PREDATION— ERRINGTON 249 



Exactly why the strongest environment can apparently take care of 

 only about so many wintering quail from year to year is not clear.^'' 

 Intolerance of the quail themselves toward too much crowding doubt- 

 less enters into the equation. One effect of general overcrowding is 

 the forcing of some coveys or groups of birds into locations that are 

 plainly unfavorable and of others into a dismal round of wandering 

 from one uninhabitable or filled up covert to another. Badly situated 

 coveys, whether they keep moving or attempt to station themselves in 

 inferior environment, bear the brunt of pressure from enemies. 



The reader may perceive from table 1 that insecure populations are 

 not always heavily preyed upon by the horned owls living in their 

 vicinity. This does not mean, however, that the insecure populations 

 are no longer being preyed upon ; it usually means that some creature 

 besides horned owls is doing the preying. One thing that seems char- 

 acteristic of insecure populations is their common vulnerability to a 

 number of different predators, even predators differing greatly in 

 prowess and hunting tactics. 



It doesn't seem to matter much what, or, within limits, how many 

 predators may do the preying as long as the basic insecurity of a 

 wintering quail population continues unrelieved — at least, this seems 

 to be true in the north-central States' quail range. 



A few horned owls seem to eliminate the vulnerable surplus of a 

 wintering quail population about as effectively as many horned owls ; 

 and, in the absence or scarcity of horned owls, the reduction seems to 

 go on anyway through the medium of other predators. Marsh hawks, 

 foxes, and house cats, compared with horned owls, are very inefficient 

 winter enemies of bobwhites; and clumsy Buteo hawks, small owls, 

 and dogs are lesser enemies, indeed ; but these and even rodents, pheas- 

 ants, poultry, and the quail themselves may kill quail as the opportuni- 

 ties multiply with biological unbalance. 



The generalization appears to be sound that if the bobwhite suffers 

 severely from winter predation there is a good reason for it. McAtee's 

 contention that predation tends to be indiscriminate in action and in 

 proportion to population " is supported by the Iowa and Wisconsin 

 data on predation and wintering quail, as relates to the net effect of 

 predation upon excess populations or populations otherwise rendered 

 vulnerable. Any relief that vulnerable populations may gain from a 

 specific enemy (always excepting man) seems more than likely to be 

 counteracted in the end by increased pressure from other enemies, 

 including some not commonly classed as enemies, or classed as enemies 

 only under extreme circumstances. 



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



" McAtee, W. L., Effectiveness in nature of the so-called protective adaptations in the 

 animal kingdom, chiefly as illustrated by the food habits of Nearctic birds. Smithsonian 

 Misc. Coll., vol. 85, no. 7, 1932. 



