THE SWIFT. 5 



in August and occasionally even in July, but I have not seen a 

 bird taken in Europe which was moulting its wing- or tail-feathers. 

 Only a few winter specimens are available for examination and 

 in these body, wings and tail have been moulting in Nov., Dec. 

 and Feb., so that it is difficult to decide whether there is one moult 

 or two. There is no difference in winter and summer plumage. 

 Remains of sheath are to be found on outer primaries occasionally 

 as late as March. It is possible that body-feathers moult twice 

 (autumn and spring) but apparently wing- and tail-feathers moult 

 only once very gradually from Nov. to Feb. Late in summer 

 plumage becomes less glossy and browner by wear. 



Nestling. — Down absent. Inside mouth flesh, small pale 

 brown spot at tip of tongue ; externally flanges at base dull white, 

 along edge of bill brown becoming dark brown at tip. 



Juvenile. — Upper-parts as adults but browner and with less 

 gloss, feathers of fore-head with wider whitish tips giving it a hoary 

 appearance, feathers of crown with narrow whitish tips and those 



Primaries of juvenile Swift (Apus a. apus) showing white edgings Note also attenuated 



tip of 1st primary. 



of mantle, rump and upper tail-coverts with whitish tips slightly 

 more prominent than in adult ; chin extending to gape, throat 

 and lores white (white purer and more extensive than in adult) ; 

 rest of under-parts as adult but whitish tips to feathers more 

 prominent ; under wing -co verts with much broader white edgings ; 

 tail- and wing -feathers paler than in adults and with narrow whitish 

 margins at their tips ; all wing-coverts paler than in adults and 

 with narrow whitish tips and edgings, especially prominent along 

 edge of metacarpus. 



First winter. — No specimens available for examination. After 

 moult (which appears to be a complete one) in winter, bird appears 

 to become exactly like adult. 



Measurements and structure.— <$ wing 167-177 (one 182) mm., 

 tail: central pair 40-48, outer pair 72-81, tarsus 10-12, bill from 

 skull 10-11.5 (12 measured). $ wing 164-179. Primaries : 2nd 

 usually longest, 1st occasionally equal, very rarely 1-2 mm. longer 

 and usually 1-5 shorter, 3rd 7-10 shorter, 4th 21-27 shorter, 5th 

 40-47 shorter ; primaries very narrow and incurved towards their 

 tips, webs not emarginated but tip of 1st much attenuated and 



