur J Wildlife Res. 2014;60:695–698. doi:  10.1007/s10344-014-0820-5.

Clench MH, Mathias JR. The avian cecum:  A review. Wilson Bull. 1995;107(1):93-121.

Costanzo A, Ambrosini R, Franzetti A, et al. The cloacal microbiome of a cavity-nesting raptor, the lesser kestrel (Falco naumanni). PeerJ. 2022;10:e13927. doi: 10.7717/peerj.13927. PMID: 36221261; PMCID: PMC9548316.

Graves GR. Field measurements of gastrointestinal pH of New World vultures in Guyana. J Raptor Res. 2017;51 (4): 465–469. doi:  10.3356/JRR-16-62.1.

König HE, Korbel R, Liebich HG (et al). Avian Anatomy: Textbook and Colour Atlas. Sheffield: 5M Publishing, 2016.

Lacasse C. Falconiformes (falcons, hawks, eagles, kites, harriers, buzzards, ospreys, caracaras, secretary birds, Old World and New World vultures). In: Fowler 8. 127-128.

Nagai K, Tokita KI, Ono H, et al. Hindgut bacterial flora analysis in Oriental honey buzzard (Pernis ptilorhynchus). Zoolog Sci. 2019; 36(1):77-81. doi: 10.2108/zs180121. PMID: 31116541.

Ponder JB, Willette MM. Strigiformes. In: Miller RE, Fowler ME (eds). Fowler’s Zoo and Wild Animal Medicine Volume 8. St. Louis: Elsevier Saunders, 2015. Pp. 189-190.

To cite this page:

Pollock C. Raptor gastrointestinal anatomy and physiology. July 15, 2023. LafeberVet Web site. Available at https://lafeber.com/vet/raptor-gastrointestinal-anatomy-physiology/