ROOK 287 



Rooks are not averse to nesting in trees in towns provided suitable 

 feeding grounds are available fairly close at hand. On account of its 

 parks Inner London preserved a few rooks until comparatively recently. 

 A small rookery that existed for many years in the garden of Gray's 

 Inn in the City lasted till 1915, its abandonment being variously attrib- 

 uted to disturbance by recruits drilling under the trees or to the 

 depredations of carrion crows. Other details about London rookeries 

 are given by Macpherson (1929). 



In hilly or partly hilly districts the main concentration of rookeries 

 will be found in the lowlands, the density of rook population beginning 

 to fall oflf at a comparatively inconsiderable elevation. In southern 

 and midland England, at any rate, the decrease above about 400 feet 

 is quite definite, though it is evident that the determining factor is the 

 more extensive cultivation of the lowlands, whic.h provide better feeding 

 grounds than the hills, and not altitude as such. In the writer's home 

 county of Somerset quite large rookeries of 200 nests or more occur 

 up to 1,000 feet, and the highest site (with 38 nests in 1933) is at 

 1,350 feet. On the Carboniferous limestone plateau of Derbyshire 

 nearly all rookeries are between 1,000 and 1,200 feet. 



Rooks nest in both broad-leaved trees and conifers, and, provided 

 the trees are of substantial size and of a habit of growth such as 

 will provide suitable lodgement for the nests, they seem to have no 

 special preferences, their choice of trees in any area depending primarily 

 on the relative abundance of the species of tree available. Occasionally 

 rookeries are found with the nests built in saplings of only some 25 

 to 35 feet in a hedgerow, but sucjh sites are not common. Quite ex- 

 ceptionally nests have been built on buildings such as church spires. 

 Up until 1835 a pair occupied such a nest on the weather-vane of the 

 steeple of Bow Church, in London, and other cases are recorded by 

 Yarrell (1882). 



The size of rookeries varies a great deal, from half-a-dozen nests, or 

 even fewer, to hundreds. Rookeries of over a hundred nests are 

 common, but small colonies are most numerous and in most districts the 

 commonest size for a rookery is something under 25 nests. The 

 largest English rookery, to the best of the writer's knowledge, is one 

 of over 600 nests in a small wood in Oxfordshire, but in parts of 

 Scotland there are immense rookeries of over 1,000 and even over 2,000 

 nests, whic^ have no parallel south of the border. Several colonies of 

 the same order of size (the largest with 2,400 nests) exist in Holland. 

 In both countries it seems possible that the great size of the colonies 

 may be correlated with a certain scarcity of suitable sites in areas not 

 90 well timbered as many in which rooks are found. 



