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down from a bough above on to the female's back, gives her food and 

 simultaneously amidst much wing-flapping mating is accomplished" 

 (Yeates, 1934). It should be observed that during incubation, which is 

 normally performed by the female only, the male habitually supplies 

 his mate with food, but the feeding has then an obvious function to 

 perform as such and is no longer of a purely ceremonial character. 



Recrudescence of sexual behavior takes place long before actual 

 breeding commences. Sporadic displays, and occasionally even coition, 

 may be observed in the fall, and both have been recorded as early as 

 October, though at least as regards coition this must probably be re- 

 garded as exceptional. From late in November to December, when 

 the weather is mild, coition seems to be not uncommon, and ceremonial 

 feeding has been observed from the end of December. A mutual 

 fondling of bills, which is often observed in mated birds, has also been 

 recorded in fall. These expressions of affection outside the breeding 

 season are probably in the main not merely promiscuous. There is 

 good reason for supposing that rooks pair for life, as is known to be 

 the case in such solitary Corvidae as the raven, and that "married 

 couples" maintain their association in the flocks. Nevertheless a 

 certain amount of promiscuity does take place at the rookeries, in the 

 form of sudden assaults on incubating females by intruding males in 

 the absence of the regular mate. In this connection reference must 

 be made to the violent scuffles between several or a number of birds 

 which occur from time to time in every rookery, centering round a 

 nest. Selous (1927) was the first to recognize that these are, at least 

 generally, attacks by neighbors on a pair engaged in the sexual act. 

 But Yeates (1934), who had the advantage of making his observations 

 from a hide in the tree tops, obtained fairly strong evidence for the 

 unexpected conclusion that the attacks are generally confined to pro- 

 miscuous mating where the male is an interloper. Although he ob- 

 served coition repeatedly he found that such mobbings occurred only 

 occasionally, and in three instances observed while he was specially con- 

 centrating on this point there was a very strong presumption, amounting 

 to virtual certainty in two of them, that the male involved was not the 

 mate of the female. He writes: 



"On these three occasions referred to the evidence in two of them 

 was, to my mind, quite certain. At one nest a male c,ame down, mated 

 and was mobbed and driven off. The very next minute the rightful 

 male came with food. He could not possibly have collected it and re- 

 turned in the interval. At the second nest mating took place and a 

 very violent mobbing scene resulted (there were four birds attacking). 

 Within a few minutes the rightful male came and again mated — and 



