THE PROBLEM OF CONTROL 



347 



Another highly significant feature is the fact that in 1935 very similar results followed the 

 control of foxes and weasels only, thus verifying the conclusion that they are the paramount 

 nest destroyers in this region. 



The one covert where complete elimination of all predators was attempted in 1934-35 had 

 too few nests to merit comparison although none of these were broken up. Similarly the 

 number which have been located on the Valcour Island area have been too small to be indica- 

 tive. That it has undoubtedly been effective on the latter area may be inferred from the 

 fact that in 1940 only three broods were found (no spring census was made) and in 1941, 

 after only six months of control work, three broods resulted from 13 breeders, while in 1942 

 a spring population estimated at 22 jiroduced 1 1 broods and 33 breeders produced 13 broods 

 in 1943. 



Brood Period 



In contrast with the nest period the ])redator control carried on had little effect on losses 

 among grouse chicks (table 471. As discussed under another topic* mortality during the 

 brood ])eriod seems in large measure due to something other than predation. Beyond this 

 the Cooper's and sharp-shinned hawks were, perhaps, the least well controlli'd of the impor- 

 tant species on Connecticut Hill. Even on the unit where complete control was undertaken 

 during 1934-35 a brood mortality of 73.9 per cent was recorded. 



T\Hr>E 17. COMPAHISON OF MHOOI) MOItTM.ITV ON \HK\ SrH-IKCTHD TO PHKOVTOR 

 CONTllUL AND O.N CllliCK AKli.\— CO.NNKCTICLT HILL -1931-193.) 



^Control limited to foxes and weaacls. 



On Valcour Island the mortality of three broods in 1940 before any control had been prac- 

 ticed was 74.3 per cent. The next summer afler some eight months of work a loss of only 

 42.9 per cent was recorded, also based on onh three broods. That this cannot be construed 

 as indicative, however, is demonstrated by the fact that in 1942 the proportion was 65.4 per 

 cent in spite of the evident reduction of nesting losses as already noted and in 1943 it was 

 56.1 per cent. 



Adult Period 



Results at this time have been variable. The great majority of adult losses take place 

 between fall and the following breeding season and predation is an important decimating 

 agent. Yet control of predators has had no consistent effect on the degree of mortality. In 

 fact, paradoxical as it may seem, in two of the four years it has been higher on the controlled 

 area than on the check (table 48). Furthermore, the complete control attempted in one covert 

 in 1934-35 failed to prevent a loss of 71.3 per cent, although some of this is attributable to 

 dispersal. 



* Si'f discuaaions tif Kitlc of Pit-ilaliun During Briiod Periinl. p. ,^l(i. 



