230 SEA-BIRDS 



In order to begin breeding there must be a suitable environment 

 against which the mutual stimulation of the sexes will become effective. 

 Probably in most if not all gulls it is the male which sets up this environ- 

 ment by occupying the breeding site first and displaying towards later 

 arrivals. Almost as soon as the shortest winter day is past lone males of 

 the herring-gull (which in the British Isles is largely a sedentary 

 species) settle on cliff-sites on fine days (Lockley, 1947) and give the 

 moaning call at sight of another gull passing near. Each male parades 

 on or near a suitable platform in the rocks cliffs or dunes. He chal- 

 lenges a neighbouring male by drawing his head in stiffly. He picks 

 up small pebbles or plucks the stems of plants much as a farmyard 

 cock will peck and pluck at the ground when approaching a rival. 

 Usually the challenged male begins to pluck also as if warning the 

 intruder that he has come far enough. The warning often suffices; 

 energy has been released without wasteful fighting and each male 

 retires to his own plot of territory. Even if a scrap develops no real 

 wounds are inflicted. The unmated continues to show hostility to all 

 comers (unless he is a very mature male experienced in sex and mate 

 recognition) but gradually changes his mood if a female persists 

 in visiting him. Once male and female have accepted each other the 

 herring-gull pair recognise each other up to a distance of 30 yards 

 apart; in view of this fact it is remarkable that the herring-gull is 

 quite unable to distinguish between its own eggs and those (differing 

 in pattern much more than male and female gull do in appearance) 

 of another gull if given a choice test (Tinbergen^ i950' 



The mutual display of gulls has already been described (p. 170). 

 It is generally considered however that the food-begging ceremony 

 is performed more often by the female. In a typical instance the 

 head is jerked up and down in front of the male's bill which may 

 be actually struck or tapped thus imitating exactly the behaviour 

 of the young bird. But much of courtship "feeding" is a mock affair, 

 and often no food is transferred, probably because the male's stomach 

 is empty, although the bills may be locked for a moment. Sometimes, 

 in a crowded colony, a female may be "fed" by a second male; at 

 all times the female appears anxious to beg food, even in winter. 

 This must be derived from behaviour as a chick and a juvenile; 

 for juveniles will beg food of any adult in winter, though rarely or 

 never with success. This supplicating of the adults by immatures 

 far from the breeding ground has given rise to the belief that the young 

 bird remains attached to its parents long after the nesting season. 



