Buffalo Bill played his designated role in reducing the American bison from an estimated population of 60 million to near extinction. In 1867, under a contract to provide food for railroad crews, he and his men killed 4,280 animals in just eight months. His slaughter may have been indiscriminate, but the resulting beef was not wasted. Other despoilers of our natural heritage killed bison with even greater abandon, removed the tongue only (considered a great delicacy in some quarters), and left the rest of the carcass to rot.
Tongues have figured before in the sad annals of human rapacity. The first examples date from those infamous episodes of gastronomical gluttony—the orgies of Roman emperors. Mr. Stanley, Gilbert’s “modern major general,” could “quote in elegiacs all the crimes of Heliogabalus” (before demonstrating his mathematical skills, in order to cadge a rhyme, by mastering “peculiarities parabolous” in the study of conic sections). Among his other crimes, the licentious teen-aged emperor presided at banquets featuring plates heaped with flamingo tongues. Suetonius tells us that the emperor Vitcllius served a gigantic concoction called the Shield of Minerva and made of parrot-fish livers, peacock and pheasant brains, lamprey guts and flamingo tongues, all “fetched in large ships of war, as far as from the Carpathian sea and the Spanish straights.”
Lampreys and parrot fishes (though not without beauty) have rarely evoked great sympathy. But flamingos, those elegant birds of brilliant red (as their name proclaims), have inspired passionate support from the poets of ancient Rome to the efforts of modern conservationists. In one of his most poignant couplets, Martial castigated the gluttony of his emperors (circa 80 A.D.) by speculating about different scenarios, had the flamingo’s tongue been gifted with song like the nightingale’s, rather than simple good taste:
Dat mihi penna rubens nomen; sed lingua gulosis
Nostra sapit: quid, si garrula lingua foret?
(My red wing gives me my name, but epicures regard my tongue as tasty. But what if my tongue could sing?)
Most birds have skinny pointed tongues, scarcely fit for an emperor, even in large quantities. The flamingo, much to its later and unanticipated sorrow, evolved a large, soft, fleshy tongue. Why?
Flamingos have developed a surpassingly rare mode of feeding, unique among birds and evolved by very few other vertebrates. Their bills are lined with numerous, complex rows of horny lamellae—filters that work like the whalebone plates of giant baleen whales. Flamingos are commonly misportrayed as denizens of lush tropical islands—something amusing to watch while you sip your rum and coke on the casino veranda. In fact, they dwell in one of the world’s harshest habitats—shallow hypersaline lakes. Few creatures can tolerate the unusual environments of these saline deserts. Those that thrive can, in the absence of competitors, build their populations to enormous numbers. Hypersaline lakes therefore provide predators with ideal conditions for evolving a strategy of filter feeding—few types of potential prey, available in large numbers and at essentially uniform size. Phoenicopterus ruber, the greater flamingo (and most familiar species of our zoos and conservation areas in the Bahamas and Bonaire), filters prey in the predominant range of an inch or so—small mollusks, crustacea, and insect larvae, for example. But Phoeniconaias minor, the lesser flamingo, has filters so dense and efficient that they segregate cells of blue-green algae and diatoms with diameters of 0.02 to 0.1 mm.
Flamingos pass water through their bill filters in two ways (as documented by Penelope M. Jenkin in her classic article of 1957): either by swinging their heads back and forth, permitting the water to flow passively through, or by the usual and more efficient system that inspired the Roman gluttons—an active pump maintained by a large and powerful tongue. The tongue fills a large channel in the lower beak. It moves rapidly back and forth, up to four times a second, drawing water through the filters on the backwards pull and expelling it on the forward drive. The tongue’s surface also sports numerous denticles that scrape the collected food from the filters (just as whales collect krill from their baleen plates).
The extensive literature on feeding in flamingos has highlighted the unique filters—and often neglected another, intimately related, feature equally remarkable and long appreciated by the great naturalists. Flamingos feed with their heads upside down. They stand in shallow water and swing their heads down to the level of their feet, subtly adjusting the head’s position by lengthening or shortening the s-curve of the neck. This motion naturally turns the head upside down, and the bills therefore reverse their conventional roles in feeding. The anatomical upper bill of the flamingo lies beneath and serves, functionally, as a lower jaw. The anatomical lower bill stands uppermost, in the position assumed by upper bills in nearly all other birds.
With this curious reversal, we finally reach the theme of this essay: Has this unusual behavior led to any changes of form and, if so, what and how? Darwin’s theory, as a statement about adaptation to immediate environments (not general progress or global direction), predicts that form should follow function to establish good fit for peculiar life styles. In short, we might suspect that the flamingo’s upper bill, working functionally as a lower jaw, would evolve to approximate, or even mimic, the usual form of a bird’s lower jaw (and vice versa for the anatomical lower, and functionally upper, beak). Has such a change occurred?
~~The Flamingo's Smile -by- Stephen Jay Gould
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