British Birds, their Nests and Eggs. 139 



season with the breast bare of feathers, caused 

 by sitting on the eggs ; and the writer knows 

 of his personal knowledge that the shep- 

 herds on the Cumbrian mountains occasion- 

 ally kill dotterel on the actual nest, and 

 that these almost invariably turn out to be 

 males. In winter the colouring of the sexes is 

 almost identical ; but when the breeding season 

 comes round the female dons a well-defined, 

 conspicuous plumage, while it is found that the 

 dull-coloured male alone sits upon the eggs. 

 Mr. Wallace has pointed out that bee-eaters, 

 motmots, and toucans among the most brilliant 

 of tropical birds all build in holes in trees. In 

 each of these cases there is but little difference 

 in the plumage of the sexes, and where this is so 

 the above rule is almost invariable. Again, our 

 native kingfisher affords an illustration. The 

 orange-plumaged orioles have pensile nests, 

 which is a characteristic of the order to which 

 they belong, most of the members of which are 

 conspicuous. Bird enemies come from above 

 rather than below, and it will be seen that the 

 modifications referred to all have reference to 

 the upper plumage. 



In 1888 an egg of a great auk was sold for 

 one hundred and sixty guineas, whilst more 

 recently an egg of the same species fetched two 

 hundred and twenty-five pounds ; and although 



