THE TONGUES OF BIRDS. 1013 



Other types of tongues are doubtless found in other groups of birds, 

 but whatever the general plan on which the tongue is built, the varia- 

 tions' in the execution of details appear to be almost infinite in num- 

 ber, as if nature had striven to have no two tongues exactly alike. 



It is a question of interest to ornithologists wiiether the tongues of 

 birds are modilied according to the nature of the food, or whether, 

 underlying all modifications, are certain definite plans of structure 

 indicative of relationship. If the tongues of birds do bear a direct 

 relationship to the character of the food, or the manner in which it is 

 taken, we should not be surprised to lind that birds which are only dis- 

 tantly related have very similar tongues, provided their food or feeding 

 habits were similar, while near relatives might be very different in this 

 respect. We should also be able in many cases to see the connection 

 between the shape of the tongue and the character of the food. On 

 the other hand, if the tongue is of any value in classification, it should 

 be possible to tell something of a bird's affinities from an examination 

 of the tongue. Theoretically, too, we would suppose that the less the 

 tongue was used the smaller the probability of its being adaptively 

 modified, and that the chances of finding a likeness between the tongues 

 of the various members of a group ought to be greatest in a group in 

 which the tongue played an unimportant part in getting or manipulat- 

 ing food. Conversely, diflerences between the tongues of nearly related 

 species might be expected if those species used their tongues, while the 

 greater the similarity between the two species in the manner of obtain- 

 ing food the greater would be the chances of finding their tongues 

 modified in the same manner, although small differences might be 

 expected since the chance of absolute identity would be small. 



To make a fair test of the correctness or incorrectness of these proj)©- 

 sitions, we should compare nearly related species with entirely different 

 food habits, or very distinct species with similar food habits. 



Were we to be guided by the members of a group like the humming 

 birds, we would at once say that the tongues did have a decided value 

 in classification, since we find that all these little birds have the same 

 style of tongue. To offset this, we have the fiict that the humming 

 birds have all practically the same habits, eat the same kind of food, 

 and take it in the same manner, so that really they throw no light on 

 the subject. The penguins present an analogous case, for while the 

 tongues of all are strikingly similar to one another, the habits and food 

 of all are also similar. 



The tongues of woodpeckers, at least those of our North American 

 species, can readily be distinguished as such, although they differ con- 

 siderably from one another in length and in the amount and character 

 of the barbing at the tip. It is an easy matter to follow, step by step, 

 the changes by which the sharp barbed tongue of the pileated wood- 

 pecker is converted into the brushy tongue of the sapsucker, and as 

 we pass from species to species we can see the barbs becoming more 



