16 BIRDS OF NORFOLK. 
but several persons believe, and with some show of 
reason, that a bird, or even two birds, lingered on in this 
tract till 1843 or even 1845. This last date, however, is 
the very latest that can be assigned, and the probability, 
from the evidence available, is in favour of the exter- 
mination having been thoroughly effected seven years 
earlier—namely, in 1838. 
Though it is desirable to mark, as has been done, 
the former existence of two distinct droves of bustards, 
it must not be inferred that the birds belonging to the 
one just spoken of in the country round Swaffham, 
and included entirely in Norfolk, did not occasionally 
commingle, by the route already indicated, with the 
other drove haunting the tract nearer Thetford, and 
stretching from Brettenham and Snarehill, in Norfolk, 
across the county border to Barnham, North Stow, 
Icklingham, and much further into Suffolk, till with 
perhaps a slight interval it joined the tract around 
Newmarket, celebrated by Ray as a locality for this 
species, while westward it was only bounded by the fens, 
and at Lakenheath became almost conterminous with 
the southern limits of the Swaffham tract. There is an 
additional reason, also, for considering this tract sepa- 
rately from that first spoken of. It seems probable that 
the causes which effected the extinction of the bustard 
there had but little to do with it here. Owing to the 
comparatively poor soil the staple crop of grain in this 
locality has only very recently been changed from rye to 
wheat, if, indeed, the change is now entirely consum- 
mated. Another cause must, therefore, be sought, and 
this appears to have mainly been the planting of long 
belts of trees with the object (as briefly stated in the 
“‘Introduction”) of sheltering the arable land from the 
violence of the wind, the ill effects of which in blowing 
the light sand, here chiefly composing the surface soil, 
is one of the most serious obstacles with which the 
