|Behavioural mechanisms of avian drinking|
Zweers, G. (1992). Behavioural mechanisms of avian drinking. Neth. J. Zool. 40: 60-84
In: Netherlands Journal of Zoology. E.J. Brill: Leiden. ISSN 0028-2960, more
Avian drinking mechanisms are reviewed. Two major classes of drinking are considered: tin up and tip down drinking. Each class show a variety of physical mechanisms of taking water in the oropharynx and then swallowing it. In tip up drinking the water is taken in the oropharynx by a few motion cycles of beak and tongue while the beak tips are immersed. The gathered water mass is stored in the oropharynx while tipping up. The mass is then swallowed by some motion cycles of the larynx. In tip down drinking, however, beaks are not tipped up and a water dose is transported each motion cycle directly to the esophagus. Motor patterns of jaw apparatus and cervical column show that internal constraints and kinematic principles (partly) control these patterns. Highly specific integration of the oro-pharyngeal and cranio-cervical systems is present, which is subject to change during ontogeny being regressive or progressive. Evolutionary diversification of avian drinking is shown to be strongly connected to trophic adaptations and occurs either to release throphic adaptations from drinking constraints or to economize drinking secondarily. A set of principles is developed to systematize present knowledge of avian drinking. One major principle is that chicken-like drinking and its development represent avian ancestorlike drinking.