THE ALPINE SWIFT. 3 



tail-feathers dark brown slightly glossed greenish ; outer webs 

 and tips of wing-feathers and primary-coverts still darker and 

 when freshly grown with more distinct greenish gloss and with 

 very narrow whitish edges to tips and inner webs ; wing-coverts 

 as rest of upper -parts. This plumage is acquired by complete 

 moult. From Mar. to Nov. adults are in every stage of moult 

 but the wing- and tail-feathers do not appear to begin to 

 moult until May or exceptionally in April and the moult is usually 

 finished by October. There appears to be no moult from Dec. 

 to Feb. but specimens taken in these months are scarce. It 

 would thus seem that there is really only one moult, which is 

 a gradual one extending throughout the summer. 



Nestling. — (Not examined.) 



Juvenile. — Like adult in fresh plumage and difficult to dis- 

 tinguish except by the rather more distinct white edgings to 

 wing -feathers and coverts and these make it more easily dis- 

 tinguishable when compared with adults in worn plumage. 



First winter. — Very difficult to distinguish from adult. The 

 juvenile body -plumage is moulted Aug. -Oct. but apparently not 

 wing- or tail-feathers or wing-coverts until summer when bird 

 appears to have a complete moult as adult. 



Measurements and structure. — <$ wing 220-228 mm., tail : 

 central pair 55-64, outer pair 77-90, tarsus 16-18, bill from skull 

 15-16 (12 measured). $ wing 207-221. Primaries : 2nd usually 

 longest, 1st occasionally equal or 1-2 mm. longer but usually 

 2-4 shorter, 3rd 10-15 shorter, 4th 27-32 shorter, 5th 50-58 shorter. 

 Rest of structure as Swift. 



Soft parts. — Bill brown-black ; feet dark flesh-colour ; iris 

 dark brown. 



Characters and allied forms. — A. m. africanus (Abyssinia, East 

 and South Africa) has broader breast-band. Large size and white 

 breast and belly distinguish it from other British Swifts. 



Field -characters. — Frequents gorges or cliffs among mountains, 

 as well as buildings and old walls in plains. Easily distinguished 

 from common Swift by its large size and white belly. Flight 

 appears to me less rapid than that of Swift, but this may be owing 

 to larger size of bird. Note a loud persistent " chitter." (H.F.W ) 



Breeding-habits. — Nests in crevices, under eaves in buildings 

 and also in holes of ruins, and in natural fissures in cliff -faces. 

 Nest. — Composed of materials picked up on the wing, agglutinated 

 with saliva, such as bits of straw or grass, feathers, leaves, husks 

 of buds and seeds of trees. Eggs. — Normally 2, but not infre- 

 quently 3, rarely 4, dull white. Average of 81 eggs, 31.1 X 19.2 mm. 

 Max. : 34.3 X 19.5 and 30.1 x 20.5. Min. : 27.5 x 20.2 and 

 30.7 X 17.8. Breeding-season. — End of May and early June. 

 Incubation. — By hen only (Naumann) : by both sexes (S. B. 

 Wilson) ; 18-21 days. Single brooded. 



VOL. H. B 2 



