Visual display of the Aldo Leopold papers : 9/25/10-4 : Species and Subjects

				
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~eprite from ScizNcE, May 27, 1927, Vol. LXV, No. 1691, pages 528-529. 
 
A CRITICAL FACTOR IN THE EXISTENCE 
OF SOUTHWESTERN GAME BIRDS 
COMPLAINT is continually- made, on the part of 
both sportsmen and bird lovers, that despite all sorts 
of protective measures the wild quail in many dis- 
tricts of California are disappearing. Even in locali- 
ties which have been set aside under public or private 
auspices as game refuges, and where prohibition of 
shooting is enforced, this diminishment in the num- 
bers of quail continues to be reported. 
Sportsmen are prone to ascribe the disappearance 
of game birds, where living conditions otherwise re- 
main seemingly favorable, to the activities of so- 
called "vermin" of various kinds, giving little weight 
to the fact that in most parts of the country said 
"vermin" (hawks, owls, foxes, wildcats, etc.) have 
also become greatly depleted since the time when the 
original balance prevailed. 
In casting about for some cause to hold respon- 
sible for the diminishment noted in such birds as the 
California quail, the student of natural history may 
properly proceed to check off the various factors 
known by him to bear importantly upon the existence 
of the species in question, one by one, and see what 
may be left. On certain brush-land areas in south- 
ern California, familiar to the writer now and thirty 
years ago, I am quite sure of the following conditions: 
(a) The food supply remains, in so far as I can see, 
in both kind and amount about the same; (b) shelter, 
that is, "cover," is of quite the same character and 
quantity as formerly; (c) natural enemies are most 
certainly fewer in individual numbers and hence levy 
less of a draft on the quail population than formerly; 
(d) hunting by man has in large measure been done 
away with on the particular territories in question. 
Sportsmen and some biologists have stressed the 
probability of some disease having invaded the quail 
population. Upon this question I have nothing worth 
serious consideration to offer one way or the other, 
save to point out the opportunity afforded for infec- 
tion by domestic birds of drinking places accessible 
on country farms to wild game. However, my pres- 
ent inclination is to minimize the chances of this sort 
of factor entering into the present problem. 
Then what critical factor does remain, to account 
for the marked decrease of the quail, even where gen- 
eral conditions remain altogether favorable? 
I originally got the idea set forth in the following 
paragraphs from a sportsman long resident in Marin 
County, north of San Francisco Bay. It involves a 
factor active chiefly, but nevertheless vitally, in a 
 
very short segment of the life cycle of our quail. 
Briefly, a brood of newly hatched quail must find 
itself within walking distance (walking distance, be 
it emphasized, for the little quail) of water to drink 
by them, within a few hours of hatching. Anticipat- 
ing this need, the old quail seek nesting sites accord- 
ingly. For without water the young are doomed to 
perish, if time of hatching happens to fall within a 
rainless or dewless period of weather. Failing to 
find such a propitious site, the nesting of a given 
pair of quail is a failure for that season. 
Throughout the southwestern United States the 
thing of very greatest economic demand by the 
rapidly increasing human population is, not land, 
not minerals, not timber, but water. Every surface 
trickle, in every foothill ravine, which will yield water 
at the close of the rainy season, usually in April, and 
throughout the long late spring and summer dry 
season, is being tapped. At first the surface water 
is led off by pipe line to the thirsty ranch below. 
But a next step quickly follows: The seepage is 
tapped underground, a tunnel being driven in, and 
the water is drained from the porous rock or bed of 
sand below the surface. Then the mouth of the tun- 
nel is screened, for the very purpose of keeping out 
animals of all sorts (so as to prevent "contamina- 
tion"). In other words, the natural water supply, 
under original conditions provided at the surface, 
and accessible to the water-dependent wild animal life 
in the vicinity, has disappeared. It is only available, 
at best, in the very near vicinity of some human 
habitation far below, to which the pipe line leads, but 
where house cats, dogs and human beings prevent 
safe approach by quail. Not only for the thirsty 
youngsters but for the adult quail the original water- 
ing place has vanished. 
There is, I believe, a critical distance, which, rain 
or dew failing, is the absolute limit a quail's nest 
may be located from safely accessible water and re- 
sult in a matured brood. I estimate, from an ac- 
cumulation of impressions (I grant) of my own, that 
maximum distance to be 400 yards. If a pair of 
quail can not find suitable cover and safety for its 
nest within that distance from water which will be 
accessible by the newly hatched young on foot, either 
the attempt is abandoned or that nesting is destined 
to failure. The common observation that few quail 
are raised in years of severe drouth supports this idea. 
Immediate accessibility to water under conditions 
of safety, on the part of the little quail before they 
acquire wing power which will enable them to go 
 
 

					
				
					
long distances between forage grounds and possible 
drinking places, is then, I think, the prerequisite to 
maintenance of our quail and certain other upland 
game birds, even where all the other critical factors 
are favorable. And that factor of water supply, in 
the breeding season of the quail, is the one which, 
under the stress of human population growth, is be- 
coming more and more the determining one. Prop- 
erly safeguarded watering places are becoming fewer 
and fewer, with the inevitable result that large tracts 
 
of foothill brush-land otherwise suitable for the sup- 
port of an abundant quail population come to lie 
untenanted by these esthetically attractive and recrea- 
tionally valuable game birds. 
The water supply available in the dry season is a 
factor delimiting not only human but certain other 
vertebrate populations in the arid southwest. 
JOSEPH GRINxELL 
MUSEUM OF VEATEBRATE ZOOLOGY, 
UNIVERSITY o CALIFORNIA