AKT,19 CONCERNING BIRDS ' TONGUES GARDNER 11 



In addition a most difficult problem is the explanation of varia- 

 tions in closely related birds where presumably the diet is very 

 similar. Thus Lucas ^ called attention to the variation found 

 in the genus Melospiza. In M. fasciata a much-frayed tip is 

 found, while in M. lincoVni the tip is only slightly bifid and not 

 frayed. To this may be added the genus Zosterofs^ with a forked 

 and smooth tongue in Z. lateralis^ while it is much curled and 

 frayed in Z. slmphx and Z. japonica. Still again among the 

 warblers of the genus Dendroica it varies from a flat and only 

 slightly split organ in D. petechia (fig. 155) and D. fusca (fig. 158) 

 to a much curled split and frayed one in D. tignna (fig. 2). 



The taxonomic value of the tongue in birds is an interesting 

 question which can only be answered by a systematic survey. It is 

 evident that the most useful characters for classification are those 

 founded on strict morphological bases and any structure highly 

 modified in response to external stimuli is of the least value. But 

 no one organ has ever been found that can serve as a complete 

 basis for classification. The history of ornithology evidences many 

 mistakes due to the use of one character alone, as witness the old 

 group Pinnatipedes, including phalaropes, coots, and grebes, through 

 similarity of foot structure. In considering the value of the tongue 

 it must be recognized that it is a highly adapted organ, but this 

 should not rule it out from all taxonomic consideration. If every 

 structure adaptively modified be omitted no part of a bird can be 

 used, since to a greater or less extent this includes the whole 

 organism. Lucas,^ taking note of the adaptive modifications, gives 

 it very little taxonomic value. There is, however, need of a sys- 

 tematic study of this organ in every group, with an evaluation of it 

 in each one. While tongues are adaptively modified it may well be 

 that these changes are constructed on a type pattern distinctive of 

 the group to which the bird belongs and thus indications of affinity 

 be given. 



Order COLYMBIFORMES 



Loons are distinguished from grebes by the fact that the tongues 

 of the former have a large patch of spinose processes at the base, 

 while the grebes have but a single row posteriorly. Gavia immer 

 (fig. 23) has a relatively large patch, while this is not so prominent 

 in the Pacific loon, Gavia pacijica (fig. 22). Podilymbus podiceps 

 and JEchmophorus occidentalis among the grebes have but a weak 

 row of spines, which in the eared grebe Golymbus nigricollis cali- 

 fornicus (fig. 24) are prominent but broad and flat. 



* Lucas, F. A. The Taxonomic Value of the Tongue in Birds. The Auk, vol. 13, No. 2, 

 April, 1896, pp. 109-115. 



