65 



Case 232 — continued. 



(d) Size of Egg. — 



Eggs vary much in size, for example note the egg of Ostrich 

 (54) and Humming Bird (55). A large egg usually means that 

 the young chick is hatched in a less helpless condition than from 

 the small egg, as a much larger amount of food yolk is present, the 

 incubating period is longer and the chick is more developed when 

 hatched. Generally, but not at all constantly, the size of the egg is 

 proportional to the parent, as the number of eggs to be covered by tne 

 bird must be considered. The following examples illustrate the size of 

 eggs m comparison to that of the parent. 



The egg of the partridge (56) although a much larger bird is no 

 larger than the egg of the Snipe (57). Again the Blackbird's egg 

 (58) is much smaller than the Snipe, although the birds are about 

 equal in weight. The young Blackbirds are helpless when hatched, 

 but the young Snipe are able to run about immediately. The 

 Cuckoo and Missel Thrush are of equal size, but the egg of the 

 former (Cuckoo 59) is much smaller than the latter (Missel Thrush 

 60), and is but slightly larger than the Sparrow's egg (61). Again 

 the Guillemot egg (62) is considerably larger than the Raven 

 (63) although the birds are about equal in size, whereas the Imperial 

 Eagle is five or six times larger than the Guillemot, but its egg (64) 

 is no larger. 



(e) Form of Eggs. — 



The shape of the eggs is fairly constant in the various groups of 

 birds. The principal varieties may be classed under the following 

 heads : — Ovoid, Pyriform, Bi-conical, Oval, and Spherical. 



Ovoid. This is the most common and familiar form — that of 

 the Common Fowl. Nearly all Game Birds, Gulls, Ducks and 

 Perching Birds have this type of egg. Examples shown are 

 Partridge (65), Great Black-backed Gull (66), Jackdaw (67) and 

 Nightingale (68). 



Pyriform. The pear shaped eggs are characteristic of Snipe, 

 Plovers, etc., the Guillemot and Great Auk. The pyriform shape 

 of egg is especially useful where little or no nest is made, and its 

 shape causes it to roll in small circles if disturbed. The examples 

 of this variety shown are — Godwit (69), Ring Plover (70), Lapwing 

 (71), and Guillemot (72). 



Bi-conical. Eggs pointed at both ends are characteristic of 

 the Grebes, i.e., Great Crested Grebe (73) and Little Grebe (74). 



