I have a big beak and a small tongue: Hornbill feeding

In the movie Roxanne, Steve Martin’s Cyrano-esque character has a scene where he’s supposed to drink from a small fluted wine glass, but his character’s large schnoz makes it impossible. That’s sort of the task faced by several birds species with large, lengthy bills.

Feeding is no small task for birds. Keep in mind that birds have no hands to manipulate their food, and a bird’s bill is completely inflexible. Imagine trying to eat without moving your lips.

Hornbills (like Aceros cassadix, pictured) have a world-class long beak. It seems likely that this dramatic elongation isn’t tied in with feeding, but may be related to some other kind of physiological or ecological demand. Indeed, to make matters more difficult for feeding, these animals have a very short tongue.

Here you can see a picture of the short tongue in Buceros hydrocorax, taken from a paper by Baussart and Bels. These researchers had previously examined feeding in toucans, also renown for their large beaks, and wanted to see if hornbills fed in a similar way. They recorded three individuals from three different hornbill species on high-speed video.

All the hornbills feed in roughly the same way. They position feed in their beaks, and use a head movement to get food down their throats. Feeding doesn't involve the tongue at all. A few other birds use similar kinds of mechanisms, but hornbills move their heads much more horizontally than other birds.

Buassert and Bels call this way of feeding “ballistic food transport.” Other birds also use some head movements in feeding, but these large beaked birds appear to have taken it a bit further. Indeed, this is probably the only way that they would be able to feed.

I wonder how they drink?

References

Baussart, S., & Bels, V. (2010). Tropical hornbills (Aceros cassidix,
Aceros undulatus, and Buceros hydrocorax) use ballistic transport to feed with their large beaks Journal of Experimental Zoology Part A: Ecological Genetics and Physiology DOI: 10.1002/jez.590

Aceros cassadix photo on Flickr, used under a Creative Commons license.