SOCIAL AND SEXUAL BEHAVIOUR I71 



responds; he uses the threat display — the only social behaviour or 

 reaction he is, by use, familiar with. As the sexes are so alike it has 

 been suggested that, if he is inexperienced and attempting to breed 

 for the first time, the male may not know the sex of the responding 

 bird, but must find out by a closer acquaintance, by trial and error. 

 His behaviour suggests this: the male tern or gull threatens, even 

 attacks, the newcomer. If the arrival is male he will fly away or 

 engage in a dispute for the territory; if female she will stay, and by 

 her refusal to fight indicate her readiness to pair. She may remain 

 quietly near him, watching his threat display, or responding with 

 similar movements, but without being aggressive. Her behaviour 

 acts as a releaser or signal that elicits the beginning of the love-bond. 

 Threat-display wanes in favour of mutual attitudes of appeasement, 

 expressed by turning away (upwards or aside) the conspicuous bill 

 and head (gannets, cormorants, gulls, terns, skuas, auks). Sex-recog- 

 nition has taken place, and with it begins mate-recognition. 



In the love-ceremonies that follow the barrier of individual distance 

 is gradually broken down. Yet although the head, with all its apparatus 

 of intimidation — coloured bill and gape, facial adornments, raised 

 neck-feathers, is turned away in the appeasing movements, in order 

 to become intimate the bills, and in order to copulate the bodies, 

 must be brought together. The female gull, skua and tern indulge 

 in a food-begging ceremony in which she crouches in a supplicatory 

 attitude before the male, her bill towards his, her mouth open, thus 

 unconsciously imitating her behaviour as a chick. Females of other 

 species — gannets, cormorants, tubenoses and auks — touch bills with 

 their males in head-shaking, scissoring, and clashing movements, 

 ceremonies likewise derived from the chick stage. Stimulating contact 

 has been made, and soon coition follows, usually in the nest, and the 

 barrier between female and male temporarily disappears. The mated 

 pair now stand or sit (or fly) side by side. The male of the more mobile 

 species (gull, skua, tern, puffin) establishes a somewhat larger "mated 

 female distance" or sexual territory around his mate and the nest-site, 

 from which he drives away or intimidates all other males. For this 

 purpose the familiar threat display is used. She will also attack — other 

 females. On their territory the pair are invincible; moral right is 

 stronger than physical might in defence of the home. 



After pairing the love-ceremonies do not cease. The establishment 

 of the family bond is imperative if the young are to be reared by joint 

 effort. The pleasurable ceremonies are continued after coition has 



