io6 DAVID JENKINS AND ADAM WATSON 



Table IV. Numbers of each age-sex group of grouse caught and tabbed 

 each autumn 1956-9 



reflect differences in behaviour. We suppose that young cocks move about 

 during late July to September, selecting their territories, while young hens 

 stay together on the family range till October or later. Birds in each class 

 come to the stubbles in turn as they start wandering from their summer 

 quarters. 



Each year the older (second year or older) grouse were mostly resident 

 but many first-winter birds disappeared. The date of trapping made little 

 difference to whether the young birds concerned disappeared or not (Table 

 V). This suggests that the birds trapped were not a biased sample (i.e. they 

 were not particularly liable to move in comparison with the remainder of 

 the population). There was no tendency for one lot of grouse to come to the 

 traps and then go away, and for another lot of birds to come and stay; they 

 tended to disappear evenly throughout the autumn, and this was probably 

 typical of other unmarked individuals in the population. Fewer young cocks 

 disappeared than young hens (Table V) and more young cocks were retrapped 

 than young hens every autumn. All the tabbed birds recovered more than 

 two miles from the study area have been hens marked in their first winter 

 and it seems that in the trapping time (October to December) first-winter 

 hens are more hable to move than other age-sex groups. 



Many more tabbed grouse disappeared from the study area each winter 

 than could be found dead then or later (Table VI), and presumably most of 

 the missing grouse left the area. Distant recoveries confirm this; 528 grouse 

 have been tabbed altogether and of 164 recoveries, 24 per cent (thirty-nine 

 birds) were found more than one mile away. Perhaps readiness to come to 

 the stubbles and dispersal were consequences of the same behaviour pattern. 

 The furthest recoveries so far, both hens moving in their first winter, were 

 22*4 km (14) and 32 km (20 miles) away in September 1958 and April 1959. 



The numbers of tabbed birds are checked two or three times a week on 

 small areas where we are doing behaviour studies. This is impossible for the 

 whole study area which is checked in detail four times a year, on about 31st 

 December, ist April, and at the beginning and end of shooting, as minimum 

 routine and additionally as time permits. The checks are done mostly from 

 a car; they are not confined to the study area but we also look over ground 

 an extra quarter to half-mile round about. 



