5 



The eggs of Terns, Plovers, and other birds which nest on bare 

 ground, especially eaiad and shingle, are good examples of eggs 

 which are blotched with half-tones as well as with more conspicu- 

 ously coloured markings. The effect of these half-tones is to 

 dissolve or break up the outline of the eggs and so to render them 

 less conspicuous. 



The eggs of the Nightjar {Caprimulgus europceus) are laid on the 

 bare ground, and form another good example of eggs with protective 

 half-tones. A clutch of these eggs is shown in the next series. 



The Coot {Fulica atra) is an inland water bird inhabiting reed- 

 grown lakes. The nest is large and built of rushes and reeds. The 

 eggs are the colour of the dead reeds among which they are laid. 

 Examples of these and many other birds may be seen in the bird 

 gallery at tbe British Museum, where they are mounted with tlieir 

 nests and eggs in their natural surroundings. 



CLUTCHES. 



A set of eggs found in a nest at one time is termed a clutch. 

 There is a distinct tendency to uniformity between the eggs of a 

 clutch : thus two clutches, laid by two birds of the same species, will 

 be found to differ somewhat from each other, although all the eggs 

 individually will have the same general character, and can be 

 readily recognised as belonging to the same species of bird. 



The number of eggs in a full clutch varies in different species of 

 birds from one to as many as twenty. In many groups of birds the 

 number is distinctive. 



One. — When a clutch consists of only one egg, this is generally 

 very large in comparison with the parent bird. The following are 

 some examples of birds which lay but a single egg: — The Guillemot 

 {Uria troile), Razor-bill (Alca tonla), Great auk (Alca impennis). 

 Puffin {Fratcrcula arctica), and Stormy petrel {Procellaria pelacjica). 



Two. — A clutch of two eggs is constant among the Pigeons 

 (Colum'biformes)y our common Nightjar {Caprimulgus europams), 

 the Divers (Colijmhiformes), and many Birds of Prey (Accipiiriformes). 



Two TO Three. — The Gulls (Lariformes) commonly lay either 

 two or three eggs, as do many of the birds of prey ; although some 

 of the latter, such as the Sparrow hawk (Accipiter nisus) and the 

 Short-eared owl {Asio accipitrinus) will sometimes lay from five 

 to ten. 



