5o 4 BIRD BEHAVIOUR xvn. 8- 



different species. It may be either (i) a mating arena only, as in the 

 ruff and blackcock mentioned above, or (2) it may be a mating station 

 and nest as in the plover and swallow, which birds will not allow 

 others near the nest, although all mix freely for feeding. (3) In 

 sparrows and herring gulls the nest is likewise defended, but is not a 

 mating station. (4) In the warblers investigated by Howard the ter- 

 ritory, besides being a mating station, is also a feeding-ground. The 

 significance of this in spacing out the birds remains, however, doubt- 

 ful. It may limit the effect of predators, by ensuring dispersal. (5) In 

 still other birds, such as the robin, it is a feeding-ground mainly, and 

 therefore it is kept throughout the winter. Examination of the ter- 

 ritory concept thus shows that birds have a strong sense of place 

 and that they associate this in various ways with their life, especially 

 during the breeding-season. It is certain that the occupation of ter- 

 ritory helps in the initiation and maintenance of the pair, but not yet 

 proved that it serves to limit the breeding density and ensure a food- 

 supply for the young. 



9. Mutual courtship 



In many birds courtship displays do not necessarily end in coition 

 and may continue long after the eggs have been laid. A classic example 

 of this sort is the great crested grebe, a water-bird watched by J. 8. 

 Huxley (Fig. 303). The male and female birds do not differ greatly 

 and the ceremonies are mutual. One bird may dive and come up 

 close to the other and they then approach with necks stretched out on 

 the water, giving a curious ripple pattern that Huxley called the 

 plesiosaur appearance. When they meet the birds come together neck 

 to neck and a period of swaying ensues and may sometimes end by 

 the mounting of one bird by the other, not necessarily the female by 

 the male. At other times the diving bird comes up with pieces of nest- 

 building material and elaborately presents them to its mate. This is 

 apparently a symbolic act; the material is not actually used to make the 

 nest and it is not far-fetched to suppose that such behaviour is an 

 expression of the mutual activity in which the birds are engaged. In so 

 far as it has a biological function it serves, like the rest of the ritual, 

 including post-ovulatory copulation, to keep the two individuals 

 together while rearing the young. 



As already mentioned, courtship may include ritual feeding of the 

 other sex during display and often before coition, for instance, in 

 pigeons and gulls, and this again may have a symbolic function. It is 

 perhaps not fantastic to find analogies between behaviour of this sort 



