The Anatomy of Birds 25 



The beak part of the skull, as just stated, is subject to great modifications 

 connected with the taking or manipulation of food, and may be long and slender 

 like a probe, broad and flat, or short and strongly made for crushing seeds. The 

 extent to which habit and modification may go is shown in the Pelican, Gannet, 

 and Cormorant, and in all these diving birds the nostrils are completely filled 

 up and the roof of the mouth strengthened by the growth of the bone. 



The Cormorant starts in life with open nostrils, but by the time it is ready to 

 take to the water and seek food for itself, the nostrils are completely closed by the 

 growth of bone and overlying horny beak. These changes are accompanied by 

 others in the bones of the palate by which the structures of this region are entirely 

 changed and its real characters obscured. 



The hyoid, all but the front portion, corresponds with the first gill arch of a 

 fish and supports and controls the motion of the tongue. The tongue itself is 

 built upon the front portion of the hyoid, which is subject to little modification, 

 but the extent to which the tongue can be protruded depends on the length of the 

 bones of the hinder part. Hence in the Woodpeckers, which use their tongues as 

 probes, the hinder parts of the hyoid curl up around the back of the head and 

 may even, as in Colaples, pass over and into the nasal chamber nearly to the tip 

 of the beak. Thus from bill to toes, not merely the external form of the bird, 

 but the underlying skeleton as well, is fashioned to adapt the bird to its surround- 

 ings. As William Kitchen Parker used to say, "Adaptation, adaptation is the 

 keynote to the structure of a bird." 



