134 BIRDS' NESTS 



dentally we may remark that the eggs of not a few 

 of these species building concealed or covered nests 

 show a strongly-defined tendency to paleness or loss 

 of coloration when compared with the eggs of other 

 species in the same family or genus that are incu- 

 bated in more open structures. The eggs of the 

 Robin, as compared with those of the Nightingale, or 

 those of the Pied Flycatcher with those of the Spotted 

 Flycatcher, may be taken as illustrative instances. 



