T B C H N I C A L T E K M S. 35 



serviceable only as a protection to the parts which they sur- 

 round; they unite without any regularity with the plumage of 

 the back and wings. 



9. The rump feathers and upper-tail coverts. — These feathers 

 are the continuation of the covering of the back, and are strong 

 in proportion to the peculiar habits of the bird. In the Wood- 

 pecker tribe, for instance, these feathers are very strong and 

 unusually long, as they make constant use of the tail as a 

 support and aid when climbing the trunks of trees; and so 

 it is with some water-fowl not webfooted, but obliged frequently 

 to take flight from the water. The tail feathers in these last- 

 mentioned birds afi"ord the greatest assistance in springing into 

 the air. 



10. The vent feathers and under-tail coverts, that extend from 

 the anus, or vent, to the tail underneath. These feathers are 

 much longer in some tribes of birds than others. Those that 

 have a constant habit of flirting up their tails — like, for example, 

 the Rallus Carolinus, and several species of small shore-birds — 

 have the vent feathers unusually well developed. 



The tail feathers are various in size and numbers, and are 

 generally the most ornamental part of a bird. The tail per- 

 forms the most necessary office in the navigation of the bird 

 through the air; in fact, it is the rudder by which its course is 

 determined, and acts in concert with the will of the bird as freely 

 as a ship obeys her helm. 



11. Loral space. — The space between the bill and eye. 



12. Frons. — The forehead. 



13. Corona. — Crown of the head. 



14. Occiput. — The hind part of the hea'?. » 



15. Flexure. — Bend of the wing. 



16. Tarsi. — Shanks of the legs. 



17. Tz6ta.— Thigh. 



The upper and lower hills are called the superior and inferior 

 maxilla, or upper and lower mandibles. 



Iris — irides. — The colored circle surrounding the pupil of the eye. 



