^Ir. J. Blackwall's Ornitholoyical Notes. 169 



their vociferous calls and wheeling about in involved curves, as 

 they are joined by newly-arrived groups, or even without any 

 apparent cause whatever. This liabit of congregating in an 

 evening continues till the next breeding season, and 1 have some- 

 times observed betwen 100 and 200 individuals in a Hock. 



The Rook, Corvus frugilegus. 



Bewick, in treating u])on the rook in his ' History of British 

 Birds,' vol. i. p. 71, has remarked that he is inclined to consider 

 the naked condition of the base of the bill and the anterior re- 

 gion of the head in this species as an original peculiarity, appa- 

 rently intending to intimate thereby a belief that at no period of 

 its existence arc the parts in question covered with feathers, a 

 construction of the passage which is countenanced by his having 

 omitted to notice the fact that young rooks, before their first 

 moult, do not exhibit this dcticiency of plumage. Now as young 

 rooks, when they quit the nest, have the base of the bill and the 

 anterior part of the head amply provided with feathers, the ques- 

 tion naturally arises, How is the nudity of these parts in old birds 

 occasioned ? 



On referring to my 'Researches in Zoology,' p. 174-175, it 

 will be seen that in the year 1834 I advocated the opinion pre- 

 valent among ornithologists, that the loss of the feathers alluded 

 to above is attributable to the habit which the rook has of thrust- 

 ing its bill into the groimd in search of food. 



An extensive examination and comparison of specimens had led 

 me to observe that the nudity extends fmlher and is more com- 

 plete in some individuals than in others ; that the more promi- 

 nent and exposed parts are first deprived of feathers, and that 

 short filiform processes, bearing a close resemblance to new 

 feathers enveloped in membrane, frequently occur on the less 

 prominent and less exposed parts, particularly on the flaccid skin 

 which occupies the angle at the base of the lower mandible. In 

 addition to these facts, I may remark that an opportunity had 

 presented itself of inspecting a rook whose mandibles were so 

 greatly curved in ojiposite directions, and, consequently, so much 

 crossed at the extremities, that it could not possifjly thrust its bill 

 into the ground, and the base of that organ and the anterior part 

 of the head did not manifest the least deficiency of plumage. 



With such evidence in its favour, I was induced to adopt the 

 popular hypothesis, which I now abandon in consequence of 

 hanng recently proved by experiment that it is erroneous. 



Being supplied by George Davies, Esq. with two young rooks 

 taken from a nest in his rookery at Cj'ffdu on the 17th of May 

 18-43, I put them into a large wooden chicken-pen, purposing, 

 when they could take their food without assistance, to remove 

 one of them to a garden enclosed with walls, where it might have 



