CONTROL OF ASSOCIATED ORGANISMS 069 



If, however, a program of this kind seems juslified, one should first acquire some idea of 

 the species of predators with which he is dealing and the numbers of each. For nutmmals, 

 this can best be done in the winter when snow affords suitable tracking conditions. For 

 predatory birds, the breeding season, which in the case of the horned owl may commence 

 as early as February, is probably the best time. Such an inventory will enable one to for- 

 mulate a plan for the most effective use of his efforts as well as to judge when such oper- 

 ations can logically be suspended. 



In New York the predators of primary concern to the grouse manager are the fox, weasel 

 and great horned owl. The two mammals are the outstanding nest robbers, while the other 

 is the most successful predator of the grouse themselves. All these are permanent residents of 

 the region. 



Other species may, of course, present problems now and then. Raccoons, skunks, opos- 

 sums, crows and even woodchucks, will eat eggs when they find them. Temporary over- 

 abundance of goshawks may accompany winter invasions from the north from time to time. 

 Cooper's and sharp-shinned hawks destroy many grouse chicks. By and large, however, these 

 species are of much less consequence than those noted in the preceding paragraph. 



In view of this, selective control, directed at the particular species involved on the indi- 

 vidual area under consideration, is recommended. It is obvious, therefore, that such work 

 should be carried out only by qualified persons. Moreover, the species with which one is 

 most concerned are also the more shy and elusive ones. The services of a first class fox 

 trapper are highly desirable. While the amateur can attain considerable success in taking 

 predatory birds, the trapping of the mammals, especially the fox, requires considerably more 

 knowledge and skill. Ability to distinguish the different hawks and owls is also important. 



With res|)ect to methods, each trai)j)er has his own |)et sets and scents for the furbearers 

 and other mannnals. In regard to the taking of predatory birds, howev-er, a few words may 

 not be amiss. For the horned owl. pole-trapping is the most effective practice. At the same 

 time, it is indiscriminate and, unless employed with considerable discretion, will destroy 

 many desirable birds. To reduce this dilliculty to a minimum, it should be carried on only 

 during the winter and traps located where other birds are least likely to be caught. A better 

 method, whenever possible, is that of shooting. 



Among the other avian species, the woods-frequenting "blue darter" hawks (Cooper's, 

 sharp-shinned and goshawk) are the ones most often troublesome. For these, shooting resi- 

 dent birds during the breeding season is by far the most effective practice. Goshawks may 

 have to be hunted during the winter, also. 



There are available a number of designs for live-traps which permit the release, unharmed, 

 of individuals taken unintentionally. Also various devices can be used to make traps more or 

 less selective through adjusting the pan or trigger in such a way that a certain weight or 

 force is necessary to s])ring it. Their use is desirable wherever they can be employed ef- 

 fectively. 



Trapping may be continued the year around, if necessary, for species on which there is 

 no closed season but it is better, whenever possible, to confine the taking of furbearers to 

 seasons when the pelt is prime. Similarly, with respect to birds, operations should be reduced 

 to a minimum or suspended completely during the periods in spring and fall when migra- 

 tory species are passing through, since the majority of such transients have little effect on 

 any particular local area. 



