ON THE HABITS OP THE ROOK. 53 



difficulty in getting their nests completed; for the old inhabitahtS invariably 

 pull their nests to pieces as often as opportunity offers. Occasionally, though 

 rarely, a bird with the feathers still remaining at the base of the bill, pairs 

 with what, for the sake of distinction, I will call an old bird. The time 

 and mode of getting rid of these feathers have been the subject of much 

 dispute; and, though I do not pretend to settle the question, yet it is, I think, 

 a fair subject for discussion in a rambling paper on Rooks. First for the 

 facts. 



Many young birds may be seen consorting with the old ones in the 

 roosting woods in January, and the beginning of February; they then, for the 

 most part, disappear, though here and there one may still be observed. Go 

 to the Rookeries in the breeding season, and a few may be seen then engaged 

 in rearing their offspring. Have the greater part of them at this time lost 

 the feathers at the base of the bill? I think not: and I account for their 

 disappearance by supposing a migration; for simultaneously, with the sudden 

 disappearance of the birds, having the distinguishing mark of young ones, I 

 note, at least in Kingerby wood, where my observations have been made, that 

 the number of Rooks coming to roost, is materially diminished. Again, did 

 they stay in their native neighbourhood, either the old Rookeries must increase 

 greatly every year, or many new ones must be established. Mr. R. P. Alington 

 has furnished me with a calculation, that every year there escape from the 

 Rookery at Swinhope, about one hundred and fifty young Rooks. He has 

 also furnished me with a list of twelve places, within six miles of his residence, 

 where there are Rookeries, many of them much larger than the one at 

 Swinhope. Taking them, however, at the same size, this gives, (supposing there 

 are three birds to a nest, and allowing three-fourths of the whole number hatched 

 for the destruction by the Rook-shooter, and other casualities,) no less than 

 two thousand as the annual increase, in that small district. The fact is, 

 however, that the old Rookeries do not increase. We are, therefore, driven 

 to this; either the number of young birds that escape, is not more than 

 sufficient to fill up the vacancies caused by death among the old ones, and 

 the above calculation is wrong; or they migrate. I think the latter supposition 

 is the correct one; for on no other can I account for the sudden and con- 

 siderable decrease in the birds roosting in Kingerby wood, noticed before; that 

 decrease taking place, as far as I can observe, entirely among the young, or 

 black-billed birds. Taking the facts into consideration, I come, therefore, to 

 the conclusion, that the denudation of the base of the bill does not generally 

 take place till the birds are at least a year old. 



Now for the mode or cause of the denudation. The question on this point 

 may, I believe, be fairly stated thus: is it caused by abrasion, or is it the 

 natural state of the adult bird? I incline to the latter opinion, because, first, 

 though the Rook is a great delver, yet he does not at all seasons dig equally; 

 and at some seasons so little, as to allow the feathers to grow, at least 

 partially, were abrasion the sole cause of their absence. Secondly, the mode 



