Bird Tongues

I have written before of the different methods that our resident birds use to chow down on sunflower seeds at the feeder. Birds with beaks that are slender and pointed (like titmice, chickadees, and nuthatches) will grab a seed, fly to a nearby perch, wedge it with their feet against something, and hammer away with their bills until the husk cracks and exposes the inner meat. Others with stronger bills (finches and cardinals) will squat right at the feeder, pick up a seed, crunch down, and spit out pieces of husk. It’s fun to watch each technique and guess how they’re doing it.

While watching these contrasting methods recently, it occurred to me that, while I was interpreting the finches to be chewing on the seeds, it couldn’t be. Birds have no teeth! At best they are cracking the seed shell. So how do finches separate the “wheat” from the “chaff,” or husk from the nut? They’ve got to have a pretty adept tongue, I realized. If you think about how we humans eat, our tongue is very active, shoving food around our mouth and placing it between molars, so it can be ground into mush. (Except when we’re not quite a deft as we could be and grind down on our tongue. Ouch!) So I did a little research on the mouth organ of birds.

Their tongue is quite similar to ours—being attached to the floor of their mouths, from which it sallies skillfully and rapidly around to manipulate food into place. But there’s nothing scarcer than hen’s teeth, as the saying goes, so a bird cannot chew… thus in the case of the finch, it cracks. A bird’s bill is a horny material, much like our fingernails. In place of jaws they have an upper and lower mandible. Since they can’t chew, they have three ways of ingesting food: swallowing it whole (such as bugs) or breaking it up with either that tough bill (finches) or bashing it with a lance-like beak (titmice).

A finch has a long and fat tongue—shaped, as is the case for all birds, like its bill. The upper finch mandible has grooves inside it, into which the tongue maneuvers a seed, the viselike lower mandible closes for the crunch, and the shell is cracked. The finch quickly rotates the seed with that dexterous tongue and crunches again. It then spits out the husk pieces, still maneuvering that nimble tongue.

I’ve watched a cardinal or goldfinch perform this deft and rapid task many times—not able to understand the intricate tongue work happening. From now on I’ll see it weaving around inside that bill, with my mind’s eye. Hmmm, I wonder if they ever bite down on their tongue. I’ve not yet seen a finch flinch or yelp like I do when I crunch down on my tongue. Maybe there’s an advantage to having no teeth!