BIRDS' EGGS. 



(See desk-cases in Hall No. 208, and Local Collection, Hall No. 303.) 



Number of Eggs in a ^^ Set" or " Clutch." — The number of eggs 

 comprising a full "set" or "clutch" ranges from one to as many 

 as twenty. No law governing this number is known. Generally 

 speaking birds of the same family lay approximately the same 

 number of eggs, but there is much variation between birds of 

 closely related families {e.g., Loons and Grebes), while birds of 

 similar nesting habits may not lay the same number of eggs {e.g., 

 Quail and Meadowlark) . 



The number of eggs in a set, or clutch, is no indication of 

 the fecundity of the bird. At the time of laying the ovary con- 

 tains a large number of partly formed eggs, of which, normally, 

 only the required number will become fully developed. But if 

 the nest be robbed, the stolen eggs will sometimes be replaced. 

 The long-continued laying of our domestic fowls is an instance of 

 this unnatural stimulation of the ovary caused by persistent 

 robbing. 



Size of Eggs. — The size of the egg depends primarily upon the 

 size of the bird. The graduated series, from an Ostrich to a Hum- 

 mingbird (Alcove No. 3, Hall No. 208) represents the range of 

 variation among the eggs of living birds. Size, however, is further 

 influenced by the condition of the young when hatched. Praeco- 

 cial birds, for example, the domestic fowls, lay relatively larger 

 eggs than altricial birds, for example. Pigeons. 



This will be appreciated by comparing the egg of the Crow 

 with that of Wallace's Megapode, or the eggs of the Meadowlark 

 with those of the Bartramian Sandpiper (See desk-case. Alcove 

 No. 3, Hall No. 208). The young of the Crow and the Meadow- 

 lark are hatched naked and are reared in a well-formed nest. 

 The Sandpiper lays its eggs in a slight depression in the ground, 

 and its young run about soon after birth. The Megapode buries 

 its egg and leaves it to be hatched by the heat generated by 

 decay of the vegetable debris in which it is placed. The young 

 are bom fully feathered and ready to fly. 



