246 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



Such action might arise from an angry impulse to "punish" the 

 owls for behaving in a manner perfectly normal to wild animals in 

 the presence of an available food supply, or it might originate in 

 an intelligent desire to give the quail needed protection before they 

 were completely cleaned out. But, whatever else would be done, one 

 almost certain result of any concerted action would be the killing 

 of owls, and there would possibly be more or less talk about how 

 many quail were saved thereby and some pencil-and-paper figuring 

 as to how many more quail there would be next year. 



Suppose, then, that some person said that, so far as quail con- 

 servation was concerned, the owls might as well have been left in 

 peace; and that, for all of the owls killed, there probably would 

 not be appreciably more quail surviving the winter than there would 

 have been otherwise and that the figuring did not mean a thing? 

 It may not sound like good old-fashioned horse sense, but sucn a 

 person would stand an excellent chance of being right on all counts. 



The evidence bearing upon this subject may be briefly reviewed. 



The field studies of bobwhite populations had been carried on in 

 Iowa and Wisconsin for 4 years, when it gradually became apparent 

 that a given tract of land could winter an upper limit of only about 

 so many birds under the most favorable of climatic conditions. The 

 survival records obtained from local populations that had not suffered 

 losses from shooting or from storm or starvation emergencies fur- 

 nished the basis for the first accurate calculations of carrying capac- 

 ity.* It was found that, while carrying capacity could be either 

 raised or lowered, it commonly was remarkably definite for successive 

 winters on a given area in established quail range, although not the 

 same for all areas. 



In the course of the field studies, it was seen that populations 

 within the carrying capacity of their environment would usually 

 survive the winter with slight loss except in the event of starvation 

 or other emergencies brought on by deep snow, etc. ; whereas, if the 

 populations exceeded carrying capacity, the surplus birds would 

 either have to leave or sooner or later be killed by natural enemies." 



Table 1 was prepared for the convenience of readers who may wish 

 to see how the pressure exerted by horned owls on wintering bob- 

 whites relates to bobwhite population densities and carrying 

 capacities. 



Quail remains were found in 119, or 7.9 percent, of the 1,504 winter 

 horned owl pellets gathered from those areas where predation and 

 bobwhite population studies were jointly carried on. Seldom would 

 any single pellet be composed wholly of quail remains, and, even in 



"Errington, P. L., Vulnerability of bob-white populations to predation. Ecology, TOl. 

 15, pp. 110-127, 1934. 



•Errington and Hamerstrom, op. cit., footnote 5. 



