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xA1rar om ~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