xvii. 8 (503) 



8. Bird territory 



The element of threat in singing and display has a further impor- 

 tance in connexion with the territories that many birds establish 

 around their nests. Eliot Howard especially has developed the con- 

 cept of bird territory as a result of observation mainly of warblers 

 and buntings. For instance, in the warblers (Sylviidae) the males, 

 returning from migration some days earlier than the females, establish 

 themselves on a certain area, singing often from a tall tree or other 

 headquarters near its centre. As other males arrive boundaries develop, 

 so that the region becomes divided up into a number of areas, at first 

 each of about 2 acres, later reducing to 1. When the females arrive 

 they pair off with the males and throughout the whole season the two 

 birds occupy a single territory, driving off other birds that encroach 

 and in this way establishing quite definite boundaries to their area. 



Howard supposed that this arrangement was widespread in birds 

 and that it has four desirable effects for the species. 



1. Uniform distribution over the habitable area is ensured. 



2. Females are assisted to find unmated males. 



3. The two birds are kept together and are not distracted by 

 wanderings far from home. 



4. It is possible to find adequate food without travelling far from 

 the nest, this being especially important during the period of incuba- 

 tion and rearing of the young. There is no doubt that many birds do 

 remain mostly in the area around their nest and that they may resist 

 invasion. It is probable, however, that the territory is usually less 

 rigid than Howard implied, and there is certainly much variety 

 between different species. According to Lack the territory is often 

 mainly associated with the sexual display of the male; it is his area, 

 part, as it were, of the method he adopts to stimulate the female and 

 to keep the pair together. By establishing a territory he ensures the 

 opportunity to display and copulate without disturbance, a very 

 necessary precaution since he is vulnerable at these times and other 

 individuals may attack a copulating male, trying to displace him. 

 The complicated song, characteristic of so many male birds at the 

 breeding-season, is, on this view, partly an attraction to the female, 

 but largely also a threat to warn off other males. We cannot exclude 

 that it serves as a stimulus to the male himself. The impression is 

 strong when one hears a thrush 'singing for joy' at his headquarters 

 or a lark soaring above his patch of ground. 



Territory is therefore, according to Lack, put to various uses in 



