344 PRE DAT I ON 



Over 20 per cent had eaten insects. Among the other items identified garter snakes have 

 been found in a number of instances. 



While no grouse were recorded one specimen contained pheasant remains. McAtee*" 

 however, found grouse in three of 754 stomachs and it was also found in two of 193 rec- 

 ords from Pennsylvania^'. Yet game birds comprise only a small proportion of its usual 

 food. 



Red-shouldered Hawk 



Although no less a mouser this species — another of the soaring hawks — has taken small 

 birds more frequently than the red-tail. No game birds of any kind were recorded in the 

 food material examined. One instance of its feeding on grouse has been reported"*. 

 McAtee'" has also noted a "strong taste for amphibians and reptiles"'. 



Marsh Hawk 



Beating back and forth over meadow and marsh this harrier hawk feeds mainly on 

 small mammals, mice and rabbits pred(jminating. It does, however, prey to some extent 

 on young pheasants and smaller birds when they are available. Randair'' reports that in 

 Pennsylvania juveniles of many small ground nesting species were the most important 

 items of food during June and July. Confining its activities almost entirely to open areas 

 it seldom encounters grouse. Nevertheless, the latter were found in four of 601 stomachs 

 reported by McAtee'". 



It is evident from these brief resumes that, for the grouse predators of the Northeast as 

 a group, small manunals. mainly rodents, are the staff of life. Only in the "blue-darter" 

 hawks do we find s|)e(ies whose principal diet consists of birds and among them only the 

 goshawk customarily takes grouse as an appreciable proportion of its food. At the same 

 time all predators are opportunists and quickiv take ad\antage of variations in prev avail- 

 abilit) . I'hus deviations from the general rule may take place in accordance with local 

 conditions. 



Interpredator Relationships 



Predators are usually thought of as spending most of their time harrying and killing the 

 unfortunate species upon which they depend for food. One seldom stops to think that they 

 also prey upon each other. Yet such strife among themselves goes on constantly in any 

 habitat. 



The peculiar taste of the great horned owl for skunks has been noted many times. 

 Weasels are also taken frequentiv by this owl and it has also been known to feed on 

 many of the smaller owls as well as the Cooper's hawk, sharp-siiinned hawk and opos- 

 sum. Likewise the fox now and then catches a weasel. Skunks, raccoons and house cats 

 sometimes fall prey to this animal too. On the other hand, in the North, the lynx is a tra- 

 ditional enemy of the fox. Very often young hawks disappear from the nest long before 

 they are ready to fly. An instance of a red-tailed hawk feeding nn a freshly killed red- 

 shouldered hawk has also been reported"'. To just what extent, however, such habits may 

 serve to limit the numbers of the various species is still a problem for the future. 



There is also some indication of a reciprocal relationship between predator populations. 

 This may be the reason why in certain areas the great horned owl is predominant, while 

 in others the barred owl is most numerous. But data of this kind are few and fragmentary. 



