128 
THE CONDOR 
1 Vol. Ill 
Selasphorus rufus is typically a bird 
of the Humid Northwest Coast Boreal 
(of Merriam). The extreme of brown 
coloration is reached in both sexes of 
this species ; and it is a matter of long 
observation that the brightest browns 
are developed in birds of that region, 
whether resident, or present only dur- 
ing the breeding season as in the case 
of the Rufous Hummer. For it is 
also known that the breeding environ- 
ment of migratory species is much more 
potent in its effects than is their envi- 
ronment during the rest of the year. 
Now the Humid Northwest Coast 
Boreal extends southward along the 
Pacific Coast from the vicinity of Sitka, 
Alaska, to Humboldt Bay, California 
( fide Merriam). N. breeds abund- 
antly in most of this faunal area, and 
thus if it breeds at all in California I 
should expect to find it in the Humboldt 
Bay region, but not south of that vicin- 
ity. Selasphorus alleiii is known to 
breed abundantly in the San Francisco 
Bay region and north through Marin 
County and south through the Santa 
Cruz and Santa Lucia Mountains to the 
Santa Barbara Islands. Now the “ San 
Francisco Bay Region” is principally 
Humid Upper Sonoran, and the narrow 
coast belt to the north up to Humboldt 
Bay and southward through the Santa 
Lucias is Humid Pacific Coast Transi- 
tion as well as Humid Upper Sonoran. 
N. alleyii appears to be exclusively a 
breeding bird of this Humid Transition 
and Humid Upper Sonoran, and I do 
not know of its breeding outside of 
those faunal areas. The Allen Hum- 
mer is characterized by a less extensive 
brown coloration in both sexes than the 
Rufous. This is according to our 
theory, for the humidity and cloudy 
weather is less in the summer habitat 
of the former than in that of the latter. 
But the considerable amount of brown 
of N. alleni still shows it to be a normal 
inhabitant of a moderately humid area. 
And, in fact, do we ever find it breed- 
ing in any of the arid portion of the 
interior and Southern California? It 
seems to me probable, therefore, that 
the form alleni has evolved in this 
southern less humid coastal area at 
first as a geographical race or subspe- 
cies of N. rufiiis. Or, perhaps, since the 
origin of the hummingbirds is undoubt- 
edly neotropical, the reverse was the 
case; that is, that rufius evolved from a 
lighter-colored ancestor more nearly 
like alleni. At any rate my point is 
that Selasphorus alleni and N. rufus 
should be as yet confined to separate 
zonal or faunal areas in the breeding 
season. I believe geographical isola- 
tion to be absolutely essential to the 
differentiation of two forms. N. alle^ii 
and N. rufus are very much alike ; their 
distinguishing characters are slight and 
not altogether constant, and perhaps 
intergradation may still exist some- 
where in the Humboldt Bay region. I 
do not think it quite reasonable to ex- 
pect to find two such close forms breed- 
ing in the same locality or even any- 
where in the same fauna, such as in- 
cludes the San Francisco Bay region, 
where N. rufus has been reported nest- 
ing so often, but where I know that 
A. alleni is a very common breeder. 
Of course it is possible, even accept- 
ing the above doctrine, that after the 
complete differentiation of the two 
forms and disappearance of interme- 
diates, A. rufius may have invaded the 
breeding habit of A. alleni, and that the 
two species may thus now nest in the 
same area. And this is undoubtedly 
what has happened in the case of other 
species of hummingbirds breeding in 
the same locality, but which are much 
more remotely related. Yet it seems to 
me that the present case is not so far 
properly proven. It must be kept in 
mind that both A. rufus and A. alle7ii 
occur broadcast during the migrations, 
and the males, immediately after mat- 
ing may wander many hundred miles 
in search of favorable feeding grounds, 
and thus occur at the same season and 
in the same locality with other breed- 
ing species of hummingbirds, mingling 
with them in combat or play. I there- 
fore repeat the query made in the May 
Condor. Joseph Grinnet.i.. 
