CHAPTER XII 



REPRODUCTION— CONCERNING EGGS 



Number ot eggs in a "clutch". Shape of the egg. Size. Texture and 

 thickness of the shell. Colours of eggs. Origin of the colours. Patterns of 

 coloration. Colours of eggs in relation to classification. Coloration in relation 

 to environment. White eggs and their meaning. Structure and composition 

 of the egg. 



BIRDS, like their cousins the reptiles, are oviparous : but 

 they differ markedly from the reptile in the relative 

 fewness of the eggs laid in each " clutch " as well as in 

 the fact that these eggs are commonly coloured externally. 



With regard to number it is to be noted that this may vary 

 from a single egg, as in the case of the Guillemot, for example, 

 to as many as twelve or even twenty, as in the Common Par- 

 tridge. That is to say, except when more than one brood is 

 reared in each year, this number is not exceeded ; but if the 

 eggs be removed or destroyed, more are laid to replace them, 

 and this may be repeated many times during each season, until 

 the maternal instincts are gratified, or the bird becomes ex- 

 hausted. 



Man has taken advantage of this fact to supply himself 

 with food, or for other less excusable ends. Thus the Lap- 

 wing, one of our most useful birds, is mercilessly robbed year 

 by year to supply " delicacies " for the table, and similarly the 

 colonies of Gulls and Guillemots are systematically plundered, 

 the former supplying the shortage in the market of " Plovers' " 

 eggs, the latter furnishing their ova for commercial purposes. 

 As a rule, however, a few eggs are left to hatch, for the pur- 

 pose of preserving the stock. The Eider-duck and the Golden- 

 eye Duck are still more systematically victimised, the latter 

 even being induced to lay in artificial nest-boxes. 



While in many species the number in each " clutch " varies 

 considerably, as in the case of the Partridge, in others it is very 



195 



