£28 



T. H. BLANK AND J. S. ASH 



Table VI. The relation between crop distribution, breeding density and 

 recruitment rates, 1949-59 



grass-leys increased, reaching its greatest extent in 1954. After that date the 

 ley-grass area has fluctuated irregularly around a sHghtly lower mean 

 (Table VI, Fig. 4). 



A third factor which may affect the rate of chick survival is the incidence 

 of diseases of various kinds. While young partridges reared in captivity may 

 suffer from several different diseases, in wild birds known deaths from these 

 causes are relatively rare. After severe weather, several chicks may be col- 



225 



i2 200 



^ 175 



o 150 



125 - 



50 13 



12 



40 II 



10 h 

 a 2. 



3-0;^ 9 ^ 



20 7 



i-O 



1949 I950 1951 1952 1953 1954 1955 1956 1957 1958 1959 

 Fig. 4- — Crops grown, breeding density and recruitment rate, 1949-59- 



