290 BULLETIN 191, UNITED STATES NATIONAL MUSEUM 



slugs): millipedes, spiders. Carrion (dead lambs, etc.) occasional: birds 

 killed in hard weather and young or eggs frequently taken (game-birds, 

 duck, Stone-Curlew, Lapwing, and many species of small birds) : small 

 mammals (mice, shrew, young rabbit) : small fish also recorded." 



W. E. Collinge (1924), who analyzed the contents of 1,306 stomachs, 

 found that the food was made up of 59 percent vegetable matter and 41 

 percent animal matter. The vegetable matter was made up of 35.1 

 percent cereals and 13.4 percent potatoes and roots, and only 6.1 percent 

 of items considered "neutral" from an agricultural standpoint. Of the 

 animal total 28.5 percent consisted of forms considered injurious to 

 agriculture (the great bulk being injurious insects), while 3.5 percent 

 consisted of beneficial insects and 9 percent of "neutral" insects and 

 earthworms. On this basis 52 percent of the rook's food consumption 

 inflicts damage to agriculture, and only 28.5 percent is beneficial. The 

 influence of the rook on British agriculture has been much discussed, 

 but until recently all such discussions suffered from the vital defect that 

 the crucial information on the actual density of the rook population was 

 lacking. But thanks to recent accurate census work over large tracts of 

 agricultural country in England, taken in conjunction with the requisite 

 statistics on crop production and ColHnge's data already quoted, it can 

 now be stated with considerable confidence that in spite of widely held 

 opinions to the contrary the numbers of rooks are nowhere sufficient to 

 exert any important effect on the crop production of the country, or of 

 any considerable district, as a whole, and this may be stressed as a good 

 illustration of how census work undertaken primarily for its biological 

 interest may have a very real economic value. 



Behavior. — The ordinary gait of the rook, like that of other crows, is 

 a sedate walk, which may be interrupted by one or two less dignified 

 hops if the bird is bent on securing some tasty morsel ahead of a com- 

 petitor or otherwise feels the need of hurry. The flight, when making 

 for a definite objective, is direct and deliberate, with regular wing beats 

 varied only by gliding where air conditions are specially favorable, as 

 when crossing a valley or when about to pitch. But on more desultory 

 flights about the feeding grounds and around or above the rookery more 

 irregular wing action and a good deal of gliding may be observed. Emi- 

 nently gregarious, rooks are usually seen in parties or flocks, which may 

 be of large size, differing therein from the carrion crow, which is much 

 more of an individualist, though it must not be supposed that either 

 single rooks or flocks of carrion crows are very unusual. 



Voice. — The cawing of rooks, though it cannot be called melodious, 

 is to most lovers of nature a pleasant sound, redolent of the country. 

 The ordinary note may be described as a hoarse kaah, and typically it 



