THE CLASS BIEDS. 



deserted farm steadings, on which they sought their food, 

 coloured natives called them "Hadada." R. K.] 



317 



The 



Fig. 293i. Head of the Ibis; taken from a mummy, by M. Olivier. 



Most birds perch, and it is easier for them to spread their 

 wings and take flight when perched on a branch of a tree or 

 rocky edge than when resting on the level ground. In order 

 to perch with safety, they embrace the bough closely with 

 their toes ; and if this required an incessant muscular effort, it 

 could not be supported for any length of time. A mechanical 

 contrivance enables the bird to dispense with this even whilst 



Fig. 294. Common Penguin, also called Eazor-billed Auk; 

 Aptenodytes. 



asleep. The flexor muscles of the toes pass over the articula- 

 tions of the knee and heel in such a way that, whilst they are 

 flexed they act on the tendons of these muscles, and so flex 

 the toes. The weight of the body assists in this movement, 

 which enables the bird to perch without fatigue. 



The differences which exist in the form of the feet of birds 



