13 



far north as Angermanland, and is common on Bornholm, Oland and 

 Gottland. To Norway it is principally a visitor on migration, but a few 

 remain to breed. 



Both in the British Isles and on the Continent many rookeries are 

 built in the immediate neighbourhood of heronries, and though sometimes 

 both species remain on good terms with one another, this is by no means 

 always the case, and one large heronry in east Suffolk has been decimated 

 by persistent egg stealing on the part of the rooks. 



These vary considerably in size, those built by young birds being Nests. 

 more slight in construction than those of older birds, which are frequently 

 built on the foundation of the old nest of the previous year, repaired at 

 intervals in winter and early spring. They are about 2 feet across and 

 are built of sticks and twigs, mixed with clay in order to give stability, 

 and bits of turf. The lining material varies a good deal; roots, dead grass, 

 straw, hair, wool, dead leaves and occasionally feathers, are to be met with, 

 while in the Orkneys fish bones and dry tangle are used (Saunders). The 

 cup is not so deep as in the nest of the Hooded and Carrion Crows. 



The clutch varies from 3 to 6, but the latter number is rarely met E^rgs. 

 with and the usual number is 3 to 5. In type they are distinctly corvine 

 and much resemble some varieties of Carrion and Hooded Crows' eggs, 

 but they are never found entirely without markings, as is sometimes the 

 case in the species previously treated of. The single egg with an decided 

 blue ground in a normally coloured set, so often found in the crows, does 

 not occur, or at any rate very rarely. On comparing a large series, a decided 

 tendency to olive brown markings and a less decided blue ground is seen 

 to be characteristic of the Rook's eggs. Mr. R. H. Read has almost spotless 

 eggs from Yorkshire. Baron Konig-Warthausen obtained 3 clutches of 

 the red variety of this egg in 1893 and 1894, probably the produce of 

 a single hen, and in 1896 von Wangelin obtained two eggs from the Ober- 

 forsterei Gliicksburg, one of which is illustrated on PI. 41, fig. 3. It is 

 interesting to notice that the normal eggs of the South African Corvufi 

 capensis Licht. are of a similar type of colouring. As the rook sits at 

 night after the first egg has been laid, there is often a considerable difference 

 in the state of incubation of a clutch of 5 or 6 eggs. Eggs placed in 

 an incubator were hatched on the 17th and 18th days (Evans), which 

 corresponds with results obtained by watching. 



As an interval of over a month often elapses between the laying of Breedins 

 the first and last eggs in a rookery, it is difficult to give exact data, but season. 

 in the south of England full clutches may be taken from mid-March and 

 occasionally in February, while in the Midlands the last week in March 

 and the first few days in April is the best time, and further north the 

 first half of April. In mild autumns the rook occasionally mades premature 



