PRBDATION— ERRINGTON 251 



paratively little quarreling may not be suflBcient to accommodate the 

 same population at the height of the period of sexual adjustment. 



The 388 summer pellets of table 2, which were obtained almost 

 entirely through the tethering ^^ of owlets in the quail observational 

 areas, contained remains of adult quail in 13. No recognized traces 

 of young bobwhites were discovered in pellets collected as late as 

 August nor amid the prey debris at feeding places of the owls. 

 Remains of immature bobwhites have been found in fall horned 

 owl pellets, however ; but pellets of unquestionable horned owl origin 

 are so difficult to procure at this season that the scanty data do not 

 justify conclusions. 



According to indirect evidence, the extent and effect of summer 

 predation upon young bobwhites are both variable. The bobwhite 

 tries to bring off one annual brood and may make repeated nesting 

 attempts if the earlier egg clutches are lost or abandoned. One 

 bird of the pair, usually the female, does the incubating; but if that 

 bird is killed, the mate may take over incubation duties and com- 

 plete the hatching of the clutch or may find another mate and start 

 over again.^* Both birds are active and capable in caring for the 

 young, and either one may perform this function alone, if neces- 

 sary. In this way the species is somewhat safeguarded against 

 excessive interference with reproductive endeavor through preda- 

 tion. The horned owl is scarcely under suspicion as a predator 

 upon quail eggs, but surely some of the pressure it exerts upon sum- 

 mer adults is borne by nesting birds. 



On the southern Wisconsin observational areas, the rate of in- 

 crease of bobwhites from breeding stock seems to be influenced by 

 how much the habitable environment is filled up to begin with; 

 if the environment is pretty well saturated by the adult popula- 

 tions, the chances of many young reaching maturity seem to be cor- 

 respondingly diminished.^* Nature is ever prodigal with the lives 

 of young animals and becomes more so as population densities rise 

 to the degree that individuals are compelled to live at an increasing 

 disadvantage. 



Then, as winter comes and finds adult populations at their highest 

 level of the year and carrying capacity shrinking with the dropping 

 of leaves from trees and brush and the drying up of weedy vege- 

 tation and the falling of the first snows, quail remains may be rep- 

 resented more and more in the horned owl pellets. And, as winter 

 settles down and the status of the quail may be further compli- 



" Owlets are tethered In the vicinity of their nests by means of chains and leather 

 anklets, In order that records may be kept of the food brought them by adults after the 

 time that they normally would have left — see Errington, P. L., Technique of raptor food 

 habits study. Condor, vol. 34, pp. 75-86, 1932. 



" Stoddard, op. cit., footnote 4. 



** Errington and Hamerstrom, op. cIt., footnote 5. 



