428 A HISTORY OF BIRDS 



be actually disadvantageous, since the labour expended in 

 thrusting out the tongue and secreting the saliva would be out 

 of all proportion to the capture made. But the development 

 and perfection of this peculiar method of feeding was, so to 

 speak, worth while, inasmuch as it enables these birds to avail 

 themselves of a supply of food inaccessible to ordinary birds ; 

 while at the same time it can as easily secure spiders, larvae 

 and other insect food, fruit and seeds, as its less-favoured neigh- 

 bours by means of its beak in the usual fashion, and indeed 

 during a large part of the year it is compelled to adopt a mixed 

 diet of this kind. Further, even among Woodpeckers many 

 feed but seldom, and some apparently never, upon ants, but in 

 these cases the mechanism of the tongue is less perfect. This 

 mechanism, and one or two features associated therewith, compels 

 at least a short examination. 



Varying in perfection in accordance with the use to which it 

 is put, it reaches its highest development in the Genus Colaptes, 

 though in our British Green Woodpecker (Gecinus viridis) it is 

 scarcely less complete. This extensibility then is gained by 

 the elongation of the hyoid bones — a pair of long rods passing 

 backwards from the base of the tongue immediately under the 

 head. In the genera in question these rods are of enormous 

 length, extremely slender and very elastic. Continuing their 

 backward course they pass upwards on to the top of the head, 

 where they meet, and passing forwards in a deep groove in the 

 skull continue their course, turning to the right — occasionally to 

 the left — and passing into the right nasal fossa. In Colaptes 

 they then turn downwards and run along the floor of the 

 olfactory chamber to the end of the beak. By means of the 

 muscles attached thereto these rods can be pulled backwards, 

 downwards and forwards, and thus the tongue is thrust out, the 

 salivary glands simultaneously pouring out their sticky secretion 

 over the exposed portion. This is armed with varying devices 

 of backwardly directed barbs and hairs, which serve two different 

 purposes. The longest tongues have few barbs along their 

 edges, and are used mainly for the capture of ants. Apparently 

 for the sake of increasing the thickness of the salivary coating 

 on the back of the tongue a rough surface is provided by means 

 of a large number of tiny recurved, and backwardly directed pro- 

 cesses. The hairy and downy Woodpeckers, on the other hand. 



