I am inclined to believe that Sclater’s (13) designating the Colorado Crow as hesperis was made on purely geographical grounds, because the collection then at his command, (that at Colorado College, Colorado Springs) contains but one crow skin, a partial albino, which proves to be, under examination, subspecies brachyrhynchos. E. R. Warren allows me to state that he has no Crow skins in his collection, and that he made his subspecific diagnosis of hesperis, for the birds seen near Bulah, Colorado, on geographic grounds only. In later records Warren (14) wisely refrains from trying to decide as to the subspecies, when listing the Crows seen in Montrose County, and in northern Colorado, mentioning the birds merely as Corvus brachyrhynchos, and Henderson (18) did likewise in his Boulder County List.
I do not know on what grounds Hersey and Rockwell (11) made their statement that subspecies hesperis was to be found on the eastern slope of the Rockies.
Since Cooke’s last word on our Colorado avifauna, two more writers have given the Crow as a species found within the State, each listing it as hesperis, and both records are for the Atlantic slope. I am permitted by F. C. Lincoln (15), the first of these two writers, to say that he did not take any Crows in Yuma County, and that he made his subspecific diagnosis on geographic grounds alone. It is now, unhappily, impossible to determine what led Betts (16), the second of these two writers, to conclude that the Boulder County Crow was hesperis. I do not know whether he collected specimens in Boulder County; but Junius Henderson informs me that Betts sent crow eggs to the National Museum. But he probably did not send skins for, as has already been said, there is not a Crow skin in the National Museum collection, from Colorado. The internal evidence (18) points to the belief that Betts too, recorded the Boulder County Crow as hesperis, on geographic grounds alone.
Crows seen by Warren (17 and 20) in other parts of the State are given as subspecies brachyrhynchos, but again named on regional grounds only.
From the foregoing it appears that the Crows of Colorado were listed, principally as Corvus americanus up to the acceptance of subspecies hesperis in the A. O. U. ‘Check-List,’ and since then variously listed as Corvus brachyrhynchos, Corvus brachyrhynchos brachyrhynchos, or Corvus brachyrhynchos hesperis, but, to repeat, so far as I can learn, in no instance have any of the last two kinds of records been made on skin determinations. This statement is based on a study of the published records, and on a considerable relevant correspondence with my associates throughout the State; if I err the statement is open and subject to correction.
The western third of Colorado lies on the Pacific slope, and the eastern two-thirds on the Atlantic and on both of these slopes the Crow has been detected, and variously recorded as to subspecies. The A. O. U. ‘Check-List’ does not speak of hesperis actually extending eastward to the Rocky Mountains, but Mr. Ridgway, in a recent communication said to me “I feel quite sure that any Crow found west of the Divide in Colorado would be C. b. hesperis. On the other hand, those found on the eastern side would almost certainly be C. b. brachyrhynchos.”
I am fortunate, not only in having material in my own collection, which substantiates Ridgway’s belief, but in also having had access, thanks to my obliging friends, to specimens and data which also show that his belief is essentially correct.
I have been able to study fourteen Crow skins from the eastern side of the Rockies in Colorado, six males and eight females; of the males three are typical brachyrhynchos, two are clearly hesperis, and the last is mainly brachyrhynchos, but with weaker bill and tarsus than is ordinarily found with that subspecies. It is of interest to note that this last specimen was taken in Weld County close to the locality whence came the two previously mentioned hesperis skins. It is much more difficult to allocate the females of this group of skins; however four are more typically subspecies brachyrhynchos than is another female in my collection which I collected many years ago in New York, and another female is also of this subspecies, but with a weak bill, while the remaining three are too near the dividing line to be definitely located as to subspecies, all showing characters of one or of the other of the two forms under study, in varying degrees of intensity.
I have been able to study but one Crow skin from the western slope in Colorado, to-wit, a skin in my collection, which was taken at Ignacio, Colorado, in October, 1917, by my friend and colleague, Dr. Walter L. Mattick; fortunately it is the skin of a male, and is typical hesperis.
We are now on firm ground; those skins from the eastern slope which are most likely to be characteristic of a given subspecies, to-wit, males, show that both brachyrhynchos and hesperis are to be found on that slope, and the Ignacio skin proves that hesperis occurs on the western slope.