422 BULLETIN 15 3, UNITED STATES NATIONAL MUSEUM 



writes that jacksoni is little more than a northern race of deckem^ 

 but because of the geographical overlapping is forced to grant it 

 specific rank. Sclater '* limits jacksoni to " Northern Uganda and 

 Kenya Colony between Lake Rudolf and Mt. Elgon." On the 

 other hand, Rothschild " saj's that jacksoni occurs in the southern 

 part of the range of deckeni and occurs alone in parts of Uganda. 

 The truth of the matter is that both species occupy much the same 

 range. I have examined specimens of both from as far north as 

 central Ethiopia and as far south as central Tanganyika Territory. 



Being so much alike, and occupying the same general area, geo- 

 graphically and ecologically, one wonders how two such species, ap- 

 parently only recently separated phylogenetically, could have come 

 about. It would be well worth while to investigate the breeding 

 seasons of each to see if there might not be any physiological isola- 

 tion to render them mutually more distant and to make the competi- 

 tion between them less keen. 



The Juvenal plumages of the two are very similar, and as the bill 

 character is not yet well developed, the young birds are difficult to 

 identify. On the whole, deckeni is very slightly lighter brown above, 

 but I freely admit that there are specimens that I can not place 

 with any great degree of certainty. The similarity between the two- 

 birds in juvenal plumage, coupled with the fact that jacksoni retains 

 the white spots on the upper wing covers in adult plumage, while 

 deckeni does not, but becomes uniformly black in those parts, sug- 

 gests not only community of descent, but also that jacksoni is the 

 more primitive of the two. It would then appear that, since deckeni 

 is considerably more numerous than jacksoni^ the newer species (if 

 such it really be) is gradually crowding out the older one and replac- 

 ing it more and more. 



In the course of the present study I have examined a series of 49* 

 specimens of deckeni from Ethiopia, Kenya Colony, and Tanganyika 

 Territory. As may be seen from the following table, northern birds 

 do not differ from southern ones, the overlapping is as great as the 

 variation, and consequently races based on sizes are not possible. In 

 the table only adult birds are listed. 



''* Syst. Avium Ethiop., 1924, p. 228. 



'«Ann. Mag. Nat. Hist., ser. 9, vol. 14, 1924, p. 317. 



