NORTHERlSr BLACK SWIFT 263 



age is worn, or how soon the white tips wear away, we do not know ; 

 but evidently this plumage is worn until after the birds leave for the 

 south. 



Considerable discussion has occurred and much has been published 

 on the plumages of the black swift, particularly on the significance 

 of the white spots on the under parts, as sex characters or age 

 characters. 



Mr. Eidgway (1911) evidently considered this a sex character, for 

 he says: "All the sexed specimens examined by me, from whatever 

 locality, show that all those with white-tipped feathers on posterior 

 under parts are females and all those without these white-tipped 

 feathers are males." This is not so in a series of 42 specimens, of vari- 

 ous ages and sexes, that I have examined. More than one-third of all 

 the birds that showed conspicuous white spots, or more or less white 

 tips, on the feathers of the abdomen and under tail coverts are sexed 

 as males, and less than two-thirds are sexed as females. Perhaps this 

 character is more persistent in females than in males. 



Mr. Drew (1882) implies that the sexes are alike in all plumages, 

 and says: "In birds of the second year the general plumage has a 

 brownish cast ; feathers of back tipped with brown, the head whitish, 

 belly feathers j'^et broadlj^ tipped with white." He seems to be sub- 

 stantially correct on both of these points. The white-spotted birds 

 that I examined were collected mainly in June, though two were 

 taken in May, two in July, and one in August. All these birds have 

 square, or slightly emarginate, tails ; and none of them white-tipped 

 remiges, which are characteristic of the juvenal plumage, as indicated 

 above. They could not be young birds of the year, for the young 

 birds of the year were still in the nests at the time nearly all of these 

 birds were collected. They agree perfectly with Mr. Drew's descrip- 

 tion of the second-year bird, and I am inclined to think that that is 

 what they are. They are numerous in collections, as perhaps immature 

 birds may be easier to collect than adults. If this assumption is cor- 

 rect, then the conspicuous characters of the second-year plumage are 

 the absence of white tips on the remiges and the presence, in varying 

 degrees, of white spots or tips on the feathers of the abdomen and 

 under tail coverts. This assumption has been made after giving due 

 consideration to all that has been published on the subject and a lot 

 of data from and correspondence with my friend S. F. Rathbun; he 

 has made an extensive study of the black swift for many years and 

 is inclined to agree with Mr. Eidgway ; but it seems to me that all the 

 evidence fits into the theory advanced above and agrees with Mr. 

 Drew's (1882) idea of a second-year plumage. 



Mr. Drew's statement, that "four years are necessary for them to 

 acquire their complete plumage," seems open to question. He says 



