THE THRUSH GENUS 379 



cup formed by the exterior material of the nest, in some cases of 

 moss only, but with what is uncertain. Nor is it clear how the bits 

 and chips forming the plaster, which is thick enough to show them 

 superimposed one upon the other, are cemented together. Some of 

 the decayed wood in the nests examined had the appearance of 

 having been reduced to a state of pulp by pressure upon them when 

 wet, but separate bits were numerous, and in one lining I found a 

 flat piece an inch long by a quarter of an inch broad. Naumann, 

 who found several linings of this type and held they were the most 

 common, suggested that the necessary cement was supplied by the 

 saliva of the bird. The bits are certainly often gathered dry ; I have 

 seen a thrush emerging from the interior of a hollow trunk with a 

 supply in its beak. What shows in the beak is but a small part of 

 the load carried, as I found out one day after examining a nest in 

 process of building. As I turned away from it a little shower of 

 something fell on my shoulder ; there I saw a number of small bits of 

 wood, and above me on a bough the owner of the nest with its beak open, 

 and an air which might well have been one of disgust or of astonish- 

 ment or both. Whether these bits were moist I did not note, but 

 in any case those carried visibly in the mandibles would not be 

 moistened by saliva, unless the bird, when in the nest, deliberately 

 took them up and turned them about in her mouth. Seebohm states 

 that when the thrush is unable to get its wood wet, she moistens it in 

 the nearest water, but he does not make it clear that he saw this 

 happen, nor does he give any authority for the statement. 1 It is 

 quite possible that the wood is laid on a damp substructure, wet 

 enough to soak more than one layer in the plaster, some of it being 

 reduced to pulp by pressure. The plaster is found wet when com- 

 pleted, and is left to dry, unless the bird is in a hurry. 



It is difficult to find an explanation of the variations which occur 

 in the composition of the thrush's nest-plasters. It may be that the 

 instinct of the species is to seek decayed wood, using it alone or 



1 British Birds, i. 218. 



