194 Strong, Habits of the Herring Gull. [April 



Though the general form, size, and location of the nest are char- 

 acters of the species, the variations which fit the nest to its special 

 location, for instance, are no more stereotyped than various acts 

 of man which are called intelligent. 



As a consequence of persistent nest robbing, gulls at certain 

 breeding places have been reported as taking on a tree nesting 

 habit. I know of no evidence worth considering for believing that 

 the recent ancestors of such birds were tree nesters, and we have 

 every reason for considering the inherited choice of location for 

 most Herring Gulls as on the ground. 



We have already seen in this paper that even the structure of the 

 nest may be modified in adaptation to the location in a tree. More 

 skill is shown in weaving the nest, according to reports, so that it 

 will hold together in its tree location. Of course it may be said 

 that tree nesting by the Herring Gull may be due to a so-called 

 latent instinct which appears when persecution compels the bird 

 to seek a safer place for its nests. We have however, no reason to 

 believe that instinct behaves in inheritance differently than other 

 characters. Our knowledge of the laws of inheritance does not 

 furnish any basis for thinking that an instinct for tree nesting can 

 exist for long periods of time in a species that has anotiier habit, 

 without itself appearing. 



Herrick ^ seems to consider tree nesting for the Herring Gull to 

 be a variation without much significance. He found a small 

 percentage of gulls nesting in trees at a height of from six to ten 

 feet. In his judgment, this position affords no protection to the 

 birds. I have seen no nests above the ground though trees and 

 bushes cover most of the ground on all but two of the islands where 

 I have seen gulls breeding. 



To me such tree nesting as Audubon ^ described suggests real 

 resourcefulness, but we know too little about it to be warranted 

 in making any generalizations concerning the intelligence it may in- 

 volve. In some colonies tree nesting may possibly be the inherited 

 habit or instinct of certain strains or " pure lines " of Herring Gulls. 



The nestling offspring of tree nesting gulls are reported as re- 



1 Herrick, F. H. Nests and Nest Building in Birds. Part II. Joum. Animal 

 Behavior. July-August, 1911. Vol. I, No. 4, pp. 244-277. 



2 Audubon, J. J. Ornithological Biography. Edinburgh. 1835. Vol. Ill, 

 pp. 588-589. 



