FLUCTUATIONS IN A RED GROUSE {L AGO PUS SCO TIC US 

 (LATHAM)) POPULATION, 1956-9 



David Jenkins and Adam Watson 



Nature Conservancy Unit of Grouse and Moorland Ecology, 

 Natural History Department, Marischal College, Aberdeen, Scotland 



INTRODUCTION 



During the last two decades fewer red grouse have been shot in Scotland 

 than previously, and the primary object of the present research was to 

 discover possible reasons for the grouse shortage. The work was inaugurated 

 by the Scottish Landowners' Federation, in co-operation with the Nature 

 Conservancy and Aberdeen University, on study areas in Glen Esk, Angus. 

 Numbers of grouse have declined less on this estate than in some other places 

 and the study provides a basis for comparisons elsewhere. It is envisaged as a 

 long-term study and the present paper is a preliminary statement of data 

 acquired so far. Discussion is minimal since each year has been different and 

 subsequent work may well cause us to revise our present ideas. 



The research is primarily a population study and the basic techniques are 

 counting and marking. Methods and the sample obtained by trapping are 

 therefore described in some detail. Particular attention is paid to the results 

 obtained in autumn and winter, when the population is exploited by man. 

 Breeding success will be considered in another paper later but some data are 

 already available in mimeographed reports circulated annually (Jenkins, 

 1957, 1958(7, 1958^, 1959, i960, 1961). 



GROUSE BEHAVIOUR 



Red grouse in Scotland live on heather, Calluna vulgaris (L.), at all seasons 

 (Committee of Inquiry on Grouse Disease, 191 1), though they will readily 

 take other items such as grass seeds and berries. They also visit stubbles in 

 the early autumn where they glean the scattered grain. 



Family parties begin to break up in mid-July and thereafter well-grown 

 chicks may be found alone on the moor. These are usually cocks and the 

 first song-flights ('becking') are seen at this time. More and more cocks start 

 singing during August and September, mostly in the mornings and some- 

 times on fine evenings. This behaviour continues through the winter and 



