172 SEA-BIRDS 



ceased, and throughout incubation and rearing. Gannets clash bills, 

 puffins rub beaks, shearwaters yodel and interlock bills, gulls and terns 

 beg for food, throughout the summer, until at last the urge wanes 

 with the fledging of the young and the onset of the moult and migration. 

 Mutual display late in the season may be of a playful or recreational 

 significance, an outlet for surplus energy. 



There are other interesting, and some quaint, ceremonies. Thus at 

 the nest relief, after the greeting display of billing and harsh cries is 

 over, gulls and gannets will add material to the nest if prevented 

 from brooding by the refusal of a mate to leave the eggs. This is a 

 'displacement activity', and it takes various forms. All nest-making 

 sea-birds toy with material, placing it over the shoulder, or throwing 

 it in the air and even swallowing it (gannets and gulls), while puffins, 

 which do not make more than a slight lining to the nest (sometimes 

 no lining), aimlessly pick up, carry and drop grass, feathers and stones. 



Does mate-recognition last for more than one summer, that is to 

 say, do sea-birds pair for life? By his behaviour and voice the mature 

 female recognises a male calling her to a nest-site; by his voice and his 

 occupation of the familiar nest-site she probably finds the identical 

 mate of last spring. To that extent the monogamic sea-birds may be 

 said to be faithful so long as both shall live; proof has been forthcoming 

 in recent studies of ringed shearwaters, penguins, guillemots and 

 razorbills. Even so, before the love-bond is re-affirmed in the spring 

 the same ritual of threat — followed by appeasement — gestures is 

 carried out; just as it is, in more or less degree, at every reunion of the 

 pair at the nest throughout the summer. Yet the sequence now is 

 bivalent — it has become less a display serving its original purposes 

 than a ritualised greeting between mated pairs. Elements of two main 

 drives in the life of the bird can be detected in the love-ceremonies: 

 thus the frenzied billing of gannets and nose-rubbing of puffins seem 

 to exhibit something of the desires of both self-preservation and 

 reproduction inextricably mixed. Fighting and love-making behaviour 

 are nearly akin, as hate is to love; both are highly stimulating. The 

 winter habit of keeping at a safe distance from a neighbour seems to 

 be latent in every sea-bird, and the arrival of even its mate at the nest 

 tests the nervous organisation of a bird severely, so that its first reactions 

 may be mixed, with the self-preservation drive on top. This is demon- 

 strated by the actions of a herring-gull if its mate's return is sudden — 

 according to the mood of the bird at home it may move away or attack, 

 until full recognition occurs and the ceremonies of greeting take place. 



