hoanal Slit
Raptors have no soft palate, there is just a hard palate. There is a slit in the roof of the mouth that connects the trachea to the sinuses and the nares. Indeed, in a properly functioning healthy bird a drop of saline can be placed into the nares and should appear coming out the choanal slit inside the mouth. Some species have ridges called papillae around this slit, some are small and rounded and others are sharp jagged formations. Malformations of these ridges may mean a deficiency of Vitamin A.
At the base of the tongue is the glottis which is a valve that closes to prevent food or liquid from passing into the trachea. When a bird's mouth is closed, the glottis fits precisely into this choanal slit making one continuous tube from the nares through the choanal slit and into the glottis and trachea allowing air to pass directly into the trachea without entering the rest of the mouth.
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Choanal slit of a Red-Tailed Hawk. (cadaver) |
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Choanal slit of a Gyrfalcon. (cadaver) |
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Choanal slit of a Barn Owl. (cadaver) |
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Choanal slit of a Great Horned Owl. (cadaver) |
More information on avian biology, particularly of the head:
Avian biology http://www.exoticpetvet.net/avian/anatomy.html