INIRODUCTION. IX 



In our Oecini, many species, or all, may have had the same an- 

 cestors, and whether we take it that the original form had the malar 

 stripe red in holh sexes, or black in both sexes, or red in the male and 

 black in the female, yet every conceivable variation has sprung from 

 these, viz. : G. viridis, in which the male has a red malar stripe and the 

 female a black one ; G. awoh'ra, in which both sexes have the malar 

 stripe red ; G. vaillantl, in which the malar strijic is black in both 

 sexes ; G. canus, with the malar stripe black in the male and absent 

 in the female ; and that we do not find these species interbreeding, 

 or varying to any extent, or it may be reverting to an earlier form, 

 probably is because no cause exists why they should do so ; such 

 cause may exist among the CoJaptes, although we cannot account 

 for it. It ma}' be, however, that in some of the Gecini there has 

 been a decided reversion to an earlier form, which, from its fixed 

 character, we now regard as forming a species. 



The original form of Colaptes may have come from the north, 

 diff'erentiating in the eastern and western branches, and when uniting 

 again producing the varied form G. ayresi ; or the species may have 

 radiated from a centre, say from a bird resembling C chrysoides, the 

 various branches retaining certain characters and acquiring others : 

 C auratus retaining the yellow wings and tail, having the red 

 malar stripe replaced by a black one, and acquiring a red nuchal 

 band ; C. niexkanus retaining the red malar stripe and acquiring 

 red wings and tail ; and C. chrysoides, possessing some of the 

 characters of each of these species ; the union of two of the branches 

 producing the varied race now under our consideration, which is 

 certainly more nearly allied to C. chrysoides, but wants the fixed 

 characters of that species. 



In the Picidce the top of the head, the nape, the malar region, and 

 the abdomen are the centres of change of plumage, and in genera 

 not possessing a single species with a red nuchal band, an individual 

 specimen will sometimes have a trace of red on this region, and 

 certain instances could be given of individuals presenting, upon one 

 of the above-mentioned regions, a character not possessed by typical 

 birds. If this resulted from a tendency to differentiate and acquire 

 a new character, I think it would be more frequent and occur where- 

 ever the surrounding circumstances favoured it, but its infrcquency 



