370 OUR RARER BIRDS 



The Eobin's eggs, as compared with those of its ally, the 

 Nightingale, furnish another instance. The Eobin's nest is 

 well concealed and often built in holes, and its eggs are often 

 white or only faintly spotted ; the Nightingale's nest is open 

 and more or less exposed, and its eggs are dark green and 

 protective in colour. 



What do all these interesting facts teach us ? From a 

 careful study of them we learn that birds' eggs exhibit such 

 great diversity of colour for other and far more important 

 ends than that of mere beauty : and their varied tints must 

 be viewed (with all other beauty of colour in Nature) as an 

 object by means of which great ends are attained. 



The true relationship of birds is often demonstrated by a 

 study of their eggs. The family likeness of birds, which 

 extends through entire natural groups, is stamped indelibly 

 on their eggs. Thus the experienced oologist, guided by their 

 peculiar characteristics, is able to separate at a glance the eggs 

 of the Shrikes, the Crows, the Snipes, the Birds of Prey, or those 

 of any other great natural group of birds. This is almost as 

 apparent in shape as in colour. Snipes' and Plovers' eggs are 

 extremely pyriform; Kingfishers' and Owls 'are round; Pigeons', 

 Goatsuckers', and those of the Sand Grouse are oval ; Grebes' 

 are pointed at each end. We find these characters constant in 

 each group respectively. Take, for instance, the great family of 

 the Ducks, numbering nearly two hundred species distributed 

 throughout the world. All their eggs possess certain 

 characteristics which enable us readily to identify them. The 

 same remarks apply to the Sandpipers and the Plovers, each 

 of which great natural group numbers upwards of a hundred 

 species, which are as cosmopolitan as the Ducks ; and the 

 eggs of both are so characteristic that a glance is sufficient to 

 recognise them. Take, as another instance, the eggs of the 

 family of Gulls. Those of the true Gulls most nearly 

 resemble those of the Sandpipers in colour, whilst those of 



