FLUCTUATIONS IN A RED GROUSE POPULATION iii 



less the different stages were quite distinct each year. Apparently the annual 

 decreases in numbers conformed to a defmite pattern. 



Periods of stability at mid-winter occurred each year but were particularly 

 noticeable in the last three seasons. In these cases five, six or seven count 

 totals were similar. It is instructive to compare known losses from the 

 population with the count figures during this period. Comparable figures 

 for tabulation are available each year for December (Table VIII). These 

 show clearly that the population did not decrease to the extent expected 

 with regard to known losses. 



Table VIII. Early winter losses of tabbed birds compared with numbers found 

 dead and changes shown by counting 



Year 

 1956-7 

 I957~8 

 1958-9 

 1959-60 



Number tabbed 

 before 30th Nov. 

 , K 



Number 

 Total on % 



tabbed 31st Dec. lost 



63 38 



lOI 



183 



132 



47 



56 

 23 



Total found 



dead 

 Nov.-Dec. 



II 



49 



43 



10 



Count figures for 

 whole population 



Nov. 

 total 



531 

 507 

 412 

 241 



Dec. 

 total 



471 

 496 

 392 

 228 



Decrease 

 between 

 Nov. 

 and Dec. 



No. 

 60 

 II 

 20 

 13 



0/ 

 /o 



II 



2 

 5 



5 



Details for the different years are as follows. In 1956 numbers fell between 

 November and December, so this year is not considered. Between 25th 

 November 1957 and 31st January 1958 (counts 5 and 11 in Table III), when 

 counting suggested numbers were stable, seventy-two grouse were found 

 freshly dead and at least seventeen tabbed birds disappeared. Losses of this 

 order should have been detected by counting if they were not made good 

 by immigrants. Between the end of September and 31st December 1958, 

 about eighty tabbed grouse disappeared from the study area (Table VI), 

 presumably through movement out as few were found dead, and over sixty 

 other grouse were found freshly dead (Table VII). In this case at least 140 

 grouse disappeared from a population in which the density stayed steady. 



In 1959 between September and the end of the year forty-nine birds 

 disappeared, including twenty-five known casualties and twenty-four tabbed 

 birds, even though no fewer than seven consecutive counts showed that the 

 total numbers did not change correspondingly. Thus in the three years for 

 which we have detailed information (1957-8, 1958-9, i959-6o), a minimum 

 of 18 per cent, 32 per cent, and 26 per cent of the grouse are known to have 

 died or disappeared at times when repeated total counts were similar. How- 



