A strong prejudice is felt by many persons against Rooks, on account of their destroying grain and potatoes, and so far is this prejudice carried, that I know persons who offer a reward for every Rook that is killed on their land; yet so mistaken do I deem them as to consider that no living creature is so serviceable to the farmer as the Rook, except his own live stock.

In the neighbourhood of my native place is a rookery belonging to William Vavasour Esq., of Weston in Wharfdale, in which it is estimated there are 10,000 Rooks, that 1 lb. of food a week is a very moderate allowance for each bird, and that nine-tenths of such food consists of worms, insects, and their larvae:  for although they do considerable damage to the crops for a few weeks in seed-time and harvest, particularly in backward seasons, yet a very large proportion of their food, even at these times, consists of insects and worms, which (if we except a few acorns, walnuts, and potatoes in autumn) at all other times form the whole of their subsistence.

Here, then, if my data be correct, there is the enormous quantity of 468,000 lbs., or 209 tons of worms, insects, and their larvae destroyed by the birds of a single rookery, and to everyone who knows how very destructive to vegetation are the larvae of the tribes of insects (as well as worms) fed upon by Rooks, some slight idea may be formed of the devastation which Rooks are the means of preventing.  I have understood that in Suffolk and in some of the southern counties, the larvae of the cockchafer are so exceedingly abundant that the crops of corn are almost destroyed by them, and that their ravages do not cease even when they have become perfect insects.  Various plans have been proposed to put a stop to their ravages, but I have little doubt that their abundance is to be attributed to the scarcity of Rooks, as I have somewhere seen an account that these birds are not numerous in those counties (I have never been there), either from the trees being felled in which they nested, or from their having been destroyed by the prejudiced farmer.  I am the more inclined to be of this opinion, because we have many Rooks in this neighbourhood where the cockchafer is not known as a destructive insect, and I know that insects of that class and their larvae are the most favourite food of the Rook, which may be seen in the twilight catching both cockchafers and the large blackbeetles which are flying at that time in the evening.

I will mention another instance of the utility of the Rook which occurred in this neighbourhood.  Many years ago a flight of locusts visited Craven, and they were so numerous as to create considerable alarm among the farmers of the district.  They were, however, soon relieved from their anxiety, for the Rooks flocked in from all quarters by thousands and tens of thousands, and devoured the locusts so greedily that they were all destroyed in a short time.  Such, at least, is the account given, and I have heard it repeatedly mentioned as the reason why the late Lord Ribblesdale was so partial to Rooks.  But I have no means of ascertaining how far this is true.