8 NATURAL HISTORY OF BIRDS. 



the young plumage. Candor com])els us to state, however, tliat tlio evidence for tlie 

 white and the colored birds being only |pliases is yet insufticieiit, the more so as geo- 

 gra))hical distribution seems to have something to do with the matter, for it is stated 

 that, in Florida, the white binls are eontinetl mainly to the Atlantic coast, while the 

 colored ones cliiefly inhabit the Gulf side. The example from the herons can be 

 nearly diii>licated by the status of some forms of fulmars from the northern Atlantic 

 and I'acilie oceans, althougii in this case the geographical distribution seems to be a 

 moment of still greater importance, for I think I have proved that, in both oceans, the 

 dark jihases are predominant to the westward. We have other examjiles of dichroma- 

 tism in the same group as the dark and the white form of Ottsifraf/d (lujuntea ; and 

 Mr. nidgw.ay's suggestion, that it will lie found more extensively all through the supir- 

 family of the Tubinarcs or Procellaroide:e, is well worth consideration, l^ichrom.a- 

 tism among the owls, or erythrochroisra, as it is here called, because of rufous being 

 the color ])roducing one of the ]>liases, is not uncommon, but seems to be still nmre 

 influenced by the geographical disti-il)ution, at least in our little screech owl (Mvijd- 

 scops asid), which, in the jMississippi Valley, has more rufous than gray individuals, in 

 the Atlantic states both ]iliases nearly e(|ually represented, while west of and includ- 

 ing the Ivocky Mountains, only gray l)irds occur. Want of space compels ns to jiass 

 in silence many more examples, for instance, the white and the blue-winged snow- 

 geese, the dark and light-colored phases of many hawks (J}ii(e<»ics), but we caimot dis- 

 miss this matter without having mentioned that most perplexing (piestion to American 

 ornithologists: What are the relations of the two forms of flickers (^Cohi])tcs) and 

 their numerous intermediate individuals? 'J"he two flickers are mainly characteri/ed 

 by the color of the under surface of the wing and tail feathers, these being red in the 

 red-sliafted {('ulaptes mexicanus), gamboge yellow in the yellow-shafted flicker (('.f/«- 

 ralus), in addition to which the latter has a red nuchal crescent ; besides, the males 

 are distinguished by having a malar stri])e, which is red in the red-sliafted species, but 

 black in the other; the former is cliiefly a western bird, the latter inhabits the east and 

 the north. Hardly two species couM look more distinct than the typical s|)ecimens of 

 these remarkal)le birds; but the characttTs ;ire mixed in every ]>ossible degree in the 

 individuals inhabiting the region intermediate between the two, to such ."m I'xtent as 

 to be comi>letely without ])arallel among birds. They were generally declared to be 

 hybrids until intermediate specimens were found in localities — for exam]>le, Florida — 

 where oidy one of the typical sjiecies occur, and, conse(|uently, hybridity is an iinjios- 

 sibility. Are they incipient species? are they local varieties? or what? As there are 

 no structural characters involved, the (picstion is merely one of color ; why then not 

 seek refuge in ' dichromatism ' or rather 'trichromatism,' affected by geographical dis- 

 tribution, it is true, but not in the usual way, as there are geographical sub-species of 

 the common kind besides. We shall not attempt a solution here, but woulil like to 

 jiut the question thus : Why m.ay not the birds w ith red crescent luid red moustache 

 (this probably being the most numerous form of the so-cnlled <■ /i;/l/ridiis'), be the 

 original stock, which, westward, became moditied into 7ii<'.r!caiiii.«, eastward into 

 aunitus, the isolated individuals, with mixed characters, being due to atavism, or occa- 

 sional outbreak of the characters of the original stock, while a great many of tin 

 mixed individuals from the intprmediate region might be regarded as ]iroducls ol 

 hybridization? In other words, why not a trichromatism on the verge of forming 

 three different species, or two if — as would be expected — the original (intermediate) 

 stock died out at last? A jioiiit which seems to strengthen such a view is the fact 



