40 ALLEN'S NATURALIST'S LIBRARY. 



Studer say that many perish, as, of course, the supply of insects, 

 on which these birds entirely depend, fails them. The nest is 

 a rough structure, formed of many materials, all of which are 

 procured by the Swifts on the wing, as the short feet and long 

 wings of the bird prevent its rising when once it gets on the 

 ground, and so it is often captured when benumbed with cold. 

 Thus the nest is composed of earth procured from the crevices 

 of rocks, leaves, paper, feathers, &c., all the materials being 

 glued together into a compact mass by means of the birds' own 

 saliva. The eggs are laid before the nest is completed, and 

 much of the structure is consolidated by the sitting birds, both 

 male and female sharing the duties of incubation. In their 

 habits the White-bellied Swifts are very regular, issuing forth 

 from their retreats at break of day and foraging for food for 

 some hours, then resting in their homes during the best part 

 of the day, and sallying forth again about five o'clock in the 

 afternoon, and flying about till dark. They are very quarrel- 

 some and irritable in their nature, and make a considerable 

 noise and clatter in the places where they take up their 

 abode. 



Eggs. Generally two in number, but sometimes three or 

 even four, though it is supposed that no female lays more than 

 two eggs. Eggs pure white. Axis, i'i-i'25; diameter, 075- 

 0-8. 



II. THE COMMON SWIFT. MICROPUS APUS. 



Hirundo apus, Linn. Syst. Nat. i. p. 344 (1766). 



Micropus murarius, Meyer und Wolf, Taschenb. p. 281 (1783); 



Macgill. Brit. B. iii. p. 618 (1840). 

 Cypselus apus, Dresser, B. Eur. iv. p. 583, pi. 266 (1881) ; 



Newt. ed. Yarr. Brit. B. ii. p. 364 (1882); B. O. U. List 



Brit. B. p. 74 (1883); Seeb. Brit. B. ii. p. 292 (1884); 



Lilford, Col. Fig. Brit. B. part v. (1887) ; Saunders, Man. 



Brit. B. p. 251 (1889). 



Adult Male. Sooty-black with a slight greenish gloss, the 

 forehead slightly whiter ; chin dull white, with a few shaft-lines 

 on some of the feathers ; under wing-coverts with faintly in- 

 dicated whitish margins, these being sometimes visible on the 

 under tail-coverts ; bill black ; feet dark brown ; iris dark 



