AGGREGATIONS OF HIGHER ANIMALS 111 



slowly, but thereafter more rapidly, until there are 

 now thousands breeding on the island, and their 

 range has spread to the mainland. In Woods Hole, at 

 the present time, these birds whose return in 1913 

 excited so much comment are as common as the 

 terns. In this case, a few breeding pairs, nesting in a 

 relatively safe place, were able to regenerate the local 

 population in less than fifty years; all that was needed 

 was protection from the predations of man. 



The nesting colonies of gulls have attracted atten- 

 tion from many; a report by Darling has recently 

 appeared concerning certain relations between num- 

 bers of herring gulls in a colony and breeding be- 

 havior, and survival of young gulls on Priest Island 

 off the northwest coast of Scotland. (39) There are 

 indications that the members of larger colonies stim- 

 ulate each other to begin mating activities earlier 

 than when the colonies are smaller and, what is 

 apparently more important, there tends to be a 

 shorter spread in the time from the laying of the first 

 egg until the last one is laid. This means that the 

 breeding activities are more intense while they last. 



The period between hatching and the growth of 

 the first adult plumage is a crucial time in the life 

 of young gulls. While they are in the downy stage 

 they are preyed upon by outside predators; also at 



