316 



PRE DAT I ON 



Dead chicks have proven extremely difficuU to find. In spite of heavy losses during the 

 first few weeks after liatching the most intensive field work has revealed the remains of but 

 very few. Not until nearly the first of August does one begin to encounter tell-tale piles of 

 feathers. This means little, however, for while it is true that inanv predators devour young 

 chicks whole, it is equally true that the carcasses of indi\iduals of this age which have suc- 

 cumbed to other causes are quickly obliterated by maggots, carrion beetles and similar 

 agencies. In fact, after only two days, three specimens of this kind which had been placed on 

 the ground in the woods for observation could only be identified by the stakes to which they 

 had been fastened. Direct determination of the degree of predation at this season is thus 

 impossible, and it has been necessary to approach the problem indirectly. 



Throughout the Investigation the total brood mortality has been measured each summer 

 on the two major study areas. On both, its course has been remarkably similar, averaging 

 slightly over 60 per cent by the end of August. Analysis of the progressive rate of decline 

 indicates that the curve drops somewhat more steeply during June than it does thereafter. In 

 fact by July 1 in an average year roughly half of the total brood mortality has already 

 occurred. 



Connec+icu+ Hill I930-4-2 



>- 

 I- 



lo 



zo 



Adirondack 1332,-41 



Research Cenfer (wildeqga) 1939— 4-Z 



30 



O 



I- Ao 



Z 



o 

 a. 



a. 



50 



60 



TO 



2o 

 30 



M> 



50 

 GO 

 lO 



June I 



ie 15 Ju lu I 



July 15 

 DATE 



AuQ. I 



\ug 



15 AuQ.3l 



FIGl'RK 26. AVERACE PROGRESSION OF CKOISE BROOD MORTAIJTY ON CONNECTICLT HILL AND 

 ADIRONDACK AREAS AS COMPARED WITH THAT OF CHICKS H.\TCHED FROM WILD EGCS AT 



THE RESEARCH CENTER 



There seems little doubt that many of these chicks are consumed by predators. Yet 

 (■x])erien(c with grouse at the Research Center strongly indicates that predation is not the 

 basic cause of these early season losses even though in many cases it may be the final execu- 

 tioner. A striking parallel has been observed among chicks hatched artificially from wild 

 eggs (figure 26), although here the losses have been somewhat greater. Among the latter, 

 while it likewise remains largclv urisii!\cd. the cause is cci lainU not predation. 



This similarly suggests that the chief causes of these early losses are pci iiliar to this age 

 and that predation is secondarv. This conclusion is further su|)ported by the fact that experi- 

 mental predator control failed to alter the pattern. 



