t66 The hish Naturalist Jun^, 



breeding birds willing for matrimony in the abstract, but they 

 are equally willing, provided certain conditions occur, to 

 marry one another. 



To take an illustration : A pair of Starlings, whom we will 

 call A and B, nest in a particular crevice. Five other Star- 

 lings, C, D, E, F, and G, live in the vicinity unmated, because, 

 though of different sexes, they all fail to please one another. 

 One morning a cruel man vShoots A; and B, the same evening, 

 has found a new mate, who, according to our supposition, must 

 be either C, D, K, F, or G. Suppose it to be C There is 

 nothing remarkable so far, because, though C didn't please D 

 or F, he may well enough please B. But the next morning 

 the cruel man shoots B ; and C, before sunset, has a mate in 

 B's place. Now this must be either D, E, F, or G; but only 

 yesterday morning C was living unmated, because of his 

 inability to please D, E, F, or G. How is he able to please 

 them now, when he wasn't able a day or two ago ? I contend 

 that we must give the very unromantic answ^er — he is able to 

 please them now, because he has a bit of land. 



I admit, however, that the case of the Starling, if it stood 

 alone, would be a bad instance, because Starlings are, to a 

 certain extent, sociable in the breeding season, and therefore 

 the competition which evidently occurs between different 

 individuals or different pairs may rather be for access to a 

 particular nesting-hole, than for proprietary rights in the 

 surrounding area. Where birds learn to breed in communities 

 the form of their rivalry, of course, becomes modified ; but 

 that it is still territorial seems to me the only natural explana- 

 tion of many observed facts. In old established bird-com- 

 munities the accommodation is often obviously limited. The 

 individuals belonging to the community cannot all nest in the 

 space occupied. For example, we have a small rookery, con- 

 fined to two trees, on the lawn at Ballyhyland. In a spring 

 in which the number of nests in this rookery did not exceed 

 thirty-five, and before any young birds of the year were 

 fledged, I have several times put out of these two trees, by 

 clapping my hands underneath, flocks of more than two 

 hundred rooks. Within the rookery itself, then, there must 

 be non-breeding birds, and there must be competition for 

 space. In the instance mentioned the non-breeders must have 

 been twice as numerous as the breeders. But again, outside 



