Drinking
In birds

There are three general ways in which birds drink: using gravity itself, sucking, and by using the tongue. Fluid is also obtained from food.

Most birds are unable to swallow by the "sucking" or "pumping" action of peristalsis in their esophagus (as humans do), and drink by repeatedly raising their heads after filling their mouths to allow the liquid to flow by gravity, a method usually described as "sipping" or "tipping up". The notable exception is the family of pigeons and doves, the Columbidae; in fact, according to Konrad Lorenz in 1939:

one recognizes the order by the single behavioral characteristic, namely that in drinking the water is pumped up by peristalsis of the esophagus which occurs without exception within the order. The only other group, however, which shows the same behavior, the Pteroclidae, is placed near the doves just by this doubtlessly very old characteristic.

Although this general rule still stands, since that time, observations have been made of a few exceptions in both directions.

In addition, specialized nectar feeders like sunbirds (Nectariniidae) and hummingbirds (Trochilidae) drinkby using protrusible grooved or trough-like tongues, and parrots (Psittacidae) lap up water.

Most birds scoop or draw water into the buccal areas of their bills, raising and tilting their heads back to drink. An exception is the common pigeon, which can suck in water directly by inhalation.
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