SWIFTS. 239 



before the ground is reached he checks his rapid descent by an abrupt 

 turn, and on leisurely wing again mounts upward to repeat this game 

 of sky-coasting. At the moment the turn is made one may hear a 

 rushing, booming sound, which, as writers have remarked, can be imi- 

 tated in tone by blowing across the bung-hole of any empty barrel. It 

 is made by the passage of the air through the bird's primaries. 



In late summer Nighthawks gather in large flocks and begin their 

 southward migrations. When flying the white mark on their primaries 

 is a conspicuous character, and has the appearance of being a hole in 

 the bird's wing. 



4 2 Ob. C. v. chapman! (Coues). FLORIDA NIGHTHAWK; BULL-BAT. 

 Similar to the preceding, but smaller, and with the white and cream-buff 

 markings of the upper parts more numerous. L., 8'60 ; W., T'10 ; T., 4-10. 



Range. Breeds in Florida and westward on the Gulf coast ; south in win- 

 ter to South America. 



The WESTERN NIGHTHAWK (4*20a. C. v. henry i), a near relative of our spe- 

 cies, has been recorded from Waukegan, 111. 



FAMILY MICROPODID^E. SWIFTS. 



The seventy-five known species of Swifts are distributed through- 

 out the greater part of the world. About one half this number are 

 American, but only four are found in North America. Swifts are 

 generally found associated in scattered companies, and when roosting 

 or nesting are eminently gregarious. Hollow trees and caves are their 

 natural retreats, but in some parts of the world chimneys are now used 

 exclusively. 



They feed entirely while flying, and with their unusually long 

 wings and small, compactly feathered bodies possess unrivaled powers 

 of flight. Swifts are popularly confused with Swallows, but the re- 

 semblance is only superficial and exists chiefly in the similarity of 

 their feeding habits, while the structural differences between the two 

 are numerous and important. 



423. Chsetura pelagica (Linn.}. CHIMNEY SWIFT; CHIMNEY 

 "SWALLOW." (See Fig. 39.) Ad. Entire plumage fuscous, more grayish on 

 the throat ; a sooty black spot before the eye ; shafts of the tail-feathers ex- 

 tending beyond the vanes. L., 5-43 ; W., 4-94 ; T., 1-90 ; B. from N., -15. 



Range. Eastern North America ; breeds from Florida to Labrador ; win- 

 ters in Central America. 



Washington, abundant S. E., Apl. 15 to Oct. 10. Sing Sing, common 

 S. R., Apl. 19 to Oct. 23. Cambridge, abundant S. E., Apl. 25 to Sept. 20. 



Nest, a bracketlike basket of dead twigs glued together with saliva; at- 

 tached to the wall of a chimney, generally about ten feet from the top, by 



