° 1914 J iSwARTH, California Forms of Fsaltriparus. 523 



interest in connection with the discrimination between species and 

 subspecies. Judging from specimens alone, it is difficult to escape 

 the conclusion that the two forms intergrade completely; at least 

 I find myself unable to satisfactorily refer a very large percentage 

 of specimens obtained within the area of overlapping of their 

 respective ranges. But Mr. Oberholser, who has had excellent 

 opportunities of studying both forms in life, assures me that they 

 not only both breed in the same localities in southwestern Texas, 

 but that they each have distinctive peculiarities of voice, etc. 

 It is true that apparent intergradation does not involve adult males, 

 which are always very distinct, the difficulty being in distinguish- 

 ing those females and some young examples of P. m. lloydi which 

 have no black on the head from adults (both sexes) of P. plumheus." 



These statements are partly applicable to conditions existing at 

 the opposite, western border of the species' range, where P. plum- 

 heus meets P. minimus calif or nicus, in that, as shown above, 

 specimens were found with difficulty referred to either species. 

 It can not be urged in this case, however, that the two have any 

 distinctive peculiarities of voice or habits serving to indicate speci- 

 fic difference, for in the writer's experience there are absolutely no 

 such distinguishing characteristics. Also no evidence of intergrada- 

 tion in the juvenal stage is at hand, no undoubted example of 

 pluviheus in juvenal plumage being secured in the debatable terri- 

 tory. The specimens regarded as intergrades are all mature birds. 

 But as the young of plumbeus from other parts of its range exhibit 

 characters' remarkably similar to those of P. melanotis, it would be 

 surprising to find them here developing features similar to P. 

 minimus. 



The whole problem of the inter-relationships of the three species 

 of Psaltriparus is one of decided interest, the facts so far accumu- 

 lated being of a suggestive, though tantalizingly inconclusive, 

 nature. The three species have a continuous distribution, melano- 

 tis the farthest to the south and east, mijiitnus to the north and west, 

 and plumbeus occupying middle ground and impinging upon the 

 territories of each of the others. Melanotis and minimum have 

 peculiar and different head markings, while plumbeus is a plainly 

 and uniformly colored bird. The interesting fact has already been 

 developed (Swarth, 1913, p. 399) that in plumheus, the middle link 



