Raptor Gastrointestinal Anatomy and Physiology

Key Points

  • The raptor bill plays a role in prehension and sometimes killing. Food is torn from the carcass by the sharp cutting edges or tomia of the bill in Falconidae (falcons and caracaras); owls often gulp down prey whole.
  • The tongue has a barbed surface, allowing greater manipulation of food.
  • The esophagus is strong and distensible.
  • Most diurnal birds of prey possess a well-developed crop or ingluvies.
  • Owls lack a true crop and instead there is a fusiform enlargement or widening of the esophagus.
  • The stomach is thin-walled and muscular, adapted more for storage than grinding. The proventriculus is relatively large and highly distensible. The ventriculus is often smaller and sac-like.
  • Ceca are small, vestigial or absent in diurnal birds of prey, but large and well developed in strigiforms.
  • 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 pass 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”.

Raptors are a diverse group of birds consisting of order Strigiformes or owls and diurnal birds of prey such as falcons, hawks, and eagles. Order Falconiformes, traditionally considered a broadly defined, polyphyletic group, has recently been divided into two orders with only family Falconidae (falcons and caracaras) remaining in Falconiformes. Other diurnal raptors belong to order Accipitriformes . . .


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References

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Battisti A, Guardo GD, Agrimi U, Bozzano AI. Embryonic and neonatal mortality from salmonellosis in captive bred raptors. J Wildl Dis 34(1):64-72, 1998.

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Duke GE. Alimentary canal: anatomy, regulation of feeding, and motility. Sturkie Avian Physiology. Academic, San Diego, CA: Academic Press; 2000: 269-285.

Duke GE, Bird JE, Daniels KA, Bertoy RW. Food metabolizability and water balance in intact and cecectomized great-horned owls. Comp Biochem Physiol 68A(2):237–240, 1981.

Duke GE, Evanson OA, Jegers A. Meal to pellet intervals in 14 species of captive raptors. Comp Biochem Physiol 53A (1):1-6, 1976a.

Duke GE, Evanson OA, Redig PT, Rhoades DD. Mechanism of pellet egestion in great horned owls (Bubo virginianus). Am J Physiol 231(6):1824–1829, 1976b.

Duke GE, Jegers AA, Loff G, Evanson OA. Gastric digestion in some raptors. Comp Biochem Physiol 50A(4):649–656,1975.

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Hilton GM, Houston DC, Barton NWH, et al. Ecological constraints on digestive physiology in carnivorous and piscivorous birds. J Experimental Zoology 283(4-5):365-376, 1999.

Houston DC, Cooper JE. The digestive tract of the whiteback griffon vulture and its role in disease transmission among wild ungulates. J Wildl Dis 11(3): 306-313, 1975

Houston DC, Copsey JA. Bone digestion and intestinal morphology of the bearded vulture. J Raptor Res 28(2):73-78, 1994.

Joseph V. Raptor medicine: An approach to wild, falconry, and educational birds of prey. Vet Clin North Am Exot Anim Pract 9(2):321-345, 2006.

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Klaphake E, Clancy J. Raptor gastroenterology. Vet Clin North America: Exot Anim Pract 8(2):307-327, 2005.

Klasing KC. Anatomy and physiology of the digestive system. In: Comparative avian nutrition. New York: CABI Publishing; 1998: 9–35.

Lamberski N, Hull AC, Fish AM, et al. A survey of the choanal and cloacal aerobic bacterial flora in free-living and captive red-tailed hawks (Buteo jamaicensis) and Cooper’s hawks (Accipiter cooperii). J Avian Med Surg 17 (3):131-135, 2003.

Langlois I. The anatomy, physiology, and diseases of the avian proventriculus and ventriculus. Vet Clin North Amer Exot Anim Pract 6(1):85-11, 2003.

Livezey BC, Zusi RL. Higher-order phylogeny of modern birds (Theropoda, Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion. Zoological J. Linnean Society 149: 1-95, 2007.

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Murray M. Raptor gastroenterology. Vet Clin North Am Exot Anim Pract 17(2):211-234, 2014.

Shiina T, Shimizu Y, Izumi N, et al. A comparative histological study on the distribution of striated and smooth muscles and glands in the esophagus of wild birds and mammals. J Vet Med Sci 67(1):115-117, 2005.

Wade L. Diseases above the pylorus. Proc Mid-Atlantic States AAV 2008: 256-258.

Wade L. Diseases below the ventriculus. Proc Mid-Atlantic States AAV 2008: 261-265.

 

Further reading

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

Chaplin SB. Effect of cecectomy on water and nutrient absorption of birds. J Exp Zool Suppl 3:81-86, 1989.

To cite this page:

Pollock C. Raptor Gastrointestinal Anatomy and Physiology. March 6, 2016. LafeberVet Web site. Available at https://lafeber.com/vet/raptor-gastrointestinal-anatomy-physiology/