244 



SEA-BIRDS 



Fig. 44 



Breeding distribution of the little 



gull, Larus minutus (black line and 



dots), and of L. audouinii, Audouin's 



gull (stars) 



nest over distances of, 3, 4, 6 and 10 feet away. One bird sat on the 

 eggs after each removal, and its mate sat on the empty nest. Some 

 gulls were found by Kirkman to roll their own and other eggs back 

 into the nest from a distance of 9-12 inches from the centre of the nest; 

 this was a useful function when a gull's own eggs were retrieved, but 

 became useless when the gull collected all the eggs placed within 

 rolling reach (a distance varying between twelve and eighteen inches). 

 The perception or intelligence of the birds in these experiments varied 

 considerably. Paludan found that gulls rejected foreign eggs placed 

 in an empty nest up to nine days before the laying of their own eggs. 

 But from nine days before that event they accepted foreign eggs and 



