BIRDS' EGGS 271 



§ 9. Natural History of Birds' Eggs 



Enthusiasts on the subject of birds' eggs have invented 

 the word " oology " as the name of their science, and Pro- 

 fessor Newton, in approving of this, goes the length of saying 

 that " hardly any branch of the practical study of Natural 

 History brings the inquirer so closely in contact with many 

 of its secrets." He refers to one of the scientific triumphs 

 of the oologists — namely, discerning, from the eggs, what 

 Huxley confirmed anatomically, the affinity between the 

 Limicolae (snipes and plovers) and the Gavise (gulls and 

 terns). Eggs can be studied as scientifically as anything else, 

 and they have the fascination of great beauty of form and 

 colouring. 



Size and Number, — The smallest bird's egg is that of the 

 humming-bird, the largest is that of the extinct Aepyornis, 

 which held six times as much as an ostrich's, and a hundred 

 and fifty times as much as a fowl's. It is said that the egg 

 of the extinct Moa sometimes measured 9 inches in breadth 

 and 12 in length, but that of Aepyornis was far larger. Of 

 European birds, the swan has the largest egg, the goldcrest the 

 smallest. What is the biological significance of the differences 

 in size ? 



In the first place, there is a general relation between the 

 size of the egg and the size of the bird. In the main this 

 means that the egg of a large bird has a large legacy of yolk, 

 for it is on the amount of yolk and white of egg, not on the 

 amount of genuine living matter, that the diff^erences of size 

 mainly depend. It is the nutritive material rather than the 

 formative material that counts ; and in a general way we can 

 understand that a big bird requires a send-off of nutriment 

 on a more generous basis than a small bird. 



But there are many exceptions to the general correspond- 

 ence between size of egg and size of bird. Thus the cuckoo is 

 much larger than a lark, but the eggs of the two are about 

 the same size. The guillemot and the raven do not differ 

 greatly in size, but the egg of the former has a volume several 

 times greater than that of the latter. 



