74 BULLETIN 15 3, UNITED STATES NATIONAL MUSEUM 



black (the b^o^Yn feathers being old, the black ones new), but it has 

 the upper back, the breast, and the upper abdomen pure white. 



Of all the attempted explanations, the most likely one appears to 

 be that these unusual birds are either melanistic or that they are 

 hybrids between Gorvus cdhus and Corvus corax edithae. Of the two 

 possibilities, I incline to the latter, because such birds have been found 

 only in regions where the two species occur together. Kleinschmidt, 

 on the other hand, considers the former the more probable. If he is 

 correct, it is strange that no other area inhabited by Corvus alhus has 

 produced such specimens, and it would be just as logical to call them 

 somewhat albinistic examples of Gorvus corax edithae or to assume 

 that edithae is a phylogenetic offshoot of alhus ( ! ) and that these 

 peculiar individuals are atavistic in nature. Inasmuch as Meinertz- 

 hagen "^ and Kleinschmidt both agree that edithae is a race of Gorvus 

 corax and alhus a distinct species, an attempt to explain these aber- 

 rant birds on the basis of atavism would involve considering alhus 

 the parent stock from which corax and its races evolved, and this I am 

 sure neither would care to do. 



The fact that Gorvus alhus is an indivisible specific aggregate 

 throughout its range is due partly to its wide range of individual 

 variation. The size characters, being the easiest to record in writing, 

 may be used as an example. The wing length of adult birds (the sexes 

 are alike) varies from 295 to 382 mm, the tail from 179 to 212 mm; 

 the culmen from 51 to 64 mm, the tarsus from 56 to 67 mm. AVlien we 

 consider that in the matter of wing length the variational range is 

 more than 25 per cent of the total measurement, and that in most birds 

 the variations are usually under 10 per cent of the total size, the case 

 becomes all the more striking. 



Von Heuglin found this crow to be generally in northeastern 

 Africa, usually in pairs, but often in small flocks during the 

 nonbreeding season. Neumann ^^ found it chiefly in the high inland 

 plateau of Shoa at altitudes of from 2,500 to 3,000 meters (8,200 to 

 9,800 feet), in distinction to its predilection for lower, w^armer regions 

 in equatorial East Africa. However, the bird occurs in Somaliland 

 (although not listed by Zedlitz in his paper on that region ®^) , Eritrea, 

 and even in the Dahlak Islands, so it is by no means restricted to the 

 higlilands in northeastern Africa. The only regions where it does 

 not occur are dense forest areas. Inasmuch as most of the higlilands 

 of equatorial East Africa are cut off by forest belts from the sur- 

 rounding lowlands, it may be that the crows are more restricted alti- 

 tudinally there than in Ethiopia, where the highlands are not ecologi- 

 cally isolated, and this may account for Neumann's comments. It 



«5 Nov. Zool., vol. 33, p. 106, 1926. 

 «8 Journ. fiir Orn., 1905, p. 230. 

 «^Journ. fiir Orn., 1915, pp. 1-69. 



