78 MARCH 



Admirable as is the tongue of the green wood- 

 pecker as an example of consummate adaptation of 

 structure to requirements, it is by no means the 

 only organ which has been modified to suit this 

 bird's peculiar mode of getting a livelihood. The 

 foot is what is known as ' zygodactyle ' that is, 

 arranged with two toes in front and two behind, 

 and the tail-coverts are stiff, with sharp points, so 

 as to act as a support in climbing. Then the breast- 

 bone has been pared away in a remarkable manner, 

 so as to clear the tree-trunk in ascending, for the 

 yaffle never ' climbs down.' When he gets as high 

 on a tree as he thinks there is any need for, he 

 either begins operations again at the base, or flies 

 off in a jerky, undulating way to another. The 

 pectoral muscles are wanting in the depth and 

 power necessary for prolonged flight, which matters 

 little to a bird like the yaffle, of exclusively silvan 

 habits, though it is a mystery how some of the other 

 species, similarly specialised, can undertake their 

 regular annual migrations in spite of this disability. 

 Dr. Bowdler Sharp has recorded how five young 

 great spotted woodpeckers were brought to him and 

 Mr. Seebohm when in Heligoland. These birds had 

 alighted in an exhausted state in a potato field. 



