SS8 ■ Colorado College PuBLicAtioN 



the above named forms from its Check-List, regarding the 

 differences in color as being due to age, this being the position 

 taken by Oberholser in a paper pubHshed in 1903, in which 

 he states that a series of summer males from Colorado Springs 

 "exhibits all gradations from the green-backed to the black- 

 backed forms, representing thus psaltria, arizona, and mexi- 

 canus — all breeding at the same place!" It is very true that 

 the series of males in the Aiken Collection represents these 

 gradations, but there is one point that has been overlooked 

 with regard to the occurrence of these birds in El Paso County, 

 at least, and that is psaltria alone is the breeding form, so far 

 as at present known, the dark forms not making their appear- 

 ance until later, arizonce coming in July, and mexicanus the 

 very last of July and first of August, and their actions then 

 would indicate that they have but just arrived, nor have any 

 dark colored birds been discovered breeding in the County. 



The dates of skins of psaltria are April 20, 1900 ; June 25, 

 1898; July 23, 1899; August IS, 1907; September 2 and 5, 

 1897. Of arizoncE, July 16, 1872 (Fremont Co.) ; August 5, 

 1898 (2) ; August 6 and 7, 1897; August 12, 1907. A bird 

 seen by Warrer(, June 15, 1912, appeared to be this form. 

 Mexicanus, August 4, 1898; Salida, Chaffee Co., August 3, 

 1908; 5 or 6 seen by Aiken in yard August 11, 1907. Dr. 

 Bergtold reported seeing one in Denver, June 30, 1908, but 

 did not collect it. 



The evidence of the specimens and of field observations 

 agree very well, though it is only fair to state that it is 

 difficult to always distinguish arizonce from mexicanus in the 

 field, as the birds almost invariably appear darker than they 

 really are. These Goldfinches are often seen about the town 

 on vacant lots, especially where sunflowers have grown up and 

 gone to seed, and are easy to approach and observe, so that 

 one can readily study them. An examination of the plumage of 

 these specimens gives us no clue, for it seems perfectly fresh 

 and unworn. A possible explanation which occurred was that 



