2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO7 



such an anomaly as the supposed coexistence of "Pellorneum ruficeps 

 pectorale" and "P. r. minus" in central Burma and the Chin Hills 

 (see Smythies, Birds of Burma, 1940, pp. 502-503) or the statement 

 that "P. r. minus" occurs throughout the range of "P. r. mandellli" 

 and is also met with in the area occupied by "P. r. suhochra- 

 ceum" (see Stuart Baker, Fauna of British India, Birds, ed. 2, vol. i, 

 1922, p. 242). 



The fact is that in too many cases the type locality of the named 

 forms has not been sufficiently restricted, with the result that series 

 placed by the revisers under a single name have been composites 

 of two or more distinct races. With proper arrangement, it will be 

 seen that no two subspecies can be truly said to occur together and 

 that, accordingly, there can be no question of two specific entities' 

 having been confounded. 



Geographic variation is shown mainly by the presence or absence 

 of dark centers to the feathers of the uppermost back (present in all 

 races north of about lat. 20° N., obsolescent in borderline popula- 

 tions, and absent in the more southern groups) ; color tone of the 

 upper parts ; the width and abundance of dark centers to the feathers 

 of the breast and sides of the abdomen; the amount of bufify wash 

 over the under parts. 



What may be considered, from the broad view, individual varia- 

 tion, appears in the dimensions of bill, wing, and tail (to such an 

 extent that in most races these measurements are without signifi- 

 cance) and, within fairly narrow limits, in the several characters that 

 serve as subspecific criteria. But when a long series of a given race is 

 broken up in accordance with the various proveniences, it will be 

 found that much of the so-called individual variation is in reality 

 of a subracial nature. Variation of this sort is too tenuous to be 

 worthy of a name, but is nevertheless of the greatest interest as a 

 reflection of the extraordinary plasticity of the species. 



Real individual variation is shown by a tendency to erythrism that 

 appears in any race ; specimens exhibiting this would seem to be 

 "foxed," if others of the same place and date did not fail to show any 

 deviation from the average coloration of much more recently col- 

 lected birds. This rufescence is usual in immature examples and is 

 stronger in the young of those populations in which increased rufes- 

 cence has become a subspecific character. Worn plumage tends to 

 become grayer, but the degree of wear varies so much from one speci- 

 men to another, without regard to the time of year, that I have not 

 found it practical to divide my series on a seasonal basis. 



