TECHNICAL TEEMS. 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 afford 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 head. 



15. Flexure. Bend of the wing. 



16. Tarsi. Shanks of the legs. 



17. Tibia. Thigh. 



The upper and lower bills are called the superior and inferior 

 maxilla, or upper and lower mandibles. 

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



