244 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



that, predation still seems to be essentially a byproduct of population 

 rather than a broadly dominant influence on population. Failure to 

 distinguish between cause and eflPect is a fertile source of confusion. 



On the whole, predation seemingly depends more upon the oppor- 

 tunities predators may have to capture prey than upon any special 

 advantage the animals loosely called predators may have over the 

 prey from the mere reason of their being predators. It is true that 

 some animals are highly specialized for a predaceous life and for no 

 other, but even so they are only animals and their lives are circum- 

 scribed by natural limitations just as are the lives of animals which 

 are not usually thought of as being predators. 



Kcological studies indicate that, as concerns many wild species, 

 there is only room in a given tract of environment for an approxi- 

 mately constant number of individuals, particularly of individuals 

 that establish themselves in territories or regular home ranges and 

 resist crowding past certain densities. The better grades of en- 

 vironment are filled up to capacity and any extra individuals either 

 have to dispossess some that are already suitably located or must 

 station themselves wherever they can. Those individuals that are 

 well situated, of course, have the odds all in their favor compared 

 with the less fortunate members of their kind that have to take 

 environmental "leftovers." 



Nicholson ^ has likened such territory-holding populations to water 

 in an overflowing reservoir. It might be added that under circum- 

 stances of this sort, predation frequently seems to do little more 

 than to lap up a part of the overflow and the leakage, and not 

 always a major part of that. 



Let us consider the popular bobwhite quail {Colinus virginianus) , 

 of which more is probably known of its life history and living re- 

 quirements than is known of any other wild species. Stoddard * 

 began his work on the bobwhite in the southeastern United States 

 in 1924 ; Errington * and others have been w^orking on it in the 

 north-central States since 1929. 



In Iowa and Wisconsin, researches on the food habits of various 

 predators have been conducted along with the population studies of 

 the bobwhite and other species, in one instance for 7 consecutive 

 years on one area. The data resulting from these combined predator 

 and population studies are not without their imperfections, but they 

 are raw materials from which may be reconstructed a reasonably 

 accurate and coherent picture of the functioning of some natural 

 mechanisms. 



■Nicholson, A. J., The balance of animal populations. Journ. Animal Ecology, vol. 2, 

 pp. 132-178, 1933. 



* Stoddard, H. L., The bob-white quail. Scribners. 1931. 



• Errington, P. L., and Hamerstrom, F. N., Jr., The northern bob-white's winter terrl 

 tory. Res. Bull. 201, Iowa Agr. Expt. Station. 1936. 



