' 160 Vol. XXIII 
THE NORTHWARD RANGE OF THE ALLEN HUMMINGBIRD 
By TRACY I. STORER 
(Contribution from the Museum of Vertebrate Zoology of the University of California) 
HE ALLEN and Rufous Hummingbirds (Selasphorus allem and 8. rufus) 
have been the subject of confusion and controversy ever since the former 
was described in 1877. The ditficulty has been due in part to the close 
similarity between the two birds and in part to the fact that one species (rufus) 
passes northward in its spring migration through the range of the other 
(allent) while the latter is nesting. 
The first source of confusion was the proper geographic application of the 
specific names rufus and allen, but this is no longer a matter of dispute, it 
having been clearly shown that the name alleni belongs to the more southern 
bird. (See Henshaw, Bull. Nuttall Orn. Club, u, 1877, pp. 53-58; and 1, 1878. 
pp. 11-15; Elliot, zbad., u, 1877, pp. 97-102.) The second and more important 
difficulty, and one which still exists, has to do with the actual identification of 
individual birds, either in the field or as specimens in hand. 
Many observers, some of whom are careful students, have applied one or 
the other of the two names (rufus and allent) to individual birds seen in the 
field when as a matter of fact with specimens in hand close scrutiny is re- 
quired to name them correctly. There are already in print numerous records 
based upon specimens taken which upon re-examination of -the material prove 
to be in error. How then can sight identifications be made with any expecta- 
tion of accuracy? The regular ascription of allent as a bird of the Pacific 
Northwest and of rufus as a breeding bird in central California are cases in 
point. Mistakes of the sort indicated will continue to occur so long as attempts 
are made to identify these closely related species on any basis save that of 
carefully collected specimens. Breeding records in critical territory should 
be based upon brooding birds colleeted with the nests and eggs. ‘The well 
known but little appreciated fact that males have no part in the nesting duties 
makes it necessary to demand that only females be taken as the basis for such 
breeding records. 
The specific differences between these two species are slight yet positive. 
The principal ones may be summarized as follows: 
Alleni: Lateral rectrix on each side not more than 2 mm. wide; male with next 
to innermost rectrix on each side unnotched and back chiefly metallic green. 
Rufus: lateral rectrix on each side 3 mm. or more in width; male with next to 
middle rectrix on each side notched near tip and back chiefly cinnamon-rufous. 
Thus the identification of females rests solely upon correct measurement 
of the outermost tail feather. There is a difference in the distribution of black 
and rufous on the tail of females appreciable upon comparing representatives 
of the two, but this does not lend itself to being described in such a way as to 
prove of value when but a single example is at hand. 
My attention was drawn to study this problem by endeavoring to ascertain 
the basis for the statement in the A. O. U. Check-list (ed. 3, 1910) that Selas- 
phorus alleni ‘‘breeds from southern British Columbia to northern Lower Cal- 
ifornia.’’ The literature failed to give conclusive evidence, and then corre 
spondence was resorted to, with the net result that I can find but two positive 
