140 U.S. NATIONAL MUSEIIM BULLETIN 223 



two distinct species. The elongated tail feathers are noticeably 

 tapered toward the tip in one race of eastern and southern Africa, 

 while tliese feathers remain broad to their ends in six other forms 

 inhabiting mainly western Africa. Birds of both types, however, 

 occur together in northeastern Africa, in Kenya, and in the area from 

 Mozambique to Angola. As Chapin (1954, p. 579) has put it, geo- 

 graphic overlapping by birds of the tapered, narrow-tailed type 

 with at least two of the broad-tailed races is definitely known. If it 

 could be demonstrated that certain kinds of males mated with certain 

 kinds of females, the tapered, narrow-tailed form would merit specific 

 status, but no one has been able to distinguish forms among the fe- 

 males (only the breeding males have the elongated rectrices). "It 

 has been suggested that the tail form of males is a mutational char- 

 acter, determined by a single pair of genes and thus to be compared 

 with color phases among other birds and especially with Coliuspasser 

 ardens. Pahing would be indiscriminate, no intermediates would 

 result, and were it not that each form does occupy an area mainly its 

 own, they should not even be dignified with trinomials. Such a view 

 is reasonable but will not be easy to prove by either field observation 

 or breeding experiments." 



On the other hand, we may have two closely similar species — 

 paradisaea with tapered elongated rectrices in the adult male, and 

 aucupum (six races) with broad elongated rectrices. In an earlier 

 paper, Chapin (1922) favored this view and postulated that paradisaea 

 originated in southern Africa and that aucupum became differentiated 

 north of the Cameroons-Congo forest, which, being then much more 

 extensive to the east, formed an effective barrier between these two 

 bush and grassland birds. When the forest became reduced in East 

 Africa with the drying up of that area (there is both botanical and 

 geological evidence linking these two facts) , the two forms of paradise 

 widow bird were by then supposedly sufficiently differentiated so 

 that as paradisaea spread northward and aucupum eastward and 

 southward they presumably did not interbreed where they came 

 together. In a subsequent discussion (1932, pp. 277-278) Chapin 

 further remarked upon the influence of the equatorial forest, which 

 "once extended farther over East Africa cutting the ancestral Steganura 

 into two distinct populations." How the aucupum stock became 

 isolated from paradisaea, however, is unclear, as there is no evidence 

 suggesting that Steganura as a group is older than the equatorial 

 forest, and that the group could as a result have once been fractionated 

 by this forest and then subsequently allowed to merge again. 



Aside from the purely taxonomic problem presented, the paradise 

 widow birds appear to be essentially alike in their habits. Unfor- 

 tunately, what is known of them is still extremely fragmentary, as will 



