OYSTERCATCHER AND NATURAL ENVIRONMENT. 431 



moment, of the adjoining pairs. Each station, composed of the 

 breeding area and the local feeding-ground, has a headquarters 

 generally, but not always, situated on a small eminence between 

 the two areas. At the headquarters the birds keep watch and 

 issue challenges. All other birds of the species are driven from 

 the breeding area and the local feeding-ground. The territorial 

 arrangements show no change from year to year (1909-1914). 

 The young at first do not have an habitual range. Where two 

 territories adjoin, the young of one territory are apt to wander 

 into the other until they are called back by their parents or 

 driven away by the other pair. The general or distant (neutral) 

 feeding-ground is apparently common property. All the birds 

 of a district appear to be free of the arable land near the 

 breeding territories, and mingle without signs of hostility. It 

 is, however, probable that closer observation would show that 

 each bird has an habitual range in the general feeding-ground, 

 though there is no apparent tendency to exclude other birds 

 from its range. 



Thus the main requirement of the Law of Territory, enun- 

 ciated by H. Eliot Howard, is fulfilled in the summer environ- 

 ment of the Oystercatcher. The law should be extended to 

 apply to the birds in winter, as they then have territories, 

 though no opportunity has come under notice of a territory 

 needing to be defended against intruders. The mode of acquiring 

 the winter territory is unknown. In summer, the method differs 

 from that observed by Howard in British Warblers, as Seton 

 Gordon records that the birds ascend the rivers in pairs. My 

 own observations indicate pairing to take place on the sea-coast. 

 The subsequent course of events nearer the breeding territories 

 is not known. Howard's view that the possession of territories 

 is a biological advantage both to the individual and the species, 

 by securing an adequate, and no more than an adequate, supply 

 of food, is borne out by the general evidence derived from 

 the areas under observation, and by the results obtained at 



Eyebroughty.* 



(To be concluded.) 



* H. Eliot Howard, ' The British Warblers,' part iii., 1909 ; Part v., 

 1910; Part ix., 1914. Seton Gordon, 'Birds of the Loch and Mountain,' 

 p. 97. 



