204 OUR FORESTS AND WOODLANDS 
flagging in vegetative energy through unsuitable 
environment as to soil or situation, or have been 
subjected to injuries of any sort, as during hail- 
storms or the like. These dangers can to a 
great extent be lessened by the judicious formation 
of mixed crops, yet they always exist in a greater 
or less degree. They must just be looked on 
as the unavoidable risks inherent to investments 
offering a good return from a poor class of land. 
In addition to judicious mixture of trees in 
forming woodland crops, the very best means of 
immunity from insects lies in the protection of 
insectivorous wild birds, as advocated by the 
Marquess of Granby on pages viii to x of the 
‘General Preface’ to this Series, at the beginning 
of Sir Edward Grey’s volume on Fly-Fishing. 
The forester’s best friend in this respect is the 
starling, and everything possible should be done, 
by hanging up nesting-boxes and giving protection 
in other ways, to encourage this the most service- 
able of birds to the farmer, the market gardener, 
and the forester. The cuckoo is another ex- 
tremely useful bird, while rooks, kestrels, buz- 
zards, jays, and magpies do more good than 
harm. Even polecats, stoats, weasels, and foxes 
