Parrot Anatomy Basics

What is a parrot?

Parrots are primarily arboreal, diurnal birds found in tropical and subtropical regions of the world. Parrots belong to Order Psittaciformes and are divided into three families. There are over 350 species of psittacine birds or parrots.

Class: Aves

Order: Psittaciformes

Family: Cacatuidae: black and white cockatoos, cockatiels

Family: Psittacidae: parrots, parakeets, lories, lorikeets, macaws, etc.

Family: Strigopodea: kākāpō, kea, kākā

Most parrot species are quite social and birds often flock together. Psittacine birds are also long lived, with longevity records up to 65-70 years.2 Larger psittacine birds are generally longer-lived than smaller ones.2

If you are comfortable with the basic principles of avian anatomy and physiology, then you are well on your way to understanding psittacine birds. LafeberVet has listed 16 interesting facts about parrot anatomy and physiology that may serve you well during physical examination, clinical care, and/or necropsy. This post also brief describes the Quaker or monk parrot (Myiopsitta monachus) as well as unique features of the kākāpō (Strigops habroptilus).

 

Gastrointestinal system

Psittacine birds are also called hookbills, because of their remarkable, broad, hooked bill, which they use to aid in locomotion and climbing. This powerful beak can exert a strong bite force of approximately 400 pounds or greater.4 Some parrots also possess transverse, rasp-like, ridges within the bill that can reduce the hardest fruit stones to fine particles.5 The powerful parrot beak is also quite sensitive. Parrots possess a highly developed bill tip organ, which is a collection of sensory receptors at the tip of the beak.

Parrots are the only avian species with intrinsic tongue muscles. This dry, muscular tongue is extremely strong (Fig 1).

parrot tongue

Figure 1. Most parrots have a fleshy, muscular tongue. Photo credit:  Dr. Susan Orosz (left), julydance (right). Click images to enlarge.

 

The muscular tongue of lories, lorikeets, and swift parrots has a brush-like tip for gathering nectar (Fig 2).

Figure 2. Lories, lorikeets, and swift parrots or “brush tongue” parrots possess a papillate tip on their muscular tongues that allows them to gather nectar and pollen. Click image to enlarge.

 

Psittacine birds have a large, prominent crop (Fig 3). The crop is a diverticulum of the esophagus located on the right at the level of the thoracic inlet.

Crop anatomy overlay

Figure 3. The parrot crop is orientated transversely across the neck. Click image to enlarge.

 

Ceca are absent or vestigial in psittacine birds.

There is no gall bladder present in most psittacine species. An exception to this rule of thumb is seen in members of family Cacatuoidea, which do often have a gall bladder.4

 

Respiratory system

The presence of a cere is variable (Fig 4). The cere is a region of highly sensitive epidermis at the base of the beak. The cere is often bare, but it can be covered by feathers. The cere may or may not contain the nares.

budgie male head tilted cockatiel
BFAP eclectus female

Figure 4. The budgerigar (Melopsittacus undulatus) (upper left) and cockatiel (Nymphicus hollandicus) (upper right), have a well-developed cere compared to Amazon parrots, whose cere is covered with tiny feather bristles. The Eclectus parrot (bottom right) has a feathered cere. 

 

The right and left sides of the infraorbital sinus do not communicate in the parrot. Many species, including macaws (Ara spp.) and Amazon parrots, have extensive pneumatic diverticula that extend into the beak and skull bones.

 

Integumentary system

The uropygial gland is present in most parrots, but is absent in Amazon parrots, Pionus parrots, and the large blue macaws (Anodorhynchus spp).4

Most parrots have brightly colored plumage (Fig 5, Fig 6).

alula budgie Color Atlas

Figure 5. Budgerigars have 10 primary feathers and 11 secondary feathers. Photo credit: A Color Atlas of Avian Anatomy. Click image to enlarge.

 

Amazon wing trim BirdCareSeries

Figure 6. Amazon parrots possess nine to 11 primary feathers. Photo credit: Dr. M. Scott Echols. Click image to enlarge.

 

Birds from some parts of Africa and central Australia, such as cockatiels (Nymphicus hollandicus), cockatoos, and grey parrots (Psittacus erithacus), tend to produce a large amount of powder down (Fig 7). Powder down feathers are scattered over the psittacine’s body making some individuals so dusty that holding them for just a couple of minutes can turn a dark shirt nearly white with powder residue.

Figure 7. The first type of feather targeted in psittacine beak and feather disease (PBFD) are powder down feathers. Therefore the absence of powder down during physical examination can be clinically significant. Shown here, a sulphur-crested cockatoo (Cacatua galerita) with PBFD. Photo credit: S B via Wikimedia Commons. Click image to enlarge.

 

Skeletal system

Prokinesis or cranial kinesis is a distinctive feature present in many birds that allows movement of the upper bill or part of the upper bill while the brain case remains motionless. This movement is typically created by a craniofacial elastic zone between nasal and frontal bones, but prokinesis is particularly well developed in large parrots where the elastic zone has been modified into a synovial hinge joint.

 

Parrots are zygodactyl. Two toes are pointed forward (digits II and III) and two toes are point backwards (digits I and IV). These opposable toes are adapted for climbing and grasping or manipulation of objects (Fig 8).

A blue-fronted Amazon parrot eating Nutri-Berries.

Figure 8. Zygodactyly or a “yoke-toed” arrangement of the toes allows parrots to deftly grasp and manipulate objects.

 

The extremely large orbit is incomplete in most birds. In most birds the extremely large orbit is incomplete as a fascial band is found on its ventral border. Parrots possess a complete, ossified orbital ring.4,5

 

Reproductive system

Mostly parrots are sexually monomorphic to the human eye, but there are important examples of sexual dimorphism. The most distinctive example of sexual dimorphism in the parrot world is found in the eclectus parrot (Eclectus roratus). For many years, scientists believed these were two different species. The plumage of the female is scarlet red, while the male bird is a vivid kelly green (Fig 9).

eclectus female eclectus Gratwicke

Figure 9. Female eclectus parrot (Eclectus roratus) (left), male (right). Photo credit:  AJ Haverkamp (left); Brian Gratwicke via Flickr Creative Commons (right). Click images to enlarge.

“Feather sexing”

Most examples of sexual dimorphism involving the plumage are much more subtle.

  • The standard or wild-type male cockatiel typically has bright orange cheek patches as well as a yellow forehead, throat, and crest. There is solid black plumage beneath the wings, and male birds. (Male cockatiels can also produce a more melodious song). Female cockatiels can be identified by barring of the undertail coverts as well as less vivid yellow coloring.
  • In grey parrots, female birds may have dark (gray-black) edges on the vanes of undertail coverts while male birds have undertail coverts that are completely bright red.6
  • In lovebirds (Agapornis spp.), the vane of tail feathers is often pointed in male birds and more rounded in females.6

Cere color

In the budgerigar (Melopsittacus undulatus), the male cere is often blue (Fig 4) while the cere is brown in females (and juvenile birds).

Iris color

The iris of adult white and pink cockatoo species (Cacatua spp.) is dark brown to black in male birds. The female iris is brown to red. The iris may be light red in the female galah (Eolophus roseicapillus).6  This difference can be subtle and is most obvious when a male and female bird are available for comparison.

 

Large psittacine species typically reach puberty between 4 or 5 years of age. Smaller species attain sexual maturity at 1 to 2 years.4 During breeding, most parrot species are monogamous and many of the larger species, pair for life. The normal collection of eggs laid or clutch size usually ranges from one to five eggs 4, but parrots are indeterminate layers. This means that parrots can produce more eggs than their normal clutch size. If eggs are removed, an indeterminate layer will continue to lay eggs. Visual, tactile, and hormonal influences are required to halt egg laying in these birds. This is a normal physiologic change, but can result in pathologic conditions in captivity, such as chronic egg laying and egg binding, in some smaller parrot species, like cockatiels and lovebirds.

Parrot chicks are altricial. They are vulnerable at hatch with no or sparse down and closed eyes. Altricial chicks require a great deal of parental care. Parrot chicks grow relatively slowly when compared to other altricial species of similar size.4

 

Illegal parrots?!

Veterinarians and potential owners should be aware of laws regulating possession of specific avian species.

monk or Quaker parrots Tanaka Juuyoh FCC

Figure 11. Monk or Quaker parrots (Myiopsitta monachus). Photo credit: Tanaka Juuyoh via Flickr Creative Commons. Click image to enlarge.

The Quaker parrot or parakeet (Myiopsitta monachus) is a temperate zone species found in southeastern South America from central Bolivia and southern Brazil south to central Argentina (Fig 11).

The Quaker parrot is an extremely adaptable species. Although most parrots nest in natural cavities found in trees and cliffs,  the monk parakeet is the only psittacine species that constructs a nest using plant materials.4 Feral populations of the monk parakeet have become established in the United States. This has led to the formation of laws in some jurisdictions in the US making ownership of these birds illegal.

 

 

What is a kakapo?

kakapo plumage Dept Conserv FCC

Figure 12. The kakapo is also called the “owl parrot” because of its facial disc of owl-like whiskers. Photo credit: Dianne Mason, Department of Conservation/Flickr Creative Commons. Click image to enlarge.

The kākāpō (Strigops habroptilus) or “owl parrot” is the world’s only flightless, nocturnal psittacine bird (Fig 12). The kakapo is native to New Zealand, where it was once widespread. Prior to colonization and the introduction of predators to New Zealand, the kakapo’s natural defense technique worked well. The bird stands still when danger is near and blends into the background (Fig 13). Today the kakapo is critically endangered and is listed on CITES Appendix I. In the 1980s, the New Zealand Department of Conservation initiated the Kākāpō Recovery Programme and moved all birds to four, predator-free islands.

The kakapo is also the world’s heaviest parrots. Females average 1.4 kg. The average male weighs 2.2 kg. The kakapo uses its small wings only for balance and because there is no need for flight muscles to attach, the sternum lacks a keel.

Kakapos are strictly herbivorous and possess a muscular ventriculus.8

Unlike most parrots, the kakapo possesses a keen sense of smell, believed to be useful in their nocturnal lifestyle.

kakapo plumage Dept Conservation FCC

Figure 13. Kakapo plumage is moss-green, mottled with black chevrons and dark brown blotches over its back and the top of the retrices or tail feathers.. Photo credit: Department of Conservation/Flickr Creative Commons. Click image to enlarge.

The kakapo probably shares distant ancestry with another New Zealand parrot, the kea.

 

Additional information

For more information on parrot anatomy and physiology visit these LafeberVet resources: Avian Anatomy Basics, the Grey Parrot Anatomy Project, the phototutorial A Guide to Avian Necropsy, and Physical Examination of the Avian Patient.

RACE-approved LafeberVet webinar recordings offering additional information on parrot anatomy and physiology include:  Avian Respiratory Anatomy, Physiology & Diseases: An Overview, Avian Cardiology Essentials, and Anatomy and Physiology of the Avian Gastrointestinal Tract: Clinical Applications.

 

References and further reading

References

  1. Altman RB, Clubb SL, Dorrestein GM, Quesenberry K (eds). Avian Medicine and Surgery. Philadelphia, PA: WB Saunders; 1997:  387-393, 412-419, 517-523, 540-547, 661.
  2. Brouwer K, Jones ML, King CE, Schifter H. Longevity records for Psittaciformes in captivity. International Zoo Yearbook. 2000; 37(1):299-316.
  3. Department of Conservation. Kākāpō Recovery website. Available at https://www.doc.govt.nz/kakapo-recovery. Accessed July 13, 2022.
  4. Heatley JJ, Cornejo J. Psittaciformes. In: Miller RE, Fowler ME (eds). Fowler’s Zoo and Wild Animal Medicine, Volume 8. 2015: 172-185.
  5. King AS, McLelland J. Form and Function in Birds. London: Academic Press; 1981. Available at https://wildbirdvet.com/2019/07/29/birds-their-structure-function/.
  6. König HE, Korbel R, Liebich HG (et al). Avian Anatomy: Textbook and Colour Atlas. Sheffield: 5M Publishing, 2016.
  7. McLelland J. A Color Atlas of Avian Anatomy. Philadelphia: WB Saunders; 1991. Available at https://wildbirdvet.com/wp-content/uploads/2019/07/Color-Atlas-of-Avian-Anatomy-McLelland.pdf.
  8. Toft CA, Wright TF. Parrots of the Wild: A Natural History of the World’s Most Captivating Birds. Oakland: University of California Press; 2015: 75.
  9. Waite DW, Deines P, Taylor MW. Gut microbiome of the critically endangered New Zealand parrot, the kakapo (Strigops habroptilus). PLoS One. 2012;7(4):e35803. doi: 10.1371/journal.pone.0035803. Epub 2012 Apr 18. PMID: 22530070; PMCID: PMC3329475.
  10. Whiteway C. Strigops habroptila Animal Diversity Web. 2001. Available at http://animaldiversity.org/accounts/Strigops_habroptila/.Accessed July 9, 2016.
  11. Wildscreen Arkive. Kakapo (Strigops habroptila). Arkive website. Available at http://www.arkive.org/kakapo/strigops-habroptila/. Accessed July 9, 2016.
To cite this page:

Pollock C. Parrot Anatomy Basics. July 13, 2022. LafeberVet web site. Available at https://lafeber.com/vet/parrot-anatomy-basics/