250 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



As the reader may see from table 2, spring losses of quail from 

 horned owls may be heavy at times, notably when rather substantial 

 populations have wintered that are close to the carrying capacity of 

 the land. There may be in late March and April an increase of pres- 

 sure by the owls upon bobwhites decidedly greater than the bobwhite 

 winter losses might have led one to expect. 



Table 2. — Homed owl pressure upon spring and summer bobwhite populations 



The owls, to be sure, have large and hungry young in their nests 

 and hence a need for more food, but the connection here is not so 

 clear as it might appear at first glance. The quail seem vulnerable 

 also to the attacks of predators that do not have young to feed at 

 this season or otherwise have any greatly increased need of food. 

 Then again, much of the spring quail loss from predation occurs 

 w^hen there is presumably more food available for predators than 

 there was in late winter, such as the hosts of migrating or newly 

 returned birds, various animals that had been in hibernation or had 

 not been so accessible during the colder months, etc. 



A possible explanation seems to be that the spring rise in vulner- 

 ability shown by some quail populations is associated with the 

 increasing unrest of the quail as their own breeding season ap- 

 proaches. One of the manifestations of an overpopulated condition 

 is increased friction among the quail themselves ; and it may be that 

 the intolerance and strife and excitement of mating may have the 

 same effect as overpopulation in making the birds vulnerable to 

 predator attacks. In other words, a carrying capacity just sufficient 

 to winter a certain population level with evident security and com- 



