Vol. 12, N°' 6 
page 3 
for 33 well-established booming grounds have averaged 21*7 acres in size and ave 
ranged from 10 to 40 acres or more, depending on how field boundaries were deter mm 
(The inclusion of adjacent fields that are as open as the field actually containing 
the booming ground increases the upper range.) Well-defined booming grounds were 
established on the 77-acre Yeatter Sanctuary during three springs when 10- to ac 
fields were plowed. A booming ground also became established in the center o t e 
140-acre Zimmerman tract on a 10-acre burn made February 28, 1968. 1° 19o9, o° Y 
booming grounds of uncertain status (few cocks, irregularly present) occurre ° n ® 
Yeatter and Zimmerman tracts, possibly because available booming sites were on y 3 
acres in size. These responses, plus the fact that no nests have been found at 
Bogota closer than 117 yards from an estimated center of a booming ground, provi e 
strong evidence that fields suitable for booming should be approximately 10 acres in 
size. Fields larger than 20 acres are not desirable because the preferred zone or 
nesting apparently begins about 200 yards from a booming ground, and it is advanta 
geous to the population for hens to nest within 200-500 yards of a booming groun 
(MWRL 12 (3):3). It also appears desirable that suitable booming sites be available 
by mid-September each year. All known booming grounds that were established in 
autumn at Bogota carried over into the following spring and became stable groun s. 
6. Rabbit Management 
G. B. Rose 
Estimated assimilation efficiencies (percentages of digestible energy in t e 
diet) of growing young rabbits decreased with age. The younger rabbits (3"5 weeks) 
had assimilation efficiencies of 93 to 96 percent (averaging 94 percent); older 
rabbits (7-9 weeks) had assimilation efficiencies of 77 to 88 percent (averaging 82 
percent). The decreasing assimilation efficiencies probably reflect a change of diet, 
for, although the rabbits were fed the same diet of evaporated milk, rolled oats, 
and Purina rabbit chow, the percentage of rabbit chow eaten increased with age. 
Although the total amount of energy assimilated per animal per day increased 
with body weight (from 69 kcal/animal/day at a body weight of 186 grams to about 
95 kcal/animal/day at a body weight of 575 grams), it increased more slowly than did 
body weight, so that the amount of energy assimilated per gram body weight per day 
decreased (from 0.37 kcal/$/<fay et a body weight of 186 grams to 0.17 kcal/g/day at 
a body weight of 575 <jrams). 
