300 CORVID^. 



one case the members of a rookery seem always to keep 

 together, in another they will disperse, forming two or more 

 bands which feed and roost widely apart, only meeting in 

 the breeding-season at their common tenement ; w^hile again, 

 it is not very rare for all the Books of the district, belonging 

 to many distinct settlements, to collect in autumn and pass 

 the winter in one grand convention. But besides these more 

 obvious differences, some of which doubtless depend on the 

 capabilities of the locality, many others may easily be ob- 

 served. In one rookery trees of several kinds will be used 

 alike, in another the nests are strictly confined to those of 

 the same species, or even to such of them as have the same 

 habit of growth ; and so on with regard to minor details far 

 too numerous to mention in a work like the present. A 

 good monograph of the Book could not fail to be as interest- 

 ing as its compilation would be laborious. 



This bird is probably nowhere more common than in 

 England, Ireland and the south of Scotland ; but decreases 

 in numbers towards the north, though of late it has estab- 

 lished itself in places where it w'as, as Mr. B. Gray remarks, 

 before only known as an uncertain autumn-visitant. Thus a 

 large rookery at Dunvegan in Skye, the most western Scottish 

 breeding-station, was only established a few years before 

 1870. In 1864 its first settlements were formed in the 

 western part of Boss and Cromarty, and, according to Mr. 

 Harvie Brown's information to the Editor, a year or two after 

 in West Sutherland. In the Outer Hebrides it is only known 

 as an occasional straggler, though sometimes in large flocks, 

 from the mainland in winter, and its appearance in Orkney, 

 Shetland and the Faeroes is of the same kind.* From what 

 Jonas Hallgrimsson says of certain birds of the genus which 

 have at times visited Iceland, they must have been Books, 

 but the species has not been absolutely determined there. 

 In Norway it occurs most irregularly, large flocks sometimes 

 appearing chiefly in the south and in autumn or winter, but 

 some of them stopping to breed. It seems to have been shot 



* An example is said (Zool. s.s. p. 455) to have been taken at sea 200 miles 

 from tbe north of Scotland. 



