Ingestion in Birds


Ingestion of food and water in birds is mediated by an extremely diverse trophic system which traces back upon only two modifications of one single anatomical design, i.e. a kinetic, beaked skull. The mechanics of ingestion are characterized by lower jaw depression linked to a movable upper jaw which is highly integrated with tongue and larynx motion – though often compromised by functional demands from drinking and vocalization – controlled primarily by touch and taste.

Keywords: cranial kinesis; pecking pattern; trophic evolution

Figure 1.

Cranial kinesis. Left: Early evolution of cranial kinesis. Letters refer to similar bones, illustrating subsequent changes in their shape and presence during the processes of cranial fenestration and palate detachment. Grey areas are windows. Blue area is the quadrate (q) articulating at last with skull and lower mandible. Windows are the orbit (o), upper and lower temporal fenestrae (utf, ltf) and nares (na). Upper right: Prokinesis and coupled kinesis (crow). The right upper blue dot indicates the frontonasal hinge around which the upper mandible is elevated if the quadrate is swung forward by the protractor muscle (1) around the left upper dot. This action slackens the dashed red ligament that connects skull and lower mandible, so that the lower mandible is deblocked and can be depressed by the depressor muscle (2). Middle right: Palaeognath rhynchokinesis (ostrich). Lower right: Neognath rhynchokinesis (plover). Red bars refer to flexible areas. Dotted areas refer to upper mandible and jaw apparatus. aof, anterior orbital fenestra; f, frontal; j, jugal; l, lacrimal; ltf, lower temporal fenestra; m, maxilla; n, nasal; na, naris; o, orbit; p, parietal; pf, prefrontal; pm, premaxilla; po, postorbital; pof, postfrontal; q, quadrate; qj, quadratojugal; sq, squamosal; utf, upper temporal fenestra.

Figure 2.

Ingestion by the pecking mechanism. (a) Behavioural patterning. (Redrawn after Zeigler et al., 1980, Journal of Comparative Physiology and Psychology94: 783–794.) (b) Process of ingestion. Seed 1 is tested by touch and taste, and repositioned for proper oral transport. Seed 2 is stored and tested by taste at the lingual base prior to swallowing. A bill tip touch organ lies underneath a hard horny rhamphotheca. The dashed lines indicate areas of taste organs and mucus orifices. (c) Phases of ingestion.


Further Reading

Bout RG and Zeigler HP (1994) Jaw muscle activity and amplitude scaling of jaw movements during eating in pigeons (Columba livia). Journal of Comparative Physiology 174: 433–442.

Cooper A and Penny D (1997) Mass survival of birds across the Cretaceous–Tertiary boundary. Molecular evidence. Science 275: 1109–1113.

Feduccia A (1996) The Origin and Evolution of Birds. New Haven, CT: Yale University Press.

Padian K and Chiappe LM (1998) The origin and early evolution of birds. Biological Reviews 73: 1–42.

Unwin DM (1993) Aves. In: Benton MJ (ed.) The Fossil Record 2, pp. 717–737. London: Chapman and Hall.

Zusi RD (1985) A functional and evolutionary analysis of rhynchokinesis in birds. Smithsonian Contributions to Zoology 395: 1–40.

Zusi RD (1993) Patterns of diversity in the avian skull. In: Hanken J and Hall BK (eds) The Skull, pp. 391–437. Chicago: University of Chicago Press.

Zweers GA and Vanden Berge JC (1998) Birds at geological boundaries. Zoology 100: 183–202.

Zweers GA, Berkhoudt H and Vanden Berge JC (1994) Behavioral mechanisms of avian feeding. Advances in Comparative Environmental Physiology 18: 241–279.

Zweers GA, Vanden Berge JC and Berkhoudt H (1997) Evolutionary patterns of avian trophic diversification. Zoology 100: 25–57.

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How to Cite close
Zweers, Gart, and Berkhoudt, Herman(May 2001) Ingestion in Birds. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001836]