200 THEIR NUMBERS FLUCTUATE. [PART II. 
increase in the cultivation of the turnip-crop, the 
immigrants, finding that there was an ample 
supply of food for them, as well as the native 
birds, and finding the place suit them in other 
respects (as, for instance, affording plenty of 
covert, and that, or at least a large proportion of 
it, but little disturbed), were induced to prolong 
their stay throughout the winter, and thus became 
naturalized there. 
Their numbers still occasionally vary. During 
the years 1849 and 1850 I noticed that they ap- 
peared to be not nearly so numerous as during 
some preceding and the subsequent years. Why 
this should have been the case I do not know, for 
there was no perceptible diminution in the usual 
turnip-crop, nor apparently any other reason by 
which it could be accounted for. 
Still, each year, about the end of October or 
the commencement of November, a large propor- 
tion of the Woodpigeons appear to leave the island, 
returning again in about two months to their old 
haunts. During this period they are, I have but 
little doubt, absent on an excursion to the New 
Forest in search of beech-mast, perhaps their 
most favourite food, which is supplied there in 
greater quantities than the Island affords, and 
